FDM Part XII Cross cutting workflows

FDM Polymers — A Technical Reference ›

Part XII — Cross-cutting workflows

Material selection, calibration, bed adhesion, multi-material printing, post-processing, cost/procurement, and tribological filaments — seven synthesis chapters that consolidate the per-polymer guidance scattered through Parts II–XI into single-purpose references. Read these once after the polymer chapters; return to them as workflow questions arise.

22. Material selection decision framework

Polymer selection is the engineering decision that constrains every downstream choice on a print — process parameters, hardware, post-processing, cost, and ultimately service performance. The framework below is constraint-first: identify the hard requirements, intersect the candidate polymer sets, then refine by cost, printability, and available hardware. When two polymers tie on the binding constraint, pick the cheaper or more printable one — the volume's chapters cover when the second-tier choice is the right one to spend on.

22.1 The four decision axes

Service temperature is the first filter. The polymer's glass transition (for amorphous polymers) or melting/crystallization envelope (for semi-crystalline) sets a hard ceiling on continuous-load service: amorphous parts loaded above T_g creep; for semi-crystalline polymers the ceiling is set by HDT and creep, typically far below T_m — use the continuous-service column in Appendix A.1. Mechanical character is the second filter: stiffness vs toughness vs flexibility. Most FDM polymers are stiff (PLA, PETG, PC, nylons, PPA-CF); a minority are tough (PCTG, PC blend, PA12, PEBA); a few are flexible (TPU, TPEE, PEBA). Environment is the third filter: UV exposure, chemical contact, moisture, fuels, food contact, biocompatibility. Cost and printability are the fourth filter — usually a tie-breaker rather than a primary constraint, but decisive when the application has no special requirement on the other three axes.

22.2 Decision walkthrough

The sequence below answers "which polymer" by elimination. Evaluate all constraints that apply, mark every yes answer, then intersect the candidate sets. If only one hard constraint applies, the listed set is the starting answer; if none apply, use the default-tier choices at the end.

Step	Question	If yes ->	If no ->
1	Does the part need to be flexible (Shore D < 70)?	TPU, TPEE, PEBA, foaming elastomer (Ch 16)	Continue to step 2
2	Does the part see continuous service above 150 °C?	PPS-CF up to ~180 °C; above that, PAEK or outsource (Ch 18–19)	Continue to step 3
3	Does the part see continuous service above 100 °C?	PPA-CF, PC blend (high-PC), PPS-CF (Ch 14, 15, 18)	Continue to step 4
4	Outdoor UV exposure over months or years?	ASA, PMMA, PVDF (Ch 10, 17)	Continue to step 5
5	Aggressive chemical exposure (acids, bases, hydrocarbons, fuels)?	PP, PVDF, PPS, POM by chemistry (Ch 11, 17, 18)	Continue to step 6
6	Food or water contact?	copolyester (PCTG, or Tritan-based filament — chemically a distinct TMCD terpolymer, see §8.1; preferred — subject to the §8.9 caveat), PP, PETG (Ch 8, 11)	Continue to step 7
7	Repeated impact loading or living-hinge cycling?	PCTG, PA6/PA12, PP unfilled, PEBA (Ch 8, 13, 11, 16)	Continue to step 8
8	High stiffness-to-weight for structural parts?	PA-CF, PPA-CF, PC-CF, PPS-CF (Ch 13, 14, 15, 18)	Continue to step 9
9	Wear, friction, or sliding-contact applications?	POM, PC/PTFE, iglidur tribopolymers (Ch 17, 15, 28)	Continue to step 10
10	ESD-dissipative surface required?	ESD-PC (Ch 15)	Continue to step 11
11	Flame retardance (UL94 V-0) required?	FR-PC, PPS, PEI (Ch 15, 18)	Continue to step 12
12	Optical clarity required?	PCTG (Ch 8), PETG clear, PMMA, PC clear (Ch 7, 17, 15)	Continue to step 13
13	None of the above special requirements apply?	PETG (cost), PLA (printability), PCTG (toughness step-up)	—

_{Table 22.1 — Material selection decision walkthrough. The order of the steps reflects constraint dominance — the hardest-to-satisfy requirements come first — but real parts often answer yes to more than one row. Mark every applicable row, intersect the candidate sets, and then choose by cost, printability, and available hardware. Step 13 applies only when no special requirement dominates; it handles the bulk of hobbyist work.}

22.3 Quick-reference: by application

Application class	Default polymer	Step-up if budget allows
Display models, cosmetic prints	PLA	PCTG for toughness, PETG for cost
Functional prototyping (room-temp)	PETG	PCTG for impact, PC blend for heat
Outdoor parts (UV, weather)	ASA	PMMA for clarity, PVDF for chemistry
Electronics enclosures (passive)	ASA or PETG	PC blend for heat tolerance
Engine-bay / under-hood	PC blend	PPA-CF for stiffness + heat
Drone or RC airframe	PCTG or PP-CF	PA6-CF or PPA-CF for performance
Lab equipment, chemical contact	PP	PVDF for aggressive chemistry
Living hinges, snap-fits (high cycle)	PP unfilled, PA12	PEBA for dynamic flex
Gaskets, vibration dampers	TPU 95A	TPEE for heat, PEBA for dynamic flex
Wear surfaces, low-friction bushings	POM	PC/PTFE for load-bearing stiffness and heat, PEEK for heat + chemistry
Structural brackets, fixtures	PETG or PC blend	PA6-CF or PPA-CF for stiffness
Food contact (resin-level compliance)	Copolyester (PCTG, or Tritan-based filament)	Verify per-filament certification
Athletic footwear, cushioning	PEBA or foaming TPU	—
Aerospace, FR-rated electronics	FR-PC	PEI if hardware tier supports it

_{Table 22.2 — Application-to-polymer quick reference. Use as a starting point for procurement decisions; the per-polymer chapters in Parts II–XI carry the engineering detail needed to confirm fit and the brand surveys needed for purchasing.}

23. Calibration workflow (unified)

Every new filament — even a re-order of a previously calibrated brand and color — requires per-spool calibration on the actual machine before engineering-grade work. Resin batches drift, additive packages change between revisions, and printer state shifts with nozzle wear, extruder gear wear, and ambient conditions. The workflow below is the consolidated sequence the rest of this volume references; the sequence is order-sensitive — each step's output is the input to the next.

A word on scope before the workflow. Full calibration is worth the time when the print is functional — a part that bears load, mates with other parts to a tolerance, seals, runs hot, or will be tested or certified. For those prints the dimensional accuracy, mechanical strength, and repeatability the workflow buys are the whole point. For purely decorative or cosmetic prints — display models, figurines, visual prototypes — most of this sequence is overkill. A model that only has to look right does not need a measured extrusion multiplier or a tuned pressure-advance value; the vendor's generic profile, perhaps with a quick temperature check for surface finish, is sufficient, and the hours spent on flow and shrinkage calibration return nothing visible. The judgment is simply whether the print has a job to do beyond being looked at. The rest of this chapter assumes the answer is yes; if it is not, drying (Step 1) and a temperature check (Step 2) are the only steps that meaningfully affect a cosmetic result, and the remainder can be skipped without consequence.

