[jossa]

hi, i might be a complete tool for asking this.

is there any way to get a feedback signal from a DRO with glass scales?

i am thinking that my DRO PROS 3M kit might be able to relay the position of the table back to kflop and make it like a closed loop stepper motor system..



anyone know anything about this?

[TomKerekes]

Hi Jossa,

Good question. I did some Googling and I wasn't able to determine if the DRO PROs readout box has an encoder output.

If the readout doesn't have an output you might use KFLOP/KMotionCNC/Mach3's PC display instead. Or find a way to parallel the devices.

The Glass Scales seem to be standard digital quadrature that could be connect to KFLOP.

Glass Scales

Here is some info on KFLOP's Enoder inputs:

Dynomotion Motion Control Boards for CNC Manufacturing and Robotics Applications

Regards

[jossa]

So if i include some Dsub' for my 3 axis scales in my controller box and wire it like the document below says, it might work?
http://web5.streamhoster.com/HVP/DROPROS/DSub9.jpg



would this give any added accuracy? i can only imagine it would since it should track the table and indicate if it is out of position.

[TomKerekes]

Hi jossa,

Yes you would need to determine what type of encoders you have TTL or differential RS422 and interface it appropriately.

This could potentially increase the accuracy significantly as it virtually eliminates lead screw errors. However the overall accuracy is dependent on many things so it is hard to give a definitive answer.

Regards

[jossa]

DRO pros confirmed that it was a TTL output.

so that means that the Kflop is all that is needed?


also, the Kstep, how does it compare to a Digital hybrid driver like one from Leadshine/Geckodrive?
thinking smooth running and low resonance (like in this video: https://www.youtube.com/watch?v=iryj1bJlAd4)
(yes i am a Noob with steppers, But i want the "best" so i only need to buy once for my SX3 setup)

[TomKerekes]

Hi Jossa,

DRO pros confirmed that it was a TTL output. so that means that the Kflop is all that is needed?

That is correct. You should be aware single ended signals are less noise resistant than differential signals, so take care on shielding, grounding, termination, etc...

Kstep, how does it compare to a Digital hybrid driver like one from Leadshine/Geckodrive?

Those are better drives than KSTEP. But read this post.
http://www.cnczone.com/forums/dynomo...ml#post1478248

Most Leadshine drives require 5us of direction setup time which is incompatible with KFLOP (KFLOP provided 4us max).

HTH
Regards

[jossa]

so what i learned from the thread is that the cheep china supply's are not the best? and a good Switch mode is better then a unregulated transformer...



i was thinking of using this kit G540 4-Axis ? NEMA23 381 oz in ? NEMA34 906 ozin ? PSU 48V/12.5A | Automation Technology Inc

do you see any downsides to that?
the idea was to use the Kflop and the g540 together like this guy does..
http://www.cnczone.com/forums/dynomo...lpt-mach3.html


the reason behind my thinking is that in this kit the motors draw more amps then the 5A that the kstep can deliver... am i missing something here? (i relay want to use the kstep for the simplicity, but as far as i can see it is not big enough for my application.. tho i might have misunderstood something here)

[TomKerekes]

Hi jossa,

i was thinking of using this kit G540 4-Axis ? NEMA23 381 oz in ? NEMA34 906 ozin ? PSU 48V/12.5A | Automation Technology Inc

Yes that looks like a good kit. I would recommend it and it will work well with KFLOP.

the reason behind my thinking is that in this kit the motors draw more amps then the 5A that the kstep can deliver... am i missing something here?

Yes you are missing something KSTEP can provide more current than the G540. 5A vs 3.5A. But those motors only draw 3.5A anyway.

Regards

[jossa]

Wait what? How can you see that?

How many amps does the nema 32 motor draw at max then? And that would work on the kstep?


Just when i thougt i was beginning to understand this, boom i don`t :-P

[TomKerekes]

Hi jossa,

see:
NEMA23 381oz/in 3.5A Dual Shaft Stepper Motor KL23H2100-35-4B | Automation Technology Inc

KSTEP can drive these 3.5A motors.

Regards

[jossa]

now i see.. there are datasheets for the motors! nice

but the NEMA 32 motor in that kit (for my Z-axis) is thisNEMA34 Stepper Motor ? 906 oz in 6.1A Single Shaft (KL34H295-43-8A) | Automation Technology Inc and it is rated for 6,1A.. unless it is wired in series @ 3,05A

what would that mean for the performance of the stepper/setup?

[jossa]

now i see.. there are datasheets for the motors! nice

but the NEMA 32 motor in that kit (for my Z-axis) is thisNEMA34 Stepper Motor ? 906 oz in 6.1A Single Shaft (KL34H295-43-8A) | Automation Technology Inc and it is rated for 6,1A.. unless it is wired in series @ 3,05A

what would that mean for the performance of the stepper/setup?
in the datasheet the numbers look the same, except for the current draw.

[TomKerekes]

Hi jossa,

You are correct. I didn't notice the 6.1A motor. It would need to be wired series for either the G540 or KSTEP. A series connection has higher inductance and higher back emf which causes the current (torque) to drop off more rapidly with speed for the same supply voltage.

