Probing - Wiring Setup.and usage. #464
Comments
Form the Readme in Edge: So the probe is anything that will take pin A5 to ground when it touches your object. The probe position is relative to machine 0. A typical porbe command might be G38.2 X20 Y15 Z-100 (in mm mode). You should set a slow feed rate , e.g. F20 (20mm/min). The G38 will move to X and Y, then Z axis will lower to -100 until the probe makes contact with your object, at which time movement stops. Grbl will report the machine position of the probe touch. E.g.
If using Mach3 or LinuxCNC, then this would work directly: http://www.scorchworks.com/Gcoderipper/gcoderipper.html. Grbl doesn't do variables (yet/never?) so you would need to write some sort of preprocessor to handle the operation based on the gcode that GcodeRipper outputs. But it can be done. Just run gcode ripper on one of your gcode files and look at its output, you will see the sequence of operations. |
Including the feedrate in the same block as probe command will work as well, the resulting code is shorter |
@Protoneer : Yep. @gerritv is right. Grbl just detects a pin change on the probe pin, so any kind of device could work on it. I left it up to the user to determine what that is. A few examples that I know of are a tool length offset touch-off pad in the Carbide 3d Nomad 883 machine, a DIY touch-probe could work on this, and quick auto-leveling using John Lauer's Chilipeppr. I think he has a few videos on quick ways to do this when setting up to mill a PCB. |
Thank you very much for your answers. |
Probe goes to A5,not 5
…On Oct 6, 2017 11:52 AM, "LaserEngraver" ***@***.***> wrote:
Thank you very much for your answers.
Unfortunatelly, Pin5 is connected to one pin of the A4988 Stepper Motor
Drivers :-(
So I have to choose an other one, but it´s hard to say, which one is free
on my Eleks Maker Board.
—
You are receiving this because you are subscribed to this thread.
Reply to this email directly, view it on GitHub
<#464 (comment)>, or mute
the thread
<https://github.com/notifications/unsubscribe-auth/AQlzDNG_KLQKiohflvPDQ78Z_-EcJJajks5spj7AgaJpZM4CV18k>
.
|
ooopppppssss thank you :-) |
O.K. probe sequence is working with: But...... if an end-Switch will be touched, the axis stops at once and retracts in the other direction. thx |
I've been using the probe pin successfully (after the addition of a capacitor to eliminate false positives) for a long while now, but need to probe off unconductive materials - so I built a 3D touch probe of the always-on type. I know I need to invert the pin, but I'm unsure about this 'pull-down resistor' stuff. Does this mean that there will be a resistor in parallel to the probe itself, effectively shorting the probe pin to ground while the probe already is? When the probe stylus makes contact and breaks the circuit, then only the resistor will be grounding the probe pin? So, at no point is the pin actually floating high (due to the internal pull-up resistor)? |
Hi, Now my process looks like following: Now I have to add this switch on top of the material (if material thickness is increased, the switch is on a higher position). The code looks like: N10 G38.3 Z-140 F50 Hope this helps you. |
No, that doesn't help me. I've already been using the A5 pin to detect when the cutter contacts a conductive surface for years. This doesn't help with wood/plastic, which requires that I carefully adhere and flatten out foil onto the surface - something that is a big waste of my time, especially when I can make a probe and use that instead. Grbl supports inverting the pin specifically for these types of probes, but I'm unclear as to the pulldown resistor aspect. I'm not here to ask whether or not I need a touch probe, that wasn't my question. That boat has sailed, I already spent all my free time in the last week designing and making the probe, now I just need to know exactly what wiring it up entails. |
I made a probe that's just like these: https://hackaday.com/2011/06/09/diy-cnc-touch-probe/ and from forum posts I've dug up on the web people have been using them just fine with Grbl, but the threat of 'frying the arduino' as stated on the Github page if a pulldown resistor is not used makes me nervous. It also doesn't make sense because when using the probe pin while not inverted also fry the electronics when contact is made and GND is directly hooked up to the probe pin via cutter + worksurface? I'm wondering if the resistor is even necessary. |
just buy a small piece of copper clad blank printed circuit board, and solder a wire to one corner. that then becomes a flat conductive surface to lay ontop of the work while probing. alternativly i small piece of metall sheet with one corner bent up, and a hole drilled thought it would allow attachment of a wire with a nut and bolt. it does not matter what it is so long as the thickness is known. |
That works great for setting tool length, but not so much for things such as detecting a hole center, probing an edge, mapping a contoured surface, etc. For things like that an actual probe works well. Also, for tool setting, a non-pliable surface can result in chipping of tools particularly if the probing speeds are too fast, or if the tool is carbide. Keep the probe speeds low enough and it should be fine for HSS tools. |
My goal is to map the top surface of a workpiece for a V-carving, which is very sensitive to an irregular surface because it can totally ruin the end result if not planed out or compensated for, and because I work with various pieces of degraded wood (for aesthetic) the goal is to not plane the top surface perfectly flat. Yes, if your one and only goal is to figure out just where the tool is relative to the top surface of the workpiece then a simple little contact piece sitting on there with a known thickness is just fine. My purposes are a bit more involved than that though. I've been having no problems whatsoever with my custom-made 'always-on' probe: Originally I planned to just buy one off Ebay/Amazon, but all of them were way too long. My machine only has a few inches of travel so I needed something with a super low profile, and since apparently I'm the only person on the planet who needs a low-profile touch probe I had to design and fabricate one myself from scratch. I learned to use and drew it up in DesignSpark Mechanical - literally the first 3D CAD program I've ever used. Exported the various relevant features as DXF files and CAM'd them using VisualCAM. I then cut all the pieces out of various sheets of acrylic I had lying around from other projects, picked up some nuts and bolts at the local hardware store and was off to the races. It took some adjusting to ensure that the contacts were all level (by twisting the bolts that are screwed through the bottom into the cap-nuts inside that function as contacts against the stylus carriage's contacts) but since I got that dialed it has been working great over the last year without any problems. The real trick was wiring up to the galvanized bolts with a junky soldering iron and no flux! ;) |
I know this thread is already old, but I have a GCode / GRBL question. In GRBL, you can inverse ($6=1) the probe pin signal. But in GCode, you can also use G38.4 instead of G38.2. So, if I have an "always on" probe like @DEF7 show, can I use it with G38.4 and $6=0 ? being a little confused, here. |
This are two different thing.