23.1 Step 1 — Dry the filament

Drying is the first step because moisture confounds every measurement that follows. A wet filament shows artificially low max volumetric flow (steam disrupts melt cohesion), artificially low effective extrusion multiplier (voids in the bead reduce mass per unit length), and wildly inconsistent pressure advance values. The Part I §3.5 drying-protocol table is the reference; dry to the upper end of the recommended range and time, with 30 minutes margin beyond the spec to be safe on first calibration.

23.2 Step 2 — Temperature tower

A temperature tower prints a single tall geometry with the nozzle temperature stepped down by 5 °C per 30 mm band, spanning the vendor's recommended range plus 5 °C above and below. Score each band on three axes: surface finish (smooth and consistent), bridging (no sag), and stringing (no fine filaments between features). For cosmetic parts, the optimal temperature is the lowest band that scores well on all three; for functional parts, use the highest band that still bridges without stringing — interlayer adhesion rises with melt temperature, and the tower does not test it. Stock temperature-tower model files exist on community model repositories; the specific tower geometry is less important than scoring the bands consistently.

23.3 Step 3 — Max volumetric flow

Max volumetric flow (mm³/s) is the rate at which the hotend can melt and extrude filament without under-extrusion. The test prints a single-wall geometry with the flow rate stepped upward — typical bands span 5 mm³/s to 20 mm³/s in 1 mm³/s steps. The failure point is visible as a sudden transition from solid wall to thin, gappy, or visibly under-extruded bead. The measured maximum (MVF_max) is the highest band before that failure. Slice at no more than 0.8 × MVF_max for general work; engineering-grade work uses 0.6–0.7 × MVF_max — both fractions of the measured maximum, not of an already-derated value — to build process margin against drift.

23.4 Step 4 — Extrusion multiplier (12-sample wall measurement)

Extrusion multiplier (EM, also called flow or flow ratio depending on the slicer) is the scaling factor applied to the slicer's calculated extrusion volume. The default value of 1.0 assumes perfect filament diameter, perfect extrusion stepper calibration, and zero melt-shrinkage during cooling — rarely all true simultaneously. The 12-sample wall measurement method: print a single-wall hollow cube at a known wall-width slicer setting (typical 0.45 mm for a 0.4 mm nozzle). After cooling, measure the actual wall thickness with calipers at 12 points distributed around the cube. Compute the average; divide the slicer's target wall width by the measured average to get the EM correction. Apply, re-print, re-measure to verify within ±0.5%. Typical converged EM values: 0.93 for high-fiber-loaded grades, 0.97–1.00 for unfilled engineering polymers (some unfilled copolyesters converge lower, near 0.94), 1.03–1.05 for softer elastomers and PC blends.

The YOLO method — a faster alternative for many users. The wall-measurement method has one real weakness: a caliper reading on a single ~0.45 mm wall is at the edge of what hand calipers resolve reliably, and the vase-mode print itself can vary in width with cooling and seam placement. The YOLO flow-rate test, built into OrcaSlicer (and available as community test models for other slicers), sidesteps the caliper entirely. It prints a single plate of small blocks, each sliced at a slightly different flow modifier — typically a range of -0.05 to +0.05 in steps of 0.01 — and the user picks the block with the cleanest top surface: the smoothest fill, no gaps between the surface-pattern arcs, and no raised or sunken seam between the inner and outer regions. The chosen modifier is applied as new = old ± modifier in a single pass. Because surface quality is judged rather than measured, YOLO is often the better choice for unfilled polymers on a well-behaved machine: it is faster, needs no calipers, and judging "is this surface smooth" is a more forgiving task than resolving hundredths of a millimetre on a thin wall. The wall-measurement method still earns its place where an absolute, traceable number is wanted — qualifying a new material, documenting a profile for publication, or calibrating fiber-filled and elastomeric grades whose top surfaces are textured enough that the visual judgment becomes ambiguous. A reasonable default: YOLO for routine per-spool tuning, the 12-sample measurement when the value has to be defensible.

23.5 Step 5 — Pressure advance

Pressure advance (PA, sometimes Linear Advance) compensates for the elastic lag between extruder gear motion and nozzle bead deposition. Without PA, the bead width drifts at the start and end of every line — thin entries, thick exits. The test prints a single-layer pattern with the PA value stepped upward across the bed; the optimal value is the band where line ends and beginnings appear visually consistent with the rest of the line. Typical converged PA values: 0.020–0.040 for PLA, 0.030–0.060 for PETG/PCTG, 0.025–0.050 for PC blends, 0.04–0.08 for fiber-reinforced polymers.

23.6 Step 6 — XY shrinkage compensation

Amorphous polymers shrink 0.3–0.5% in the print plane on cooling; semi-crystalline polymers can shrink 1.5–3% depending on crystallization behavior. The XY compensation factor in the slicer scales the model outward to compensate, producing dimensionally accurate parts on cool-down. The Califlower Mk2 model — a multi-feature shrinkage test with both external and internal dimensional checks — is the practical community-standard reference. Print, measure key dimensions, compute the average shrinkage as a percentage, set the slicer compensation. Typical converged values: 0.20% for PCTG, 0.25% for nylons (CoPA and CF-filled grades), 0.35% for ABS, 0.45% for ASA, 0.5% for filled PP; unfilled PA6 and unfilled PP can run ~1–2%, consistent with the semi-crystalline range above.

23.7 Step 7 — Z shrinkage

Z-direction shrinkage is typically smaller than XY because the layer-by-layer deposition allows partial relaxation between layers. The standard test is a 100 mm tall hollow cylinder; measure the actual height with calipers, compute the shrinkage percentage, set the slicer compensation. Many users skip this step on first calibration — the magnitude is usually under 0.3% for amorphous polymers, where engineering tolerance permits it. Skip with intention rather than by accident.

23.8 Storing the calibrated profile

Calibrated values belong in the filament profile, not in the printer's persistent storage. Most slicers support per-filament storage of nozzle temperature, bed temperature, max volumetric flow, EM, PA, XY shrinkage, and chamber temperature. The pressure advance value can also be embedded in the filament-specific start G-code if the firmware supports it (the command differs by firmware: M900 K[value] on Marlin, M572 D0 S[value] on RepRapFirmware and Prusa Buddy firmware, and SET_PRESSURE_ADVANCE ADVANCE=[value] on Klipper). Store the profile, label it with the calibration date and the spool batch code, and re-verify EM and PA on first use of a new spool from the same brand — batch-to-batch drift of 5–10% is normal.

