Want to make an auto touch plate with DW660, but no ground?

CptanPanic
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Want to make an auto touch plate with DW660, but no ground?

Post by CptanPanic » Mon Oct 01, 2012 11:59 pm

I want to make a touch plate whereas the controller senses when the bit touches a copper plate. Unfortunately the DW660 doesn't have a ground pin, anybody have any ideas besides something that clips on?
Thanks,
CP

Improbable Construct
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Re: Want to make an auto touch plate with DW660, but no grou

Post by Improbable Construct » Tue Oct 02, 2012 12:33 am

I just use a clip on the bit.
I clip a wire on to the bit then slide the touch plate under it and hit the auto Z button.
Works like a champ.
Last edited by Improbable Construct on Tue Oct 02, 2012 1:49 am, edited 1 time in total.
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levlandau2
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Re: Want to make an auto touch plate with DW660, but no grou

Post by levlandau2 » Tue Oct 02, 2012 1:35 am

Interesting. Can someone elaborate on what this touch plate and auto-z function is? Where do I find this capability and how do I set it up??

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Re: Want to make an auto touch plate with DW660, but no grou

Post by Improbable Construct » Tue Oct 02, 2012 1:55 am

Levlandau2,

With some controller/software packages you can set it up so that the software slowly lowers the bit until it touches a piece of metal.
I use Mach3 with a eBay controller. Its a pain in the a$$ to set up but once its done its amazing.
Here is the youtube video that convinced me to set it up.
Shapeoko #Classified some of the bolts may be original parts.
Shapeoko 1 # ???? Stainless plates, still in the box.
Shapeoko 2 # 3926 not stock
Shapeoko 3 # 0003
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PsyKo
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Re: Want to make an auto touch plate with DW660, but no grou

Post by PsyKo » Mon Nov 19, 2012 3:16 pm

On this topic, IC are you using Grbl shield for the touch plate ? Or something else ?
I'd like to add the touch plate upgrade with GRBL shield. Anyone ever did that ?

Thanks
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Goko - Free CNC Control Software - http://www.shapeoko.com/forum/viewtopic ... 380#p44380

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Re: Want to make an auto touch plate with DW660, but no grou

Post by Improbable Construct » Mon Nov 19, 2012 6:19 pm

I am not using a grbl shield. I am using mach3 and a Chinese controller from eBay.
I don't know if a touch plate is possible with the grbl shield but you could get a simmilar setup using the continuity tester on a multimeter.
Clip the leads to the bit and to a piece of metal with a known thickness say 1mm then jog the Z down slowly until you get the beep from the multimeter. Then remove the plate, send the z down the 1mm and then zero it out.
Shapeoko #Classified some of the bolts may be original parts.
Shapeoko 1 # ???? Stainless plates, still in the box.
Shapeoko 2 # 3926 not stock
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edwardrford
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Re: Want to make an auto touch plate with DW660, but no grou

Post by edwardrford » Mon Nov 19, 2012 7:08 pm

I think the way it should work with a grblshield is to act like the z-axis home switch. However some hacking will need to be done.

General idea would be:
- Use a piece of conductive material with a known thickness for the touch plate.
- Connect a single wire to that piece of material and connect that wire to the pin that represents the z-axis home switch (pin 11?)
- Connect another single wire to the gnd on your grblshield. At the other end of the wire connect an alligator clip
- Before lowing the bit, connect the clip to your bit
- Now, when you touch the bit to the conductive material, it will complete the circuit, acting like a switch.


The problem (and the needed hack) is that unlike the x and y axis which travel in the negative direction to find home, the homing sequence sends the z-axis in the positive direction (up). So you'd probably need to reverse that in the source code in order for it to work properly. I'm not sure what that would entail. I wonder if alpha could chip in on this conversation, he just implemented homing on his rig and might be more familiar with it than me.

-Edward
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alpha
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Re: Want to make an auto touch plate with DW660, but no grou

Post by alpha » Mon Nov 19, 2012 9:11 pm

Hello

a new set of setup points in the V0.8 firmware allow to configure all this at run time so there is no need to compile.

For example my X homing switch is on the left side so I did set $18 to invert the X axis. The same is possible for the Y and Z axis as well. Here are all the parameters I use for homing right now:

Code: Select all

$17=1 (homing cycle, bool)
$18=32 (homing dir invert mask, int:00100000)
$19=25.000 (homing feed, mm/min)
$20=250.000 (homing seek, mm/min)
$21=100 (homing debounce, msec)
$22=3.500 (homing pull-off, mm)
Btw, the new command to start a homing cycle is $H or to use the machine without homing cycle $X to abort the alarm state.

The grbl team is very close to a official stable release of V0.8 branch, so I suggest you all get to familiarize yourself with the firmware update procedure. If you have question please open a new thread and I'm sure we all will figure it out together.

I will test the plate this afternoon and write a new post with my findings.

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Re: Want to make an auto touch plate with DW660, but no grou

Post by alpha » Mon Nov 19, 2012 10:19 pm

Looks like it is working, but it could be better... I changed from $18=32 (homing dir invert mask, int:00100000) to $18=160 (homing dir invert mask, int:10100000) (remember my X axis is also reversed)... now the Z goes down. I did attache a screwdriver with ground to the Z axis and a piece of aluminum foil to the Z homing pin. When I start the homing cycle it goes down first were ever it is and it stays down and tries to home X and Y and here I see some issues... that need to be worked out in grbl first. I think for now I would only recommend to use it if X and Y are already in the home position. I would first home the machine with Z+ and change to Z- and home again, this way it doesn't drag X and Y all over the machine.

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Re: Want to make an auto touch plate with DW660, but no grou

Post by cvoinescu » Mon Nov 19, 2012 11:10 pm

Alpha, I think the homing and the touchplate cycle should be different things. Maybe, in a future version, you could implement the G38 command(s)? G38.2 or G38.3 would be ideal for the touchplate cycle, and homing would remain unaffected.
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