Holding down your parts

[Jamf2]

How do you hold down your parts? Do you use a vacuum or build indiviuals jigs for each part? Has anyone made a tool changer for their router? Or used more than one router on their cnc?

[HuFlungDung]

I dunno, I just undo my belt, and they fall down and stay down, no problem. Now, where did I put my glasses?

[buscht]

Originally Posted by Jamf2 How do you hold down your parts? Do you use a vacuum or build indiviuals jigs for each part?

I do repetitive milling so I build jigs for families of parts.

Originally Posted by Jamf2 Has anyone made a tool changer for their router?

I haven't, but here is a useful link.
http://home.insightbb.com/~joevicar3/default.htm

Originally Posted by Jamf2 Or used more than one router on their cnc?

I use two routers on my CNC, one has a 1/4" bit for roughing and the other has a 1/8" ball nose bit for finish milling.

[CNCRob]

Originally Posted by buscht I do repetitive milling so I build jigs for families of parts. I haven't, but here is a useful link. http://home.insightbb.com/~joevicar3/default.htm I use two routers on my CNC, one has a 1/4" bit for roughing and the other has a 1/8" ball nose bit for finish milling.

Hey buscht, sounds like you have a pretty neat setup. Do you have a photo of it.

[JavaDog]

Originally Posted by buscht I haven't, but here is a useful link. http://home.insightbb.com/~joevicar3/default.htm

That is freaking awesome!!

[damae]

A cool trick I learned recently that does away with t-slots and clamps, vacuums and magnets:

double-sided tape.

It's very low-tech but it works fantastic! The parts come off with a little prying in the right direction. But during machining the tape is rock solid. A lot of machinists operating full size Vertical Machining Centers aparently like this trick too.

One caution - don't use the thick foamy tape. The stuff I have is about .008" thick, looks like normal clear tape, but sticky on both sides.

Another nice benefit is that you don't have to watch out for your clamps, in case the spindle crashes into them.

[JavaDog]

Originally Posted by damae double-sided tape

Short of having to scrub all your parts with Goo-Gone, how to you ger rid of the residue from the tape? Both on your parts and worksurface?

[carlnpa]

I have been using the double sided tape to hold plastic parts. The residue is usually minor but does need to be addressed. I wouldn't leave the parts stuck to the table overnight as the residue might not be minor anymore. The goo goes away with vinly gloves and toluene.
I experimented with a vacuum table but kept getting part movement. Vacuum is good for sheets but as the parts get smaller, like 4"x5", very high vacuum with high volume is required, like -10-14.7 psi. The goo goes away with vinyl gloves and toluene. If anybody has an effective alternate I'd like to hear it.

[spalm]

I have used double sticky tape for years in the wood shop for holding all kinds of things during both turning and sanding. Use the type designed to hold down carpets, not the clear stuff. It does not really leave much of a residue (the clear stuff will). Don’t leave it on overnight. Pry the parts apart with a putty knife.

One problem I found with the CNC is cutting through it into the sacrificial board. This is a bit messy for both the board and the bits. Tape the parts so the router will miss it (or clean up afterwords).

Ronson Lighter Fluid is the cheapest, easiest, cleanest way to remove sticky residue. Works on tape, stickers, Band-Aids, and chewing gum.

Steve

[Geof]

Originally Posted by carlnpa ...Vacuum is good for sheets but as the parts get smaller, like 4"x5", very high vacuum with high volume is required, like -10-14.7 psi....

It is actually quite simple: you strengthen your walls and windows and install an airlock for a door. Run the pressure inside your workshop up to 3 atmospheres absolute and vent your vacuum pump outside your workshop. This will give you a pressure differential across your vacuum table of about 40 psi quite easily. If you still need more holding power just run the pressure up and consult the US Navy dive tables to see how long you should spend decompressing in your airlock.

[JavaDog]

Originally Posted by Geof It is actually quite simple: you strengthen your walls and windows and install an airlock for a door. Run the pressure inside your workshop up to 3 atmospheres absolute and vent your vacuum pump outside your workshop. This will give you a pressure differential across your vacuum table of about 40 psi quite easily. If you still need more holding power just run the pressure up and consult the US Navy dive tables to see how long you should spend decompressing in your airlock.

Well, that is all well and good - but what about us people that live 150ft under the ocean already you insensitive sod!!



Thanks for the info re: the sticky tape, I'll file that one away...

[carlnpa]

Geof - You know your idea really isn't all that crazy, just scale it down. If you could pressurize one work piece surface you wouldn't need the vacuum, the pressure limit becomes part deformation/extruding. Unfortunately the forces on your container will be pretty high.