Custom touch plate

Questions/answers/discussion about initial setup of your CNC Shark

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Kayvon
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Custom touch plate

Post by Kayvon »

I made my own touch plate for the Shark (or anything else). New Wave sells an official Shark Touch Plate for about $100. $10 of that goes towards a cable and piece of metal. The rest goes towards paying the fee to unlock the Shark Control Panel so it recognizes the plate. If it weren't for the software key block, you could connect a $3 Chinese touch plate and do the same thing.

[attachment not working for some reason, click below]

In fact, a cheap Chinese plate is what I started with. If you hook it up to a continuity meter, you can manually lower the gantry using the Control Panel shoftware until there's contact. That works, but it's tiresome and slow. So I made a circuit to do this automatically.
2 v1 assembly.jpg
The prototype was used for testing. It lights up when there's a connection on the touchplate, so you can see that the touchplate is working before starting. It plugs into the USB port on the laptop and is recognized as an additional keyboard. When you push the button on the device, it automatically pushes the PgDn key several times a second, lowering the gantry by 0.001" and checking for a connection before continuing.
4 new and old.jpg
I remade the PCB to look nicer (using the CNC, of course!). The "brains" of the device are a simple microcontroller. I could share the compiled code if anyone's interested in making their own. I assume there's not enough interest to sell them, but if I'm wrong shoot me an IM. I've been using this solution for years now, but only posted when someone expressed interest in details.
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Rando
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Re: Custom touch plate

Post by Rando »

yeah, but have you put a dial test indicator on, and found that it doesn't actually move in 0.001" increments?
My measurements show a cycle of 0.0008, 0.0008, 0.0014. Also, the Z-axis max speed and acceleration numbers
seem to affect that incremental jog. Not to in any way diss; looks like a great idea. I'm just wondering if you've
managed to solve any of the issues I keep coming across. BTW, I've only actually measured that on X and Y, so
maybe Z doesn't, but I doubt it.

Also, does your system solve the 0.0185" depth problem? I use a vise and touch off the material directly. If I
hole, or other feature, if I touch off directly, that feature is always cut to 0.0185" deeper than the GCode says to.
Yeah, I can jog down and it's the right height, but when a program runs, it don't work. So, I use an 0.020" thick
piece of metal as a plate and tell it there is none...and it gets closer. Still never spot-on. And, it happened the
same when using their 0.375" touch-plate: everything was 0.0185" deeper than it was supposed to be.

Have you noticed this? Or is it just being mean to ME? :mrgreen:

Rando
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Kayvon
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Re: Custom touch plate

Post by Kayvon »

I have not observed the 0.0185" depth problem. If you jog down to 0", without running code, is it 0.0185" too deep? Or do you have to run code? Admittedly, I determined the width of my touchplate using the CNC (I didn't have calipers at the time), so once I contact the plate I tell the Control Panel that it's sitting at 0.776" (the height of my touchplate--I usually "round" up to 0.777").

The Control Panel confirms what you're saying about the measurement cycles. Most of the time, stepping down will move the display by 0.001". Occasionally, it'll appear not to move at all (i.e. move less than 0.001") or even move 0.002". This isn't a big issue for me. Since I only care about the point at which it contacts the plate, I could go back and touch it again with the max speed turned down. Running at less than 0.001" just means I'll get better accuracy on my touch plate measurement. Running slightly above implies I'm losing accuracy, but the <0.0005" loss doesn't bother me.

Rando
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Re: Custom touch plate

Post by Rando »

Yeah, that's the infuriating part: when I jog, it's just fine, perfect. It's when it runs code. If I have a safe-height of <0.020, the rapids plunge goes right into the surface. But jogging works fine, even doing incremental with various jog values. Hitting Home twice gets tot he right height. Crazy stuff :twisted:
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Kayvon
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Re: Custom touch plate

Post by Kayvon »

That sounds infuriating. I haven't had that issue, thankfully.

The only thing I've encountered is problems if I start running gcode when I'm not at (0,0,0). It's probably because of relative moves in g-code, rather than absolute. I haven't checked explicitly -- I just learned to start at (0,0,0) like I should be.

Rando
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Re: Custom touch plate

Post by Rando »

Kayvon:

You might check the G91/G90 setting in the post and resulting GCode: absolute mode is G90, incremental is G91.
Looking through the Vectric post processors, it doesn't seem to actually recognize any difference as it outputs
the actual GCode, in incremental versus absolute mode. The other program I use (BobCAD) does understand the
difference. That command G90 must be output before any G00/G01 move commands, so it will be at the very
top of the GCode files. It's typically in the "begin HEADER" section of the post-processor file, after all the comments.
In mine, the G90 is on about line 95, but your might be a bit earlier in the file

Yeah, I NEVER start the cutting from X0Y0, much less Z0, it's always far away at the other side of the machine.
I do a lot of work where I'm making 5, 10, 20 of a single part, and so group the toolpaths by setup and bit,
and then cycle through the parts using workstops on the vise. Thus, the spindle stays running, and I want it
WAY out of the way while I swap the parts and restart. But, that's me :geek:

Cheers!

Rando
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monitoringpost
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Re: Custom touch plate

Post by monitoringpost »

Kayvon wrote:
Tue Nov 24, 2020 12:07 pm
The only thing I've encountered is problems if I start running gcode when I'm not at (0,0,0). It's probably because of relative moves in g-code, rather than absolute.
That's perhaps the reason Kayvon. My post command is for Absolute Mode and it pretty much dead on. I know when I was a beta tester for NWA automation if my memory serves me there was some issue along this line but I thought it was only with the 4th axis and it was corrected. Joseph at the time was a little sloppy with versioning - I know for a fact that there's at least 10 builds of v23 in user hands. I don't run the latest as it had a bug (perhaps the issue that was mentioned) too but I can't find my notes - that was quite some time ago now! BTW, like your touch plate ingenuity - I coughed up the dough for the NWA accessory and I don't regret it. Personally, I like the software and USB pendant combination that I use. :)

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Kayvon
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Re: Custom touch plate

Post by Kayvon »

Rando wrote:
Tue Nov 24, 2020 4:11 pm
You might check the G91/G90 setting in the post and resulting GCode: absolute mode is G90, incremental is G91.
I'm plenty familiar with writing and reading GCode to do that, but it's just as easy for me to start at the origin, so I've never bothered. It sounds like that's more useful to you, especially with your nice spindle (I have a router), so I can see why that would be important.

Rando
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Re: Custom touch plate

Post by Rando »

Interesting...there are a whole host of scenarios that would never work for me. As in, X0Y0 tends to be up at the top-left (X-Y+), while Z0 might be deep down inside an already cut-pocket, if the feature is referenced off that previously-machined face. Or, more likely, the top-surface of the part (where Z0) was first obtained gets machined away, so some other artificial, known Z0 has to be used. Having to be at X0Y0Z0 definitely wouldn't work, or I'd have to set all the safe heights so high that it'd be going up and down for more time than cutting ;-). To each their own!

Regards,

Rando
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frogman_pep
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Re: Custom touch plate

Post by frogman_pep »

Kayvon could you share how to make this for someone with some circuitry/etc knowledge, but not proficient?

I would be open to purchase this for a proper price as well. Let me know. Thanks

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