Regards

[jossa]

so if the G540 is only capable of 3,5A per channel, that means that they intended the kit to be used with the NEMA 32 in series..

so what you are saying is at high speeds the stepper would loose momentum?
but the Z axis is maybe not the axis that needs to move the fastest? i would imagine that X and Y move alot more and faster... (the Z would be moving fast going to and from the work piece)

all in all i think it would be better to go with the Kflop + Kstep and the steppers/PSU used in the kit but bought separate and not as a kit

[TomKerekes]

Hi jossa,

so if the G540 is only capable of 3,5A per channel, that means that they intended the kit to be used with the NEMA 32 in series..

I believe they do (it is NEMA size 34 btw).

so what you are saying is at high speeds the stepper would loose momentum?

Its actually torque that drops off not momentum. In a stepper motor the current flow is one of the things required to generate torque. At high speed the drive applies the full power supply to the coil to ramp up the current. But before the current ramps up much it is already time to start reversing the current. The inductance is one of the things that limits the rate the current will ramp up. Two coils in series have 4X the inductance than coils in parallel.

but the Z axis is maybe not the axis that needs to move the fastest?

Very possible. It depends on your system, requirements, gearing, leadscrew, etc...

HTH
Regards

[jossa]

my bad.. thanks for pointing it out =)



ok, so it could potentially miss steps due to this?



Ok, so how about this:

Machine: Grizzly G0619 (aka SX3)
Leadscrews: CNCFusion delux kit for the SX3 mill

Kflop + Kstep + Independant drive for Z axis:

- X, Y and A axis of the Kstep (using an appropriate stepper not exceeding 5A per axis)
- Z axis on a separate standalone driver capable of delivering whatever the stepper needs for

All controlled by Kflop, driven from 2 different units..

could that work?






and as a separate question, does Kstep/flop support feedback, making it closed loop?
(thinking of buying steppers with encoders, if i can find that)

[TomKerekes]

Hi Jossa,

I'm not familiar with a Grizzly or Leadscrews so I can't comment on the mechanics.

Kflop + Kstep + Independant drive for Z axis:

- X, Y and A axis of the Kstep (using an appropriate stepper not exceeding 5A per axis)
- Z axis on a separate standalone driver capable of delivering whatever the stepper needs for

All controlled by Kflop, driven from 2 different units..

Yes you can mix KSTEP with 3rd party drives such as Gecko
http://www.geckodrive.com/g203v.html

You might start off with just KSTEP driving everything and if you have problems switch to parallel coils and add a higher current drive.

and as a separate question, does Kstep/flop support feedback, making it closed loop?
(thinking of buying steppers with encoders, if i can find that)

Yes, but this won't prevent stalls if that is what you are thinking.. It will detect stalls and stop. The other advantage is that position will not be lost on any type of fault making recovery easier. See:
Closed Loop Stepper

Regards

[jossa]

Thanks Tom!

i think i now have what i need and i will order the controller and driver =)




so if i focus on integrating the glass scales with the Kflop that would be time better spent?

...l

[jossa]

so the folowing is my plan..


3 of these in Bipolar Parallel (5A):
NEMA23 570oz/in 5A 1/4? Dual Shaft Stepper Motor (KL23H2100-50-8B) | Automation Technology Inc

and 1 NEMA34 1200 oz-in Stepper Motor ? 1/2? Single Shaft (KL34H2120-42-8A) | Automation Technology Inc
in unipolar making 857 Oz-in @ 4.2A (could be upgraded to 1200 oz-in with a separate driver if it is not enough)


any flaws in my plan using the Kstep with this?
(i just bought the Kflop + Kstep.. cant wait to try them out.)


what size of PSU should i use? if i add everything up i get 21A when everything is at full throttle..
biggest switch supply is 12A.. and biggest transformer @ 48V is 20A
Unregulated Linear 960W/ 48 VDC/20A Toroidal PSU (KL-4820) | Automation Technology Inc

but that is if everything is running at max capacity, witch i don't think is realistic..

[TomKerekes]

Hi jossa,

That sounds reasonable. That big high torque motor is probably limited to low speed. I didn't find a torque vs speed plot. Often we think that higher torque is better performance, but sometimes that isn't the case if torque drops off rapidly. Power is torque x speed. the 8 wires gives you 3 options:

#1 series at 3A
#2 unipolar at 4.2A
#3 parallel at reduced 5A

Parallel at reduced current might be the best option. Current at speed will drop quickly anyway regardless if the drive is set for 5A or 6A. If only 3A can be made to flow setting the drive to 5A or 6A wont make any difference. The 6A would provide more holding torque when stopped or at low speed, but that isn't usually needed anyway.

Probotix has a nice chart here:

UniPolar vs BiPolar wiring schemes for 2-phase Stepper Motors

Attachment 240992


Regarding power supply: It is more of a power thing than current. It is hard to push a lot of power into a stepper. If you choose the linear supply make sure the no load voltage is always less than 48V. KSTEP has regenerative voltage clamping so it works well with switching supplies. Again you might read this post/thread:
http://www.cnczone.com/forums/dynomo...ml#post1477470

Regards