Wow! That’s a lot less than the quote that I got for the 60kRPM version last December. "The price for our spindle HFP-6508-60-ER11 is 2358€ " (albeit for 1/2 the cutting force at the same MRR).
I believe that a steel adapter plate would be much stiffer (and harder to tap).
I’m not a ME, but I’ve heard from MEs that leadscrews can’t be back-driven. Wouldn’t that apply to ball screws too?
It could be that the 60kRPM model is just more expensive, or it could be that the price was for a full quote, including all the accessories.
Unfortunately, it’d cost me a few hundred euro to have it machined. For now, I’d like to make as much as I can on the Nomad itself, which means Aluminium. I’ll keep nicer materials in mind for later though. If I put rails on the other axes, I’m going to have to have plates machined elsewhere anyway.
“Can’t” is a strong word. I back-drive my lead screws all the time (moving the axes by hand), you just need enough force.
I’ve been working on the CAD and roughed out most of the important bits of the Z-axis at this point.
There’s a lot I could do to improve on this but I’m aiming to make the upgrade work with no mechanical modifications to the Nomad (it’ll just bolt on to the X-axis carriage), with parts that are machineable on the Nomad and without changing the travel of the Nomad.
But I think I’ve finally at least picked all the parts. The remaining pieces now are mainly basic stuff like adding some more screw holes and countersinks.
So…
One of the interesting things I’ve seen looking at designs for bigger CNC homebrew machines evolve is that frequently the advice to get travel + stiffness on the Z axis is to flip around the rail blocks and rails.
If you put the rails on the moving Z axis with the spindle and the rail blocks on the Z part fixed to the X axis then you can space the blocks further apart for better stiffness whilst not losing clearance, your spindle is way bigger than the XZ fixed part there, might be worth flipping those round in CAD and seeing how it looks?
My experience: Threads in 7075 and 2017 work fine, unless you want to unscrew them every day. In 6082, OK-ish, 5083 not so much. So - I’d recommend helicoils or other inserts in 5083, or if your want to frequently loosen the screws. Pre-milled plates of 7075 are not much more expensive and it actually cuts pretty nicely in the sense that for some reason it doesn’t appear to stick to the endmills as easily.
I really like your idea but I think the spindle placeholder is misleading. The actual spindle is 217.4mm end to end, so I modelled the placeholder as a 217.4mm long, 65mm wide cylinder. However the 217.4mm length includes the stickout of the ER-11 collet holder and its nut, which is ~30mm. If you take that away, the length of the spindle is ~187.4mm, which isn’t much better than the 185mm height of the X-axis carriage.
I could get that extra 30mm if I let the rail supports stick out past the spindle body but I’m afraid that might give me issues with clearing workholding fixtures at some point.
I have been thinking about whether it’s possible to extend those rails a bit more and get bigger carriages or more separation but I think to do that I really need to increase the height of the rail support plate (which can be mounted to the X-axis carriage with simple 90° brackets). I have plenty ~120mm of vertical space left.
The main reason I haven’t done that is that I’m worried about balance with the X-axis rods. Right now, even though I’m adding a bunch of weight and force to the carriage, I think the center of mass for the assembly will remain between the two rods. If I extend the rail support plate further upwards, there’s going to be a point where I create a big lever using one of the rods as a pivot point to exert force on the other.
Ah, that’s very good to know. I can only get 5083 pre-milled from my local supplier so that’s what I probably would have gone with if you hadn’t told me otherwise.
And once again you point me to a European supplier I was previously unaware of (previously Spanflug and Weerg). Shipping cost is a tad high but I can live with that.
To clear this up, here’s what that picture looks like with the a real spindle model mounted for 80mm of clearance:
Minor update: I made the various vertical parts parameterized based on height, so I can change the height of the spindle adapter plate with one parameter and the height of the rails, ballscrew and support plate with another.
I came up with this:
I’m going to try and fit longer carriages in there and though there’s not enough space for a 16mm ballscrew, I think there is space for a 20mm rail. I realized I can get 10mm more space on X without reducing working area due to the linear bushings protruding from the carriage.
And I think even if I can’t add in bigger carriages, just moving them further apart should have a huge effect, since I think it gives them mechanical advantage?
The question I’m trying to deal with now is tramming. I’m hoping this will be accurate enough that I can use what little slop remains to handle it, e.g. by putting some shims under the spindle holder.
People who’ve actually trammed a machine before, how does that sound?
Also, Mechatron is trying to sell me their gigantic KG5000 chiller unit for cooling the spindle. Can anyone with a watercooled spindle chime in on the practicality of that? Isn’t a repurposed PC watercooling loop plenty?
The HGR15 sized rails are rated for some pretty heavy loads already.