24. Bed adhesion strategy by polymer family

Bed adhesion is the interfacial chemistry problem framed in §3.3: wetting and intermolecular attraction between the molten first-layer polymer and the build surface. Polar polymers grip polar surfaces (PEI, glass, powder-coated steel); non-polar polymers (PP, PE) require non-polar compatible surfaces. The per-family chapters in Parts II–XI cover the specifics; this chapter consolidates the choices into one table.

24.1 Consolidated bed-adhesion reference

Polymer family	Best surface	Adhesive/release	Bed (°C)	Removal notes
PLA	smooth PEI	none	50–60	Cool fully; pops free
PETG	textured PEI	glue stick if over-gripping	80–90	Over-grips on smooth PEI; release layer essential
PCTG	smooth PEI	glue stick or PVP	70–90	Similar to PETG; release layer reduces sheet damage
ABS / ASA	smooth PEI	glue stick on first prints	95–110	Brim required for parts >100 mm; enclosure mandatory
HIPS	smooth PEI	glue stick	100–110	Limonene-soluble; brim for large parts
PP (unfilled, CF, GF)	PP-coated sheet or PP packing tape	Magigoo PP for difficult parts	85–105 (PP sheet) / 80–100 (tape) / 20 (cold-bed)	PP-on-PP self-adhesion; cool fully for release
PE / HDPE	PE-coated sheet or PP packing tape	Magigoo PP	80–100	Same principle as PP; sparse commercial PE-sheet availability
PA6 / PA66	G10 garolite	PEI + PVP as alternative	90–110	The garolite plate grips strongly; cool fully
CoPA (PA6/66 copolymer)	smooth PEI or CryoGrip Glacier	glue stick if over-gripping	50–70	Low-warp copolymer; the Appendix B bench profile runs the bed at 50 °C; garolite unnecessary
PA12 / PA612 / PA11	smooth PEI	glue stick on demanding parts	70–90	Lower-shrinkage than PA6; PEI grips reliably
PA-CF / PA-GF	G10 garolite	Magigoo PA on PEI as alternative	90–110	High warp tendency tames best on garolite
PPA / PPA-CF / PPA-GF	smooth PEI + glue stick / PVP	Magigoo PC also works	90–120	G10 garolite acceptable; chamber temperature drives success more than surface
PC / PC blend	G10 garolite (long-term)	glue stick / PVP on PEI	100–115	Over-grips PEI catastrophically; release layer non-negotiable
PC-CF / PC-GF / ESD-PC	G10 garolite	Magigoo PC	100–120	Hardened nozzle mandatory; bed temperature near upper bound
PC/PTFE	smooth PEI	Magigoo PC	90–120	All-metal hotend required; chamber recommended
TPU / TPE	textured PEI or CryoGrip Glacier (40–50 °C)	glue stick as release if smooth PEI used	40–70 (64D+ hard grades at the top end)	Over-grips smooth PEI; release layer if smooth surface needed
TPEE	textured PEI or CryoGrip Glacier	glue stick as release if smooth PEI used	50–70	Similar to TPU; higher bed than soft TPU
PEBA	smooth PEI	none	50–60	Releases cleanly without adhesive; easier than TPU
PMMA	smooth PEI	glue stick	100–110	Brittle; thermal stress dominates; cool fully
POM	glass + glue stick or POM-coated sheet	Magigoo PA	100–115	Low surface energy; brim mandatory; ventilation required
PVDF	smooth PEI	none for small parts; high-temp adhesive/release for large or warp-prone parts	90–110	All-metal hotend; chamber recommended for warp control
PPS-CF	G10 garolite	Magigoo PA	80–120	Chamber product-dependent: Polymaker and Flashforge print without a heated chamber, Bambu specifies 60–90 °C; hardened nozzle mandatory
PEI / PEEK / PEKK	industrial adhesive	beyond prosumer scope	140–155	Industrial chamber required; outside this volume's scope
PVA / BVOH	smooth PEI	none	50–65	Print directly from a dryer; ambient air degrades quickly
PVB	smooth PEI	glue stick	70–80	Hygroscopic; dry before printing; IPA-smoothable after
PHA / PLA-PHA	smooth PEI	glue stick if cold-bed	0–60	PHA prints cooler than PLA; some products require unheated bed
PCL	glass + glue stick	tape	20–30	Very low Tm; minimal bed heating needed

_{Table 24.1 — Bed adhesion strategy by polymer family (consolidated reference). G10 garolite is the engineering default for any high-warp engineering polymer where the print would damage a PEI spring-steel sheet on removal; Magigoo's family of polymer-specific adhesives handles most remaining edge cases. Cold-bed approaches (PP, PCL, some PHA grades) use room-temperature bed during printing and elevated temperature only at end-of-print for release.}

Three principles cut across the table. First, smooth PEI is the default surface for most polar polymers; textured PEI reduces grip and is preferred when over-grip damages the sheet on removal. Second, G10 garolite is the right answer for high-warp engineering polymers (PA6, PC, PPA, PPS) because it grips reliably during printing, releases cleanly on cool-down, and tolerates repeated thermal cycling without surface degradation. Third, polymer-specific adhesives (Magigoo PP, PA, PC) substantially outperform generic glue stick on the hardest filaments and are the engineering choice when print success rate is the metric.

24.2 Build-plate adhesives: the product landscape

Where Table 24.1 names an adhesive or release layer, the choice is rarely between brands that behave identically. Build-plate adhesives fall into four mechanical classes, and the class matters more than the label. Glue sticks are water-soluble solid adhesives (typically PVP-based, some PVA): cheap, available anywhere, and adequate for PLA and basic PETG, but they wear after a handful of prints and apply unevenly. Sprays coat a large bed quickly and uniformly — useful for big first layers — at the cost of overspray onto the machine and a need for ventilation. Liquid pen and brush adhesives are the purpose-built tier: formulated to grip while the bed is hot and release as it cools, lasting many prints per application. Temperature-activated adhesives are a liquid sub-type whose grip rises with bed temperature, giving strong hold on hot beds and easy release once cool. Table 24.2 surveys the products a prosumer user is likely to encounter.

