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Need advice on jig and coordinates
« on: April 20, 2012, 04:55:33 PM »
I want to make a jig for repetitive drilling.  I am not sure, however, on how to set up mach 3 so that no matter where I place the jig on the router  table, I can bring the drill accurately( to the thousand)to where I need the pieces drilled.

So far I've pocketed the shapes in the jig for my pieces. I've also created the code for the drilling. I then intend to split the code so that only the drilling is done, and I use the same jig. It's in wood, so it's not a big deal to pocket and drill in order not to lose the coordinates.

The problem is when I remove the jig and then at a later time try to place it on the table for drilling the same pieces again. If the location of the jig is slightly off, my pieces wont be drilled accurately.
This is where I am not sure as to how to proceed.  Hopefully, the more experienced will illuminate my way.

I am using Mastercam.

tc

Offline Hood

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Re: Need advice on jig and coordinates
« Reply #1 on: April 21, 2012, 04:41:40 AM »
You  need to touch off a known point on the jig to set the X Y Z coords of the jig.

Hood
Re: Need advice on jig and coordinates
« Reply #2 on: April 21, 2012, 05:16:48 AM »
that's what I was thinking. What's the most fool proof way, though?  I was thinking of using two intersecting laser beams attached to the Z axis.
Their intersection would tell me the xy point of the jig. I would also check the intersection accuracy on Mach 3 DRO( in machine mode). This procedure would ensure that, in future set ups,  the jig be located in the same spot. Am I on the right track? Thanks , Hood.
tc

Offline Hood

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Re: Need advice on jig and coordinates
« Reply #3 on: April 21, 2012, 05:35:16 AM »
You are likely getting a bit too fancy :)
If for example the corner of your jig was a known point in relation to your code for using the jig then just move close to the jig with a cutter of known Dia and use a feeler gauge of say 1mm (or whatever imperial if thats what you use) Keep moving the cutter closer to the part and keep trying to slip the gauge in, when it will not go in then change to step mode and back off until the gauge will go in, set that axis DRO 1/2 dia of cutter plus feeler gauge thickness but as a negative number. For example 10mm dia cutter and 1mm feller then you would set the DRO -6. Do the same for the other axis and you are set.
Reason you want to not move towards the part with the gauge in place is if its a carbide cutter you could easily chip the edge if you go too far, so only back away until the gauge will go in rather than tring to move onto the gauge.
This has taken a lot longer to type than it actually does in practice :D

There are also edge finders you can get but the feeler method is often just as good if not better, having said that I have an edge finder I made up myself which I use and its very accurate, within 0.005mm.

If you had accurate home switches then you could dowel the jig to the table, do the touch off then set that as a work offset such as G56 then any time you place the jig on the table  the dowels will locate it accurately and you will know what the offset is so no need to touch off again.
Hood
Re: Need advice on jig and coordinates
« Reply #4 on: April 21, 2012, 05:45:00 AM »
You're right, Hood. I like the idea of the feeler guage. Thanks a lot. tc
Re: Need advice on jig and coordinates
« Reply #5 on: April 21, 2012, 12:09:52 PM »
If your part is moveable, drill bushings, and a drill press is all that's needed.

Offline BR549

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Re: Need advice on jig and coordinates
« Reply #6 on: April 21, 2012, 03:58:30 PM »
If your table has slots then KEY the fixture to the table. that way it mounts SQUARE to the table each time. Then Machine a square 90 deg slot in the fixture itself to be able to index it to the User Coordintates.

Then Machine a part in it and MOVE over to teh 90deg slot and touch off on the X and Y axis and record THOSE number. I put them into the Gcode file as comments so they don't get lost or forgotten.

A use a simple HOLE in the fixture and use a PROBE to find the center. But I already have the probe(;-)

Comes time to set it up fasten the fixture in the slot and then touch off on the X axis and input the position value. Now do the same for Y and you have referenced the fixture BACK to the USER coords for the part program.  The X0.000Y0.000 for the part program will now be correct for the program.

Just another way to do it, (;-) TP
« Last Edit: April 21, 2012, 04:00:39 PM by BR549 »