School me on the best machine for big hardwood

[bluesking]

Hi Voicecoil, thanks for your help.

My advice if you're going to build your own is to go for a "raised side rail" arrangement, as then it's pretty easy to make the gantry detachable which would obviously help with moving the thing.

By "raised side rail" Im guessing you mean something like Washout's machine (https://www.youtube.com/user/CCWashout/videos). Doing this seems to trade gantry weight for base weight, which sounds like a good idea for general performance but doesn't that just put more weight on the already heaviest section when it comes to transportation?

But even so, I wouldn't be expecting the base part of anything that's properly rigid to be a one man lift - however if you're making one yourself you can of course build in handles/lifting points and provision for mounting it on a dolly or similar.

I needed to hear this, even if I didn't want to! My best hope I think is to rely on modular design so I can dismantle the base into components for transportation purposes. At least then I know I won't find myself stuck somewhere.

I've also had a word with my pal Mike Vanden, one of the best archtop luthiers in the country, and he said don't get too hung up on feed rates as with some fancy hardwoods you can get a poor cut if you go too fast - he tends to work his Isel machine at 2000mm/min tops on standard wood and less if doing fine work on brittle stuff. A lot of the problem is that wood isn't a completely even material and some hardwoods are a bit on the brittle side; if you hit a hard spot/twisty bit near a corner on the end grain you can easily take a wee chip out of the edge. Using downward spiral cutters and machining the end grain first can help obviously, but won't solve everything all the time.

I appreciate that advice. I am not an arch top builder - just carved tops for me. I use everything from angle grinders to French curve scrapers to fashion my tops at the moment - inconsistency in wood density and fibre is par for the course. I can't speak for Mike Vanden, only for myself, nor can I put numbers to any of my naive expectations, but I will continue to assert that I do want this performance for my top carving: https://www.youtube.com/watch?v=LLNeA1oUCGc

Although servos have better torque at high rpm than steppers that doesn't mean you can't make a machine that goes fast enough for your kind of work using steppers, it's just a matter of getting the design right, there's a very useful motor/ballscrew calculator on this forum. And then there's now the closed-loop steppers available which are kind of a half-way house.

Sounds reasonable. I think I need to spend some time comparing torque curves. Whilst I'm comfortable with HT voltages from my valve amp work, Clive's talk of NEMA 34s and HT voltages is freaking me out from a complexity point of view.

I've just read about ClearPath servos, is that what you mean by closed-loop? I'm starting to understand there are a few more shades of grey between stepper and servo than I'd initially thought.

[Voicecoil]

Hi Voicecoil, thanks for your help.

By "raised side rail" Im guessing you mean something like Washout's machine (https://www.youtube.com/user/CCWashout/videos). Doing this seems to trade gantry weight for base weight, which sounds like a good idea for general performance but doesn't that just put more weight on the already heaviest section when it comes to transportation?

Yes, something like that, though if it were me I'd have tall side rails fixed to the base all the way along rather than perched on blocks - that way they add good longitudinal strength which will win you back a fair bit of the extra weight.Even without taking account of that they need only add 10Kg or so. And the gantry won't be overly light either - with a decent spindle and z-axis, around 30Kg or more is likely to be where it's at.

I needed to hear this, even if I didn't want to! My best hope I think is to rely on modular design so I can dismantle the base into components for transportation purposes. At least then I know I won't find myself stuck somewhere.

I reckon you could get the base part (assuming it''s a table-top thing) to be a 2 man lift - all you need then is a fit mate to help you for an hour or 2. And like I said before build provision for some handles into the design then it will be A LOT easier to move

I've just read about ClearPath servos, is that what you mean by closed-loop? I'm starting to understand there are a few more shades of grey between stepper and servo than I'd initially thought.

It wasn't the Clearpath units I was meaning, but they are another shade of grey - and likely easier to use than a classic servo from what I've just read. Closed loop steppers are a stepper motor with an encoder on the back which gives feedback to make sure it got to the target position - check out brands like Leadshine and Lichuan.

[bluesking]

It wasn't the Clearpath units I was meaning, but they are another shade of grey - and likely easier to use than a classic servo from what I've just read. Closed loop steppers are a stepper motor with an encoder on the back which gives feedback to make sure it got to the target position - check out brands like Leadshine and Lichuan.

I think I understand. Something like this?
https://www.cnc4you.co.uk/Stepper-Mo...-Servo-Kit-4Nm

Clearpath do seem attractive as they are proper servos which should easily drop in place of a traditional stepper. One caveat seems to be that they are not well suited for use where multiple motors serve a single axis - though they do provide closed loop control, this control loop never exits the motor, so synchronising multiple motors seems impossible/difficult.

[Voicecoil]

Aye, they're the things - a lot cheaper on Aliexpress though! When I get my machine finished I'll bum a bit of hardwood off Mike and see how smoothly they cut it.Theoretically I can't see that there would be a lot of difference between a Clearpath and a closed loop stepper, but as always the devil will be in the detail which in this case will be the algorithms in the driver modules.

[bluesking]

Aye, they're the things - a lot cheaper on Aliexpress though!

Indeed, I'm trying to plan my build around locally sourceable components. I'll buy them from china when I'm ready but I want to know that I can fallback to something local if it gets me out of a jam or around a big delay.

When I get my machine finished I'll bum a bit of hardwood off Mike and see how smoothly they cut it.Theoretically I can't see that there would be a lot of difference between a Clearpath and a closed loop stepper, but as always the devil will be in the detail which in this case will be the algorithms in the driver modules.

I would appreciate that hugely. I assume your build is using closed loop steppers?

I'm seeing the following shades of grey at the moment:
1) open loop steppers
2) closed loop steppers
3) closed loop steppers with integrated control (e.g. https://www.zappautomation.co.uk/electrical-products/integrated-motors/integrated-easy-servo-motors.html)
4) servos with integrated control (e.g. clear path or something like this https://www.zappautomation.co.uk/electrical-products/servo-systems/integrated-servo-motors/syint080-750w-integrated-dc-servo-motor.html)
5) traditional servos (controlled from a controller)

Here is a very useful thread on this forum - clarified a lot about servos for me:
http://www.mycncuk.com/threads/11096-Advice-on-buying-servos