[007CNC]

Deep cut and slow feed or shallow cut and faster feed?
I have a not so rigid machine which works ok with plastic, but chatters with aluminum. The gantry on this machine is a lot higher than it needs to be, which makes it a lot less rigid.
I am in the process of building a much more rigid machine, but I need to use my old machine to cut out some of the aluminum parts I need for the new machine.
What will work best to help reduce chatter with this machine. A deeper cut and slower feed or a light cut and faster feed?
conventional or climb milling?
I am cuttting 0.5inch 6061 aluminum plate, and my spindle can go from 2K rpm to ~9K rmpm. I have 1/4" carbide endmills in 4 and 3 flutes, and I have 1/8" endmill in 2 and 4 flutes.
I'll appreciate any advice/tip on this.

[awerby]

Doesn't mean it really will. Gantry routers that are barely able to cut plastic don't do too well on aluminum, as you've discovered. That's why people use milling machines for this sort of thing.

Deep cut and slow feed or shallow cut and faster feed?

[Your best bet is a shallow cut and slow feed. Even if all you can do is mark where the cuts are supposed to go, that can be helpful. Follow up with a saw, if necessary.]

conventional or climb milling?

[Climb milling gives a better finish on aluminum, but it requires a rigid machine. Try both and see what seems to work best.]

I am cuttting 0.5inch 6061 aluminum plate, and my spindle can go from 2K rpm to ~9K rmpm.

[Use the highest RPM setting.]

I have 1/4" carbide endmills in 4 and 3 flutes, and I have 1/8" endmill in 2 and 4 flutes.

[The 1/4" tool is less likely to break. The 3-flute tool is less likely to clog. Squirt the cut periodically with WD-40 to lubricate the cutter and blast the chips out of the cut.]

I'll appreciate any advice/tip on this.

[If this doesn't work, send your parts out to be cut on a machine that's actually capable of doing the job.]

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[007CNC]

Doesn't mean it really will. Gantry routers that are barely able to cut plastic don't do too well on aluminum, as you've discovered. That's why people use milling machines for this sort of thing.



[If this doesn't work, send your parts out to be cut on a machine that's actually capable of doing the job.]

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

Its actually not that bad.
I have been able to cut aluminum, just not as fast as I would like to, hence I am building another machine.

the question is between deeper cuts + slower feed and shallow cuts + faster feed, which one works better.
I am currently at 0.015 DOC with 15 IPM on a 1/4 cutting bit. I am just looking to see if I can improve throughput by modulating either the feed or the DOC.

[wizard]

Better to focus on getting yor stiffer machine up and running in my mind. Make sure you are using plenty of coolant/lube and cutters designed specifically for milling aluminum. More so make sure the cutters are sharp.

Its actually not that bad.
I have been able to cut aluminum, just not as fast as I would like to, hence I am building another machine.

You are on the right track so I wouldn't bother getting off. If your machine is doing the work accurately enough get the bigger machine up and running.

the question is between deeper cuts + slower feed and shallow cuts + faster feed, which one works better.
I am currently at 0.015 DOC with 15 IPM on a 1/4 cutting bit. I am just looking to see if I can improve throughput by modulating either the feed or the DOC.

Without a hint as to what your current design is it is hard to suggest anything. That anything though would be attempts to stiffen up the current machine. If you can identify the primary weakness in you current machine you might be able to stiffen it enough with a temporary modification to speed things up.

Honestly your feed rate is extremely slow now so I'm not sure you have an avenue to go faster.

[007CNC]

Better to focus on getting yor stiffer machine up and running in my mind. Make sure you are using plenty of coolant/lube and cutters designed specifically for milling aluminum. More so make sure the cutters are sharp.


You are on the right track so I wouldn't bother getting off. If your machine is doing the work accurately enough get the bigger machine up and running.


Without a hint as to what your current design is it is hard to suggest anything. That anything though would be attempts to stiffen up the current machine. If you can identify the primary weakness in you current machine you might be able to stiffen it enough with a temporary modification to speed things up.

Honestly your feed rate is extremely slow now so I'm not sure you have an avenue to go faster.

Thanks wizard for the input.
The primary weakness in my current machine is the gantry height (too high)and the work table (not well supported). The ROI on fixing any of these is not worth the effort. I`ll rather put that effort towards getting a better machine up and running.

[brentpinfold]

How well is the aluminium plate secured? I would try 9k revs 30 - 45 ipm and 0.125 doc with the 1/4 end mill. Sometimes by pushing a weight (lead) on the centre of on the job or by where the tool is working will take away chatter.

[007CNC]

How well is the aluminium plate secured? I would try 9k revs 30 - 45 ipm and 0.125 doc with the 1/4 end mill. Sometimes by pushing a weight (lead) on the centre of on the job or by where the tool is working will take away chatter.

The aluminum plate is secured, but the table its secured to is not verywell supported.
I think you are right on the higher RPM and faster feed. Prior to reading your post, I ran a test cut at 28 IPM and 0.01 DOC, at around 5K, and surprisingly the chatter was reduced. I was worried about pushing it harder as I dont have a setup for coolant.
Though I am using a solid carbide cutter, I am worried that faster RPM could gum up the teeth and snap the bit without coolant.
I can try for higher rpm/feed and see what happens.
Thanks for the input.

[louieatienza]

I think the limiting factor here is your very light DOC. My hunch is that you'll wear the bottom of the bit way before the flank. Also, cutting 1/2" plate with .01" passes doesn't seem like a lot of fun!

In fact, when I cut aluminum, I don't worry too much about bit deflection or machine ridgidity or such. I always climb-cut, and always leave about .01"-.03" for finishing. The climb-cut will tend to push the tool away from the cut line, which can help remove some slop. Then when you do the finish pass, there won't be much deflection since you're removing minimal material.

Also if you machine is not ridgid, you should always ramp or helix in whenever possible. You can raise your work up to keep your Z travel to a minimum which will help ridgidity. I would use a squirt of lubricant at least occasionally. You'll havve to ride herd with brush or vacuumm when profiling or slotting.