advice for new KFlop-based router?

[justin.good]

Hello all,

I am planning to build a 48x48" movable gantry cnc router, using linear bearings and ballscrews. Very little else has been settled. I have no sketches to show you, but assume it will be the "high-walled" variety.

I have no experience with cnc, so I'm not tied to Mach3 or any other particular hardware or software.

I am leaning toward using the KFlop.

Although my intent had been to use steppers and a G540, none of that has been purchased and I'd like to solicit advice from the KFlop experts about the optimal setup for a new build.

I'm interested to hear about motor and driver choices, router vs spindle cutters, linear encoders, and any other sensors or safety equipment people wish they had baked into their original designs. I'm also interested in fabrication strategies. If possible, I'd like to keep my initial build robust but simple, and allow for addition of new features later. Perhaps everyone says that.

Thanks for your time!

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[TomKerekes]

Hi Justin.good,

This would be a hard question to answer because you describe so many topics and haven't really given any specifics on speed, accuracy, cost, application, etc...

But my suggestion would be to go with our KFLOP+KSTEP. The G540 is a great amplifier and can be used, but KSTEP is lower cost, allows bigger motors, eliminates most of the wiring, more efficient, and is basically plug and play with KFLOP.

We've tested it working well with these reasonably priced motors and a low cost 36V or 48V regulated supply.

http://www.kelinginc.net/KL23H2100-50-4B.pdf

HTH
Regards
TK

[czralv]

Hello all,

I am planning to build a 48x48" movable gantry cnc router, using linear bearings and ballscrews. Very little else has been settled. I have no sketches to show you, but assume it will be the "high-walled" variety.

.

That's very similar to what I'm doing, except I'll use Rack & Pinion on the X and Y axis. Same size, linear bearings, etc. but what is "high-walled" variety ?

[justin.good]

.

That's very similar to what I'm doing, except I'll use Rack & Pinion on the X and Y axis. Same size, linear bearings, etc. but what is "high-walled" variety ?

I simply meant the variation where the x-rails are higher than the bed, so that the gantry "legs" don't need to be tall. For instance like a mechmate. The most commonly cited drawbacks of this approach are the increased difficulty in loading materials from the side, and the potential for decreased Y travel (because the z-carriage may hit the sides).

I still haven't decided for sure on this approach, it just seems more rigid.

Good luck on your build czralv!

[justin.good]

Hi Justin.good,

This would be a hard question to answer because you describe so many topics and haven't really given any specifics on speed, accuracy, cost, application, etc...

But my suggestion would be to go with our KFLOP+KSTEP. The G540 is a great amplifier and can be used, but KSTEP is lower cost, allows bigger motors, eliminates most of the wiring, more efficient, and is basically plug and play with KFLOP.

We've tested it working well with these reasonably priced motors and a low cost 36V or 48V regulated supply.

http://www.kelinginc.net/KL23H2100-50-4B.pdf

HTH
Regards
TK

Well I'm sold on the KFlop+KStep if it does what KFlop+G540 would have done but with easier integration. Also, I've heard good things about the Keling motors, so that makes perfect sense.

As for more specifics on my requirements... The machine would primarily be used for wood (both carving and cutting), some foam (for casting), but also some aluminum. Precision is more important to me than speed. My budget is a few thousand US dollars.

[ltran2000]

No one will beat the performance,price,support,reliable of Kflop+Kstep, I built 4 routers ( 4'x8') base on kflop+kstep, have no problem at all, no lost steps and so reliable.

[justin.good]

I'm hoping to get some input on either immediately incorporating or allowing for the future integration of encoders. I've read Tom talking about this, so I have the impression that KFlop can handle encoders and they do in fact help stepper accuracy. However, I'm not clear on whether linear or rotary encoder are best, and bear in mind my x and y are 48" so linear might get expensive. I'd love to hear sources for these parts too!

[TomKerekes]

Hi Justin.good,

Either type of encoders can be added later. It isn't common to add linear encoders to large routers. I think this is because of the cost and probably little benefit over encoders on the motors. Even though some errors such as lead screw errors might be eliminated, other errors such as those in the structure and linear rails and so forth will not be corrected and are probably more significant.

The main benefit of adding encoders is for immediate detection of errors (following errors) and stopping. An error in motion might occur for a number of reasons: Stepper Stall, Stepper Misstep, axis binding, programming error causing a crash, amplifier fault, etc... Without any feedback an open loop system will usually just keep running the remainder of the job causing all manner of damage. With closed loop if an axis fails it will be quickly be detected and the system will stop. It is likely there will still be some defect in the part but much less overall damage.