Product	Type	Material range	Notes
Magigoo Original	Liquid pen	PLA, ABS, PETG, HIPS, ASA, TPU	The default all-in-one. Pen applicator, holds hot and releases on cool-down, ~100+ applications per pen, cleans with water. The safest general-purpose choice for common filaments.
Magigoo PP / PA / PC	Liquid pen	Polymer-specific: PP, the nylon family, the PC family	Chemistry tuned per family. Magigoo PP is one of the few practical options for polypropylene; Magigoo PA and PC target the high-warp engineering polymers where generic glue stick fails.
Vision Miner Nano Polymer	Liquid brush	High-temp: PEEK, PEI, PPSU, PC, nylon; also PLA, PETG, ABS, HIPS, PVDF	The engineering-tier choice. 120 mL brush bottle, formulated for high-temperature materials, works on glass, PEI, and carbon surfaces; a single coat lasts many prints on lower-temp filaments.
Layerneer Bed Weld Original	Liquid	PLA, PETG, ABS, ASA, PVA, CPE — not nylon or PP	An aggressive adhesive aimed at stubborn corner-lift on large flat parts. The vendor explicitly does not recommend it for nylon or polypropylene.
Bambu Lab Liquid Glue	Liquid	PETG, TPU, and other common filaments	A clean liquid alternative to the glue stick; beginner-friendly, lower residue. Often used as a release layer on over-gripping plates.
TH3D Bed Cement	Liquid	Broad; works on PEI, flex plates, glass, garolite	100 mL bottle with an applicator tip, priced near half the leading brands. Grip is good for roughly three to four prints before reapplication.
Dimafix	Temp-activated pen	ABS, ASA, PC, PP, nylon and other high-warp materials	Grip increases with bed temperature and falls away as the bed cools. Pen format; favored for warp-prone engineering filaments.
3DLAC (and similar sprays)	Spray	PLA, PETG, ABS, ASA; nylon-specific variant available	Fast, uniform coverage on large beds. Overspray and ventilation are the trade-off; on very grippy stock plates it functions more as a release layer than an adhesive.
PVA glue stick (generic)	Solid stick	PLA, basic PETG; release layer for many materials	The budget baseline — washable, universally available, reapplied every few prints. A purple-tint stick shows coverage. Adequate for undemanding work and as a sacrificial release layer on PEI.

_{Table 24.2 — Build-plate adhesives accessible to prosumer users. Material ranges are as stated by each manufacturer; treat them as starting guidance, since adhesion also depends on bed surface, temperature, and first-layer settings. Sealed-ecosystem and industrial-only products are out of scope. Prices and formulations drift — Appendix D frames the brand landscape as point-in-time.}

Two selection rules cover most cases. For common filaments — PLA, PETG, ABS, ASA, TPU — an all-in-one liquid pen such as Magigoo Original is the lowest-friction choice, and a PVA glue stick is the budget fallback; both grip adequately and release on cool-down. For engineering filaments — the nylon, PC, PPA, and PPS families, and anything in a heated chamber — a polymer-specific or high-temperature adhesive earns its cost: Magigoo's family-specific pens, Dimafix for warp-prone materials, or Vision Miner Nano Polymer for the highest heat tiers. A point worth keeping in mind from Table 24.1: with the highest-warp engineering polymers, the adhesive is not a substitute for the right build surface and chamber temperature — it is the last few percent of reliability on top of a correct surface choice, not a rescue for a wrong one. Finally, every product here is also a release agent: on a build surface that grips a given polymer too hard (PC or PETG on smooth PEI is the classic case), a thin adhesive layer protects the sheet by giving the part something sacrificial to bond to.

24.3 Build-plate types and the spring-steel ecosystem

Table 24.1 names a surface for each polymer; this section is the surface itself. Modern prosumer machines have largely converged on the flexible spring-steel system: a thin steel sheet, coated on one or both sides, held to the heated bed by an embedded magnet. The sheet flexes off the magnet after a print so parts pop free, and a machine's plate is really defined by its coating, not the steel. The coatings divide into six functional classes:

• Smooth surfaces — smooth PEI (a polymer film) and smooth-PEI-like coatings — give glassy-flat, glossy first layers and the strongest grip on polar polymers. That grip is the catch: PC, PETG, and PCTG over-adhere to hot smooth PEI and can tear the coating or pull fragments on removal, which is why Table 24.1 pairs them with a release layer.

• Textured surfaces — textured PEI, most commonly a powder-coated PEI steel sheet — trade gloss for a matte, lightly stippled first-layer finish and noticeably reduced grip, making them the safer default for over-gripping materials and for cosmetic parts where a matte underside is wanted.

• Satin surfaces sit between the two: a fine, even micro-texture that yields a soft semi-matte finish with grip closer to smooth than to coarse textured — a middle option for users who find smooth too grippy and textured too coarse.

• Patterned plates carry a decorative relief (woodgrain, geometric, marble-like) that transfers to the part's bottom face; they are a finish choice, with adhesion behavior tracking whatever base coating carries the pattern.

• Engineering plates are the high-temperature, high-warp tier: rigid G10/garolite and equivalent purpose-made sheets, used bare for PA, PC, PPA, and PPS because they grip those polymers hot and release cleanly on cool-down without a consumable adhesive.

• Cold plates are the inverse case — surfaces (and a workflow) for materials printed on an unheated or barely heated bed, such as polypropylene on a PP-faced sheet or PCL: adhesion is managed by surface chemistry and tape rather than bed heat, with the bed sometimes warmed only at end-of-print to aid release.

Surface class	Typical finish	Grip	Best-fit materials
Smooth PEI	Glossy, glass-flat	High on polar polymers	PLA, PVB, PEBA; PETG/PCTG/PC only with a release layer
Textured PEI (powder-coated)	Matte, lightly stippled	Moderate	PETG, PCTG, TPU, ABS/ASA; over-grip-prone materials generally
Satin	Soft semi-matte	Moderate-high	PLA, PETG, ABS — a middle option between smooth and textured
Patterned / decorative	Relief pattern in part underside	Tracks base coating	Cosmetic prints; adhesion follows whatever coating carries the pattern
Engineering (G10 / garolite)	Fine matte	High on engineering polymers; clean cool-down release	PA, PA-CF/GF, PC family, PPA, PPS-CF
Cold plate (PP-faced, tape, glass)	Varies by facing	Chemistry- and tape-driven, not heat-driven	PP and PP-CF/GF, PCL, some PHA grades

_{Table 24.3 — Build-plate surface classes. The class describes the coating's behavior; specific branded plates (below) are implementations of one or more of these classes. Grip is also a function of bed temperature and first-layer settings, so treat the column as a relative ranking rather than an absolute.}

Within these classes, a few product families are common enough on prosumer hardware to name specifically. G10 / garolite sheets are a glass-epoxy laminate sold as flat rigid plates (Holden Enterprises and others) rather than flexible steel; they are the engineering-plate workhorse for the warp-prone polymers and tolerate repeated thermal cycling without coating wear. BIQU CryoGrip plates are flexible spring-steel sheets engineered around a cool-release effect — grip is strong while printing and falls away sharply as the plate cools, with the Glacier variant documented for TPU and for nylon at moderate bed temperatures; in slicer terms a CryoGrip sheet is treated as a high-temperature smooth-PEI-class plate and is kept within its rated temperature ceiling. Prusa ships three spring-steel sheets that map directly onto the classes above: a smooth PEI sheet, a textured powder-coated PEI sheet, and a satin sheet, plus a separate polypropylene-faced sheet for the cold-plate PP workflow. Bambu Lab plates follow the same pattern under different names — a textured PEI plate as the general-purpose default, a smooth/high-temperature plate for glossy first layers and higher-temperature engineering work, a cool-plate option for low-temperature materials, and an engineering plate intended for the warp-prone families. The naming differs by vendor, but the underlying surface classes in Table 24.3 are what actually determine behavior; matching the class to the polymer in Table 24.1 matters more than the brand on the box.

