Re-aligning jigs on T tracks

[Max Girouard]

I've got a shopbot desktop which has T tracks installed. I usually put a spoil board on the T tracks. When using hold down fixtures or jigs, I usually just program registration pin pockets in the jigs and the spoil board to align everything so I can put the jigs in a location and ensure that everything is zeroed to the jig. As I'm limited with Z height, I'd like to start screwing the jigs right into the T track to gain a little Z, but I'm not sure how I can put the jig in the exact same spot every time. Just wondering what methods people have been using to align fixtures or jigs directly on the t tracks. Thanks!

[jzarski1]

Hey Max, I have had to do a few things like that. What I have done in the past is make two registration holes for a .25 wood dowl pin. Put the first piece on the table with the t-track holing it down. Make your first tool path the one that cuts the two .25 dowl holes in the spiol board. You are basicly making a datum where the parts will butt up against and then you tighten your hold downs. Hope this makes sense.

John

[donek]

Put a 1/4in dowel pin in your spindle or router. Run the program that drilled your holes, but stop it while it is moving in the z to drill the hole. Use the keyboard control to move down in the z such that the dowel pin drops into your hole. Clamp the board in place and repeat on the other holes. You will have to run this a couple times until the dowel pin always goes into your holes, but you'll be able to relocate your board precisely every time. When I create a fixture with holes in it like this, I actually edit the original file that did the drilling to create a version that just picks off the holes. I call this file something like locate and place it in a folder called setup that is inside the folder containing all the other tool path files for that particular project. Consistent naming conventions just make it easier to remember or perform similar setup operations like this.

[adrianm]

My jigs (over 20 of them now) all have a recess in the bottom into which I glue guides that fit into the t-track (for squareness) and a copper cap in the corner which set's the XY registration. That way I don't have to worry about where the jig is as the routines work it out from the cap.

[steve_g]

"a copper cap in the corner which set's the XY registration"

Adrian... that's what I call an elegant solution! Your zeroing mechanism travels with each of your jigs.

Max... or anyone actually, if you don't understand what's happening here, say so... or follow these links.

http://www.k4mg.com/Hobbies/CNC/xyz.htm (http://www.k4mg.com/Hobbies/CNC/xyz.htm)
http://www.iedu.com/DeSoto/SuperZero/ReadMe.html (http://www.iedu.com/DeSoto/SuperZero/ReadMe.html)

http://www.talkshopbot.com/forum/showthread.php?t=16539&highlight=copper+cap (http://www.talkshopbot.com/forum/showthread.php?t=16539&highlight=copper+cap)

http://www.talkshopbot.com/forum/showthread.php?t=5495&page=4 (http://www.talkshopbot.com/forum/showthread.php?t=5495&page=4)

SG

[gerryv]

My jigs (over 20 of them now) all have a recess in the bottom into which I glue guides that fit into the t-track (for squareness) and a copper cap in the corner which set's the XY registration. That way I don't have to worry about where the jig is as the routines work it out from the cap.

VERY neat Adrian. If you ever decide to produce a video on this concept including how you setup the files and some good jig ideas, I'll be the first guy in line to pay you a fair price for the pkg. Jig design and application is a real art that, unfortunately, seems to be disappearing.

[dana_swift]

You can read my posts on using copper sweat fittings in my fixtures so the shopbot can re-zero to the exact same location (to 0.001) each time I put the jig on the machine. Much simpler to make (it takes a hole), and cheap to replace if the bit hits them.

http://www.talkshopbot.com/forum/showpost.php?p=139151&postcount=2

http://www.talkshopbot.com/forum/showpost.php?p=139913&postcount=6

http://www.talkshopbot.com/forum/showpost.php?p=115673&postcount=6

and others...

I also put sweat fitting holes in the spoilboard for the same purpose.

[Max Girouard]

Nice, that copper cap trick looks like it will be exactly what I was looking for. Thanks!