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  1. #1
    Join Date
    Dec 2003
    Posts
    673

    Work holding irregular parts.

    Hi all, I'm not a total newb, but am when it comes to simple solutions to milling all or almost all the sides of a part.

    I make mostly small, mostly aluminum parts that are irregular in shape. When I hold them "conventionally" - in a vise, my current part takes at least 3 setups with plenty of oportunity for the features to not line up right. I also am finishing all the sides of the part. I was showing my wife a cam verify of my current part and told her about the multiple setups and the strategies I was considering for work holding, and she asked why not just use round stock and the rotary table (or "thingy" as she called it) and cut it out of round stock with one setup, with just a small tab on both ends when I'm done? I see people doing lots of different solutions, but don't see people talk about this. I was thinking the rotary table (a axis) and a center on the other end to keep it reasonably ridgid. The parts are small, and the runs are smaller (~25) so the material savings and cycle times aren't significant. Any downsides to this approach? (I guess I could look for rectangular collets and do the same with that stock too)....

  2. #2
    Join Date
    May 2004
    Posts
    4519
    You are on the right track. Women can be smart too. I suggest some crystallized carbon for Valentine's Day.

  3. #3
    Join Date
    Dec 2010
    Posts
    1230
    Rotary axis can work wonderfully for machining 4 sides of a part. With a 4 jaw chuck you can start with square material too (independent 4 jaw takes a little longer to set up, but has the capacity for higher accuracy.

    The draw back (depending on the size of your part) is that typically you will only get one part loaded at a time. Depending on the size of your table another option is buying several vises and machining several parts per set up. I personally use multiple 4" vises for small parts like that. I picked up a couple cheap 4" vises, throw on soft jaws, mark which vise they were machined on so they go back on the same one every time. By machining the soft jaws you should be able to locate your irregular shape part very easily since it should be forced back into the same place on the vise every time.

    Just zero off the rear left corner of the fixed soft jaws when you machine them. I have odd shaped jaws I reuse over and over. I tighten the rear jaw. Insert the moving jaw loosely. Put the part in and clamp to align. Open and snug the loose jaw a little, repeat. Another (maybe better?) way its to machine one side of the jaws off while machining the initial shape, but remove the spacer you are holding them apart with so the jaws are completely closed. Machine one side. lightly debur. Now when you reinstall them you can align that edge with your finger within a couple thou pretty easily.

    if you use the same tooling on all sides of the part then one set of jaws per side is all you need. Machine side one, stop program, move part to second vise, load new part in one, restart program, etc. If you use different tooling you can make 3 or 4 jaws per side, load all 4 side one jaws, pick up each jaw as G54, G55, G56, G57 and sub program the operations to repeat once on each vise. That way each time you set up you are running 4 parts instead of one.

  4. #4
    Join Date
    Dec 2003
    Posts
    673
    Thanks for the tips.. I know there are lots of potential solutions, but I make a lot of "one off" or a "few off" parts, so hate investing tons of time in custom holders... Good tips for bigger runs, and I can see how multiple setups in a vise makes sense too. Looks like the rotary method is worth a try... I'll do it this week and see how it goes.

  5. #5
    Join Date
    Dec 2010
    Posts
    1230
    Gotcha. For one off work rotary is pretty nice!

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