Official Luthiers Forum!

Well, I think I have this fleshed out. I think I'm going with:

Rhino
madCAM
Mach3
KFlop controller
Gecko Drive
2kw dual BB Teckno Spindle and Hitachi VFD

I may also end up adding T-Splines to Rhino. That seems like an amazing product. We'll see what the budge looks like when I'm all through. I like the idea of KFlop. Makes selecting a Mach3 PC much simpler. Seems like any 'ole laptop would work at that point.

I don't have an PCs laying around because I'm mostly MAC now, and the ones I do have are pretty old and suspect at this point, so I have to buy computer for Mach3 AND the CAD/CAM workstations. Still, configured very nicely with a nice spindle, stands, and great software, I'm coming in right around $10,000 or $11,000. Might be a little less when I'm done...I tend to estimate conservatively, but I'm within my budget and happy.

Any thoughts on going KFlop with KStep instead of Gecko?

Your plan sounds good. The only thing I'd suggest is that you might try going with the Kflop PC back end before going to Mach 3. Mach 3 has some weirdness to it and if you can get everything you need out of Kflop's back end, there's really little reason to go with Mach 3. The double plate tool change I think is essential for a good work flow and since you have a SW background, perhaps you could even write one if it doesn't yet exist.

If you do go with Mach 3, I highly recommend Ger's screenset which can be found here: http://home.comcast.net/~cncwoodworker/2010.html it is way way way superior to the stock screenset and includes the automatic tool height macros. There's a couple mods you'll want to do to them if you use offsets a lot (e.g. G54-G59Px) but I can send you those if you need.

Finally, regarding the Kstep - at $50 less than a G540, it seems like a no brainer. If you can find 5A motors you should be able to exceed the performance of my machine. Bob uses the Kflop and has nothing but good things to say about it. I imagine that the Kstep is also of very high quality but I don't have any personal experience with it. Since your machine is bigger than mine (kinda hate saying that) if you get a good linear power supply & motors, you should be able to really take advantage of the full 5 amps the Kstep can deliver. I'm just guessing that you'd want a 20A supply but 15A might do as well. Just make sure you find steppers that are optimized for 5A@50v - ish.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

The only thing I can add to this conversation is that over 2 years ago I ordered a CNC from xzero. Most of the parts are now here but after 2.5 years still not everything has arrived. I've had numerous promises of things going to be shipped and nothing happening. George seems like a great guy and I know he would not try and rip anyone off but the delivery of xzero stuff can be a little slow....

Please take that into consideration

Matt

2.5 years?? Well, the hemming and hawing has started already. It's gone from "In Stock" to "let me see if I can get this." I think it's just the upgraded rails that I ordered, but we'll see. I don't have near the patience that some of you have. 2.5 years is incredibly excessive. How has it gone on that long?

It took me nearly a year to get everything from XZero, which is longer than I had hoped but I have no regrets. It's a great machine, and George has been an honest guy to deal with. Just a bit overoptimistic on his shipping dates. If you're in a hurry, he's probably not the best option. If you're not, it's worth the wait.

Dave

Machine rigidity is very important but after looking at the Laguna IQ Pro I'd look to the linear bearings and rails to make a general assessment of a machine. The degree to which the rails are stout, precise, straight, stable....ect. is going to determine how accurately the gantry tracks to establish a flat plane. It seems to me that if one was impressed that a company had addressed the issue of the linear bearings and rails thoroughly...it's likely they carried that attitude throughout the entire machine design.

But this comes from someone who has never really shopped for a table top cnc. Fact is....those Laguna rails strike me as cheap looking. It makes me doubt the machine is capable of tracking a super flat plane....so one's guitar necks, for instance, would be subtly less than straight. Only a few thousands potentially...and this finally might only be a matter of principle ...but if I was shopping for a machine those rails would be the FIRST thing my eye went to.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I upgraded to SBC rails. It was a no brainer. I'm familiar with SBC's products and I've always been happy.

initially i was told it could be done and ready in a month, or might have even been a couple of weeks. I will say that weekly I try and bother him for updates, I'd say that it took well over a year for the first things to arrive, lots of promises etc. for example I've been waiting for a VFD that he's apparently had for well over 6 months, and numerous other parts.

