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  1. #1
    Join Date
    Oct 2004
    Posts
    40

    Automating the Broaching process

    I've landed a small reacurring job of cutting out various sizes and thickness of sprockets\gears out of UHMW.
    I'll be cutting the profile and shaft profile of the gears with a router.

    I've done some broaching before, but not this many.
    I'm open for any ideas how to automate the broaching process.

    Any ideas of a simple fixture?
    Using a fixture and jig with a electric motor and allthread to push the broach through?
    Hydraulic press or jack?
    Broach the keyway before I cut the shaft hole?

    Any Ideas will be greatly appreciated on this.
    I'll be doing 70 - 100 of these a month.

    Thanks in advance
    Don

  2. #2
    Join Date
    Oct 2004
    Posts
    40
    I guess nobody has any ideas

  3. #3
    Join Date
    Jul 2003
    Posts
    586
    Is this a type of plastic?When you say "automate" Do you mean placing the part broaching and removing then starting over or simply broaching the part withough using human power?Also will this material handle the forces envolved or will it crack?

  4. #4
    Join Date
    Jul 2003
    Posts
    1220
    I cut keyways with my Drill/Mill by fixing the spindle and broaching with single toothed cutter by racking up and down.
    This is manual but cutting UHMW should be like cutting cheese.

  5. #5
    Join Date
    May 2006
    Posts
    35
    I think your best bet is with a manual press. you will need a stroke length of about 300mm. you have to bore hole first to put the guide for broach in.In uhmw it should take you only about 2 mins, a keyway so I do not see the need to automate the process

  6. #6
    Join Date
    Jul 2003
    Posts
    1220
    Is it possible to push the guide and the broach together.
    Stack a number together. Start pressing, then lift off the top the ones broached and add more to the bottom.

  7. #7
    Join Date
    Oct 2004
    Posts
    40
    the4thseal,
    the material will handle the forces, as they will be between 2" and 4" thick. When I mean automate, I mean to take the time out of this, to make fool proof as I may want to have the 18 year neighbor kid do the broaching for me and not get hurt.

    Kiwi,
    I like your idea of putting a single tooth cutter and running the quill or in my case the spindle up and down, But I'll need to figure out how to lock the spindle. And yes I suppose its possible to push the guide and broach.... maybe I'll make a long guide... Thanks for your thoughts guys... guess i'll get started on something here this weekend.

  8. #8
    Join Date
    Jul 2003
    Posts
    1220
    Donald
    I wasn't imagining they were 2-4" thick..perhaps my suggestions weren't so good.
    To hold the spindle I just have a bolt through the belt cover and screw the head against the belt and pulley. This is one of the popular cheap Drill/Mills. Doesn't take a lot to hold.

  9. #9
    Join Date
    Oct 2004
    Posts
    40
    I'm cutting these sprockets\gears out with a table router. And I don't have a milling machine that I can push the broach through with the knee or head.
    I could just use a hydraulic jack to push the broach through, But since this is going to be a regular thing, I might as well make some sort of jig with a press.
    I'm finding out that there will be at leat 4 different diameters, and 2 different size shaft holes. So I think I'm going to attempt to make a stand alone fixture\jig\machine for this deal.

  10. #10
    Join Date
    Sep 2006
    Posts
    6463
    Hi Don, You can buy a small hand press on EBAY for about A$50 and This will handle up to 1 ton (2000 lb) of force. Looks like a small drill press without the table. Had one for years and it works well. It' called an Arbour press in the trade.
    Ian.

  11. #11
    Join Date
    Dec 2004
    Posts
    524
    Enco has arbor presses that are quiet inexpensive. Get one that is small enough to ship UPS and buy it with one of their free shipping offers.

    Ken
    Kenneth Lerman
    55 Main Street
    Newtown, CT 06470

  12. #12
    Join Date
    Oct 2005
    Posts
    251
    I have broached many keyways in the past. I like the single pass keyway braches made by Hassey Savage. Ream bore push broach through and all chamfers and key forms done in one pass. You do have to hold the bore size very close. +.001 - 0. We used a manual arbor press. With plastic you will get 1000's of parts on one grind and it won't take a much power to push it. Broach can be resharpened several times. They have standards and make specials. Best and most economical way for the quantity.

    To automate you can build a table with an air cylinder. Two inch bore should be good. Use flow controls to set speed.

  13. #13
    Join Date
    Apr 2003
    Posts
    170
    .