Three practical points. First, the coating is the consumable, not the steel: smooth PEI and powder-coated textured PEI both wear, and a release layer on over-gripping pairs (PC or PETG on hot smooth PEI) protects that coating directly — the §15.10 cost case for garolite on PC is exactly this. Second, surface class and bed temperature are coupled, not independent: the same plate grips harder hot, so a too-grippy result is sometimes a bed-temperature problem rather than a wrong-plate problem. Third, match the plate to the dominant material — a textured PEI sheet covers most common filaments, a bare engineering sheet earns its place the moment PA, PC, PPA, or PPS is in regular rotation, and a cold-plate or PP-faced sheet is effectively mandatory for polypropylene rather than optional.

25. Multi-material and dual-hotend printing

Multi-material printing extends FDM beyond single-color, single-polymer parts to functional combinations: rigid bodies with flexible seals, structural bodies with soluble supports, color-coded mechanical assemblies, and cosmetic models with mixed transparency. The hardware ecosystems implementing multi-material capability split into four architectures, each with distinct constraints on what can be combined.

25.1 Four hardware architectures

Single-extruder multi-material (MMU) systems share one nozzle across multiple filament feeds via an upstream switching mechanism. Filaments swap by retracting the active filament, advancing the new filament through the cutter or splicer, and purging the melt zone before resuming the print. The architecture is mechanically simple and cost-effective but introduces a substantial purge tax: typical purge volumes per swap are 50–200 mm³, accumulating quickly across a multi-color print to volumes that may exceed the model itself. Chamber compatibility between filaments is also a hard constraint — every loaded filament must tolerate the chamber temperature dictated by the highest-temperature material in the print.

Dual-hotend systems mount two independent hotends on a shared toolhead. One hotend lifts out of the way while the other prints. Filament swaps require only switching which hotend is active — no purge, no melt-zone contamination. The cost is mechanical complexity and additional calibration: hotend offset (XY and Z) must be characterized for each machine. Dual-hotend systems support combinations that MMU cannot, because the two filaments never share a melt zone — different temperature windows, different filler systems, even incompatible materials can be combined.

IDEX (Independent Dual EXtruder) systems mount two complete toolheads on independent gantries, enabling true parallel printing — two parts at once, or one part with simultaneous deposition of two materials. The cost-of-ownership and footprint are highest in this tier; the throughput advantage is meaningful for batch production.

Tool-changer systems mount several complete, independently docked toolheads that a single motion system picks up and parks as needed (Prusa XL-class machines). Like dual-hotend systems they are purge-free — each filament keeps its own dedicated melt zone — and they scale to four or more materials; the cost is per-tool XY and Z offset calibration and the price of each additional complete toolhead.

25.2 Material compatibility groupings

Filaments in any multi-material print must share a compatible chamber temperature envelope. Three practical tiers:

Tier	Chamber temp	Compatible filaments
Low	ambient – 35 °C	PLA, PVA, BVOH, PVB, PHA, PCL — and TPU/PEBA with care
Mid	35 – 50 °C	PETG, PCTG, ABS, ASA, HIPS, PA12, PA612, PP, PE — and PLA at the lower end
High	50 – 65 °C (active)	PC, PC-CF, PA6, PA6-CF, PPA-CF, PPS-CF (PEI-CF only marginally; vendor spec is 85 °C+) — and ABS/ASA at the lower end

_{Table 25.1 — Material compatibility groupings by chamber temperature. Mixing across tiers risks deforming the lower-temperature material (TPU softens above 50 °C; PLA softens above 55 °C). Filaments at tier boundaries may be mixed downward (run high-tier material at low-tier chamber if the geometry permits) but not upward.}

25.3 Support filament strategies

Support material is the most common multi-material application. Three strategies dominate:

Soluble supports (Chapter 20) — PVA paired with PLA, BVOH paired with PLA/PETG/ABS — dissolve away in a water bath after printing. Highest geometric capability (internal cavities, undercuts, trapped supports) at the highest cost (purge tax, dissolution time, filament cost).

Same-material supports use the same filament for both model and support, distinguishing them via geometry (sparse infill, thin walls, spaced from the model surface). No filament cost premium; removal requires mechanical separation. The default approach for single-extruder FDM without multi-material capability.

Breakaway interface supports — vendor-specific products like Polymaker PolySupport or specialty PPA-compatible breakaway filaments — print as the support body but with a deliberately weak bond to the model material. Snap apart on cool-down. The middle ground: lower cost than soluble supports, better surface finish than same-material supports.

Hybrid strategies are common in production work. A PC-blend model with HIPS body supports and HIPS interface layers — HIPS-on-PC is a verified weak pair, so the interface releases cleanly from the PC body without limonene dissolution, and the support volume cost is cheap HIPS. (A PCTG interface does not work here: PC and copolyesters bond strongly, so the interface welds rather than releases. For low-temperature work, the PETG/PLA pairing — either as model or as interface — is the analogous verified weak pair.)

25.4 Purge cost economics

Single-extruder multi-material printing on a four-color part with 100 filament swaps and a 100 mm³ purge per swap consumes 10,000 mm³ of purged material — roughly 12 g for a 1.24 g/cm³ polymer. For a small model the purge weight may exceed the model weight. Mitigations: reduce purge volume per swap (calibrate against actual cross-contamination; many systems use higher default purge than necessary); design the model to minimize swaps (color blocking rather than fine detail); use dual-hotend hardware which eliminates purge entirely for filament transitions; or accept the purge cost as the price of color capability.

26. Post-processing strategies

Post-processing converts a raw FDM print into a finished part. The techniques cluster into five categories — mechanical, chemical smoothing, coating, heat treatment, and assembly — each with polymer-specific compatibility constraints. The single most important reality from the per-polymer chapters: the same chemistry that drives a polymer's engineering value typically forecloses solvent-based finishing on that polymer.

26.1 Mechanical finishing

Sanding, polishing, and machining work on every FDM polymer with the right abrasive and the right technique. Three principles: wet over dry minimizes airborne particles (essential for CF/GF-reinforced grades where fiber fragments are documented respiratory hazards); progressive grit from coarse (220) through medium (400, 600) to fine (1000, 2000) produces the smoothest finish without skipping steps; polymer-specific temperature awareness matters — PLA, PETG, and PCTG smear under friction heat from power tools while POM, PC, and PPS tolerate aggressive sanding without deformation. For optical clarity on PCTG and PMMA: sand wet through 2000 grit, then polish with plastic-polish compound. For matte finish: stop at 800–1000 grit.

