Author Topic: Speeds and Feeds  (Read 2510 times)

Offline Blue Chips

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Speeds and Feeds
« on: October 06, 2012, 09:15:45 PM »
Have found it difficult to get any reliable, spelled specific, SFM for plastics, any one have a place they look to?

Thanks
Ken



Offline Lew_Merrick_PE

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Re: Speeds and Feeds
« Reply #2 on: October 07, 2012, 12:24:37 PM »
Ken,

The issue with cutting speeds and plastics usually devolves to heat rather than speed per se.  (A) Really sharp cutting tools is your first line of defense.  (B) Sucking the chips (stringies) away from the part is your second line of defense.  (C) A blast of chilling air is your third line of defense.  If you are pulling the heat out sufficiently, it is unlikely your machine will have a spindle speed fast enough to actually fail the cut.

I ran a project under the USAF/NASA Factory of the Future program back in the mid-1980's where we were working with high-pressure air bearings that allowed spindle speeds into the 350,000 rpm range.  We were using liquid nitrogen as the coolant.  We machined convex radius acrylic lenses using 3 inch cutters and ended up with surface finishes finer than 4 micro-inch smoothness and no surface distortions that would affect optical transmission.  Mind you that these machines cost upwards of $15 million to build in 1985...

Offline Deko

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Re: Speeds and Feeds
« Reply #3 on: October 07, 2012, 01:39:50 PM »
If they will fit in your workshop,then get a couple of them machines ordered Ken. :poke:

Cheers Dek. :thumbup:

Offline Blue Chips

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Re: Speeds and Feeds
« Reply #4 on: October 07, 2012, 08:48:14 PM »
Lee, that is far more complete then I had, still a little too general but a good link. Thanks

Lew, your comments are on the money from my limited experience, have had good luck with both air and vacuum but prefer air.
Use Onsrud cutters and they are quick to help but would like not to have to make a call every time. thanks

Deko, may have to wait but at least one is in my plans for sure.........saving up, already have $400 ...won't be long at all now.