PDA

View Full Version : Milling Sheet Aluminium



p1lts
10-03-2013, 10:02 AM
Im having some difficulty milling 0.9mm sheet Aluminium (5251). I know the grad isnt the best for machining but its the most readily available.

I have no issues machining 4mm plate using 3mm 2flute bit at 12000rpm 200mm/min.

The thin sheet doesnt cut cleanly and Ive tried different feeds/speeds. What I really want to achieve is this:-


http://www.youtube.com/watch?v=3wIiNVB390w

Any help greatly received.

Ian

Tenson
10-03-2013, 10:27 AM
Show a picture of how it's coming out.

I've had problems with low grade aluminium too, it gets hot and sticky then gets re-cut. Keep it sprayed with water and oil the cutter.

Also your RPM sounds way too high for 200mm/min. G-Wizard (http://www.cnccookbook.com/CCGWizard.html)suggests 1000mm/min and 18,000RPM. Or 5000RPM for 200mm/min.

p1lts
10-03-2013, 10:49 AM
Thnaks for the advice. I'll try slowing the spindle, but the slowest I can go is 150Hz which is 9000rpm and up the feed to around 350mm/min.

When you oil the cutter, what exactly do you mean. Sorry if its a dumb question.

Jonathan
10-03-2013, 11:02 AM
Thnaks for the advice. I'll try slowing the spindle, but the slowest I can go is 150Hz which is 9000rpm

Is that one of the 2.2kW water cooled spindles? If so you can go lower, it'll just be the minimum frequency setting on the VFD that needs changing. Don't expect much power though if you do change it.


When you oil the cutter, what exactly do you mean. Sorry if its a dumb question.

Just means put coolant on it - ideally lots if you're having problems.

You may also want to try a single flute cutter, more room for chips etc.

Web Goblin
10-03-2013, 11:09 AM
The sheet might be vibrating as its being cut. Can you fix it down by screwing down a bit of timber along its width above and below the cut area?
Forum time seems to be 1 hour fast. Fixed now?

Tenson
10-03-2013, 01:03 PM
Or place a 6mm mdf sheet on top and cut through it.

A single flute cutter will also let you run at higher RPM for the same feedrate.

Oil the cutter I just meant squirt some WD40 on it every minute or so. Even better you could try getting one of those plant watering spray bottles where you pump the top to pressurize it. Fill it with water and 10% water soluble cutting oil (http://www.ebay.co.uk/itm/G-P-Soluble-Cutting-Oil-Coolant-White-Water-1-x-1-ltr-/250443189387?pt=UK_BOI_Metalworking_Milling_Weldin g_Metalworking_Supplies_ET&hash=item3a4f93cc8b) (white water oil, coolant fluid etc..).

p1lts
10-03-2013, 02:58 PM
9000rpm at 550mm/min twin flute with WD40 is now producing acceptable results. I think my spindle speed was too fast and travel speed was too slow. The lub is probably helping as well.

Thanks for the help.

:-)

AdCNC
07-03-2014, 07:43 PM
Some double sided tape like 50mm wide or bigger will do the job of holding the plate down i used it years ago when i used cut ali on my router.

EddyCurrent
07-03-2014, 11:23 PM
I've been hand cutting aluminium on a overhead pin router designed for wood but it's quite robust. I found by trail and error that 9000 rpm was the best speed with a twin flute TCT cutter and not wishing to use lube I directed a good jet of compressed air onto the tool which seemed to work well. Feed rate was by hand but it seemed the faster I could push it through the better it cut. Depth of cut of about 0.6mm meant no clogging of the cutter but around 1mm depth it clogged quite regularly.