26.2 Solvent smoothing

Vapor smoothing and bath smoothing in compatible solvents produce glass-smooth surfaces by surface-only re-melting the printed bead structure. The compatibility matrix is narrow:

Polymer	Compatible solvent	Method	Hazard tier
ABS, ASA	Acetone	Vapor smoothing in closed container with brief warm-vapor exposure	Flammable; ventilation required
HIPS	Limonene; acetone with caution	Limonene bath dissolution/finishing; acetone can surface-finish but over-etches easily	Skin sensitizer (limonene); flammable (acetone)
PVB	Isopropyl alcohol	Vapor or bath; vendor-recommended workflow	Low; household-tier solvent
PLA	No safe household-tier solvent; DCM and ethyl acetate work	Heat-gun gloss possible; mechanical only for matte	DCM: see regulatory note below; flammable (ethyl acetate)
PETG, PCTG	No safe household-tier solvent; DCM works (same hazard tier as the PC row)	Mechanical preferred; XTC-3D / 2K epoxy for gloss	DCM: see regulatory note below; fume hood mandatory
PC, PC blend	Dichloromethane (DCM)	Bath or vapor; produces strong solvent-weld bond	DCM: see regulatory note below; fume hood mandatory
Nylons (PA, PPA)	No common workshop solvent works	Mechanical only; surface coatings for gloss	—
PP, PE	No workshop solvent at room temp	Mechanical only; flame treatment for paint adhesion	—
TPU, TPE, PEBA	No effective vapor solvent	Mechanical only; coatings limited by flexibility	—

_{Table 26.1 — Solvent-smoothing compatibility by polymer family. Most engineering polymers in this volume have no practical workshop-solvent smoothing route — the chemical resistance that drives their engineering value forecloses chemical finishing. Regulatory note (DCM): under EPA's TSCA final rule on methylene chloride (89 FR 39254, May 2024), all consumer uses are prohibited — DCM is no longer lawfully sold to US consumers — and most industrial/commercial uses are prohibited or phasing out; a limited set of continuing uses operates under EPA's Workplace Chemical Protection Program, and EPA has adjusted some compliance dates since publication (e.g., extensions for certain non-federal laboratories, November 2025). Status checked July 2026 against EPA's methylene-chloride risk-management page (epa.gov/assessing-and-managing-chemicals-under-tsca/risk-management-methylene-chloride). OSHA regulates DCM as a potential occupational carcinogen (29 CFR 1910.1052); IARC classifies it 2A.}

Mechanical finishing and coatings (2K epoxy, XTC-3D) are the practical routes for PETG, PCTG, nylons, polypropylene, and the high-performance specialty polymers.

26.3 Coatings and paint

Surface coatings cover three application classes: gloss and fill (XTC-3D, 2K epoxy clearcoats, plastic-bonding primers fill layer lines and produce smooth painted surfaces); color and aesthetics (automotive primers and topcoats over polymer-compatible bonding primers); function (conductive coatings for ESD, vapor barriers, anti-static treatments, UV protective clears for outdoor parts). Low-surface-energy polymers (PP, PE, POM) require flame or plasma treatment plus a plastics adhesion promoter (SEM- or Bulldog-class) before any coating will adhere reliably; standard automotive primers fail to wet these surfaces, and the 3M 4298UV / Loctite SF 770 primers are adhesive-bonding promoters (§26.5), not paint primers. Higher-surface-energy polymers (PLA, PETG, PCTG, ABS, ASA, PC) accept standard primer-topcoat workflows directly.

26.4 Heat treatment (annealing)

Annealing serves different purposes for amorphous and semi-crystalline polymers. For amorphous polymers (PETG, PCTG, ABS, ASA, PC), annealing relieves residual stress from rapid layer cooling — modest improvement to dimensional stability and creep resistance, no change to HDT. Temperature must stay below T_g by 10–15 °C to avoid distortion; typical schedules run 60–80 °C for the copolyesters and styrenics and 85–100 °C for PC blends (vendor PC schedules sit well below the theoretical T_g−10–15 ceiling of ~130 °C — see §15.11), for 2–4 hours. For semi-crystalline polymers (PLA, PA, PP, PPA, PEEK), annealing develops crystallinity — substantial gains in HDT and stiffness, dimensional change of 1–3% as the polymer chains pack into ordered regions. Schedule must stay above T_g but below T_m. Per-polymer detail in §3.6 and the polymer chapters; unfilled PPA anneals per its vendor protocol (§14.9), but without fiber reinforcement the warp risk during the heat soak is higher — support the part and follow the vendor schedule.

26.5 Assembly: gluing, fastening, inserts

Solvent welding dissolves both mating surfaces in a compatible solvent, then evaporates to leave a polymer-continuous bond. Works for ABS (acetone), PC (DCM), and PMMA (DCM or specialty acrylic solvents) — noting that EPA's 2024 TSCA rule has ended lawful US consumer sale of DCM (see the Table 26.1 regulatory note). Adhesive bonding covers everything else: cyanoacrylate (CA) for fast assembly of most polar polymers; epoxy (2K) for high-strength structural bonds; polyurethane for elastomer-to-rigid bonds; specialty polyolefin systems (Loctite Plastics Bonding System — SF 770 polyolefin primer + CA; 3M 4298UV primer + CA; 3M Scotch-Weld DP8010 structural acrylic) for PP and PE bonding. Mechanical fastening avoids the adhesive problem entirely: heat-set threaded inserts (brass inserts with a knurled exterior that engages the printed plastic) work on PLA, PETG, PCTG, ABS, ASA, PC, nylons — any polymer with a reasonable melt window. Self-tapping screws work on fiber-reinforced filaments where the matrix grips threads reliably. Press-fit and snap-fit assemblies leverage polymer-specific elasticity: PETG, PCTG, PP, and nylons hold snap-fits through many cycles; PLA fractures, and printed PC snap-fits fail at layer lines and sharp internal corners despite the resin's ductility — radius the hinge root and orient the flexure in-plane.

27. Cost and procurement landscape

Filament cost spans a roughly 30× range across the polymers in this volume — from $15/kg commodity PLA to $500/kg PEEK-CF. The cost tier drives procurement strategy as much as the technical specifications do.