Initially I had made a couple changes to my order so that may be partly the reason for the delay, but overall its gone on way too long.
I do not want to say anything bad about George though because I feel his work is great for the money. If not for the time delays it would be by far the best deal.

Sorry my story so far has not been positive with xzero, although one day I am sure I'll have a great cnc for a decent price and a lot of patience

I'm feeling comfortable right now that things are going to go smoothly, and I'm planning a nice drive up to Canada either this weekend or very early next week.

I'm not very familiar with Kflop or Kstep. They look very intriguing but I'd check them carefully vs the standard solutions first. There's a huge user base for Gecko and Mach, too.

For Kflop, does a laptop work well via USB? The usual advice for machine controllers is to use a desktop, as the laptop's power management systems can interrupt communication. I imagine that can be disabled, but I've not looked into it.

For Kstep, does it have features like microstep selection (something less than 16), step morphing, standby current reduction, and midband resonance control?

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David Malicky

C'mon - it can only be a mater of principle. Even if you cut a neck straight down to a few 10 thousands, it's going to move as soon as the cutter stops turning

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Not sure on some of that. Looking into it I will probably go desktop, BTW. I just happened to have some older laptops kicking around. The Mach3 guys seemed comfortable that it would work fine as long as I used an external controller. Andy suggested just trying the KFlop software before even fiddling with Mach3, and maybe I will, but there's such a huge user base for Mach3 that I'd like to take advantage of that. One nice think for me is that KFlops is programmed in C (or maybe C++, I forget which). For me, that means it may well be programmed in English, and really puts me very squarely back in my software engineering/robotics comfort zone for when I get the urge to start fiddling some years from now.

Again, thanks all for the incredible advice and information. I've gone from practically no knowledge to feeling pretty comfortable knowing what to get and what to expect.

The KFLop is an actual industrial grade control, just one that happens to be at a really low price point. The communication issues with Mach and other software-based stepper controllers don't apply to hardware motion controllers, so any computer with a USB port will do the trick. Andy's right that you should just use the KMotionCNC front-end that comes with the KFlop (for free). The Mach plugin is more for people that are already using Mach and want to have a seamless transition, and from what I've seen it allows some of the issues with Mach to get in the way of your KFlop.

I don't think it's worth messing with steppers if you don't need to, just go to servos and skip the hassles. You can get motors and drives from all kinds of places, though if it were me and I had a small budget I'd use Snap Amps (on top of KFlop) and DC or BLDC servos, and if I had a bit more cash I'd probably just use the packaged AC Servo/ Drive combos from Automation Technologies.

The best dollar for dollar deal for a guy with your expertise is a used late '90s Thermwood at auction, with a KFlop retrofit which will take you a bit less time than putting together a 'kit' machine. That's the route I went this time, more or less, though I spent a bit more on linear motors for my X and Y axes than I did on the machine I'm bolting them on to. If I hadn't wanted to overdo it by about four orders of magnitude with the linear motors, I'd have a functioning 4'x4' industrial machine with three 5Hp spindles, a full sized 2" thick aluminum vacuum table, and a 5000 lb all steel frame for about $7500...the two linear motors cost me that between them, though

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

You won't need the Mach user base, it's mostly there to help people deal with the issues in Mach's mysterious settings. The C thing in the KFlop will make you happy in a transcendent way deep in your soul. It can run 7 user programs simultaneously while it's operating, and all in real time on the DSP. On the Fadal I had one thread that ran my way lube system, took input from my buttons and pendant, read switches, etc which ran in a loop. I also occasionally ran programs in the second and third thread which would log data to a text file like following errors etc so I could chart how my tuning settings were working. No idea what someone could need seven threads for! You can even do some neat things like serial comms or altering tuning settings or encoder positions etc in real time in the threads.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

That's exactly what I was thinking. Mach 3 CV mode is....well....crap and it uses "bang-bang" acceleration "curves" which are very clunky at high accelerations. There also seems to be a bug in the trajectory planner that causes the steppers to lose torque (and stall...don't ask me how I know that) in certain 3D moves but that may or may not be present when mach 3 is connected to an off board signal generator.

