Z touch plate set up

Mostly Printed CNC - MPCNC Troubleshooting
1

I’m using the MPCNC as a router and I am trying to set up a touch plate for my z axis. Its basically a penny glued to a 3d printed holder. The z home works perfect, but I want to set the actual home to be lower than my touchplate. I’ve enabled eprom editing, but i haven’t had any luck with setting an offset.

http://imgur.com/ACbEZZg The touch plate in all its glory

What I want to do:
Hit home z and have bit touch the touchplate that is on my work surface.
ramps knows that my z axis endstop is 12mm too high
remove the touchplate
Run the gcode which starts cutting 12 mm lower than the touchplate

I can get around this by manually lowering the z axis then restarting ramps, or adding a move command to all my gcode to lower the z axis but I feel like there is a right way to do this.

Alex

2

Hey I’m super curious if you ever got anywhere with this? I feel like adding a z height adjustment for the endstop in the ramps firmware is probably very doable.

I also think that embedding the penny into your table also wouldnt be that hard, since it is a CNC and all. You could just cut a hole the perfect size for a penny and then glue it in there. Wires to the side or bottom.

And on another node, I’m curious if the bit of the dewalt 660 is grounded to the AC power supply ground or something like that. How cool would it be to check for conductivity against ground and not have to attach some connector to your bit every measurement.

3

I’m just using a thin piece of sheet metal. Aluminum foil would work, it’s just not very durable.

4

This must be far more accurate then a conventional mechanical lever end stop. Might have to change mine out.

5

Touch plates are good for stuff that moves, like the top surface of stuff we’re cutting. For the x and y, a switch works just fine.

6

Did you find a solution to set the z startpoint 12mm lower then the touch plate? If so, how did you solved it?

Is it possible to do what the creator of estlecam has done, but in ramps (https://www.youtube.com/watch?v=bhZdbgM6S70&feature=youtu.be). I would like to find the z, x and y start point on the workpiece

7

No, I just use a really thin touch plate. For what I use it for, the .25mm isn’t that big of a deal.

8

Many this would do it for the Z - check the part about Multi-Pass Cuts:
www.akeric.com/blog/?p=3603

9

If you haven’t resolved this, you can home Z like you’ve said then send this command: “G92 Z12”. Change the 12(mm) to whatever your touch plate thickness is. 0 will now be the surface of your material.

4 Likes
10

Brilliant! Thank you, this was just what I needed.

Alex

11

@barry How did you wire your Z touch plate up?

12

It’s wired to the Z min end stop. Alligator clip to the end mill, and the other side is attached to a thin piece of sheet metal. I don’t worry about taking the thickness of the sheet metal out, it’s thinner than any tolerances I expect out of wood. The only thing I use it for is a repeatable z height above the work piece. I zero out the x and y before a cut then write down where I set the new zero on the work piece. I only use the touch plate if I’m going to do a tool change, otherwise I just eyeball it.

2 Likes
13

Thanks man. I’m going to do this to mine today.

14

Barry I tried to the same thing you did here with the g92 script however it never changes on the display on Repetier any idea why it wouldnt work"

 

 

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15

Not sure, your screenshot isn’t repetier. If that’s not your screenshot, rename your picture to something else. The forum software has a bug where it will just reuse a photo if there’s already the same named one on the forums somewhere else.

16

That was definitely not my screen shot lol. Either way I resolved the issue by restarting Repetier and then it took the script changes!!!

1 Like