27.1 Price tiers (early 2026, 1 kg / 1.75 mm retail)

Tier	Range ($/kg)	Representative products
Commodity	15–25	PLA, PETG, generic ABS, generic ASA, HIPS, generic CoPA, eSun/Sunlu budget brands
Mid-engineering	25–50	PCTG (Spectrum, 3D-Fuel, Fiberlogy), PolyMax PETG, PolyMax PC, Bambu PC, Prusament PETG, ASA premium brands, unfilled PA12
Engineering	50–100	Prusament PC Blend, PA-CF (Polymaker, Bambu), TPU 95A premium (NinjaTek, Polymaker)
Specialty	100–250	PA-CF premium, PPA-CF (Bambu, 3DXTech), PPS-CF, ESD-PC, FR-PC, PEBA (3DXTech 3DXLABS, Fillamentum), PVDF specialty grades
Ultra	250–500+	PEEK, PEKK, PEI 1010-CF, Prusament PC Space Grade Black, ThermaX PSU/PPSU, specialty industrial-grade products

_{Table 27.1 — Filament price tiers (early 2026 retail; ±20% drift typical across regions and bulk quantities). The cost step from commodity to mid-engineering is roughly 2×; from mid-engineering to engineering is another 2×; from engineering to specialty is roughly 2–2.5×; from specialty to ultra is another 2–4×. Procurement decisions should map the cost tier to the application's binding constraint.}

27.2 Quality signals and vendor selection

Three observable signals distinguish quality manufacturers from budget-tier producers, often more reliably than price alone:

Diameter tolerance. ±0.02 mm is the engineering-grade target for 1.75 mm filament. ±0.03 to ±0.05 mm is acceptable for commodity use; looser than ±0.05 mm produces visible extrusion-rate variation in the printed bead. Batch consistency. Vendors that publish lot codes and provide consistent color and mechanical properties across batches are the engineering-grade choice; budget brands often show batch-to-batch color drift and mechanical variance. TDS depth. Published TDS data — particularly printed-specimen tensile values, not just resin-grade values — distinguishes engineering-oriented vendors from marketing-oriented ones. The depth and specificity of the TDS correlates strongly with the underlying product consistency.

27.3 Recycled-content programs

A growing set of vendors offer recycled-content products that the makers position as close to virgin material on the headline engineering metrics, though independent comparison is limited and reprocessing history affects any given batch. 3D-Fuel ReFuel reprocesses post-industrial PCTG, with the vendor reporting retention of the ISO 527 tensile envelope of virgin Pro PCTG. Fiberlogy R PP is 100% post-consumer/post-industrial polypropylene with vendor-documented mechanical properties matching virgin Fiberlogy PP. Braskem FL900PP-CF uses 100% recycled carbon fiber feedstock in the PP matrix. Fishy Filaments Porthcurno (sold in partnership with Fillamentum) is 100% ocean-recovered PA6 from end-of-life fishing nets (Part I §5.4). An adjacent sustainability program — not a recycled-content product — is Polymaker PolyTerra PLA: virgin bio-based PLA with carbon offsetting, shipped on a cardboard rather than plastic spool. These products are real progress over straight virgin filament; treat them as marginal improvements to mainstream procurement rather than as license to print wastefully.

27.4 Procurement strategy by use case

Hobbyist or casual user: stick to commodity and mid-engineering tiers (PLA, PETG, PCTG, basic PC blend, TPU 95A) and one or two budget-tier brands plus one engineering-tier brand for reference. Buy in 1 kg spools; bulk procurement doesn't pay back unless the print volume supports it. Maker space or prototyping shop: standardize on engineering-tier brands (Prusament, Bambu, Polymaker, Spectrum) for predictable results; budget tier as a secondary option for cosmetic work. Bulk 2.5 kg spools and 5 kg refills are cost-effective. Engineering qualification or production work: specialty-tier and engineering-tier brands with published TDS data are mandatory; bulk procurement of specific batch codes preserves repeatability. The cost step up the tier ladder is usually worth it for parts that will be tested or certified.

28. Tribological filaments

Tribological filaments are engineered for parts whose binding constraint is wear at a moving interface — gears, bushings, cams, slides, bearing surfaces, guides. The relevant failure mode is not fracture under load or creep at temperature but the gradual loss of material and dimensional accuracy as two surfaces rub. The polymers covered in this chapter appear elsewhere in the volume under their chemistry families — iglidur tribo-grades are commonly inferred to be PA-based, though igus does not disclose the base polymer (Chapter 13), PC/PTFE is a polycarbonate composite (Chapter 15), POM is its own family (Chapter 17) — but the tribological use case cuts across all of them, which is why it earns a cross-cutting chapter rather than living inside any single polymer family. This chapter consolidates the wear-grade options and gives the vocabulary needed to choose between them.

28.1 A short tribology primer

Four parameters govern whether a printed part survives in a wear application. Specifying a tribo filament without understanding them is guesswork.

Coefficient of friction (COF). The ratio of friction force to normal force at a sliding interface, reported as a dynamic value (sliding) and a static value (breakaway). Low COF means less resistance, less frictional heating, and less energy lost in the mechanism. Engineering tribopolymers reach dynamic COF values of 0.10–0.25 against steel dry; unfilled engineering polymers like PA6 or PETG run 0.30–0.45. COF is not a fixed material constant — it depends on the counterface material, surface finish, load, sliding speed, and temperature — so vendor COF values are comparative indicators, not design allowables.

Wear rate (specific wear rate, k). The volume of material lost per unit of sliding distance per unit of normal load, with SI units of mm³/(N·m). It is the single most direct measure of how long a wear part will last. Tribologically optimized polymers report k values one to two orders of magnitude below their unfilled base resin. A part that loses 0.05 mm of wall over a service life is functional; the same part in a high-k material loses 0.5 mm and fails on clearance or backlash.

PV limit. The product of contact pressure (P) and sliding velocity (V) defines the thermal-mechanical envelope of a sliding part. Every tribopolymer has a PV limit above which frictional heat generation outruns heat dissipation, the contact surface softens, and wear accelerates catastrophically. The PV limit is the reason a bushing that runs cool at low speed fails at high speed under the same load. Design wear parts to operate well below the published PV limit; FDM-printed parts should be derated further because layer-line porosity reduces thermal conductivity and the effective contact area is lower than a molded equivalent.

Counterface and lubrication regime. Tribological performance is a property of the pair, not the polymer alone. A polymer sliding against hardened steel behaves differently than the same polymer against aluminum, against another polymer, or against itself. Dry-running (self-lubricating) tribopolymers are formulated with solid lubricants — PTFE, silicone, graphite, or molybdenum disulfide dispersed in the matrix — so they need no applied grease or oil; this is the dominant use case for printed wear parts, because applied lubricant attracts grit and many printed mechanisms cannot be relubricated in service. Lubricated service (with grease or oil) lowers wear further but is rarely the design intent for FDM parts. Polymer-on-polymer pairs should mix chemistries — POM against PA, for example — because identical polymers in sliding contact tend to gall and adhesively transfer material.

An anisotropy caveat specific to FDM. A printed wear surface is not isotropic. Layer lines create a directional texture; sliding across the layer lines wears differently than sliding along them, and a surface formed by the top or bottom layer differs from one formed by the perimeter walls. Wherever possible, orient the part so the wear surface is formed by smooth perimeter extrusion rather than stepped layer banding, and expect a break-in period during which high asperities are worn flat before the steady-state wear rate is reached.

