PDA

View Full Version : Touching on



Gasgasbones
03-03-2015, 01:26 PM
Hi all

When I set up datums on my machine I have to touch on a known hight with the tool.
Its a little difficult to get my head in the machine and have a good look as I touch on with the tool. I have a boxfod and its in a case so space is tight to look around, i try using a jewellers loupe to look but Invariably I usually muck it up a bit an either set it to high or too low. Only by a smidgen mind but its enough to wind me up as im usually doing quit shallow engraving.

Id like to tighten up my machining and get as good as I can with setting up etc.

I see some tools that light up when touching on or make a sound but I want to bypass the electronics in my machine completely and use some kind of stand alone device.

So, whats out there fellas ?

I cant see how I can make a simple circuit either as the whole machine is metal ?!!

Cheers guys

Carl

njhussey
03-03-2015, 01:58 PM
Hi Carl, most people use a bit of PCB and a crocodile clip and wire it back to the controller (Mach3) as the PCB bottom is insulated when the tool touches the copper top it completes the circuit. As you know the thickness of the PCB you can set your zero.

Clive S
03-03-2015, 01:59 PM
To make a touch off tool system you just need a small bit of pcb with a wire soldered to it and you then can make a simple circuit with a battery and led with a resistor in series with it. Then the -ve wire will connect to the machine frame and the led wire to the pcb. You need to know the exact thickness of the pcb, Just put the pcb on the top of the job and bring the z down very slowly until the led lights up.

Then Zero Z then add the thickness of the pcb to the zero and re zero. If all that make sense. >Clive

(Neil beat me to it)

njhussey
03-03-2015, 02:15 PM
To make a touch off tool system you just need a small bit of pcb with a wire soldered to it and you then can make a simple circuit with a battery and led with a resistor in series with it. Then the -ve wire will connect to the machine frame and the led wire to the pcb. You need to know the exact thickness of the pcb, Just put the pcb on the top of the job and bring the z down very slowly until the led lights up.

Then Zero Z then add the thickness of the pcb to the zero and re zero. If all that make sense. >Clive

(Neil beat me to it)
But yours was more detailed....

Gasgasbones
03-03-2015, 02:17 PM
Of course !! I just need to isolate it dont I.
Im as thick as mince sometimes !

Im on it. haha :peaceful:

jimbo_cnc
03-03-2015, 03:14 PM
I haven't got round to buying a touch tool yet, but was planning to. Now I see this post.

At the moment I bring the spinning tool down manually, one stepper notch at a time, until it cuts. I think the method you guys described is also manually bring the tool down (just not spinning). So for my case where I can see the workpiece I don't see any advantage. Is that correct?

The touch tools you buy are sprung I think, so you drive the tool down into them? To make one I think you just need a contact on a sprung base and then either some addon software? or maybe it's already in Mach3?

cropwell
03-03-2015, 04:03 PM
For those Mach3 users who want a more automated solution; I found a macro somewhere (so I am not taking any credit for writing it).

1, you need a plate with an insulated base (if you bed is conductive and earthed). A piece of pcb is fine, but I use a piece of brass with an acrylic sheet bonded to it.
2. Measure the thickness and put the value in the 'Gage plate height' box on the Offsets screen.
3. make sure that 'Digitize' blinks on the Diagnostics screen when you touch the plate to earth. (test it against the tool to check that the spindle gives you an earth return if you don't get an earth then you will need a clip lead to earth the tool when you run the Macro)
4. On the Program Run screen select the operator tab and choose 'Edit Button Script' The programmable buttons should flash.
5. Select 'Auto Tool Zero' and copy the Macro below into the box, replacing all existing text.
6. File and Save.
7. Jog Z axis upwards to a high point and click on Auto tool zero. When the axis moves touch the plate. If the axis pulls up 10mm (on the existing settings), then it is working. If not hit the Mach3 Estop and check what was done :hororr:

To use the macro bring the tool to within a few mm of the touch plate on the top face of your work and click 'Auto Tool Zero'.

Hope you find this useful,

Cheers,

Rob


'Tool Zero Setting Macro


' Change the following three lines to suit your machine
PlateThickness = GetOEMDRO(1001) ' Thickness of touch plate
RetractClearance = 10 ' Clearance above touch plate to retract to
ProbeFeed = 20 ' Feedrate to use for probing


' Define some constants
ZDRO = 2 ' Z Axis DRO
AbsoluteModeLED = 48 ' Absolute Coordinate Mode LED
IncrementalModeLED = 49 ' Incremental Coordinate Mode LED
FeedrateDRO = 818 ' OEM code for feedrate DRO
ProbeLED = 825 ' OEM code for probe input LED
ZTouchDRO = 2002 ' OEM code for DRO that holds Z touch position


' Do nothing if probe is already grounded
If GetOemLed(ProbeLED) = 0 Then


' Wait a few seconds for user to get touchplate in place
Code "G4 P2"


' Save current feedrate
CurrentFeed = GetOemDRO(FeedrateDRO)


' Save current coordinate mode
AbsMode = GetOemLED(AbsoluteModeLED)


' Set absolute coordinate mode
Code "G90"


' Zero Z DRO
Call SetDro (ZDRO, 0.0000)


' Pause for DRO to update
Code "G4 P0.5"


' Do the touch move
Code "G31 Z-20 F" & ProbeFeed


' Wait for it to complete
While IsMoving()
Wend


' Delay a bit for
Code "G4 P0.25"


' Get the Z position where probe input triggered
ZProbePos = GetVar(ZTouchDRO)


' Go back to touch position (G31 backs off after touch)
Code "G0 Z" & ZProbePos


' Wait for it to complete
While IsMoving ()
Wend


' Set Z DRO to touch plate thickness
Call SetDro (ZDRO, PlateThickness)


' Pause for DRO to update
'Code "G4 P0.5"


' Retract Z to SafeZ, if enabled, else to RetractClearance above plate
If(IsSafeZ() = 1) Then
SafeZ = GetSafeZ
If SafeZ > PlateThickness Then
GotoSafeZ()
End If
Else
RetractHeight = PlateThickness + RetractClearance
Code "G0 Z" & RetractHeight
End If


' Tell user we're done
Code "(Z axis is now zeroed)"


' Reset feedrate to original value
Code "F" & CurrentFeed


' Reset coordinate mode to original value
If AbsMode = 0 Then
Code "G91"
End If
Else
Code "(Z-Plate is grounded, check connection and try again)"
End If


Exit Sub

jimbo_cnc
03-03-2015, 04:40 PM
I'm not goingto try to understand that code, it's easier just to ask you: Does that just bring the tool down slowly until it touches?

If so I could add a layer of slightly flexible material to the back of the plate (I'm just not comfortable with driving the tool into a solid surface).

cropwell
03-03-2015, 05:13 PM
Yes it does ! I use it without a cushion with 1mm cutters and it is fine (well it will be when I get my machine up and running again :encouragement:) You don't need to understand the code, but I went through the exercise of finding out what it did, just for the hell of it.