ER20 Spindle? Is it worthwhile?

Mostly Printed CNC - MPCNC Hardware Development
#1

Hey everyone, I’ve come to the conclusion that I need to start using bigger tools for the jobs I’m running. Huge pocketing jobs that take 7+ hours are just a bit too much for a 1/4" bit, and I would like to have the ability to use larger bits.

It seems as though ER11 spindles only support a maximum of a 1/4" bit, whereas an ER20 spindle supports up to 3/4".

If I buy one of these fancy super high powered ER20 spindles, is it going to be bottlenecked by the machine? Is the MPCNC rigid enough to make use of this spindle, or is it going to be a waste?

I’m also wondering where to find these things in the US or Canada, since all of the ones I found are 220V or 3-Phase.

If anyone has any ideas, please let me know!

#2

The spindle alone weighs 12pounds! That’s not going to work.

#3

How about a smaller version of the LowRider, it doesn’t have to cut full sheets, It uses a bigger tool. Probably cost the same as the spindle.

#4

Yea, I would make a lowrider, but I need a Z height of at least 6 inches, and I currently have about 8 with my MPCNC… What other spindle can I use? Do you guys have any ideas?

#5

You need 6 inches of cutting or clearance? Clearance is very easy for the lowrider just make the rails higher than the table, mine are 1/2 higher, but if it’s cutting, how do you do that with 1" long bits?

#6

So the 660 comes with a 1/4 collet and you can get bits with a 1/4 shaft and larger cutting diameter. Although I doubt you will gain any time that way. How fast and deep are you running your 1/4" now? In what material? To cut faster you can always go deeper. I can’t imagine your pushing a 1/4 very fast. I run 1/8 shallow and slow can’t imagine a 1/4 let alone something wider.

#7

No not 6 inches of cutting height, 6 inches of clearance, or at least, 6 inches of Z travel distance. I actually built the MPCNC for work, and we’ve been using it to make enclosures out of MDF, softer woods and aluminum, and it works great for rapid prototyping. What I’m trying to do now is bamboo, and bamboo is super hard to cut, which is why I would like the larger bits.

I’m using 1/4" solid carbide bits, and I can push them to about 10mm/s XY or so before they begin to struggle. That’s with a 2mm depth per pass. I don’t know all that much about bamboo, but my current approach does work, it just takes 7 hours is all…

My machine is 2.5’ x 2.5’ if that makes any difference, but I don’t think I’m pushing the machine all that hard, probably just the spindle…

#8

I could be wrong, but it is probably just the whole system. The 660 should have more than enough power for what you are doing, the problem is when you do start pushing it hard enough to flex the machine the cutter is no longer parallel or perpendicular and the cutting gets funky. You should really spend a little time trying to maximize what you have by doing test cuts, if you can make the machine any smaller or shorter and you can cut faster or deeper. Try a different bit, single flute instead of a dual flute you would be surprised at what is out there. There are wood bits and metal bits. Maybe using a 1/8" at 8mm per pass would run faster. Deep roughing passes and a nice finishing pass should be the ticket though. Or shallow and fast with a finishing pass. Way to many options to cover here.

A bigger bit and heavier spindle is definitely not the right direction though more flex, more deflection , slower cutting.

Milling is extremely complicated, lots of different things to try.

#9

Yea you’re probably right, upgrading the size of the bits does seem to the be brute force method of machining faster, but I guess I’ll try to see what I can do about maximizing what I have to work with. I’m no machinist, so this is all new to me, but hopefully it’ll get easier.

Thanks for the help!

#10

I’ve not tried bamboo yet, but do want to. Might see if you can do trochoidal tool paths for your pockets. It’s supposed to let you cut deeper with less force.

#11

I didn’t even think of that Barry, so many way to change a cut…

#12

See that’s the thing, trochoidal works perfectly, but the problem is that I’m milling STL files, so 3D toolpaths, and Estlcam won’t let me use trochoidal milling on 3D toolpaths… Does fusion 360 do that?

#13

Probably not. I’ve never seen anything do 3d toolpaths other than straight back and forth cuts. Even the big beefy routers cut in straight lines.

#14

Yea, and that’s the thing, if I can’t compensate for speed using software, I think my next approach will have to be a hardware improvement… Maybe I can convince my boss to let me build a $5K machine and do a 1-1 comparison with the MPCNC!

#15

High five if you can!

#16

Please don’t compare it to a $5k machine.

If the budget is $5k I need to know what the target capabilities are and I would make something specialized. Matter of fact there are tons of them out there. This is a machine that can do many things well for very inexpensive price. For the people that make things and enjoy the process. If you are trying to do production with it than it probably is no the machine for you (although I do production with it for the last almost 2 years now and am happy with how much it cost me and how fast it runs).

Tricoidal is cool, but it is not any faster. It is a means of using more of the cutting surface of your endmills. if we do 1mm DOC all the time we only wear out that first 1mm of the tool. Our bits are so cheap I would rather do normal cuts and save the time and just replace the tools more often (although I have not dulled an endmill yet, still using the first one I ever bought).

#17

Haha, trust me, I’m not expecting the MPCNC to compete with a $5K machine, I’m not crazy! Actually, everyone at my work was so impressed with this build that we’ve actually been using conduit for support structures and even as cheap linear rails and things like that.

I’ve been using the MPCNC almost daily for the past 4 months since I’ve built it, and I’ve learned a lot about CNC machining in general. I’m no engineer or machinist, I’m a 19 year old college student and this is my first look into the world of CNC. I built this machine to prove to everyone that it can be done, because no one believed that you could make a real CNC out of printed plastic and electrical conduit, but here we are!

The only reason I said I’d make a comparison is because I know there are going to be diminishing returns, and I want to see just how much better a machine 5x the cost will be. I’m not going to be paying for it, but I am going to be building it, and I would love to see them in action!

For the price though, absolutely nothing I’ve seen beats the MPCNC. You deserve an award for bringing CNC to the masses, because this is truly an incredibly design.

#18

Thanks for all the compliments.

Sounds like you know what you are doing you’ll be fine.

When I built it and showed a senior level engineer the video and the aluminum 3d milled part(vid is still up) he said it was absolutely impossible…hahahahaha…wrong!