New Acme or similar--recommendations?

Looking to get recommendations/suggestions for a possible new machine and possible options (such as bar feed, etc).
Supplier has a smaller (up to 1.25" bar stock) older Acme,
and the idea is to be able to make the vast majority of parts on a new machine--but keep using the older one for the smaller sizes if it is cost-effective--and to be able to run large and small sizes simultaneously if needed.
Parts to be made are from round or hex stock, size ranging from 9/16" hex up to 2.25" hex (across the flats). Part length ranges from about 5/8" up to about 3".
Materials to be machined: aluminum (75%), low-carbon steel (20%), and stainless steel (5%).
I have already looked at the B&K web site for Acme, and have requested a quote with potential options.
They are not the only supplier of this type of equipment. So, I am looking to get info and recommendations (buy or avoid--and why) regarding other machines and manufacturers.
Meeting with the money-boys (not acct dept) in less than six weeks, so the reason for asking is pretty simple. I want to be able to tell them which are the most reasonable choices, and why.
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On Wed, 20 Aug 2008 00:24:26 -0500, F. George McDuffee

We are a startup and our initital stocking quantities are reasonable, 10k/size times seven sizes. Then there are the same parts (in lower quantitities) made from low-carbon steel and stainless steel to serve other markets. Expected total initial order to be near or over 100k pcs.

Expected repeat orders of 1k, 5k, or 10k for each size re-ordered--quantity depends on how fast the first batch sells. Lead times are 4-6 weeks, typically.

CNC.
Designs have changed/modified over time, and future changes will occur. However, they will be relatively small in terms of these parts and easily accommodated. The two largest sizes could be made on a single spindle, as those are usually made 50-100-200 at a time.

That is why I am looking at machines and options, and asking for opinions and recommendations.
In money terms (once we get going), we could afford to buy and use our own CNC (say $500k + $150k for tooling/etc) to make our parts (and do so cost-effectively) and be profitable. However, a machine really needs to run 24/7 to be productive, and that means doing a wide variety of jobs for multiple customers who have the same issue/problem (can't run their own machine 24/7 to justify the high cost of buying the new toy).
However, we really don't want to be running a machine shop even if it is worthwhile in terms of money. I used to run a small machine tools builder and was responsible for all inventory and production. I made the business profitable without cutting jobs under Reagan (1981-1985)--while competitors were closing.
Our management time is better spent running and promoting our business (and not trying to work out problems on a machine shop floor), so I prefer to leave the machining to those who want to do it because they like doing it. That is why they are in the business, and why I am willing to pay for their services.
The objective of this posting is to determine which are the best options for new/refurb equipment as the old/small Acme is not sufficient (in terms of bar capacity--1.25" max) to meet our needs (although it is cost-effective at what it can do) and then go from there. If another (larger) Acme is the best general recommendation, then that is fine.

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It depends on the spline. If it is an involute spline with any kind of tolerance then rotary broaching is out of the question.
On a CNC Lathe or Swiss you might be able to hob it right in the machine.
Another option is to use this "shaving" cutter from Schwanog. You take five passes on the first tooth, then one pass on each subsequent tooth. This system works very well.
<http://www.schwanog.com/produkte/produkt.php?idu &PHPSESSID479a18dd077b76156c52504b336ba7>
or <http://tinyurl.com/5dyv4o
If your parts are high volume you would be better off to design the spline in such a way that it can be rolled as a secondary operation. Rolling is by far the least expensive way to manufacture a spline.
--

Dan

CNC Videos - <http://tinyurl.com/yzdt6d
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On 23 Aug 2008 17:02:35 GMT, D Murphy

We are talking about 60 splines in a 360 degree circle, each 6-degree spline identical (center-to-center or valley-to-valley). The front of the spline is open (no material blocks access). The problem is the spline is .030" in front of a feature that is a "wall" that can't be moved.
The Schwanog looks good (as long as it does not require more than say .025" clearance behind the cut area), but is it a time hog? Adding seconds to the total cycle time is no big deal, but adding a minute (or more) would be a killer. Initially, the idea was to broach in the CNC. Then it was changed to rotary broach (while still in the CNC).
I think getting a complete part out of an initial--but more complex--setup on one machine will be cheaper (overall) than doing a finishing secondary operation on a second machine. I am thinking runs of 5k to 10k at at time, for now.
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Can the 0.030" be relief? IOW, if it is the same diameter as the spline then it becomes difficult to rotary broach as the broach will leave long burrs, connected chips actually, on the surface of the part. One of the big problems with multi spindles is that you can't recall a tool. So there may be no way to come back and re-cut that diameter to remove the attached chip.
The other issue might be that there simply aren't enough tool stations on the multi to accoodate the broach. The other weakness of a multi is there are a limited number of tool stations and they are best suited to simpler parts that have fewer features.
Providing an undercut between the spline and the shoulder (wall) is that it might make it possible to roll the spling from one of the cross slides on the multi spindle. Again not being able to see the whole part makes it difficult to know whether or not all the positions are being used for other ops.

Same issue as the rotary broach as far as relief. The Schwanog will be a lot slower than rolling, slightly slower than rotary broaching, and a whole lot faster than hobbing.

Complete is almost always better. You'll never be able to run 5,000 piece lot sizes as efficiently on a multi as on a single spindle. Particularly with a complex set-up. Just as a single spindle will never run a million piece lot size as efficiently as a multi.
And a 3" capacity multi will choke on small parts.
Perhaps it would be best to vend out the lower quantities until the volume ramps up? Or maybe consider an operating lease on single spindle equipment until the volume gets to the point where a multi spindle makes sense. With an operating lease you simply return the machine at the end of the term.
In any case partiing off large diameter parts from bar is a problem. On the multi you might want to consider a Watkins saw attachment.
<http://www.championscrew.com/watkins.htm
Another possibility would be to use automated six or 8 spindle chuckers and feed them pre-cut blanks.
Shimada Machinery makes great quick change over CNC multi spindle chuckers.
<http://www.smd.co.jp/en/multi-spindle.htm
<http://www.smd.co.jp/en/products/cn660.htm
You could use an old clapped out multi to cut the blanks to feed the CNC chucker. This could be advantageous since you are cutting aluminum. Your RPM won't be hampered by bar whip.
Some more food for thought...
--

Dan

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On 24 Aug 2008 00:29:02 GMT, D Murphy

The .030" is a gap that can drop slightly (.004") below the spline, so it is a "clear space" behind it. The diameter of the base of the spline (the bottom of the "valley" between splines) is .004" greater than the bottom of the gap.

They want payment for a rotary broach tool for the multi as part of the initial tooling cost, so there are sufficient tool stations (IMO).

There is a .030" gap.

Slightly slower is fine. Adding say five seconds to the total operation won't kill me.

That is why the 1.25" helps. It can do the smaller parts.

Will take a look. Thanks.
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