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James Webster
Registered
Username: Wti
Post Number: 31
Registered: 02-2007
| | Posted on Tuesday, April 03, 2007 - 07:26 am: | 
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I just saw some PK296-01aa Motors for $45 at All Electronics:
http://www.allelectronics.com/cgi-bin/item/SMT-96/search/HEAVY-DUTY_2-PHASE_STEP PING_MOTOR_.html
These sell for $139 direct from Oriental, so these may help out somebody. |
fabrica
Registered
Username: Daya
Post Number: 320
Registered: 10-2006
| | Posted on Tuesday, April 03, 2007 - 09:27 am: |
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James, Are you sur that they are brand new and without defects.If so I would not mind buy a few. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 1210
Registered: 11-2005
| | Posted on Tuesday, April 03, 2007 - 10:18 am: |
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The PK296-01AA has 50% less torque than the PK299-01AA. The difference is the length of the armature (rotating permanent magnet) inside - the higher torque motor has double the armature length of the smaller one. |
James Webster
Registered
Username: Wti
Post Number: 32
Registered: 02-2007
| | Posted on Tuesday, April 03, 2007 - 04:48 pm: |
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Yes, they are brand new and without defects. We order from AE all the time. Shipping is a flat $7 no matter how much you order from them (more for international, of course).
I compared the 2 motors on Oriental's web site and saw the difference in torque. I figured that some people are going to build a MM and not need anything more that the PK296-01AA, like people who will go Plasma, Laser or maybe even a conventional router.
If I were on a budget, I would trust these Oriental motors over some "no name" Chinese steppers any day. |
Mike Richards
Registered
Username: Richards
Post Number: 101
Registered: 05-2006
| | Posted on Tuesday, April 03, 2007 - 07:23 pm: |
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Trying to determine whether a motor is 'big enough' to do the job depends on a lot of factors. Personally, I like a motor that delivers about 200 oz*in of torque minimum at the RPM that I will use with the motor; then, I'm counting on multiplying that 200 oz*in by using a 3:1 belt-driven gearbox. That will give me about 600 oz*in of torque. Using a 30-tooth spur gear will give about 1.57" of linear travel per rotation of the shaft (using a 3:1 gearbox). With a desired feed speed of at least 6-ips, that means that the motor's shaft has to turn 3.82 times per second, or 229 RPM. Then, when we look at the charts, the PK299-01AA motor shows about 175 oz*in at that speed. It's a little light, but not too much. A point of interest is that the PK299-01AA motor produces a LOT less torque at that speed. It comes in at about 75 oz*in. In fact, at speeds over 100 RPM, the PK299-01AA motor sheds torque rapidly. So, for direct-drive applications (without a gearbox), and at speeds upto about 4-ips, the PK299-01AA motor is a powerhouse. Even, the little PK268-02AA motor, when used with a 6:1 gearbox, will perform very well up to about 500 RPM, which means that it will produce 600 oz*in (with a 6:1 gearbox) up to about 6.5-ips. However, the PK268-02AA has a 1/4-inch shaft and, because of its small size, it gets hot in a hurry - there's just not enough mass to radiate the heat away from the motor.
There are a lot of motors and a lot of choices. Frankly, almost any modern motor is probably usable if you know its torque curve and know how to best use its power. |
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