Spacing the rails and bearing blocks further apart reduces the leverage that the spindle loads have over them when loaded in X and Y. At what spacing it becomes the mounting materials which are deflecting more than the rails becomes the key question there. HiWin do publish deflection loadings for their rail blocks.
Ideally you’d want flat face contact for the spindle holder to the Z carriage, or any tramming adjustment. You can rotate this, ideally with eccentric or set-screws pushing the spindle mount to rotate into X alignment and then lock it in place with the main bolts.
The Y alignment is harder, either you rotate the X rail mountings at the Y plates or have to do things with spacers & shims. Like on the Shapeoko there doesn’t seem to be any obvious bolted joint that allows for Y alignment of the spindle bracket.
You may have trouble using all the Watts of the spindle even in a super-Nomad. Unless there’s a big saving buying it all in one go I might grab a CW3000 or clone first.
I believe Mechatron are decent enough to specify the required flow rate and supply water temp for their spindles.
HIWIN stiffness specification:
So,
It’s probably not worth spending extra effort to try and make bigger rails fit. It may be worthwhile to consider buying well-defined quality however. I’m not sure all of the aliexpress vendors know which preload class they are selling. (Tuli, that you linked to earlier, looks pretty reliable).
Thanks, that sounds like a good idea, much simpler than the things I was looking at.
I think I can deal with Y alignment where the plate attaches to the X-axis carriage. I think I’ll have to use right-angle brackets, so I can just leave a little bit of wiggle room in the holes for them.
How about a PC water cooling loop? Just a couple of radiators, fans and a pump? I’m looking for quiet and I’m afraid these larger chillers will be too loud. Have you used one? Do you maybe know how loud they are?
Yeah, that I’m definitely doing. I’m not buying random stuff from AliExpress for sure.
The problem for me at the moment si that Tuli charges a bunch for machining the ends of the ballscrews. Dold Mechatronic sells ballscrews pre-machined for a much better price but they have literally no specifications for their ballscrews…
Just in case you have not seen it, we had a thread a few months ago about the CW-3000, how loud/quiet it was with and without mods, alternatives solutions people have used, etc… It’s running near my desk as I write, after adding fan control I can’t hear the fan anymore, but the pump itself is not silent, so it really depends where your personal threshold for quietness is.
Thanks! I indeed hadn’t seen that thread. It looks like that cooler would suit me just fine. The 50ish dB you report is plenty quiet. My concern is more 60-70dB like the compressor I bought.
Have you considered an electric fan cooled HF spindle as discussed here? Their ER-20 collets would allow you to use larger cutters for higher MRRs without increasing forces.
Also please note that you can go up to 5/16" (8mm) tooling in an ER-11 collet:
Yes, I considered Sorotec’s various offerings, including the Teknomotor products. Two categories I ruled out entirely:
That left the Teknomotor electrospindles. Those looked good and I like that they have electronic fans but I noticed that they’re larger and heavier than the Mechatron spindle (4kg for 800W vs. 2.4kg for Mechatron) and when I searched around, I couldn’t really find anyone who’s used one.
I did consider the ER-20 collets. I’ve seen a bunch of my machinist YouTubers using indexable tooling and thought that surely I should have it too but when I read up on it, it didn’t seem like a clear win. The Nomad is a small machine and I don’t think I can physically fit in pieces of stock large enough to use such large tools.
As for larger endmills, that’s true but most of the endmills I’ve seen have recommended surface speeds around 500m/min, which I already get with 6mm tools at 30k RPM. And again, bigger tools work great for bigger pieces but the Nomad can’t physically fit a whole lot in there.
And I know I sound obsessed when I talk about MRR but I don’t really need anything extreme. The Nomad currently maxes out at ~0.5cm³/min before it hits its limits, which is… Insufficient… But with the new spindle, the 30k RPM alone allows me to get ~9x MRR over the stock spindle, while keeping the same cutting forces. That means a job that previously took the whole day takes just an hour now.
With a Nomad that’s no longer like a blob of jelly and the improved spindle, I might be dreaming, but it could be possible to push it to 42cm³/min of MRR (84x stock). At that point, the modded Nomad can do in an hour what takes a stock Nomad 2 weeks. That comes with peak forces of ~82N but with axes built on ballscrews and linear rails, maybe it’ll be okay?
To be clear, even if it’s possible, I don’t think I’ll routinely push the Nomad that hard, I just wanted to think about what might be theoretically possible.
And back to ER-20, I won’t have it now but since I have flexibility, I can always swap in a new spindle in the future, just to try it out.
I’ve also been tempted by the idea of some insert tooling but Luke’s very helpful post here damped that enthusiasm quite a bit;
Wouldn’t it be 3X MRR (3X Speed/Feed)?
When I put it into Millalyzer, it showed ~1/3rd of the force on the spindle even with the tripled feed rate, so I could bump up the depth of cut 3x as well while keeping the same force.