  14. #14
    Join Date
    Sep 2006
    Posts
    6463
    Hi Donald, if you're going to automate a job to do 100 a month, it will cost you more for the set-up than the jobs worth. BTDT.
    The big problem is insurance. If someone can get a finger stuck in a hole while the machinery is working then it is the next door neighbour's kid who's got his mind on whatever is happening in the neighbourhood, or your lack of proper guarding.
    Where I last worked we employed operators both male and female, and the simplest job required the most sophisticated guarding to ensure that NO-ONE could overcome a safety feature and get hurt.
    When you talk about automating a job, start thinking DANGER!
    Once the process is underway then it only takes a lack of concentration to end up with bits missing from the anatomy.
    Anyone who doesn't think this will happen, is an accident waiting for a place to happen. If you don't believe me check with your insurance company and see what they say. You don't have insurance? GOODBYE.
    Ian.

  15. #15
    Join Date
    Oct 2004
    Posts
    40
    handlewanker, lerman. I've seen and used the arbor presses and yes they work pretty good and easy. And will probably have to start with something like this. Thanks...

    handlewanker I understand and know what you mean by making it idiot proof if someone else is doing the work for you. and I think its possible, I just need to think it through first. Thanks...

    ctate, I've checked into purchasing broaches. They've got the kind where you need to use the shims between the broach and broach bushing. And then there are those that are a 1 pass broach. The one pass broach is twice the cash, I'm wondering if this would be the better deal of the two. Since one don't have to keep putting the shims in all day long??

    I do appreciate everyones input. :cheers:

  16. #16
    Join Date
    Oct 2005
    Posts
    251

    Heck yeah!!!!

    Worth every dime. Done in one pass and no shims to lose. I would not consider the shim and bushing style for your job. Don't forget operator can broach 100 parts with wrong shim or bushing. With single pass there is only broached an non-broached. Easy visual inspection.

  17. #17
    Join Date
    Jul 2005
    Posts
    12177
    The single pass broach is going to cost a bit; if possible try and get a trial run. UHMW cuts very nicely but it is not a rigid plastic; it is almost impossible to ream because even with the sharpest reamer the plastic distorts and sort of flows around the cutting edge. If the behaviour was the same with the broach you might find the finished keyway is too small for a standard key; an oversize broach may be needed to compensate for the flow effect. It is probably superfluous to say if you do get a broach it never, never gets used on any metal if you want it to still be useful on the UHMW.

  18. #18
    Join Date
    Mar 2005
    Posts
    1136
    Ian gave good advice. problem with automating, is what are you automating? The act of pulling down on the handle on an arbor press takes seconds, so even if its 10 seconds, at 100 month that's 1000 seconds or just under 17 minutes. but you haven't saved that because it still takes 17 minutes to run the broach through (whether it's automated or not), now your operator is standing there instead of pulling the handle on an arbor press. or are you thinking of making some sort of auto loader for 100 a month??

    as broaches are delicate, there might be savings in making a pull broaching device rather than pushing with a press, the way the bigger ones are done. less chance of busting a broach - then again being its in plastic i doubt that's an issue.

    the other thing would be getting a slotting head for a bridgeport or an old shaper (great excuse to get a wonderful tool and they go cheaply). that way you're reducing tooling costs as well. this would be more a consideration if you were broaching steel or CI, but with plastic you're best to use conventional bushed broaches in an arbor press, imo.

  19. #19
    Join Date
    Sep 2006
    Posts
    6463
    Hi Donald, whatever type of broach you choose, just make sure the broach starts off vertically SQUARE to the job, otherwise as the ram pushes the broach down it will try to bend, and as it's probably HSS will break.
    Whenever I had to use one of these I always lifted the ram as it was halfway down to make sure the broach wasn't being pushed off centre. I learned the hard way by breaking one when in a hurry.
    I suppose you could always mount the job in the lathe and hand crank the carriage to push the broach, with the job held in the three jaw chuck or in a jig on the faceplate.
    Nowadays I cut keyways in the lathe, by using a single point tool in a boring bar with the tool cutting sideways and the chuck held from turning by putting a small jack under it. It takes a bit more skill as you have to feed the tool towards you with the crosslide till you hit depth. Once you've done one, set the crosslide dial to zero the others are done to the same setting.
    Cutting plastic should be a piece of cake.
    I just remembered I recently cut the 6 splined bore in two "special plastic" gears, for the screw cutting train of my lathe , using the boring bar and single point tool method,
    Ian.

  20. #20
    Join Date
    Oct 2004
    Posts
    40
    McGyver, I totally agree and understand what your saying about saving time. I thought that it'd be nice to take some of the small worries out by having a jig fixture and fixed broach ( pull or push ) and not have to worry about all the shims and needing extra hands and such.

    Ian, I like your idea about using the crosslide on the lathe. I'll have to see if I can attempt this.
    I do appreciate everyones input. Thanks..

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