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Author Topic: My first CNC (plasma) machine  (Read 13449 times)

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Offline stirling

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Re: My first CNC (plasma) machine
« Reply #20 on: March 14, 2015, 06:38:06 AM »
Think that will be light enough for two 1232 oz. In. Steppers to move around?  Stirling, could you nudge me in the right direction with the 23 vs 34 topic? Ive searched but cant seem to find anything on this forum comparing the two.

GENERALLY 34's have higher inductance. Therefore to realize their potential in a CNC environment you need BIG voltage drivers and power supplies. GENERALLY 34's have higher mass rotors meaning more power is used just to accelerate the motor's own rotor mass. Post your motor, drive and power supply specs and we can take a quick stab at it if you like. Curiously, I thought this was pretty well known, certainly amongst the regulars here. I'm a tad surprised no-one's stepped up.
Re: My first CNC (plasma) machine
« Reply #21 on: March 14, 2015, 11:44:56 AM »
Ok, and thank you for the help. Before I post the info, I just want to mention that I purchased them from Longs Motor off of ebay. It was a 4 axis Nema 34 kit including the motors, drivers, power supplies, and Breakout board. Also, note that the drawing of the motor has been converted to inches. I have a bigger version of this saved and will gladly send it to anyone that would like it. It was a big time saver when I was designing my machine.

Motor(s):

http://www.longs-motor.com/
Part No.:                    34HS1456
Frame Size:                  NEMA34
Step Angle:                  1.8 degree
Voltage:                       3.08V
Current:                       5.6A/phase
Resistance:                  0.55 Ohm/phase
Inductance:                  5.5 mH/phase
Holding torque:            8.4N.m           1232oz.in
Rotor inertia:                2700g-cm2
Number of wire leads:  4
Weight:                        3.8 kg
Length:                        118mm
The stepper motor is single shaft, the diameter of axle is 14mm,and the length of shaft is 37mm with 25mm length flat.

Drivers:

http://www.longs-motor.com/
DM860A
Details
Features:
l High performance, low price
l Average current control, 2-phase sinusoidal output current drive
l Supply voltage from 24VDC to 80VDC
l Opto-isolated signal I/O
l Overvoltage, under voltage, overcorrect, phase short circuit protection
l 14 channels subdivision and automatic idle-current reduction
l 8 channels output phase current setting
l Offline command input terminal
l Motor torque is related with speed, but not related with step/revolution
l High start speed
l High hording torque under high speed
 
Electrical specification:
Input voltage
24-80VDC
Input current
< 6A
Output current
2.8A~7.8A
Consumption
Consumption:80W; Internal Insurance:10A
Temperature
Working Temperature -10~45℃;
Stocking temperature -40℃~70℃
Humidity
Not condensation, no water droplets
gas
Prohibition of combustible gases and conductive dust
weight
500G

I have the dip switches set up as such:
Current: 5.7A peak 4A RMS
Pulses per Revolution: 2000

Power Supply:

The only info I could find is the power output is 350 Watts 60 volts/5.83A
Re: My first CNC (plasma) machine
« Reply #22 on: March 14, 2015, 11:46:26 AM »
Nema 34 motor size converted to inches.

Offline stirling

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Re: My first CNC (plasma) machine
« Reply #23 on: March 14, 2015, 01:09:39 PM »
Unusually for a kit, that looks to be not too badly matched so maybe you'll be fine - only one way to find out. Still think at the very least though they're massive overkill. I'll be interested to see when you're done, what accel and speeds you can get.

Ian

Re: My first CNC (plasma) machine
« Reply #24 on: March 14, 2015, 01:15:13 PM »
I was hoping that myself. I hope to also attach a spindle to this machine and route wood as well. That and I knew that my gantry was going to be heavier then most, judging by the materials I had available. Also, do you think I have the driver dip switches set properly? I think I do but, a little reassurance would help calm my nerves a little bit. Thanks again to everyone answering my new guy questions.

Offline Chaoticone

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Re: My first CNC (plasma) machine
« Reply #25 on: March 14, 2015, 01:37:42 PM »
For sizing motors I have used tools (I think it was an actual program) similar to this before but can't remember the name. http://www.orientalmotor.com/support/motor-sizing.html I would think the one at the link would be pretty good but I am guessing it will give a part number for motors they offer instead of specs. (which could vary a lot from others even if they are the same size, sometimes even from the same manufacturer). Each motor will have its own specs. (torque Vs speed curve, holding torque, etc.).   

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!

Offline stirling

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Re: My first CNC (plasma) machine
« Reply #26 on: March 14, 2015, 02:24:16 PM »
Also, do you think I have the driver dip switches set properly? I think I do but, a little reassurance would help calm my nerves a little bit.
That - as they say - is a good question. Depends on what you read and who you believe. This is MY understanding. Others may disagree.

Motors are usually spec'd in RMS. So in your case 5.6A. (if you can actually confirm that's RMS then that would be good).

IF you're FULL stepping then peak = RMS. But you're (quite rightly) microstepping so you're tending towards sinusoidal. A pure sine wave would mean to get 5.6A RMS you'd need to set 1.414*5.6 = 8 peak.
Re: My first CNC (plasma) machine
« Reply #27 on: March 14, 2015, 02:52:48 PM »
Chaoticone- That is an awesome calculator. I am definitely bookmarking that tool for future reference. Thanks alot. according to that tool I should be alright when it comes to the motors.

Stirling- I have emailed longs motor and asked about the rated current, and if it is RMS or peak current thats listed. My driver allows me to go up  to 7.8A peak / 5.6A RMS. But, that would mean I would need bigger power supplies, as they are only rated at 5.6A. I emailed longs motors and asked about the specs on it. They do not have this model on their website.

Offline stirling

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Re: My first CNC (plasma) machine
« Reply #28 on: March 15, 2015, 04:48:58 AM »
Stirling- I have emailed longs motor and asked about the rated current, and if it is RMS or peak current thats listed. My driver allows me to go up  to 7.8A peak / 5.6A RMS. But, that would mean I would need bigger power supplies, as they are only rated at 5.6A. I emailed longs motors and asked about the specs on it. They do not have this model on their website.
Leave your drives at 5.7A peak for now and see what happens with what you have. Your supplies should be fine because chopper drives will only draw 2/3 of the current from the supply that they're set to deliver to the motors.
Re: My first CNC (plasma) machine
« Reply #29 on: March 24, 2015, 04:44:24 AM »
Ok stirling, I will do that. I havnt had much time lately to work on it. Between a full time job, being a full time studenand house shopping with my wife, theres been little free time. But, I have the sheet metal for the enclosure, and the 3/16" plate for the new lighter gantry. I did find the time to start cutting it apart. This is why I only had everything tacked together. I eliminated the channels and now have the rails mounted to the much lighter square tubing. I figure changing the gantry plates from 3/8" to 3/16" will shed quite a bit as well. All the rest will be aluminum as far as the Y axis and z axis, so that shouldnt add too much weight. Im hoping to find some time throughout the week and this weekend to get some work done on it.