Machining and cost of nylon, UHMW-PE, etc.? - Router Forums
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post #1 of 21 (permalink) Old 06-11-2012, 06:26 PM Thread Starter
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Question Machining and cost of nylon, UHMW-PE, etc.?

I want to use my woodworking power tools and make flat curved parts up to approx. 10 inches in size/diameter and 7/8 thick from very strong plastics. These should never break, are held/handled as standalone items by people and have a rather smooth but NOT supersmooth/supershiny appearance to make handling comfortable but not slippery. I need something low cost and stronger than Finnish multiply. I am thinking of nylon (very strong but seems really too expensive) or UHMW-Polyethylene or any low cost plastic I can machine myself, or as a last resort request a contractor to do it with CNC machining. All the parts will have 1/4, 5/16, 3/8, 7/16 or 1/2in rounded edges (roundover). Any recommendations? Thanks.
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post #2 of 21 (permalink) Old 06-11-2012, 06:55 PM
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I have used very cheap cutting boards from homeware stores as material on my boat. Cheaper than ply and no maintenance.

It saws, drills and files like wood. I have not routed but I power planed the stuff.

Not 7/8" thick though.

Tks
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post #3 of 21 (permalink) Old 06-11-2012, 07:03 PM
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I've machined UHMW on a milling machine and it cuts like butter. If you use a router I would slow it down as much as possible. I don't know how it will react at those speeds.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #4 of 21 (permalink) Old 06-11-2012, 07:10 PM
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Nylon, Delrin, PVC, PE and AC, all easily machineable at normal woodworking speeds.
Not a problem in RouterDom, but not cheap either.
For example, the square foot price of 12mm Acrylic runs between 5.50$ and $8.
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post #5 of 21 (permalink) Old 06-11-2012, 09:35 PM Thread Starter
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Thanks for the responses. I got a small sample of .75 nylon and 1.0 UHMW today and it machines amazingly well, I would say better than hardwood. It's a little bit dangerous in smaller holes/cutouts as the router bit sometimes nearly grabbed into the plastic. Maybe the router bit is getting dull.

They told me that CNC machining of these plastics is done at very high speeds to avoid local melting, at much higher speeds than woodworking tools. I did not know if that was true but I took it very easy anyway just to be sure and had the router bit remove only a little layer at each pass and never stayed at one spot or redid the same area within seconds. The sides and edges all came out fine.

However there is a problem: the roundover edge to flat transition is never smooth. The lines are all noticeable and can be easily felt and there is no way to sand them smooth I think. I hope I don't need a chemical to polish these transition lines smooth (or other areas of the part when needed). Any solution or recommendation?
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post #6 of 21 (permalink) Old 06-11-2012, 10:36 PM
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"Any solution or recommendation?"
******************
Don't use a bearing on the work or templet.
& if you must, isolate the work such that nothing can move.
Moreover, neither the templet nor the work can express any millmarks or chops.
Workpiece control & fixture rigidity cannot be compromised, lest the chatter you're experiencing. Requires lots of homework to overcome, has taken me years.
**********************
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post #7 of 21 (permalink) Old 06-12-2012, 08:01 AM
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How about Corian cutouts for a counter fabricator?
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post #8 of 21 (permalink) Old 06-12-2012, 12:33 PM Thread Starter
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What are Corian cutouts?
"Don't use a bearing on the work or templet"??
Can you explain: no bearing, no template? I am using both, on a benchtop table router.
I think your point is that chatter, vibration, slight motion, etc., will lead to inaccuracies and unsmooth transitions. However I am thinking that with woodworking tools I can never get a perfect part, e.g. due to small surface problems, roundover edge problems, small template damages, etc., etc. . So I am trying to find out if there are good ways to IMPROVE a plastic part after machining (as you can do so perfectly with wood by sanding).
To hand machine a part perfectly
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post #9 of 21 (permalink) Old 06-12-2012, 07:30 PM
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Trade the bearing for a collar guide-bush system.
It does not turn and does not vibrate.
Its lateral force loads are transferred to the subbase not the cutter/armature system.
Don't use a bearnig guided cutter. Comprende?

Last edited by Quillman; 06-12-2012 at 10:38 PM.
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post #10 of 21 (permalink) Old 06-12-2012, 07:51 PM
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Quillman nailed it perfectly. All of that stuff machines very easily. Most of my invention prototypes are used to make injection-molded plastic parts. Heat is your enemy - if you will keep that in mind, you'll do okay. Corian was asked about above - it machines just as well, but can get overheated also. Polymeric products are best machined in quick movements with plenty of cooling time in between. I don't know what you call it, but I have some small hand-held tools in my shop that are used to provide fillets on edges of plastic parts. It works great, costs about $10.00; but don't expect perfectly smooth everywhere - it ain't gonna happen without some very skillful work with a hot torch and this is something I can never get satisfaction with - unless one particular employee is doing the work. With him it becomes perfect, with me it gets kinda drippy!

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