Also decided to leak test the water cooling loop in the bathtub.
I have to say: WOW this is quiet. I can’t hear the pump over the near-silence of the bathroom.
I’ve got Noctua fans in the electrical cabinet, BeQuiet! fans on the radiator and the VFD doesn’t have a fan at all so I think the out-of-enclosure noise is going to be negligible.
Yep those Eheim pumps are pretty quiet. If it starts to clank a bit in a year or two it wants a new impeller and you can get them cheap on eBay.
All the cuts looked to be full-engagement and RPM was 30000. The last cut was ~0.4mm DOC, 1500mm/min feed rate.
I think.
It’s been a long journey to get here and I was excited just to see if it cut after what feels like a year of figuring out which parts to use, designing the Aluminium parts to glue them together, buying them, assmembling them, buying the electronics, assembling the electronics without electrocuting myself, debugging the electronics… I didn’t pay much attention to correctly zeroing and I may still need to adjust the steps/mm for the Z-axis.
And I’m really happy with how quiet everything is. I was mildly concerned that the spindle would be louder or that the VFD would whine or something but the loudest thing in the room by far is the set of BeQuiet! fans on the radiator for the water loop. The spindle is a pleasant buzz from inside the enclosure, much more pleasant than the old Nomad spindle.
I’ll likely play with it some more tomorrow.
Another project I need to do before I go too crazy with it though is finding a solution (like a bigger enclosure) for the lack of space for the spindle power cable and coolant pipes. As-is, if the spindle is somewhat high, they drag along the ceiling of the enclosure or look like they’ll snag on stuff, which I really don’t like.
Okay, did a few more test cuts to get a feel for the spindle.
Best cut I was able to do in terms of MRR was ~5mm axial, 2.4mm radial, 30k RPM, 600mm/min with a 3-flute, 6mm Hartner endmill. Not very exciting to look at but here’s a clip.
IIRC, that’s over 7x the maximum MRR I was able to get out of the old spindle, so, uhh, looks like the upgrade worked?
The problem now looks like workholding. You can see in the video that the stock had lifted out of the vise. I’ll try again later with clamps on the T-slot bed or threaded table.
I also tried to do a rough stiffness measurement and got a maximum of ~0.1mm of movement when I pulled on a 6mm rod in the spindle, so the Z-axis did give some improvement there.
And finally, damn this spindle results in some nice surface finishes. I need to surface something with it.
So it turns out I was babying the spindle too much. Using settings closer to the manufacturer recommendations, I was able to more than triple MRR again. I’m now at ~26x the maximum stock MRR.
Cut parameters:
Nice conversion but that last cut doesn’t look good at all. I’d stick to Vince’s recommendations and go with low DOC and high WOC. The amount of chatter you have is crazy and will kill your endmills in no time.
Good point but the chatter, as far as I can tell, isn’t really related to the feeds and speeds. The same feeds and speeds that work just fine on the far right side of the stock start to chatter on the left side of the stock. This was the same with the stock spindle so I think there might be a mechanical issue with the machine (like some nut being more worn out on one side than the other).
My theories for the chatter are:
@Vince.Fab @spargeltarzan don’t suppose either of you have theories or opinions on my theories? Vince, could this be what you were talking about regarding the AB-nuts?
Have you done any maintenance on the AB-nuts recently? I filled my X-axis nut up with grease the other day and saw a massive improvement from ~0.5mm to unnoticeable by eye (very scientific™) movement when pushing on the axis by hand. This is before: https://photos.app.goo.gl/yxdqUNyxJHyqJVhu9
Another though: Could it be that you are overpowering the AB-nut springs, since you’ve now got the spindle power to put a lot more force on the axis?
Good idea but I think I’m just going to try to take it easy on X and Y for now.
Thinking about it some more and after discussing it with a friend, I think I need to replace the X and Y leadscrews with ballscrews.
Vince has already pointed to the AB-nuts as a problem when he did his spindle upgrade, so I think the chances are fairly high that I’m running into the same issues he did.
