Some Questions

[691175002]

Hi, I'm interested in the KFlop board as an alternative to mach3. Given the insane capabilities of the hardware and software, being able to buy a KFlop for 250$ is an incredible deal.

I am a little confused as to how the built in control loops of the KFlop board interact with external servo amplifiers.

If I am using gecko/DMM tech servo drivers, do I ignore all the servo/control loop tuning stuff and just output step/dir pulses?

Would there be an advantage to installing a second encoder or providing encoder feedback to KFlop even when using an external driver?

If I am using a servo for the spindle motor, does KFlop require encoder feedback for rigid tapping?


It feels like having KFlop manage the servos directly is a better option, but using two snapamps would be overkill and expensive for a benchtop mill.

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[arvidj]

+1 on these questions. I feel a KFlop is the best solution for me and I am very interested in the offerings ... though have not actually contacted them yet ... from DMM.

I am also making the assumption that I will be able to mix a DMM servo solution on the X-Y-Z axis and a stepper solution on rotary table with a KFlop.

Arvid

[TomKerekes]

Hi Arvid,

Yes you can mix and match various motor and amplifier types for each axis. For Step/Direction drives they are basically open loop from KFLOP's perspective so all the Servo Tuning Parameters are not used.

Instead of adding a second encoder to feed position back to KFLOP you can probably just parallel the existing encoder back to KFLOP. This allows KFLOP to monitor the position and following error. This allows fault detection so the system will stop if the following error gets big for whatever reason. Another advantage is fault recovery. After a fault the commanded (Step/Dir position) can be set to the Encoder postion to resync everything to where the tool really is.

Probably not applicable for you but another possibility is to add a linear glass scale and feed that position back to KFLOP. KFLOP can then make adjustments to the commanded Step/Dir position so the table in in the right place with respect to the glass scale.

Regarding Rigid Tapping: the Z axis can be slaved to either the commanded position of the Spindle or the observed encoder position of the spindle. If your Spindle servo works well there should not be a big difference.

HTH
Regards

[arvidj]

I feel bad about asking questions ... I am not trying to hijack the thread and will start another one if offends anyone ... but until then ...

The mill already has linear glass scales on it for the DRO so the question then becomes how to create a parallel interface that will feed both the DRO and the KFlop. And in my opinion that would be the best of both worlds ... with the servo\encoder combination providing the major movement and positioning "unattended" with the KFlop handling the details.

I believe the scales have TTL outputs as the DRO specs is for TTL Square Wave input and the following suggested specs for the scales … power voltage: +5V; signal; TTL square signals are send out from two channels with a phase difference of 90° (with zero position signal); current: 50 mA.

I am wondering if an additional buffer would be required to provide the electrical drive necessary to feed both the DRO and the KFlop.

[TomKerekes]

Hi Arvid,

Good question. I don't know that I have a definitive answer but here are some thoughts:

#1 - I'm not sure why the DRO is really needed as the Encoder position can be displayed on the PC.

#2 - Our KFLOP only has single ended encoder inputs (our Kanalog and SnapAmp options provide differential inputs). The inputs are high impedance (meg ohms). So if placed in parallel with the DRO it will not necessarily provide a double load. But some moderate termination (pull down) resistance should probably be added (maybe 400 ohms) to reduce ringing and add damping.

#3 - US Digital sells some low cost (~$15) cable options to buffer encoder signals. Some of their encoders output fairly weak TTL signals that only pull up with 400uA of drive so they sell cables with drivers built in. They also sell modules to convert single ended to differential and also differential to single ended receivers.

US Digital | Products » EA Incremental Encoder Adapter


Regards

[691175002]

Thanks for all the great answers so far. The more of the documentation I read the better the board looks. I am really looking forward to writing some C, Mach3 scripting was painful.

Does KMotionCNC support software limits?

Can the encoder inputs be used for an MPG? Would you have to pretend the MPG is an axis to read the encoder?

[TomKerekes]

Does KMotionCNC support software limits?

Not directly, but it can be done with a User program. The simplest seems to be to create Virtual Limit Bits that can be configured as normal Limit inputs.

Can the encoder inputs be used for an MPG? Would you have to pretend the MPG is an axis to read the encoder?

That is possible. Typically MPG inputs are fairly low resolution and slow enough that they can be monitored (counted) in software. That way any 2 KFLOP inputs can be used so one of the 8 dedicated hardware encoders or Axis Channels is not consumed to maintain the MPG position. User programs basically run at a 5KHz rate which is usually fast enough for MPGs. If the rates are faster we have a software trick that determines how many quadrature changes were missed based on current speed. It works amazingly well up to nearly 100 KHz.

You can download our software, run KMotion, goto the C Programs Screen, and open the MPGSmooth.c example.

[arvidj]

As mentioned earlier I am in the "virtual" phase of a conversion of my mill to CNC. As such am trying to virtually put together the pieces before I commit real money to real products. And therefore end up asking a lot of "how well might this work?" questions. I appreciate everyone's patience.

I am under the impression there is a need for CAM functionality between my CAD program and the KMotionCNC software and ultimately the KFlop. My current preference if to us MeshCAM. Does anyone have any real world experience with this environment … or lacking any real world feedback would anyone like to speculate on how well that scenario might work?

Regretfully the documentation on the MeshCAM site is pretty sparse so even putting the pieces together on paper is difficult.

Thanks,
Arvid