28.2 Wear-grade filament survey

The hobbyist-accessible tribological filament market clusters into four groups: dedicated tribopolymer compounds (the igus iglidur filament family), PTFE-modified composites of otherwise-conventional polymers, neat POM, and the carbon-fiber-reinforced engineering grades that deliver wear resistance as a side effect of stiffness.

Filament	Base / type	Tribological character	Best use
igus iglidur I150	Tribopolymer with solid lubricant (base polymer undisclosed; commonly inferred PA-class)	Dry-running; low wear against steel and against itself; 65 °C continuous limit; not the food-contact grade — igus positions i151 as the FDA / EU 10/2011-compliant, optically detectable grade	Gears, bushings, sliding parts in general service; specify i151 for food-adjacent work
igus iglidur I180	Tribopolymer, higher-temperature grade	Dry-running; wear-rated similarly to I150; 100 °C continuous service vs I150's 65 °C; enclosure recommended for printing	Wear parts at service temperatures beyond I150's 65 °C limit
igus iglidur RW370 / J-class	High-temperature and specialty tribopolymer grades	Dry-running; extended PV envelope or temperature range per grade. RW370 is industrial-tier — ~350–360 °C nozzle, bed >180 °C, chamber ≥160 °C — far beyond the prosumer envelope, like the PEI/PEEK rows	Wear parts at elevated temperature or higher PV than I150 tolerates; RW370 only via industrial hardware or outsourcing
PC/PTFE (e.g. Spectrum)	Polycarbonate matrix + dispersed PTFE	Low COF from the PTFE phase; PC matrix carries structural load and heat	Load-bearing wear parts that also need PC-class stiffness and HDT
POM (acetal — Gizmo Dorks)	Neat polyoxymethylene	Low COF, excellent fatigue resistance, low and stable wear; no solid-lubricant additive needed	Gears, cams, low-friction mechanisms; the default printed-gear material
PETG-PTFE	PETG matrix + dispersed PTFE	Lower COF than neat PETG; modest wear improvement; easy to print	Light-duty sliding parts where PETG printability is wanted and loads are low
PA-CF wear grades	Carbon-fiber-reinforced nylon (PA6-CF, PA12-CF)	Wear resistance as a by-product of fiber stiffness; abrasive to the counterface	Stiff structural parts with incidental wear; not a first choice for pure bushings
PA + solid-lubricant blends	Nylon compounded with PTFE, MoS2, or graphite	Dry-running; between neat PA and dedicated tribopolymers on wear	General wear parts where a dedicated tribopolymer is unavailable

_{Table 28.1 — Hobbyist-accessible tribological filaments. The igus iglidur filament family is the only group engineered specifically and solely for wear; the others deliver tribological performance as either a PTFE-additive modification (PC/PTFE, PETG-PTFE) or an inherent property of the base polymer (POM) or the reinforcement (PA-CF). Picking a CF-reinforced grade for a pure bushing application is a common error — the fiber that provides stiffness also abrades the metal shaft running inside it.}

The iglidur filament family is igus's adaptation of its molded tribopolymer bushing materials to FDM filament form. The grades carry the same naming as the molded-part and bar-stock lines: I150 is the general-purpose dry-running grade and the most widely stocked (the igus i151 page explicitly says to choose I150 only if FDA food conformity is not necessary — i151 is the food-compliant, optically detectable blue grade); I180 extends continuous service temperature to 100 °C versus I150's 65 °C at the cost of more demanding processing (enclosure recommended); specialty grades extend the temperature or PV envelope further. All are formulated to run dry — the solid lubricant is dispersed through the polymer, so a freshly printed part is self-lubricating with no break-in grease required. iglidur filament is the engineering default when wear is the primary design constraint and the part does not also need to carry a heavy structural load.

PTFE-modified composites — PC/PTFE and PETG-PTFE — take a conventional matrix polymer and disperse PTFE through it to lower the coefficient of friction. They are not equivalent. PC/PTFE keeps polycarbonate's stiffness, impact toughness, and ~110–140 °C service envelope, so it suits wear parts that also carry load or see heat; it demands an all-metal hotend and the PC-class process discipline of §15.7. PETG-PTFE is a light-duty material — it prints as easily as PETG and lowers friction usefully, but the wear improvement over neat PETG is modest and the PETG matrix limits it to low loads and near-room-temperature service. Treat PETG-PTFE as a friction-reduction convenience, not a true bearing material.

POM deserves its standing as the default printed-gear material. It delivers a low and stable coefficient of friction, excellent fatigue resistance under cyclic tooth loading, and a low wear rate without any solid-lubricant additive — the tribological behavior is intrinsic to the acetal chemistry. The trade-offs are covered in §17.2: difficult bed adhesion and a genuine formaldehyde-emission hazard that mandates ventilation. Where those can be managed, POM outperforms every PTFE-modified composite on gear and cam duty. POM against PA — acetal gear on a nylon gear, or acetal on an iglidur bushing — is a particularly good polymer-on-polymer pairing because the dissimilar chemistries resist galling.

28.3 Selecting and designing a wear part

Match the material to the dominant duty. For gears and cams — cyclic tooth contact, moderate load, the failure mode is tooth wear and rising backlash — POM is the first choice, with iglidur I150 the alternative when POM's bed adhesion or ventilation requirements cannot be met. For plain bushings and sliding bearings — continuous rubbing against a shaft, the failure mode is bore wear and growing clearance — a dedicated iglidur grade is the engineering answer; the dry-running formulation is exactly the design intent. For load-bearing wear parts — a slide or wear pad that also carries structural load or sees heat — PC/PTFE is the choice because the polycarbonate matrix supplies stiffness and thermal headroom that neither POM nor iglidur matches. For light-duty low-friction parts — a drawer slide, a low-load guide, a part where smooth motion matters more than service life — PETG-PTFE is adequate and the easiest of the group to print. Avoid CF-reinforced grades for pure bushings: the exposed carbon fiber abrades a metal counterface, and the application is better served by a dedicated tribopolymer.

Three design practices materially extend printed wear-part life. Print the wear surface from perimeter walls, not layer banding — orient the part so the sliding face is formed by smooth perimeter extrusion, which gives a more uniform surface and a lower steady-state wear rate. Use high wall and infill density at the contact zone — internal porosity beneath a wear surface reduces both load capacity and thermal conduction, pushing the part toward its PV limit sooner; solid or near-solid infill under bearing surfaces is worth the material. Allow for break-in — printed wear surfaces shed high asperities during the first hours of service before reaching steady-state wear, so size clearances expecting a small initial dimensional change, and where the application is critical, run a deliberate low-load break-in before putting the part into full service.

Cross-references: iglidur calibration values appear in Appendix B and the PA-family process guidance in §13.5; PC/PTFE process and the mandatory all-metal-hotend requirement are in §15.7; POM bed adhesion, the formaldehyde-emission hazard, and ventilation requirements are in §17.2 and §5.3.

---

← Contents · ‹ Part XI — Support and niche polymers · Appendices ›