First from electrical points.
$6=0 means that if the pin touch GND the probe trigger. Instead
$6=1 means that there is a external pulldown or it is push/pull driven
and high level trigger the probe.
And from probing point:
G38.2 - probe toward workpiece, stop on contact, signal error if failure
G38.4 - probe away from workpiece, stop on loss of contact, signal
error if failure
As example it is normal to probe G38.2 at higher speed, and then at
lower speed use G38.4 in order to find the point with high precision.
and then retract again at higher speed.
Further some CNC have a 3 pos toggle switch with probe disconnected,
connected and
inverted. This allows to use as example touch probes to sense height
and length probes or 3d touch probes that require continuity of signal
to work.
Others use 3 signal jack with gnd/5V/signal interface where the 5V
have two 100ohm resistors 1/4W in parallel and protection diodes in
order that it supports 12/24V and gnd shorts and active circuits
inside touch probes or height sensors for inverting the signal
and signalizing the state.
As attachement a possible solution for having passive touch plate and
passive touch probe connected at the same time.
Chris
|
Thank you for your great answer, @cri-s , much clearer for me know. Just one thing: I don't see your attachement? |
For v-cut engraving, i use a F.E.T, which is a floating engraving tool, it
spring loads the engaving tool tip so it will follow the contors of the
work surface. You can get them from cncaid.com
…On Wed, 28 Aug 2019, 15:48 Bernard Grosperrin, ***@***.***> wrote:
Thank you for your great answer, @cri-s <https://github.com/cri-s> , much
clearer for me know. Just one thing: I don't see your attachement?
—
You are receiving this because you commented.
Reply to this email directly, view it on GitHub
<#464?email_source=notifications&email_token=AAADRSOD2XAM6QW5JZLXAIDQGYUURA5CNFSM4ASXL4SKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD5KGVDI#issuecomment-525625997>,
or mute the thread
<https://github.com/notifications/unsubscribe-auth/AAADRSI6Z34NF4YAQWBL7QLQGYUURANCNFSM4ASXL4SA>
.
|
The attached image is here, https://imge.to/i/vvOuVf , it is just one example.
The digitizer input need to be shorted when not used and not connected.
Jack connectors have a NC pin that implement that automatically.
Low current led could be added inside the digitizer in order to show
there ready state.
2019-08-28 11:56 GMT+02:00, Tim Hawkins <notifications@github.com>:
… For v-cut engraving, i use a F.E.T, which is a floating engraving tool, it
spring loads the engaving tool tip so it will follow the contors of the
work surface. You can get them from cncaid.com
On Wed, 28 Aug 2019, 15:48 Bernard Grosperrin, ***@***.***>
wrote:
> Thank you for your great answer, @cri-s <https://github.com/cri-s> ,
> much
> clearer for me know. Just one thing: I don't see your attachement?
>
> —
> You are receiving this because you commented.
> Reply to this email directly, view it on GitHub
> <#464?email_source=notifications&email_token=AAADRSOD2XAM6QW5JZLXAIDQGYUURA5CNFSM4ASXL4SKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD5KGVDI#issuecomment-525625997>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AAADRSI6Z34NF4YAQWBL7QLQGYUURANCNFSM4ASXL4SA>
> .
>
--
You are receiving this because you were mentioned.
Reply to this email directly or view it on GitHub:
#464 (comment)
|
Ha, yes, thank you. Looks like a good idea. I'll think about that. |
I had a quick look at the Wiki page but there were very little details about the probing feature in V0.9.
My questions are around:
x How does the wiring work?
x What kind of probes can be used?
x General overview of the probing process...
Thanks.
The text was updated successfully, but these errors were encountered: