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  1. #11
    Hi Voicecoil, thanks for your help.

    Quote Originally Posted by Voicecoil View Post
    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?

    Quote Originally Posted by Voicecoil View Post
    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.

    Quote Originally Posted by Voicecoil View Post
    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

    Quote Originally Posted by Voicecoil View Post
    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.

  2. #12
    Hi bluesking

    I can see why you want to go for larger cutters and for roughing I would agree, however there is another factor to maybe consider dependant on the guitar design/type you are looking to machine. I'm sure you're aware that most routed pockets on say a Les Paul or Telecaster are a. imperial, but b. also are designed for a set of cutters that have certain corner radii e.g. 1/8 inch which means using a 1/4 inch cutter for most humbuckers. So you may be able to rough out the pockets with an 8-12mm cutter, but will have to do a tool change and a clean up operation with a smaller cutter to clear out the corners.

    Also I am using 70v nema 23 steppers on my machine and it easily goes to 15mm depth per pass and I could make that 20mm without too much if any additional tool wear - see here: https://youtu.be/WVf5J8XytSA

    BTW if you want the CAD for a "normal" Tele I have that linked in video #9 of the series above. There's a thread on here somewhere as well, as it was a kind of community project.

    Chris
    Last edited by Washout; 18-04-2019 at 11:06 AM.

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  4. #13
    Quote Originally Posted by Washout View Post
    Hi bluesking

    I can see why you want to go for larger cutters and for roughing I would agree, however there is another factor to maybe consider dependant on the guitar design/type you are looking to machine. I'm sure you're aware that most routed pockets on say a Les Paul or Telecaster are a. imperial, but b. also are designed for a set of cutters that have certain corner radii e.g. 1/8 inch which means using a 1/4 inch cutter for most humbuckers. So you may be able to rough out the pockets with an 8-12mm cutter, but will have to do a tool change and a clean up operation with a smaller cutter to clear out the corners.

    Also I am using 70v nema 23 steppers on my machine and it easily goes to 15mm depth per pass and I could make that 20mm without too much if any additional tool wear - see here: https://youtu.be/WVf5J8XytSA

    BTW if you want the CAD for a "normal" Tele I have that linked in video #9 of the series above. There's a thread on here somewhere as well, as it was a kind of community project.

    Chris
    Hi Chris,
    In my experience, traditional LP and tele style guitars are designed to be cut using 1/2" diameter cutters - you can cut pickup cavities, neck pockets and control cavities all using a 1/2". This is also true for a basic Strat design too. It is certainly true for my own designs, which are my focus.

    Good to know what sort of cutting performance you are achieving, the results look good. My biggest focus is on top carving - in fact I only went down the CNC path after deciding that I would build a duplicarver for this job alone - and realised that it would be crazy not to look into CNC. Do you have any example of top carves you've produced on your machine?

    Thanks for the CAD link, can never have too much source material.

  5. #14
    I don't have any drop/carve tops yet, but do have the design run up for an RG/Super Strat custom design with a carve which I'll be cutting, once I have finally finished my AS Tele project. The strategy I'll be using for that will be similar to the video you linked, but will use Fusion 360's Adaptive (trochoidal) clearing rather than a traditional slot/side milled waterline strategy. The reasons for that are that it vastly reduces tool and machine wear and you can run at very high speeds (with careful tuning) - you can see the strategy at work on that Tele video when its roughing out the front side cavities where I'm running at approx 3,500mm/min on a single flute cutter, but could increase that dramatically using 2, 3 or 4 flute cutters.

    The carve will then be "smoothed" out on a finishing pass using a ballnose cutter of 8+mm, which should then only leave light sanding. You can see some of that in the neck cutting videos on my channel.

    The "problem child" cuts for guitars are the final cut outs I've found, where unless you have the room for "adaptive clearing" in a gutter around the body shape, you'll be using slot milling, which means reducing the depth of cut, as it tends to brutalise the machine and cutter otherwise. Doesn't mean it won't do it, but it just takes a lot longer than adaptive clearing. Again you can see the slot milling cut near the end of that video to compare feeds and speeds.

    Hope that helps.

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  7. #15
    Quote Originally Posted by Washout View Post
    I don't have any drop/carve tops yet, but do have the design run up for an RG/Super Strat custom design with a carve which I'll be cutting, once I have finally finished my AS Tele project. The strategy I'll be using for that will be similar to the video you linked, but will use Fusion 360's Adaptive (trochoidal) clearing rather than a traditional slot/side milled waterline strategy. The reasons for that are that it vastly reduces tool and machine wear and you can run at very high speeds (with careful tuning) - you can see the strategy at work on that Tele video when its roughing out the front side cavities where I'm running at approx 3,500mm/min on a single flute cutter, but could increase that dramatically using 2, 3 or 4 flute cutters.

    The carve will then be "smoothed" out on a finishing pass using a ballnose cutter of 8+mm, which should then only leave light sanding. You can see some of that in the neck cutting videos on my channel.

    The "problem child" cuts for guitars are the final cut outs I've found, where unless you have the room for "adaptive clearing" in a gutter around the body shape, you'll be using slot milling, which means reducing the depth of cut, as it tends to brutalise the machine and cutter otherwise. Doesn't mean it won't do it, but it just takes a lot longer than adaptive clearing. Again you can see the slot milling cut near the end of that video to compare feeds and speeds.

    Hope that helps.
    Thanks Chris,
    A little over my head! I'm certainly no CNC expert, my work to date has stopped at the CAD point (using CAM only for inlays and fret slots). I know I'm probably putting the cart before the horse but I need a machine that will be capable of working in a way I understand - I've clearly got a lot of learning ahead of me.

    Worst case scenario, if I can at least automate template production I will already be way ahead. My latest design takes me a couple of weeks to manufacture by hand - I'm not expecting it to jump off the CNC ready for finishing:

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    If I can cut the time down to 1 week I will be happy, but I need a machine that will bend to my needs rather than vice versa.

  8. #16
    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.
    Last edited by Voicecoil; 18-04-2019 at 01:40 PM.

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  10. #17
    Quote Originally Posted by Voicecoil View Post
    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.

  11. #18
    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.
    Last edited by Voicecoil; 18-04-2019 at 08:37 PM.

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  13. #19
    Quote Originally Posted by Voicecoil View Post
    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.

    Quote Originally Posted by Voicecoil View Post
    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
    Last edited by bluesking; 18-04-2019 at 10:48 PM.

  14. #20
    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!
    Last edited by bluesking; 20-04-2019 at 01:46 AM.

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