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  #1  
Old Mon 17 October 2011, 19:19
telah
Just call me: telah
 
quebec
Canada
G540 with KL34H260-35-4B

Greeting,

I have been browsing thru those forum for about 6 month's in the hope of one day start working on my own mechmate to replace my current cnc machine.

Me and a friend finally decided to seriously start putting on paper everything that we need to build one and see if we possibly can reuse stuff we already have in hand.

We are currently using a G540 with a 24V power supply to drive 4 small nema24 stepper, for sure the powersupply will need to be upgraded and the nema24 are way too small to drive the mechmate.

I was thinking of reusing the G540 and get 4x KL34H260-35-4B
you can see the spec here the motor is a nema34 rated at 3.5A with an inductance of 4.2mH which make it perfect for the G540. the downside is the torque is only 465 oz-in... but the price!! 69$ each

after seeing a couple post on belt reduction drive, I was wondering if those motor would work on a mechmate using a 4:1 ratio to increase the torque.

my concern on this would be
1. will the speed be reduced too much to be efficient to drive the mechmate properly?

2. are those motor with the belt reduction drive going to be strong enough for the mechmate or they will most probably overheat or die prematurely?

3. Are we going to sacrifice too much trying to save money ?

and last question is about the powersupply, would a 48V 12.5A be a good choice if this setup work ?

this forum as been an inspiration for so long and all the information in there is just gold, can't wait to start getting my hand dirty

Luc
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  #2  
Old Mon 17 October 2011, 21:03
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
With a 4:1 belt, you have 465 * 4 = 1860 oz-in. That will be fine. The torque value would only be questionable if you ran without the belt reduction.

There should be no heat problem with that motor paired with a G540.

You should use a power supply in the 40v+ range. Experience has shown that a 300VA supply is sufficient for a mechmate; 300VA / 40V = 7.5A and 300VA / 48V = 6.25A; thus a 48V 12.5A supply is arguably overkill and would work well; 48V, 8A would be sufficient.

I don't see a sacrifice, provided that you have costed out and planned the belt drive build, and you are comfortable with it.
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  #3  
Old Tue 18 October 2011, 08:24
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
I agree with Brad about the power supply. Anything in the 40VDC to 50VDC range will work very well. Remember that the G540 is limited to 50VDC.

My test bench theories are based on tests, not on long term usage. I would prefer a 500VA toroid transformer, although I have used a 250VA without any heat problems. A 30VAC transformer will give you about 42VDC. A 33VAC transformer will give you about 46VDC.

Be sure to use enough capacitance to smooth out the ripple. You'll need 15,000uF to 20,000 uF, depending on how hard you push the motors. On one test bench, I use 11,000 uF, which seems to work very well with most of my testing.

On actual projects, I like to use the calculated values, rather than the test values, so if I were building a controller for those motors, I would use a 30VAC to 33VAC 300VA or 500 VA transformer and at least 20,000 uF 65V (or higher working volts) capacitance.

Speed should not be a problem. Mach3 can easily send 45,000 pulses per second on most computers. A 1.5-inch pinion gear (30 tooth) moves 4.7124 inches per revolution. When geared down 4:1, it moves 1.1781 inches per revolution. The Gecko requires 2,000 steps per revolution, so it will move 0.000589 inches per pulse. Multiply 0.000589 by 45,000 pulses per second and you get 26.5072-inches per second. A 1.25-inch pinion (25 tooth) will give you 22.0893 inches per second. With proper ramp settings, you'll have more than enough speed.

(I always limited my jog speed to 12-inches per second. Hitting the stops with a geared motor really makes a lot of noise. Limiting the speed gave me time to hit the emergency stop button when I realized that I'd put the wrong values in my cut file.)
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  #4  
Old Tue 18 October 2011, 10:14
telah
Just call me: telah
 
quebec
Canada
Thank you so much both the quality awnser, I am really happy that we will be able to keep some of the stuff we already have do drive it

when we start building I will make my own thread to post picture and will provide performance result.

Luc
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  #5  
Old Thu 01 March 2012, 08:32
telah
Just call me: telah
 
quebec
Canada
bit of update on this...

When I went to place the order I was informed that those motor are not available anymore...

