Proxxon MF70 for making injection molds

[AdieR]

What size moulds are you looking to do? What tolerances (deviation from given size) are you allowing? What accuracy are you expecting?

Beware, aluminium can be a PITA to get a decent finish on, especially if you haven't done it before (esp if you try running high speeds / feeds, or take big cuts).

If you're doing ali, keep some paraffin as a coolant.

[forrest]

Good questions :) The overall mould size would be 50x50x50mm approx so two halves of 25x50x50mm. The actual part size to be moulded initially is only 8x8x15mm. As for tolerance I guess I would be looking at a minimum of 0.1mm,

It would be intesting to see what results other people have had from a proxxon as it looks like the ideal machine to start to learn about cnc machining

I could ask my dad to hand mill the overall mould dimensions then use a proxxon to do all the intricate work, or my other thought was to machine the mould out of brass which would machine better but might not be as good for the injection moulding bit,

I might just buy an normal proxxon to get used to it(see if it might be capable of doing what I want), then cnc convert it, at the moment whilst a self build looks tempting I neither have the time or experience to build such a beast.

The bench top injection moulder I have is a Small power machine co SP2 with an air operated piston, my other possible plan is to cast a mould with aluminium powder loaded epoxy resin, but whilst I have heard people talk of doing this on the net I havent seen any results yet,

[Jonathan]

I could ask my dad to hand mill the overall mould dimensions then use a proxxon to do all the intricate work, or my other thought was to machine the mould out of brass which would machine better but might not be as good for the injection moulding bit,

I think that could be a good way of doing it. The main problem might be finding a CAM program that can generate toolpaths from a partially machined item. If your dad can get it close enough that the whole thing can be machined on one or two passes then it could be efficient. If there's too much material left then you've got to work out where it is and add roughing operations to remove it - doable even with a simple program like cambam, but tedious if you have a lot to make.

Brass can be much quicker to maine (SMM is very high), however you're limited by spindle speed and the cutting force...

Beware, aluminium can be a PITA to get a decent finish on, especially if you haven't done it before (esp if you try running high speeds / feeds, or take big cuts).
If you're doing ali, keep some paraffin as a coolant.

And equally if you feed it too slowly the cutter may rub and leave a poor finish.
I think paraffin could be bad for the machine, having such low viscosity means it's going to get into everything.

[M250cnc]

I will add that it appears that the tables are made from ali so it ain't gonna last long.

As Jonathan mentioned to do 3d , cam software is expensive.

When doing 3D the software i use is able to rough out using large cutters then doing REST machinning using smaller cutters to get efficient toolpaths.

On a shape i programmed which was in your work envelope the machining time was in the order of 18 hrs this was using a roughing toolpath so even longer using a single smaller cutter.

Good Cam software can cost £3K +

Phil

[AdieR]

"I think paraffin could be bad for the machine, having such low viscosity means it's going to get into everything."

Paraffin is no worse than standard water-based coolants in this regard.

What I have done before today is to put some paraffin in a bottle (500ml Coca Cola bottle or similar), with a small hole punched in the top, and squirted it when and where I wanted it, that way you don't have a huge amount of mess to clean up (Just make sure you identify what's in the bottle so it doesn't get mixed up...)

Not sure I'd be using brass for Injection moulding though, I'm not convinced it would work.

What temperature you anticipate running your moulding machine at?

[Colin Eldon]

Hello from California.

I was a field salesman for The Small Power Machine Co from 1971 until 1976 and traveled the UK with an SP1 and an SP2 in the trunk. Richard Benson and Pete Glasson ran it, Ian Berg was the Sales Manager, John Few ran the molding shop and me and Dave Hiscock ran around doing the selling. Boy, have I got some stories to tell. The worst was blowing up the machine - split the barrel, heater bands became shrapnel and the guards shattered. It was at The Royal Ordinance Factory in Bridgewater trying to mold a tensile test bar outa solid rocket fuel. They assured me it was inert and just the matrix with no explosive.....WRONG. Ian Bergs sympathetic reply to me shaking on the phone was "That's sales for you". I named the last machine they made "The Hotshot". I would love to get a picture of an SP2 and in particular the optional Ejector Unit.

Cheers Colin Eldon
[email protected]

Good questions :) The overall mould size would be 50x50x50mm approx so two halves of 25x50x50mm. The actual part size to be moulded initially is only 8x8x15mm. As for tolerance I guess I would be looking at a minimum of 0.1mm,

It would be intesting to see what results other people have had from a proxxon as it looks like the ideal machine to start to learn about cnc machining

I could ask my dad to hand mill the overall mould dimensions then use a proxxon to do all the intricate work, or my other thought was to machine the mould out of brass which would machine better but might not be as good for the injection moulding bit,

I might just buy an normal proxxon to get used to it(see if it might be capable of doing what I want), then cnc convert it, at the moment whilst a self build looks tempting I neither have the time or experience to build such a beast.

The bench top injection moulder I have is a Small power machine co SP2 with an air operated piston, my other possible plan is to cast a mould with aluminium powder loaded epoxy resin, but whilst I have heard people talk of doing this on the net I havent seen any results yet,