If I had the software skills and some time on my hand, I'd consider writing a user friendly front end for K-flop with all the features in CNCwoodworker's screenset for the K-flop. Could probably charge for it.

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http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

You know, one thing that I don't quite understand with the micro-stepping, and it's something that I've run into numerous times in the past, is that if you ever disable power to the stepper, it will end at a full step...and no way of knowing which one. You'd think that the errors would just cancel out over time and that you'll never get further than a step or two off, but that's not what happens at all. The axis do the equivalent of a "drunk walk" and tend to wander quite randomly. The only real effective solution when you power down is to make sure you've landed on a full step. Actually, you generally don't really want to hold at a micro-step either. Maybe my experience is different than what we're doing here.

I don't know enough about these controllers to really understand what they're doing, but I wonder how they handle this? I can only assume that micro-stepping is just used for smooth acceleration and motion but that actual control points end up on full steps? I would guess that functionality is buried in he control software, which is smart enough to know it's micro stepping and keeps track of such things? Is that correct or am I missing something? When I've had to write my own control software, it was pretty trivial to keep track of everything, but is that what these controllers do? I'm just curious. I'm sure it all works out fine when it's up and running.

re: setting idle current
I don't see anywhere that the idle current can be set on the KStep board, but it seems pretty trivial to add a bit of code to KFlop to PWM the enables and get whatever duty cycle I want when it's idle. That said, there are definitely some limitations in the KStep board. KFlop and Gecko may well be a better option. I'm just thinking out loud, hoping that the gurus here that have been through this learning curve continue steering me right

I'm very skittish to go servos right now. Maybe in the future. It is very tempting, though, but I really need to stay to a reasonable budget. Also, again maybe my experience doesn't transfer over and I'm off base but I can foresee spending many many hours getting everything configured and working properly, and many hours tuning the loop parameters and filters. I've done it enough that I just don't want to go there right now, and I don't think it brings enough advantages to the table to warrant it. I'm new to all of this. I need simple and straightforward to get me up and running.

What's really funny is I was looking through my goody box just the other day, and I have things like cameras, lenses, stages, vernier heads, some steppers, and even a controller. I have no idea why I have any of this stuff. I must have been using it for something at some point. I need to look at it to see what I have, but I may have a useable fourth axis kicking around and didn't even know it.

With something like Mach 3, once you power up the steppers are always powered up! According to my calcs, my machine should move around .002" with every full step. With micro-stepping I get 5 moves per thou and, it's pretty repeatable. There's a lot of discussion about the value of micro-stepping and whether it's truly valuable but I can tell you with certainty that I can get back to within +/- .005" with my machine.

If you do lose power to your steppers, YOU MUST RE-HOME.

With a quick experiment, I found that with my current homing speeds, I can only get within about .002" (in one direction, forget which - mostly it's better than .002 but that's the worst I saw after homing about 10 times) but, if I slow down the homing feed rate it's under .001. Next time I re-cut my fence, I'll slow my homing feed rate to improve that.

Mach 3 doesn't know if it's hooked up to a micro-stepping drive and in my experience, it doesn't lose position just from running. I'm sure that servos are better but you'll do just fine and be very happy if you can find some nice motors that can handle 5A @ 50v. In fact, I know a guy who might be selling some but I'm not sure if they're NEMA 23's or 34's. I can find out for you if you're interested.

There's a nice little article on the Gecko website on selecting motors. Basically, you have to find a 5A stepper who's reluctance is a match for 50v using their formula.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

I'm surprised that there is not a more intelligent home routine kicking around. For steppers, you would typically drive into the home switch (quickly), jog off and then slowly jog back onto the switch (or just simply slowly jog off and use that). Is that what the default home routine does? You end up with a much faster and more accurate home routine because the actual zeroing never takes more than than a couple of eye blinks so there's never any temptation to speed it up

If I decide to go with the KStep, I'll upgrade to some beefier motors. If I stay with Gecko, I'll just grab that combo that you pointed out. Either way, I think KFlop makes a lot of sense, and I think I will follow the prevailing wisdom here to just use KMotionCNC until there's a reason not too.

