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[machinist] Would a HBM work for making this part?
- From: Lawrence London <lfljvenaura@gmail.com>
- To: machinist@lists.ibiblio.org
- Subject: [machinist] Would a HBM work for making this part?
- Date: Mon, 10 Feb 2014 14:19:58 -0500
http://www.practicalmachinist.com/vb/general/would-hbm-work-making-part-279889/
Thread: Would a HBM work for making this part?
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02-09-2014, 10:50 PM #1
- Join Date
- Jul 2004
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- Asheville NC USA
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- 8,096
Would a HBM work for making this part?
I've made a few prototype pieces of the pictured part for a customer. Did them in a cnc mill using a fairly coarse stepover distance on the final pass with an inserted ballnose cutter, and then smoothed out the ridges with a flap disc on a handheld grinder. Meets the customer's requirements, but takes way too much time. The part is a couple feet long, about 6" wide, and the radius is about 8". Material is mild steel.
So, I've got a 4" table type HBM with outboard support and a good selection of bars up to 4" dia. Also have a 12" dia boring head (for lack of a better name) made to fit on and key to the 4" bar.
Total DOC is a bit less than .600" so I'm thinking I can modify the head to hold 4 turning tools spaced at 90*, set the tools such that each will take about .150 DOC with axial spacing greater than the feedrate such that the tools engage the blank in the proper order and make this part in a single pass with a whole lot less time than the previous method. Thinking I can set the spindle rpm to produce about 300 sfm cutting speed and use a roughing grade of carbide to handle the interrupted cut.
Any thoughts? Tried this and it didn't work? Threw my part through the wall? Etc Etc.... -
02-10-2014, 08:00 AM #2
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- Jan 2013
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- Plainfield, Indiana, USA
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- 406
Sounds to me that it just might work. Your SFM is pretty optimistic but it should run automatically so just set stops on travel and use a timer to let you know when to check on it. Let us know how it works! (Always better to let others experiment and glean the answers)
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Figured out and partially tooled a similar set-up around a third that size to run on a lathe when friend John needed to cut a rack style "nut" section from phospor bronze bar. Used a fixture plate and "shim" on the lathe saddle to mount it and took two two passes, first direct on the plate second shimmed up. Three cutters on the bar. 50 thou ish cut per cutter sounds about right, too long back to remember tho'. John reported that the roughing out and shimming for second cut went fine but when we took the job off the fixture plate after third operation, cutting the acme thread, it bent and twisted every which way due to locked in stresses.
Clive -
How many? To me, if there are enough parts, its a job for a big conventional horizontal mill with a profile ground slab mill. It would also work well on a planer with either a rotary head or a tracer.
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I've done it many times on a lathe, a HBM with and outboard support and 4'' Bars will eat that job for breakfast.
TIP - On a multi cutter head, ensure that one cutter is out of cut before the next enters.
I remembered
- If you've enough room on the bar - set two heads just over the
workpiece length apart, rough with the first multi cutter head and
finish with a single on the second, - one pass and a finish like a
baby's bum, = jobs a goodun.
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Could be "roughed" close with big (actually not big, just the right size) tilted face mill if that seemed an advantage.
See that section in Treatise on Milling and Milling Machines by Cincinnati (NOT the 1916/1919 version though
)
Tyrone Shoelaces likes this. -
02-10-2014, 09:43 AM #7
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My thought is if the part is only 6" wide, why not fixture multiple pieces on your CNC and run unattended every night? Or if you have an indexer you could do a 4 sided fixture, and then you could tip the part to use more of the side of the ball instead of the tip. You could probably cut you CNC time down quite a bit doing that and with better finish ball tooling.
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02-10-2014, 12:24 PM #8
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- england
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John Noder's idea is a good 'un. We used to do stuff like this all the time with an " Elgamill " using the double swivel milling head. It's beyond me to work out the angles though. Regards Tyrone.
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02-10-2014, 02:10 PM #10
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- Apr 2006
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- england
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- 2,753
You could bore a square block and cut four out of the block at a time. Beat that Johnny. Regards Tyrone.
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- [machinist] Would a HBM work for making this part?, Lawrence London, 02/10/2014
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