NEED HELP Machining glass filled nylon (Haas)

Hey guys,

First post here. I am running a Haas VM3 and have a glass filled nylon project. About a 6" part with some fine details. Would like some starting speeds / feeds and some tool suggestions. Also, Can I run coolant on the part or is Nylon going to absorb it? I hear 2 stories on that. Appreciate the help and am happy to be here.

D

Too many variables we don't know. However, speaking generally, I tend to run GF as fast as my spindle will go, with speeds and feeds set from there, appropriately based upon mill size and operation. ( for us that is 10Krpm ) I have done likely tons of GF. Literally. Using from as large as 3/4" for roughing, down to 0.010" ball and flat mills for details. If you have a compressor that can keep up, I like to use a cold air gun, but coolant is fine. 99.9% of the GF parts we make are for prototyping, so a little moisture absorption won't be the end of the world. Smaller parts are fairly straight forward, but things like handle halves of power tools and surgical instruments may need proper precautions taken to avoid minor distortions. There is no magic answer. The cold air gun means you are vacuuming and cleaning the machine afterward. Period. Do not pass GO. Do not collect $200. End of story. Coolant means that you are either taking extra ( and sometimes extreme ) measures to protect and filter your coolant, or you are cleaning the sump and lines for weeks afterward.

As far as moisture goes, by the time you get the material, it should already have absorbed enough water to stabilize it. If the part is critical on dimensions, I would hog out the part leaving enough for cleanup. Then let it sit overnight in either a moist room or in a coolant tank (if you are using coolant) and finish it up the following day. The glass stabilizes the part mechanically but there can be residual stresses. Is the raw material cast or extruded? The amount of water absorbed also depends on the resin, 6, 6-6, 6-10 or 6-12. The most common is 6-6. 6 absorbs the most, 6-12 very little. For instance, DuPont 70G33L is 33% glass lubricated 6-6 nylon.

Tom

Like Tom said the exact type of nylon is very important to how much moisture it will absorb. I would rather machine it with flood coolant but try to keep it as dry as possible. I would not store it submerged, you don't want to saturate it, you want to stabilize it at normal temp and humidity that the customer will inspect it in. Keep chip loads as high as you can for tool life, limitation may be chipped corners on the part. Tools for aluminum are acceptable, plastic specific are worlds better. If you are just doing a few parts use new aluminum specific tools and run it like aluminum, as long as you can hold onto it. Do as much deburring on the mill as possible, much easier and will look better than what you do by hand. Don't expect your tools to work too well on aluminum afterward.

Glass is nasty stuff to have in your coolant.

How much glass in the nylon? 40% glass filled nylon is a little different than 10%.

As for tooling, carbide is a must and even then they are going to wear out fast.

plastics change size alot with temperature and nylon changes with moisture content
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moisture as much as .010" change per inch although usually its less. .001" per inch is common after parts machined and put in a drawer and has time to dry out over many months.
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i have seen bearings pressed in with .001" undersize bore and months later bearing falls out. basically bores get bigger and outer edges gets smaller. it shrinks towards center of mass
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part can easily measure over .001" different if warm or extra cold. drilling and mill slotting if heat builds up you can get melting. most do not drill or slot mill at high rpm cause of this. obviously if material abrasive it dulls cutter and heat builds up faster with dull cutter
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parts are easily squeezed or distorted by chucking and or vise pressure. much more than metal.
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i have also seen 6" round nylon crack radially like a wood log when a hole was drill down the center. dry nylon can be under stress and as material is removed it can crack as well as warp, distort, curl etc after material removed and then unchucked or removed from vice

We have machined a lot of G10 and needed to isolate the pump in its own tank with a double filter so it gets clean coolant from an air operated pump that moves it thru the filters to the clean tank. We pretty much had to use this mill for that job only. we use coolant carbide end mills and it is a P.I.T.A.

yes some coolant systems have screens and long stringy plastic chips can clog the screens. if screens clogged badly coolant can overflow and get on the floor. better systems you can easily pull the screens out to clean them after doing a plastic job

Thanks for the help guys. The GFN is 30%. The part is structurally stable but I might stick with the air blast for now. I guess I'm looking for some roughing parameters. Probably starting with a 1" flat carbide to get most of the material out.

Thanks...….

Keep in mind that whatever tools you use are going to be relatively useless for anything else. Plastics and glass filled especially dull tools differently than metal. If you try using your tools on aluminum after cutting much plastic they just won't work worth a shit and will burr like crazy.
Rule of thumb with plastics is to take as large a chip load as possible, chipping and surface finish will be your limiting factors. Keep your spindle speed as low as possible to improve tool life and reduce heat. The worst thing for tool life is high speeds and light feeds.
I would say program for aluminum and start running it with the spindle at 25% and feeds around 40% with coolant. Without coolant but with air blast I find I have to run parts at 50% of what I can run with coolant, drilling is even slower than that. With glass I would not want to run air blast to keep the glass from getting airborne.

I need to machine some PA66 / GF30. Never machined it before.
I only need to machine 1 part, so no production.
Endmills for Aluminium would work? Don't want to buy diamand coated tooling for a one off part.
Flood coolant should be turned off if I understand above posts. And a airblast would be enough?