Plasticwork

[jimbo_cnc]

There's metalwork and woodwork forum areas, what about plasticwork?

Where's the best place to discuss Plastic?

I was hoping for advice on spindle power. For my upcoming 6040 purchase I couldn't decide between 800W and 1500W spindle. Obviously I'd prefer 1500W.

However I've put in an ebay offer for a 800W machine now because the asking price for the 1500W ones are about £250 more. The 800W machine comes with a 1500W inverter, and the 1500W spindles can be had for £85. So it looks cheaper to do the upgrade myself if more power is needed. All I'll have to make is a new spindle clamp. Delrin OK for that ?

[Boyan Silyavski]

I doubt it would make a difference for plastic. you said before small details. The 800w is ok. Anyway, plastic melts so you can not reap it like other materials.

[mitchejc]

I don't have a lot of experience cutting plastic and I've only tried normal 2 flute 6mm cutters on a 1.5kw spindle. Acrylic is relatively easy to cut but some of the softer varieties like HDPE can be difficult to get a good surface finish. One has to keep the rpm surprisingly low not to melt the cut and ruin the piece. Maybe those expensive specialized single flute cutters works the magic on the softer plastic? Not sure about the power requirement but I did not get the impression that one needs a big amount of power but considering the relatively low rpms I would not go to small on the spindle.

[jimbo_cnc]

Is this what you mean? I bought some of these because they are from UK and I needed cutters fast. http://www.ebay.co.uk/itm/291185073866

I'll be using delrin at first because I've got some and it seems to be the easiest to machine. Then I'll try nylon.

I've got a bunch of 2 flute endmills coming, mostly 3.175 and 6mm diameter.

I haven't worked out an RPM, speed, DOC, overstep etc yet to start with. Any ideas for dia 3.175 2 flute ?

[mitchejc]

Yep I suspect something like that will work a lot better than the standard 2 flute HSS slot drills I've tried. Not sure about the feeds for the 3.175 cutters but if I recall correctly I got ok'ish results in HDPE with something like 12,000rpm 2000mm/min and 2mm DOC and sprayed with WD40 with the cheap 6mm cutters. I stuffed around with a piece of acetal at some stage and from my little experience it cuts a lot easier and neater than nylon. I think acetal might be the same as delrin but don't take my word for it.

[Boyan Silyavski]

read post 13 http://www.mycncuk.com/threads/7666-...9535#post59535

these are good starting points for excelent finish. Play with the depth of cut, depending on your machine stiffness and cooling. Blowing air into the cutter from old fridge compressor helps greatly increase the depth of cut. You should have nice chip if you use very sharp polished cutter, which is a must with plastics.

[jimbo_cnc]

I haven't learnt much about RPM, feed, doc yet, because everything I try works! I love Acetal.

I could keep cranking up the speed and doc I suppose, but I'm doing small one-offs mostly. 3 hours designing and drawing, 10 mins setting up. 5 mins cutting.

When I get into batch production I will look more at speeds.

[Boyan Silyavski]

http://zero-divide.net/?page=fswizard or maybe even his payed version HSM advisor, which i have installed from a couple of day and i like it very much.

Its not a question of production or no, its a question of quality finish, saving the tools to last longer and reasonable time when doing something 3D.