Author Topic: Problem with upgrade nema 23 to nema 34  (Read 5119 times)

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Offline kri5too

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Problem with upgrade nema 23 to nema 34
« on: September 21, 2016, 06:40:50 AM »
Hello. Im quite a new in this field and my english is not so good, sorry about that :) But i hope i can get some knowledge here.

My setup
I have three axsis woodcutting machine. 1.2m x1.2m
All axes are using Nema 23 3nM 4.2 Amps motors that are directli connected to leadscrew  1 rev=5mm.
Im using  Leadshine DM556 Digital Stepper Driver Max 50 VDC with 5.6A drivers and Ethernet Smoothstepper.
Power is connected with two 48v 5A supplyes  to din rail = 10 A
Everything worked well , i got 6000mm/min feed.

Now i made changes. I replaced nema 23 with nema 34 8.5nM 5A to axis x . With 1/3 gear to leadscrew.
And there is the problem, i will get only 7000mm/min feed. So it is only 1000mm/min more than with nema 23 and no gear.
If feed is more than 7000mm/min then the motor stalls.
I changed pulse width, microsteps, but i cant get higher results :(
Can someone help me? What to do? What to check
« Last Edit: September 21, 2016, 06:43:34 AM by kri5too »

Offline Tweakie.CNC

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Re: Problem with upgrade nema 23 to nema 34
« Reply #1 on: September 21, 2016, 08:38:40 AM »
I am confused about your 1/3 gearing. Is the maximum rpm of your NEMA 34's now lower or higher than the maximum rpm of your NEMA 23's ??

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline kri5too

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Re: Problem with upgrade nema 23 to nema 34
« Reply #2 on: September 21, 2016, 09:09:30 AM »
Its is lower.
With nema 23 it was 1revolution -5mm move (6000mm/min)
With nema 34 it is 1rev -15mm move . (7000mm/min)travel speed.
The problem is that i cant get feed over 7000mm/min,because the motor stalls.
How is it possbile,where is the mistake ?
« Last Edit: September 21, 2016, 09:12:28 AM by kri5too »

Offline Tweakie.CNC

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Re: Problem with upgrade nema 23 to nema 34
« Reply #3 on: September 21, 2016, 10:57:21 AM »
So your NEMA34’s are stalling out at around 500 rpm.
Your gearing has increased the torque required to drive the axis by a factor of 3 and my best guess would be that your motors do not have quite enough torque at that particular rpm (I am assuming you have increased the DM556 current setting to match the NEMA 34’s current rating).

Just my opinion…

Possibility of mid-band resonance but this could easily be ruled out by attaching a small (reasonably light-weight) flywheel directly to your motor shaft. This would alter the mass of the armature and if the behaviour of the motor was different (different point of stall) then I would investigate fitting the proper dampeners to your motors.

Alternately reducing the up-gearing would reduce the required axis torque. This would increase motor rpm (reducing motor drive torque) but I would expect >1000 rpm from those motors when driven at 48 volts.

Tweakie.
« Last Edit: September 23, 2016, 10:37:16 AM by Tweakie.CNC »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline kri5too

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Re: Problem with upgrade nema 23 to nema 34
« Reply #4 on: September 21, 2016, 11:37:25 AM »
I also tried 1/2gearing.Same results motor wont go over let say 500rpm .

Offline garyhlucas

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Re: Problem with upgrade nema 23 to nema 34
« Reply #5 on: September 21, 2016, 05:44:41 PM »
You don't mention the inductance rating for the Nema 34 vs the Nema 23. If the Nema 34 are high inductance compared to the 23s the torque will fall off faster. I drive low inductance Nema 34 with 68 volts and get over 1500 rpm with no problems.

Offline RICH

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Re: Problem with upgrade nema 23 to nema 34
« Reply #6 on: September 21, 2016, 06:54:38 PM »
Gecko Drive site has  a lot of "basic" information on steppers that is worth reading.... better word would be studying.
In that info you will find answers to your questions / concerns.
I highly recommend the reading.

RICH

Offline kri5too

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Re: Problem with upgrade nema 23 to nema 34
« Reply #7 on: September 22, 2016, 05:31:51 AM »
Inductance  is 11mH±20%(1KHz)