A friend also pointed out that the Nomad doesn’t look mechanically ready for this. The leadscrew is fairly wimpy and it looks unsupported, all the cutting force is applied axially to the stepper motors, which is usually pretty bad for them. Vince’s teardown shows what might be axial bearings but it’s hard to be sure.
Vince has shown that putting ballscrews on X and Y isn’t too big a hassle and now that I’ve done a ballscrew on Z, I’m feeling a bit better about doing it on X and Y.
I would get comfy with and indicator and check everything, see whats really going on.
No matter what mods are done, you’ll always be able to overpower the sprung nut. When converting to the ballscrews for X/Y and leaving the Z leadscrew, the difference in movement was painfully obvious.
Integrated screw Nema steppers have a little different bearing arrangement than non captured. Even when roughing heavy, you’ll unlikely see enough force to really make a difference BUT…everything worth doing it worth doing overboard. Right?
The space the Nema 17s currently occupy would make for a nice spot for ballscrew bearing assemblies. Then just drill through the frame and outside mount Nema 23s with isolation couplers!
Is there anything in particular you’d check?
I like the idea but need to think more about the specifics. I might need to make a custom ballscrew bearing assembly and get some unusual machining done to the ballscrew to make that plan work…
I haven’t looked into it more than a quick google, but some variant of this looks almost like a drop in replacement. Am I hoping for too much?
My concern with that style of motor is that I’d like to put substantial axial load onto the screw and these motors either have no ratings or low ratings for axial load.
For example this listing gives an axial load rating of 25N/65N push/pull. Have a look at my cut from earlier and you can see that I easily exceeded 25N.
Compare that to the fixed support I used for my Z-axis: the load ratings are in the kilonewtons.
Ah, that explains it. I noticed in the product page you linked that they had ratings for single- and double-side support, which got me thinking: would it be doable to mount the integrated ball screw style with proper support at the opposite end of the motor?
I think from a physics perspective that should work but in order to put the other end of the screw in a fixed support, you’d have to get some custom machining done to the screw. I’m not sure whether that would be feasible, as it’d be difficult to put the assembly (including the stepper motor housing and ballscrew nut) into a lathe and I’m not sure if you can safely remove the ballscrew nut. You’d have to get the machining done prior to assembling the motor.
@Vince.Fab which screws/nuts specifically did you use? I detached the X-axis nut so I could easily get a look at the carriage and it looks like the cutout for the nut is 20mm wide. You said earier that you used 1204s like I did, were you able to find 1204 ballnuts with a 20mm diameter?
Hmm, I found a 12mm ballscrew with a 20mm diameter ballnut, the complication is that the pitch is only 2mm. I suppose the issue is that the higher pitch screws have physically larger bearings inside, and so need a larger diameter housing to contain them.
At the higher feedrates I’d be able to run with this spindle (e.g. the 3600mm/min I did before), I think I’d need to make bigger changes to accommodate this screw. 3600mm/min with a 2mm pitch is 1800RPM from the stepper. The stepper I used for the Z-axis can do it but torque would be ~0.2Nm.
I also looked at the various dimensions and given I have the most space to spare on the outside of the Nomad’s enclosure, I think the inside would just have the fixed support for the ballscrew. The ballscrew end would protrude out and I’d put the coupler and stepper motor on the outside of the enclosure.
Something like this:
I also stumbled across these sexy things and I’m thinking of swapping out my stepper drivers (again) and going closed-loop. I think I can make enough space between the stepper housing and the coupler to fit an encoder. A 14-bit encoder is ~$50 and those drivers are hella expensive but I’d be able to reuse them if I end up upgrading to servos one day.
Or I could go straight to servos…
If you have the means to re-work the end of the screw (usually hardened to > 55 HRC), you could do that mechanically, but then you would have two fixed supports taking axial loads. You might get away with it, but that is not good engineering practice, because any kind of minor variation (thermal expansion of the base plate when the machine heats up, tolerance stack-up) will create very large stresses in the screw and bearings.