It occurs to me that this thread got away from my initial, "Hey, how are you guys liking your CNC", and got much deeper into techie stuff. I wonder if maybe it should be moved to the CNC section.

Yes, that Laguna uses profile rail for the long direction but supported round for the other axes. In the compression direction, supported round is 3x more flexible than profile rail, and probably much worse in the "pull" direction, as there's only 1 or 2 ball tracks to resist tension. Here's an Asian block showing just 1 ball track to resist pull forces: http://i01.i.aliimg.com/img/pb/439/493/ ... 39_025.jpg
I think most Thompsons use 2 ball tracks near the opening, but the design just doesn't allow a very strategic orientation of the tracks, so it's inevitably weak in tension / pull.

Probably the best way to orient supported round on the gantry is to point them up and down (away from each other); then they don't see tension, and the span between them is maximized. Still, this puts the trapezoid base in bending -- supported round is really only good in compression. Laguna points them in the same horizontal direction, with less span than space to the table --> lots of force on that lower rail.

Stuart, along the same lines as your comment, supported round is pretty forgiving of mounting surface flatness problems, while profile rail is not. So if a company is using profile rail, the mounting surfaces are probably quite flat. If supported round is used, hard to say.

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David Malicky

Thanks, Bob -- that's great info. I will study up on the KFlop. Would you know if it's a reasonably mature product (bugs have been worked out, easy to get running)?

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David Malicky

Pretty much yes, that's what it does. When you hit "home" it sequentially moves the Z, Y then X in the direction of home at some specified %-age of your rapid speed. When it hits home, it overshoots a bit and switches direction. When the home switch becomes inactive, it stops. As far as I can tell, Mach 3 uses the same speed irrespective of which direction it's going.

I think the inaccuracy is simply because Mach 3 has a lot going on and with windows not being a real time OS it just can't react fast enough. For sure, when I slowed down the homing speed I got more reliable results.

It is possible to make the machine home all 3 axes simultaneously but then you need to use more inputs on your control box. When done sequentially, you only need to use one input.

By the by, I'm using hall effect sensors from DigiKey to do my homing. I've got 3 sensors and 6 magnets. The raptor is built such that you won't damage it if you run into a hard stop, at least not with 381's on it.

_________________
http://www.birkonium.com CNC Products for Luthiers
http://banduramaker.blogspot.com

Hey John, I'm a little late to the party. I picked up my machine earlier in the year and have been gradually working it into my routine. Though my K2 isn't close to industrial caliber and I have to take things a bit slower than others may, it provides way more accuracy than I could ever achieve without it. Monday night I had it whittling away at a bridge while I inlaid side position markers on a fingerboard. I started the program, and by the time I finished the inlays, the bridge was done! It's like having a second set of hands.

I own RhinoCAD and RhinoCAM, but the CAM software is the basic version. I'd like to have some of the features of the Pro version, but I can't justify the $5K. I demo'd MadCAM for a month. In fact, the two neck programs I am now milling with were setup using MadCAM. However, the software was short in a few useability areas that kept me from buying it. A new version is being worked on for Rhino 5. If some of the annoyances go away in the next version, I'll probably pick up a copy.

Good luck!

Ken

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http://www.casperguitar.com

This illustrates the point I was making earlier. You pay more later by not paying now. Sorry Ken....it's inevitable.

Only the upper end cam programs are truly versatile to produce the toolpaths required for a guitar neck...which GUARANTEE the result. Some may argue that they get along fine with a cheaper package but when I sit down to write a toolpath, I need capabilities that GUARANTEE a cleanly produced part. It's one thing to have the basic surfacing features. It's quite another thing account for every sliver being intact when the part is complete. I hate throwing away invested time. Since building a neck compounds one's effort as the neck progresses...I take no risks and leave as little to chance as possible.

I find that having the ability to project toolpaths onto a surface is indispensable. Any cam package I use must include that. Without mentioning EVERY feature I might require and without explaining exactly how projected toolpaths are used to guarantee a result...I will say that no cam package that I've seen that HAD the ability to project toolpaths left out any other feature I needed. When shopping for cam software you'll see this feature is rarely included in the lower tier offerings of the name brand software companies.

_________________
I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic