Machining the extrusion drill

Hi folks,
I’ve got my 4th axis ready and also my large metal lathe is now converted to a CNC lathe.
I saw here in the forum people using relative inexpensive (~50 Euro) wood drills (‘threaded Tip Hex Shaft Wood Auger Drill Bit’). I can’t remember where but someone said it’s good a thing when  the heated plastic gets compressed at the end of the ‘drill’…can someone confirm this ?

However, I’m designing now such drill in Fusion-360, ready to get milled/turned on the CNC. I was wondering :

– what outer diameter do you recommend ?  I saw in the documents 26mm and I’m rather looking for the max. ‘through output’, I guess I have to increase just the heating capabilities
– it’s easier/cheaper to use aluminium, i can’t see much trouble in doing so

If someone has recommendations or experiences to share, I’d be happy to take into account :-). I’m happy to provide this drills in the bazar. There are offers for 300 Euro but I’m sure this thing can be machined for much less, eg: doing it in Aluminum shouldn’t require more than 100 bucks in labour and materials 🙂

thanks in advance

Hello @mc007

its always good to see people thinking such that your are.
thats really cool to have your mini lathe and mills working in CNC.
that being said…
I’m not trying to sound like negative NANCY here but
aluminum will not work.  It has too much thermal expansion,
galls really badly when it rubs on all other metals and
is not strong enough for the amount of torque and torsion
that will be required to convey, melt and build pressure
in your screw and barrel.

Also, there are several topics here that talk about the clearance required between the screw and barrel.  It’s best to check those threads.

best of luck!

Hello @mc007

You are looking for this thread for what size and how to design an extrusion screw. Keep in mind that typical screws are hardened and made with very tough abrasion resistant metals. Typically that means high chromium metals.

The quest for the ultimate extrusion screw.

The quest for the ultimate extrusion screw

Best of luck in your machining!

ok, thanks! I will go for metal then 🙂

Would be nice if people could give more input on the perfect ‘drill’. Right now, the only thing which puzzle’s me is the max. diameter and length. I can machine up to 1.30 meter length, and diameter up to 20 cm (just saying).

My goal is to produce larger quantities of stock plastic: cylinder & bars or bricks, with max. speed & size possible, also to make sure that my clients are in good position to get into business with local industry, being able to make a living with plastic, ASAP 🙂

see you in a while, with hopefully something good to report or show 🙂