Involute Gear Shape Options

[prmod3d]

You have a LOT on your plate at the moment with all the improvements and new features you're adding to Layerling, so if you don't have time for this in the near future that's understandable!

With the massive Layerling improvements over just the past week or two <!> I'm finding myself on the fence about spending the massive amount of time to learn FreeCAD (who just released their major v26.3 RC1 update) or put all my time and support into Layerling. All I know for sure is that I've definitely outgrown Tinkercad and need a suitable opensource non-cloud-based alternative.

So far I've only been experimenting with simple shapes and basic design functions in Layerling as new features are rolled out at a breakneck pace <!> but am considering redesigning my current project in Layerling to really test the experience of using it as a daily driver.

That project includes a lot of gears... and I find the Gear shape options in Layerling lack the most important "involute" shape feature of the teeth on a usable gear. Currently, the Layerling gear shape is a novel decorative shape at best and not really useful for practical purposes.

Ironically, this is one area where Tinkercad still excels. Their options for gear design are quite basic, but at least the involute gear shape is offered. When I need more options (which is often) I usually go to one of Makerworld's gear maker utilities (based on the opensource SCAD platform) to generate and then export/import STL files into my project. It's clumsy -- especially when minor changes are required -- but is better than nothing!

Is improving the Gear shape options within the scope of future Layerling development? I wonder if the SCAD engine could even be directly implemented (or included as an extension/addon) to facilitate opensource SCAD scripts, of which there are tons!

Anyway, here's a few of the Makerworld parametric gear design utilities I've been using if you want to take a look with regards to the feasibility of inclusion -- or perhaps only to see the options and freely-accessible code via the "Code" button at the top of the Configuration options -- which may allow for a quick implementation of more options to the Gear shape currently available in Layerling (I think a Bambu login may be required):

Ultimate Gear Parametric Generator

Bevel Gear Generator

Planetary Gearset Generator

[henmedia]

@prmod3d, you're right - today's teeth are simple trapezoids, fine for looks but not for gears that really have to mesh. I'll change that:

• Involute teeth for the spur and the helical gear, set the way gear generators do it: module, number of teeth, pressure angle (20° by default) and backlash. The diameter follows from those, so two gears with the same module mesh, and layerling shows the centre distance for a pair.
• Existing designs keep their current teeth, so nothing changes in them.
• After that: an internal (ring) gear and a rack, which together give you a planetary set.

The bevel gear keeps its approximate teeth for now; a true bevel involute is a bigger job.

Running OpenSCAD scripts inside layerling is possible in principle, but it is a big project of its own, and the results would arrive as meshes rather than editable shapes. I'll leave that open as an idea and see whether others ask for it too.

I'll come back here when the involute gear is in.

[henmedia]

@prmod3d @luk-saw, involute gears are in 1.56.0:

• New gears have involute teeth, set by number of teeth and module; the outside diameter is module × (teeth + 2). Pressure angle (20° by default) and backlash (0.2 mm per pair by default) sit under the teeth.
• Select two gears and the properties panel gives the centre distance they mesh at and how far apart their centres are now, or tells you their modules differ.
• A helical gear's angle is now the true helix angle, so a pair meshes with the same angle, one positive and one negative. The bevel gear takes the same teeth, tapered - still an approximation.
• The edge tool and STEP take the exact body with smooth involute flanks.
• Existing designs keep their old teeth ("Simple" under Tooth Shape) until you switch them.

@luk-saw, thanks for the pointer to Useful gear: its pitch is π × module here, and its slop is what Backlash does. A ring gear and a rack come next. Here is how it works.

[prmod3d]

Thanks! I still see the inclusion of OpenSCAD as useful even if the results are non-editable meshes transferred to the Workspace. Especially if the custom shape parameters are saveable on the SCAD side (like Makerworld does with their generators), since it would be a LOT more convenient to flip back and forth within Layerling (similar to how Sketches are currently managed) than to switch to a 3rd-party app, export the object, and import into Layerling.

I'm only aware of a very small subset of what must be a massive library of OpenSCAD scripts, so I think there might be a lot of people interested in having this option integrated into Layerling -- even if they don't know they need the feature yet!

Perhaps asking the question in the "Poll" category of your discussion board would be helpful to gauge the interest? I'd post the question myself, but am unsure of the proper language and terms to use that would convey the idea accurately.

[luk-saw]

Thank you. These are great additions.
A new tooth profile drop-down opens the door for other profiles like the circular one seen in the Useful gear.
While the classical involute is great for bigger gears, when parts get smaller it's difficult to print with adequate precision and the gears tend to clinch with each other. The cylindrical profile seems to be much more forgiving in that regard, offering much lower resistance when rotating.
The ring and the rack would be awesome and will definitely complement the mechanical gear offering of the Layerling 🎉

[luk-saw]

I was just exploring the gear shape and was about to ask a similar question. The current gear shape definitely is challenging to create multiple gears that will work with each other if you are looking for a specific size or gear ratio.

