Will this Router Mill Aluminium?

Hi guys, I'm interested in making a new CNC machine that is a bit better suited for my needs and has a flat bed. My Chinese one is all warped as I found out when I was making PCBs with an engraving endmill. Even a 9cm x 10cm PCB was so warped that I had to use various tricks to get the traces to turn out workable. It's fine for crude work and it's not like I'm going to throw it out, it does have uses, but I have realised that I would like something done a bit more 'right'. Fingers crossed it can be done DIY - assemble all the pieces, I won't be able to machine parts for it that would be accurate enough.

Anyway, I found a CNC router on youtube that looks really nice, but I'm wondering how good/bad it would be at working with aluminium which is what I hope to be able to work on it as well as all the other light stuff.

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Originally Posted by Atomic_Sheep

Sorry, looks like the youtube links didn't work, please search:

"2.2Kw Spindle on newly complete Z axis with new Y axis rails in place "
"My 3 Axis CNC Router base almost finished"
"My CNC Router progress update 2"

All videos are by Glen Lewis

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Also, I plan on using some NEMA 24HS39-3008D steppers which I have already bought, but I was wondering how good/bad these would be for aluminium work? Here are the specs:

Model
24HS39-3008D

Rated Current(A)
4.24 (3.5A)

Phase Resistance(Ohm)
0.7

Phase Inductance(mH)
3

Holding Torque(N.cm)
566 oz-in (467 oz-in)

Rotor Inertia(g.cm2)
980

I have a small chinese router that uses small end Nema23 motors.

I do a lot of aluminum. I keep the rpms high say 20000+, depth of cut about 0.15mm or 0.005" with a feed rate of about 1000mm/min
with a 1/8 carbide two flute endmill.

I get decent finishes, takes a while but its a hobby so I do it to enjoy it.

I have no problem letting my machine run 6 or 12 hours at a time....

Never any problems.

My machine uses NEMA23 3A motors, the PSU is 42V, unregulated and is based on toroidal transformer. It is a moving table type, so it is pretty solid and I also have acrylic side windows, so the chips don't fly around and when/if a cutter breaks and fly away it is always captured by the acrylic protection. It does not happen often, but since I am sitting often side by side, I appreciate that it hits the window with a large bang and not my face or eyes. It has no problems at all milling aluminium.

...but...

If I had a machine with a warped table I'd fix that first, or would use a waste board and levelled that with the machine itself. That way you can mill PCB as well. This is necessary, even if you build a new machine. The copper layer is simply too thin, so if you want good results it is necessary that the table is levelled. I don't use any auto leveller, but have a flat surface under the PCB. That surface is levelled every time I feel the need for levelling it, I mill PCB is single pass, and that works fine, but of course, it always demands a flat surface, so I use double sided tape if it is large PCB and make sure that the PCB is also flat.

Definitely YES, an 800 watt spindle can efficiently cut aluminum, how much more the 2200 watts, it can eat aluminum for lunch anytime swiftly :)

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Anyway, I found a CNC router on youtube that looks really nice, but I'm wondering how good/bad it would be at working with aluminium which is what I hope to be able to work on it as well as all the other light stuff.

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I'd make some changes to that design.

1) Do not use round rails. Use Hiwins or another profile linear bearing. They are far more rigid than round rails.
2) Make the gantry from one large single beam, rather that two smaller ones. Again, it will be much more rigid.
3) Make the gantry (and sides) lower.

These will make the machine much better. I'd also make the frame from steel, as that aluminum one looks a bit too lightweight to me.

As for the motors.
I'd get some good drives, like Leadshine AM882's or EM806's, or Gecko G201X's, and run them at 60V. They should be fine.

I haven't given up on aluminium on my machine completely but I'm starting to think is just not rigid enough. The times I tried, the thing was visibly moving around. So it seems like it can do it but I need to reduce my deapth of cut a lot... I'm seeing a lot of success with 0.2mm as you suggested but I haven't tried it yet.

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Originally Posted by A_Camera

If I had a machine with a warped table I'd fix that first, or would use a waste board and levelled that with the machine itself. That way you can mill PCB as well. This is necessary, even if you build a new machine. The copper layer is simply too thin, so if you want good results it is necessary that the table is levelled. I don't use any auto leveller, but have a flat surface under the PCB. That surface is levelled every time I feel the need for levelling it, I mill PCB is single pass, and that works fine, but of course, it always demands a flat surface, so I use double sided tape if it is large PCB and make sure that the PCB is also flat.

