Cheapest way to make a part? 2

[cpat]

I have a part which is a 3/8 X 3/4 X 9" aluminum bar which has 8 irregularly spaced inline 7/16 tapped holes. I'm attempting to determine the cheapest way to manufacture lots of 1000 or more. I was thinking of multiple spindle drills vs gang drilling vs NC drill. I need to determine how many could be done per hour.

 

[MikeHalloran]

Probably an NC mill, which allows you to mill the threads, _much_ faster than tapping. Maybe a second a hole, with the spindle going as fast as it can.

That way, the limit on throughput is the time it takes to unload and reload the fixture. You should be able to do 20..50 parts in a cycle with a simple fixture on a modest mill. The lower number is if you have to mill both ends of the bar.

If you do, it may be quicker (than sawing and handling short bars) to load long stock into the fixture and mill across to separate the parts.



Mike Halloran
Pembroke Pines, FL, USA

 

[tripleZ]

In my mind, it depends on what your annual volume is, and how long the project is expected to last for. If the annual volume is extremely high (with small lot sizes) and is going to last for a year or two, I'd probably look at a custom machine with several stations, all based on a rotary nest design. Maybe 4 stations, 2 for drilling and 2 for tapping? As your tapping procedure will likely be your slowest procedure, your hourly throughput will be based on tapping machine throughput. And, once you have the machine dialed in, you really should only have to start it up and quickly run your 1000 parts. We have a similar machine in house that does drilling, tapping, and a broach deburr. I think that one ran us around $40K. It doesn't have the bells and whistles, but it's accurate and fuctional.

If it's not that high, the NC machine will likely be your best friend, especially if you already have one in house.

 

[MadMango]

What grade aluminum? What spec on the threads? What's the annual volume? What's the application? What loads? What are the environmental considerations? Questions, questions, questions.

Why limit yourself to machining? Cheapest for high volume would probably be some sort of casting or possible metal injection, with cast threads or threaded inserts.

[green]"Art without engineering is dreaming; Engineering without art is calculating."[/green]
Steven K. Roberts, Technomad
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[MedicineEng]

Did you considered outsource that part?
It might be someone out there making similar parts with all the investment in machining already done.

 

[cpat]

Thanks to all who responded.

As to the outsourcing, I would have to find someone producing a similar part, unless it was an NC job hich could be modified easily. My experience with outsourcing a few years was that it was cost prohibitive. To avoid the investment in equipment, I've found leasing the machine to be a preferred option, although I would still have the labor and consumables to deal with.

There is nothing complicated about the part, standard threads, 6061 material. If I knew the total annual volume, I would not have a need to pose the question.

Which is why I'm leaning toward the NC option to begin with, then if the volume ramps up, I like the dedicated machine.

 

[MedicineEng]

Outsourcing costs have coming down in recent years.
There are many hidden costs in making the part yourself: Logistics (handling raw material suppliers), maintenance and set up, breakdown costs, etc.
These are very difficult to put in the balance that is why they are easily forgotten until the day that they start bitting your profit.
I am just saying htat you should notrule out htis possibileity just because some years ago the cost was prohibitive.