There is one tool in particular that I keep using for multiple projects - "Useful gear", which proved to be very reliable in 3D printing, rendering little resistance and transferring force well when multiple gears work together. The pitch determines the teeth size, and the teeth count will determine the overall size of the gear. So keeping the teeth size the same, you can make gears of different sizes by playing with the teeth count, and that guarantees they will work together. The "slop" parameter can be considered clearance, making the teeth smaller but preserving the overall teeth count.

Just throwing it out as inspiration to consider; maybe it will be simpler to implement.

[prmod3d]

I've used this gear option in Tinkercad as well on occasion. It can actually be the preferable choice for some small gears when the relatively low resolution of 3D printers isn't able to correctly resolve the details of an involute gear. At larger sizes though, nothing beats the accuracy of an involute, especially when also incorporating a helical angle.

Maybe surprisingly, I use the "Useful gear" mostly for creating knobs and other gripped surfaces on cylinder shapes, and would like to see its inclusion in Layerling as well!

[henmedia]

@prmod3d, good points, thanks.

For small gears and for grips, the old tooth shape is still there: Tooth Shape → Simple, with tooth size and tooth width set by hand. For knobs there is also the Knurl shape, straight or crossed. Could you say what Useful gear does differently - rounded teeth, a different flank? Then I can see whether one of these covers it or whether a third tooth shape makes sense.

[prmod3d]

In the Simple Tooth Shape of "Gear" I was not able to create the smooth peak-and-trough curves of the 'Useful gear' -- the result is still very angular which makes for an unpleasant feeling knob as well as taking longer to print. 3D printers really like curved sections rather than corners -- zoom-zoom!

The Knurl shape more closely replicates the knob effect of a 'Useful gear' with the exception of the grooved peaks and valleys rather than curves. If a curved option could be included in this shape than it's another win for the migration (and improvement) of shapes from Tinkercad!

[RobbieKnobbie]

I was going to ask for this to be added into Layerling, but I thought that might be asking too much.

But this implementation sounds great, and if you're producing true involutes, these should be fairly strong - even 3d printed

THANKS for suggesting, and THANKS Stefan for putting all this together. I may give up my seat of SolidWorks if this keeps going!

[henmedia]

@prmod3d @luk-saw thanks, that makes sense. I'll add a third tooth shape, Round: tooth tips and gaps as round arcs that run smoothly into each other, like Useful gear. It is set by module and number of teeth like the involute one, so round gears with the same module mesh, and it doubles as a smooth grip for knobs. The ring gear and the rack are still on the list, but they take longer.

@RobbieKnobbie thank you, glad it's useful! The involute teeth are true involutes, so printed gears should hold up well.

If you find layerling useful, a small donation helps me keep improving it. Thank you!

[luk-saw]

This is amazing! Thank you for all these new features 🍻

[henmedia]

@prmod3d @luk-saw The ring gear and the rack are in 1.58.1. Both are types of the gear, next to spur, helical and bevel: Gear Type → Ring gear or Rack, set by teeth, module, pressure angle and backlash like the involute gear, with involute or round teeth.

• The ring gear has its teeth pointing in, plus a Rim field for the ring outside them. A gear of the same module runs inside it at a centre distance of module × (ring teeth − its teeth) / 2; select both and the properties panel gives that distance. For a planetary set: ring teeth = sun teeth + 2 × planet teeth, e.g. 30 = 12 + 2 × 9.
• The rack is teeth × π × module long, so racks of one module line up end to end, and its depth is free. A gear rolls on it with its centre teeth × module / 2 in front of the pitch line, a module behind the tips.

Both are exact bodies for the edge tool and STEP, and switching the gear type keeps the module. Here is how it works.

[luk-saw]

Fantastic, this opens up a whole new level of possibilities for more mechanical designs! 🎉

[prmod3d]

Excellent! Being able to properly work with gears without flipping between 3rd-party apps and exports/imports is a real time-saver.

Unfortunately the calculations for planetary gear sets -- which take into account not only the "ring" gear, but also the number of "planet" gears, the size of the "sun" gear, and the desired drive ratio -- requires more options than this new Shape tool provides. But I suppose one could do all the manual calculations if so inclined!

For most every other application of gears, though, this addition is most welcome. Thanks!

[henmedia]

@prmod3d Thank you! layerling is not a gear calculator, so the planetary arithmetic stays with you, but it is short: ring teeth = sun teeth + 2 × planet teeth; planets space evenly when (sun + ring) divides by their number; with the ring fixed, sun in and carrier out, the ratio is 1 + ring / sun (ring 30, sun 12, planets 9 gives 3.5 : 1). Build the three gears with one module, select sun and planet, or planet and ring, and the properties panel gives each centre distance.