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I wouldn't know where to start in terms of leveling it. I tried the spoilboard method but that didn't work. I thought levelling a spoilboard would make it completely flat but no. Definitely not flat enough for PCB. I had to run the program 2ce with the second attempt deeper than first.

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Originally Posted by ger21

I'd make some changes to that design.

1) Do not use round rails. Use Hiwins or another profile linear bearing. They are far more rigid than round rails.
2) Make the gantry from one large single beam, rather that two smaller ones. Again, it will be much more rigid.
3) Make the gantry (and sides) lower.

These will make the machine much better. I'd also make the frame from steel, as that aluminum one looks a bit too lightweight to me.

As for the motors.
I'd get some good drives, like Leadshine AM882's or EM806's, or Gecko G201X's, and run them at 60V. They should be fine.

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Thanks for the suggestions. But just to confirm I understood your point regarding #2. So rather than 2 pieces, one behind each guide rail... just use a single piece?

In relation to point 3.) I would like to have the biggest z axis that I can get away with because my z axis on my current cnc is rather limiting. I can't even fit a basic small vice to my machine right now... let alone have have enough room to play around with dial indicators on top of that. Plus, I've been entertaining the idea of adding a 4th rotary axis, so a lathe to it, so would need a decently high z axis for that

How would it be possible to improve rigidity for a taller gantry?

By frame, do you mean the base/bed/legs? (Because the gantry (apart from your comment regarding the back plate being 2 pieces) looks pretty study) I was wondering about that myself. Looks quite flimsy. Not sure whether I would beef up components or like you suggested whether simply having it from steel would suffice.

In terms of drivers, what about if I use my current G540 for it? I have a pretty decent control box I think. Has good components and I have the most powerful Nema motors already bought that the G540 can handle. I was thinking of running the cables from my current cnc to a switch board which will also have cables going to the new machine and then the switch board will go straight to the gecko. That way I can just switch between the two machines at a flick of a switch.

The other thing tha got me worried is my 2.2kw spindle. It seems like it's min RPM is 8000. That seems much too high for aluminium? But there's a lot of videos on youtube of people using it for aluminium. But I'm guessing the cutting is generating a lot of heat and quickly dulling the tools. But I'm not sure, haven't read or watched enough on the topic or indeed know enough about my spindle yet. Maybe it can do slower RPMs.

Can this machine mill aluminum? Its all relative. I know a fellow who was making aluminum casting and low pressure injection molds with a plastic frame CNC router. It was slow, but the router was about as cheap as you can get and it worked for him.

Any modestly solid aluminum or cast iron frame router is going to be a step up from a cheap import router. My problem with machine upgrades is that I find their limits, back just off, and then tend run them right there. Near their limits. The machines then need more frequent service because I am always pushing them hard.

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But just to confirm I understood your point regarding #2. So rather than 2 pieces, one behind each guide rail... just use a single piece?

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Yes, one large beam.

This thread has some good info on gantry design.
https://www.cnczone.com/forums/diy-c...cad-posts.html

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How would it be possible to improve rigidity for a taller gantry?

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Make everything bigger and stronger. The taller you make it, the weaker it'll be, so if you really need more height, than you need to build it stronger.

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In terms of drivers, what about if I use my current G540 for it?

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You'll only be getting about 70% of what the motors are capable of with a G540. If you want to stick with a G540, then smaller motors may perform better.

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The other thing tha got me worried is my 2.2kw spindle. It seems like it's min RPM is 8000.

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When you slow the spindle down, you increase the chip load, which increases the cutting forces, which requires a stronger machine. There's no problem at all cutting aluminum at 8000RPM, or even much higher.
Say you are cutting at 8000 rpm and 100 ipm. That's really no different than cutting at 50ipm and 4000rpm.

Carbide cutters in aluminum can handle some pretty high speeds, especially with the right coatings. Typical SFM is between 600 and 2000 for carbide. At 2000 SFM a 1/4" EM would be at 30k RPM and a 1/2" would be at 15k. Feed speed at those rated surface speeds for 3 flute end mills is typically in the 60-300 ipm range. With a light weight router you probably want to stick to the minimum feeds (or even a bit below, but not too far.)

Is your spindle air or water cooled? If it's water cooled, you can probably run it slower than 8000 RPM, it usually takes tweaking the VFD parameters just right so the torque doesn't drop way off though. Also keep in mind that a 3HP 24k spindle only has 1HP at 8000 RPM (that's a ton for a light router though.)
If it's air cooled, 8000 is probably a realistic minimum without adding some sort of external blower or something.