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  #1  
Old Mon 20 October 2008, 14:53
boutzo869
Just call me: boutzo
 
ohio
United States of America
Required Torque for possible upgrade ??

I am currently deciding wheter or not to upgrade the motors of my current machine (Digital Tool DR-903). It's an older machine. I am currently cutting 1/2" MDF with a 2 flute 3/8" bit in one pass at 60 ipm (Probably wrong setting). My motors are Pacific Electric 466 oz/in unipolar with a 8:1 gear reduction running at 1/2 step (controller also ancient). Is there a formula to calculate what torque is needed to cut 1/2" MDF in one pass. I'm asking because I want to know if I want to upgrade my motors and controller and possible reduce gear reduction to say 3.6:1 what type of motor would be best while keeping top speed of 300 ipm (if I could increase this all the better).


Sorry if this is to vague I'm in a rush to get this out. If anymore info is needed please let me know.

Thanks,
Boutzo
  #2  
Old Mon 20 October 2008, 15:01
boutzo869
Just call me: boutzo
 
ohio
United States of America
By the way I'm running a 5hp Perske spindle 19,000rpm
  #3  
Old Mon 20 October 2008, 15:56
Marc Shlaes
Just call me: Marc
 
Cleveland, OH
United States of America
Send a message via Skype™ to Marc Shlaes
This is probably the wrong forum for this type of question. This forum is dedicated to the building of the MechMate CNC router (and the crazy crop of characters who dare to do it!)

The CNC Zone is more appropriate for that type of question.
  #4  
Old Tue 21 October 2008, 08:00
boutzo869
Just call me: boutzo
 
ohio
United States of America
I understand. Would love to build one as a second machine I have the space and need). The reason I ask is that the mechanics are similar, rack and pinion drive stepper motors ect... According to what I've read with a 8:1 gear reduction, thats 8x the torque. Is that overkill for what I'm doing. I noticed on Geralds youtube videos he's machine is cutting MDF. Just trying to get someone to cite examples. I've gotten alot of useful info from this site in understanding the pricipals of this kind of drive system with steppers. I will try the cnczone. I just thought someone here could help out using MechMate as an example.


Thanks again,
Boutzo
  #5  
Old Wed 22 October 2008, 08:04
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
It's hard to recommend the size of motors on dissimilar machines. If your machine has similar mechanical resistance to mine, then you should be able to cut 1/2-inch thick MDF easily at 300 inches per minute using a spindle and a two flute cutter with steppers that put out at least 600 oz*in. That's how my machine was first configured. The motors were 1:1 at a little less than 600 oz*in.

If you change your motors and drive your motors with Gecko stepper drivers, with the power supply properly sized and configured to let the motors give all that they can, you should be able to easily cut at 300 inches per minute,

With my current setup, I've cut 1/2-inch MDF at much higher speeds than 300 ipm. My current motors put out about 1,300 oz*in maximum with their mechanical gearing. My spindle pulls a "smallish" 5.75 Amps when making a full through cut, so, according to a HP/Amps chart, that is less than 2A from my 240VAC power.

Using a chipload of 0.015 to 0.020, I normally run the feed speed at about 540 to 600 ipm with the spindle set to 15,000 RPM. Tool life for a 3/8-inch spiral 2-flute cutter is about 40 to 60 sheets of material at those speeds.

With a 3.6:1 gear ratio, a 1.5" pitch diameter spur gear (30-tooth) and Gecko stepper drivers, 600 inches per minute only requires a stepper pulse train of about 12,000 pulses per second.

The PK296A2A-SG3.6 motors are limited in their torque by the gearbox, but a standard PK296-03A motor attached to a 3.6:1 belt-drive system would put out about 1,000 oz*in of holding torque when wired half-coil. The larger PK299-03A motor would put out about 1,800 oz*in of torque. The PK299-03A motor would require a 35VAC toroidal transformer to output about 50VDC. The motor is rated at 4.5A, so the VA rating of the 35VAC transformer without derating would be about 650VA; however, a 500VA transformer should be adequate. With Gecko G203v stepper drivers and Mach 3 properly setup (acceleration, top speed, etc.), the Oriental Motor PK299-03A with belt-drives would be a heavy-duty high-speed performer.
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