I could not find any nema34 motor that run under 3.5A with enough holding torque and within the inductance required for the G540, so I decided not to use the G540 as it restrict me too much on motor selection.

from the research I did so far and experience with some provider, I really want to stick with Kelling as it the 5th time I buy there and never had any issue, i'll never buy from china again I only had but trouble with product from there.

the 2 motors I am looking at is the 1200 oz/in that I would use direct shaft without a gearbox or beltdrive ( I could do a 3:1 beltdrive but would that be overkill? ).

http://www.automationtechnologiesinc...2120-42-8B.pdf

main issue I see with that motor is the 6.3 mH inductance? is that too high for the gecko G201X drivers?

second option is to go with 640 oz/in motors with 3:1 homemade beltdrive

http://www.automationtechnologiesinc...H280-55-4A.pdf


what in your opinion would give the best performance and quality ?

Luc
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  #6  
Old Thu 01 March 2012, 10:03
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Let's work backwards. Start with the minimum acceptable distance moved per step.

A direct drive motor will move 0.0015" per step with a 1" pitch diameter spur gear, 0.0019" with a 1.25" pitch diameter spur gear, or 0.0023" with a 1.5" pitch diameter spur gear.

A direct drive motor producing at least 600 oz*in will work (based on my Shopbot which came with direct-drive, 580 oz*in motors, and 1" pitch diameter spur gears. The stepper motors on that machine had 1,000 steps per revolution instead of 2,000, so my per-step movement was 2X larger than the figures above).

Using a 300 oz*in motor with a 3:1 belt drive will give you 900 oz*in or holding torque and 3X better per-step resolution.

My choice would be to find a motor that is similar to the Oriental Motor PK296-F4.5A motor. That motor, when wire half-coil, works very well with the G540 stepper driver if you use current limiting resistors to limit the current to 3A or less. If used with a G201x or G203v, you can wire the motor bipolar parallel and run it at 6.3A.

Other manufacturers may have 8-lead motors that have similar specifications.
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  #7  
Old Thu 01 March 2012, 10:37
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
People are using these KL34H280-45-8A And the Gecko203V drivers and they are working fine. 5N48 Volt Power Supply .
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  #8  
Old Thu 01 March 2012, 11:33
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Eeek, it's the 1,200 oz again. See here (unless the world has changed).

Looking again at Keling's page, it appears that the KL34H260-42-8A, or KL34H280-45-8A would work with the G540 (on the latter, you won't use the full current, just like with the PK296-F4.5A that Mike mentioned). You would want to beltdrive them. You could also use the larger drivers.
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  #9  
Old Fri 02 March 2012, 12:51
telah
Just call me: telah
 
quebec
Canada
Thank you all for the valuable information, so trying to make the right choice I made a comparison between the 3 motors below and still have a couple question.

1. When you say Half coil do you mean Unipolar?

2. Since I already own a G540 what is the best setup for a kelling motor with a 4:1 beltdrive?

3. Would I get a benifit by putting the G540 on the side and buying 4 203V gecko drive ?

it look like the KL34H280-45-8A in parallel on 203V drive with a 3:1 belt drive would be the ideal setup, am I wrong ?



PK296-F4.5A

Connection Torque oz/in Torque N/m A/Phase VDC Res/Phase Inductance
Parallel 440 3.1 6.3 1.4 0.24 1.5
Series 440 3.1 3.18 2.8 0.96 6
Unipolar 310 2.2 4.5 2 0.48 1.5

KL34H280-45-8A

Connection Torque oz/in Torque N/m A/Phase VDC Res/Phase Inductance
Parallel 640 4.5 6.3 2.3 0.71 2.2
Series 640 4.5 3.2 4.5 1.42 8.8
Unipolar 465 3.2 4.5 3.2 0.36 2.2

KL34H260-42-8A

Connection Torque oz/in Torque N/m A/Phase VDC Res/Phase Inductance
Parallel 400 1.6 6 1.6 0.27 1.65
Series 400 1.6 3 1.6 1.08 6.6
Unipolar 282 1.2 4.2 1.2 0.54 1.65
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  #10  
Old Fri 02 March 2012, 14:02
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
We mean BiPolar Half Coil, but you can use the UniPolar numbers. UniPolar drivers use 6 wires, and turn alternate half coils on and off. BiPolar drivers use 4 wires, and reverse the polarity of a single coil. If that single coil is a half coil (which is what we recommend), then you still have effectively a half coil on at a time, which is electrically equivalent.

Unless there is some budgetary reason to do otherwise, I'd run the KL342H280-45-8A on the G540, and I wouldn't worry about 3:1 vs 4:1 - build whichever is easier.

If for some reason you're unhappy with the performance, which I think is unlikely, you could do a later upgrade to the 203V or 201x drives, and you aren't out any money.
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