A second benefit is to be able to recover from errors without having to re-home or re-reference the axes. The encoders will keep track of the actual position.

Another benefit that is overlooked is diagnostic information. If you build up a system and have problems without any feedback you are basically operating in the dark trying to find the problem. With encoders it is like having a built in scope to show you exactly where, when, and how the problem is occurring.

HTH
regards

[spank]

Tom,
I am looking at ordering some new motors in the next few days that have some encoders attached, and the ones I am leaning towards have these characteristics:

Encoder Feedback Type: Incremental
Two feedback resolutions: 200 and 400 pulses/rev. (leaning towards 400pulses)
2-channel or 3-channel

Can Kflop accept 3 channels? Is 400 pulses/rev enough resolution?

[TomKerekes]

Hi Spank,

Higher resolution is better unless you exceed the 1 MHz count rate of the KFLOP encoder Inputs. "pulses" is always confusing whether it means cyles or quadrature counts. KFLOP counts 4 quadrature counts for each complete cycle.

1MHz at 400 cycles/rev woul limit the max speed to:

1MHz/400/4 x 60 = 37,500 RPM

so choose the higher resolution.

Purchase encoders that have differential outputs if possible.

The 3rd channel is usually a Z index pulse that occurs once per revolution. You can connect this to KFLOP if you need it. It can be connected to any spare input.

HTH
Regards

[spank]

Thanks Tom. 400 count it is then.

[spank]

Tom,
You mentioned differential outputs if possible for the encoders, but is it a problem if the Encoders are TTL?

[TomKerekes]

Hi Spank,

Differential Driver outputs are like two complementary TTL outputs. So there are A+ and A- and B+ and B- outputs. That is the most flexible because they can be connected to differential inputs or to single ended inputs (by just not connecting the A- and B- signals).

Single ended connections are more noise sensitive than differential connections.

KFLOP by itself only has single ended inputs. So if you are connecting directly to KFLOP's single ended inputs you could just use single-ended TTL output encoders - but later if you change your mind and decide to go differential it will be more difficult. So my suggestion is if you are buying encoders and it is only a few extra dollars go for the differential option.

HTH
Regards
TK

[justin.good]

KMotion supports 8 axes, but KStep supports 4.

If I wish to have two motors for the X axis (plus one each for Y and Z), then the KStep is fully consumed. In this case, what do you recommend for a fifth rotary axis? Assuming that I will never need more than 5 axes on this machine, should I just add a Gecko?

[ngr1]

Is it possible to use the kstep without the kflop? If so how and is it really advisable to do so? Thx.

[spank]

Justin,
You have all kinds of drive options for your 4'th axis. I'm assuming you won't have a terribly large motor driving that axis, and that gives you some flexibility with regards to choice. You can get away with something less expensive than a Gecko if you want. These are good for example:

Intelligent Motion Systems Inc IM483 IMS | eBay

[TomKerekes]

Is it possible to use the kstep without the kflop? If so how and is it really advisable to do so? Thx.

It probably doesn't make a lot of sense to use KSTEP without KFLOP. A main feature of KSTEP is to eliminate all the wiring hassles of wiring up multiple drives to KFLOP. You just plug it on and you are ready to play. The additional I/O (16 optos, 2 relay drivers, and analog output) would be difficult to use without a KFLOP.

But that being said, pretty much any 3.3V TTL Step/Dir source could be connected to KSTEP.

Regards

[ngr1]

Thanks for the feedback Tom. I would only consider any combination of equipment that is approved or endorsed by the manufacturer like yourself. When you say "any Step/Dir source could be connected to KSTEP" does that mean you would support a common break out board (BOB) like the C10? If so can you also provide wiring diagrams for mating your product with others?

Ultimately I am try to decide between your KSTEP without KFLOP, the G540 and the chinese drivers you find on ebay like
Stepper Motor Driver DQ542MA:Stepper Motor Driver DQ542MA wholesaler

Thx.

[justin.good]

Again on the topic of adding additional drivers beyond the KStep, does dynomotion recommend any particular brands or at least particular characteristics that we should look for? For instance, would a Keling KL-5042 be any better or worse than a Gecko G250X, with respect to maximizing the potential of the KFlop? If so, why?

[TomKerekes]

KFLOP has a problem with drives like Keling KL-5042 because they specify that they require 5us of Direction setup time before any Step Pulse. KFLOP only provides a maximum of 4us. One User tested it and there didn't seem to be any problem but I can't recommend operating something out of specification. Another User with similar drives put in a Schmitt Trigger RC Circuit to delay the Step Pulse by ~2us to put it within specification.

There are no problems with any of the Gecko Drives.

Regards