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  #1  
Old Sun 16 June 2013, 11:54
spank
Just call me: Spank
 
New Hampsire
United States of America
DYNOMOTION KFLOP highly recommended

Hey all, I've been hanging around this forum since the beginning, and I've always planned on building a Mechmate, and still will at some point!... but in the intervening time, I've built a couple of other machines and worked with a few different control options. The obvious two big ones were Mach 3 and Linux CNC (EMC2). My CNC partner and I used Linux CNC for a few years before switching over to Mach 3 after it just became a hassle to find hardware that would work without any issues with the Real Time processing of Linux CNC. I really like Linux CNC vs Mach as far as its interface goes, but Mach proved to be more reliable given our hardware in the end.

More recently I built a 2'x 4' machine with Vexta PK299 DBA motors, and I decided to go with Dynomotion Kflop for the control (http://dynomotion.com/). This is a dedicated control board that does not rely on the computer at all as far as sending a pulse chain to the drivers. You can run Steppers or Servos, 8 axis, and they make a bunch of peripheral boards that integrate with Kflop as well, including Kstep, which is a 4 axis Stepper driver board that can run up to 5amps per axis.

I just went with the Kflop, and I found some nice Centent CNO165 drives on Ebay for a very good price, but I know people that have gone with Kstep have been really happy. At any rate Kflop runs on C, which is intimidating to a lot of people, but the truth is I don't have any real experience with C programming at all, and I had it up and running in an afternoon after I had finished wiring up my control box. They make a plugin for Mach3 that allows people to use the Mach interface to run the Kflop board, although I think you lose the slick trajectory planning and motion algorithms built into Kmotion CNC when you do that. You do however take advantage of the clean/high volume pulse chain and real feedback loop. The motors run like silk with Kflop vs my experience with software based CNC control. I have NEVER lost a step, and it comes with its own simple CNC control software called KmotionCNC. Kflop is $249, which is quite reasonable given how solid it is and how configurable it is. What is really special about the board is that you can have a true closed loop stepper system if you attach linear scales or encoders to your machine. Depending on how you set it up, you can have the machine simply stop when steps are lost, or you can have it correct issues as it goes along (up to a point as far as how big the error is). This is something that typically costs thousands of dollars to achieve.
With the flexible C-based interface, you can really do anything you want with the board, and Tom, the guy behind all of this is incredibly responsive to questions and troubleshooting. There is a forum on CNCzone and also a Dynomotion Yahoo group that users and potential users post on, and Tom always responds within the day. That part of the whole deal is fantastic, and of course like I said, I really couldn't be happier with how smooth and reliable my machine is with this board.

It would be great to see some Mechmate users using Kflop. This forum is really the best CNC forum on the internet because everyone is dedicated to a common cause and improving upon that base. In that light I thought people here should be made aware of this terrific piece of hardware that truly ups the robustness of any machine that it is paired up with. I'm happy to answer any questions that I can should anyone have any.
Cheers,
Spank
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  #2  
Old Sun 13 October 2013, 20:20
Alan Stewart
Just call me: SOS
 
Chapel Hill (NC)
United States of America
spank,

I am still in the reading phase of my Mechmate build but I am planning to build my control box around the Kflop Motion Control Board so I was glad to see someone post about it here when I typed "Kflop" into the MM search field.

I plan to use 4 of the "standard recommended" PK296_2A-7.2 OM motors on a ~6x12' Router table.

My current question revolves around power supply and driver selection. I would prefer to use the Kstep board with the KFlop to power these motors. $200 versus 4 Gecko 203v drivers would save a few hundred bucks but will it be able to handle the motor draw.

Gearald wrote that 4 of these motors should draw about 8amps at ~35-40V which I think is in the range of the KStep board but nearing the high side.

Why do we need such high voltage and amperage on these Gecko 203s anyway? 70V and up to 7A for each motor which only needs 40V and 2A?

Kstep or Gecko?
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  #3  
Old Sun 13 October 2013, 21:02
shipbldr
Just call me: Charles
 
Maryland
United States of America
If anyone would like a deal on a Kmotion card, New in box, never installed along with a Kanalog card... let me know. We have had one sitting on the shelf for about a year.

We thought we were going to use it for a project that never got off the ground...
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  #4  
Old Mon 14 October 2013, 07:57
riesvantwisk
Just call me: Ries #46
 
Quito
Ecuador
Send a message via MSN to riesvantwisk Send a message via Skype™ to riesvantwisk
Alan,

I believe the reason why separate stepper drivers are preferred above one single board for all motors is that if one breaks you only have to buy one stepper instead of a complete board.

I do believe this is all to personal preference, budget and your own experience.

My setup is around a LinuxCNC machine, a PDX board and 4 separate gecko drivers. The reason for me is simple. I am in a country where I cannot quickly import anything and what they manufacture here is just way to expensive and bad quality. So having things separated out is a huge gain for me because I am very flexible and if really needed I can buy a local driver if really needed just on case one of my drivers die and keep working while I order a new Gecko or PMDX (takes anywhere between 2 to 6-8 weeks to arrive here).
I bought the Gecko v203 drivers because they are a couple of times over engineered making them more robust (philosophy). You don't 'need' 80VDC x 7A' but having it over engineered will help lowering breakdown of components.

Now, since you are located in the US of A, you have very quick ordering times (1-5 days??) and far more options in buying equipment. If for you something breaks down, you can properly find a replacement component somewhere in a near city. So feel free to use anything that's suitable for you.

The Mechmate was designed in such a way that it could be build and operated reliable in many countries, not only in the western countries, this is where some of the design recommendations came from.
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  #5  
Old Mon 21 October 2013, 21:46
spank
Just call me: Spank
 
New Hampsire
United States of America
I would go for the Kstep. I have nice Centent drives that can handle 80volts and over 10amps/phase, and I am at max voltage, which makes the torque characteristics of my motors much more desirable than running them at lower voltages. In your case, you don't need more than 40, so kstep represents a much better solution. If I were to do it again, I wouldn't hesitate to go with the kstep over other drives, and pick a motor that suits the amps and volts it can send out. The reason for going kstep are simple: first off, it dead simple to wire to the kflop... It just snaps on and you're done. Secondly, and more importantly, the kstep gives you the opto isolated inputs for any sensors that you may be integrating into your control. Since kflop operates at 3.3v, it is tough to find an off the shelf solution as far as integrating sensors and the like that wont fry your board. Most solutions only drop voltages down to 5v, which kflop is tolerant of, but it is not recommended. I ended up getting a Kanalog for this purpose, and I'll also use it for spindle control and any other peripherals that I want to control.... I would have saved A LOT of money had I gone with the kstep. All of that said, my Centent drives (very similar to geckos as they were also designed by Maris) are excellent, as are geckos, so it's not like you will have made a bad choice, you just ensured that you'll be spending a lot more money to achieve the same thing with more hassle.
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