School me on the best machine for big hardwood

[bluesking]

I've been hammering the research trying to find a reasonably simple and economical way of accessing K2 servo performance. I've managed to gather as much data as I can on the electronics in that K2 system to copy it: https://www.machsupport.com/forum/index.php?topic=462.0 (notice this post, although over 10 years old, is by yet another luthier, hint hint, nudge nudge)

Promising candidates were closed loop steppers, I think they probably offer huge advantages but I'm left unsure as to how close they would perform to the K2 I've become so enamoured with.

Clearpath servos look very simple to integrate, but if you want to buy into their ecosystem things get expensive real quick and their torque performance curves leave me questioning how closely their performance mirrors a traditional servo. (https://www.teknic.com/clearpath-acc...d-dc/#overview)

DMM kits also look good, but not cheap and it is hard to spec them for similar performance (https://store.dmm-tech.com/products/...c-servo-system)

Chinese servo/driver offerings are well priced, but scarcity of documentation, as well as the rareness of servo builds around here makes me question my ability to integrate them. (https://bstmotion.aliexpress.com/sto...d_324926.1_6_2)

Many of the above use non-standard mounts (even if they do claim to be NEMA23 compatible!) which is a ball ache for someone who just wants to get the job done.

Finally, I followed breadcrumbs from the Gecko G320X drivers used on the K2 and found this. I think its quite reasonably priced, specced similar to the K2 (just a little bit better all round) and comes as a kit, with a decent wiring diagram, and using fairly common (if American-centric) components:

https://www.automationtechnologiesin...-gecko-driver/

Theres also NEMA 34 versions, and an interesting kit with 2xNEMA23 1xNEMA34 axes:

https://www.automationtechnologiesin...3-axis-nema34/

Conveniently, the drawings show that the NEMA23 mounts are indeed standard and that the shafts are 1/4" which will make it easier to buy-in compatible pulleys for the inevitable gearing reduction.

I'd welcome any comments on these components as they are my current top pick for my machine.

One of their downsides is that I think brushed DC servos are used - so they will have a finite life, I will swallow that.

Another downside is they have no auto-tune capability, so I'll have to fiddle with trimpots and microswitches to tune them for my purposes. Luckily, I'll be coming at them armed with a few control systems courses under my belt and an oscilloscope!

[Voicecoil]

One of their downsides is that I think brushed DC servos are used - so they will have a finite life, I will swallow that

At least the brushes appear to be easily externally accessible - so easy to change I would guess.

Do those motors have integral brakes? If not, you might need to add one on the Z axis if you're going to run a big fat (end hence heavy ) spindle - servos don't have the stiffness that steppers have when the power's off, and depending on gearing etc., you might get a slowly drooping spindle when you switch off.

[bluesking]

Do those motors have integral brakes?

An excellent point which I had not considered! Unfortunately no brake.

I plan to use the following 3.5kW spindle and VFD:
https://www.aliexpress.com/store/pro...1bdf23a8f7ed5m

https://www.aliexpress.com/store/pro...2e6c275cpko9w1

At 8kg, this spindle may well cause problems.

I will most likely use a fairly high gear reduction on the Z (maybe 5:1 or even higher as compared to 2:1 on X/Y). Perhaps this will amplify any holding force/friction enough to keep it in place when powered off. If it does turn out to be a problem I guess I could always buy an external brake like this (though I won't have a convenient 24v supply for it, nor will I know how to connect it, maybe using a relay on the BOB or something...)
https://www.zappautomation.co.uk/24v...brake-2nm.html

I'm also not particularly happy about the C10/C11 breakout board that comes with the kit. The wiring diagram is a bit scant and I am not sure it has all the features I need for spindle control - and I don't know what a charge pump is, or if I need one, but it doesn't seem to have one.

If I am feeling up to it I may use the kit as an inspiration to piece together my own system using some more custom parts - but I'm already overwhelmed by the complexity of all this!

you might get a slowly drooping spindle when you switch off.

That's what she said

[Voicecoil]

FY! a charge pump is an electronic circuit that's usually used to generate a low-ish power but higher DC voltage from the existing DC supply using capacitors, rather than an inverter/transformer/boost converter arrangement - e.g. generating 10V from a +5V supply.

That's what she said

lol

[bluesking]

I've created a build log where I can press ahead with my ideas: would welcome any more comments you guys may have!