What can I do with this motor?

[walter]

It`s DC servo, brushed (pics attached)


Torque stall 200 oz/in Cont
Max Speed 4500 rpm
Max Voltage 100 V dc
Current Const 8.22 A
Current Peak 26.62 A
Tachometer 7 V/Krpm
Encoder 1000 L
Connector 16 pin

Can I use this to direct drive medium to large sized router (4tpi leadscrew)?

Thanks

[Evodyne]

Walter,

I've got several of these Baldors. The Stall Torque spec is a bit confusing on these. Here's why: they are telling you the motor can draw a max of 8.22 amps of continuous current without overheating. That's why it called continuous-you can run the motor at that level all day long and not stress it. Now at that 8.22 amps (when running at the rated voltage) the motor will generate 200 oz-in of torque. This value ought to just be called continuous torque (without the "stall" term). Their wording stinks.

Stall torque is the torque the motor generates when driven at it's rated voltage (the voltage that gives the rated speed) and you stall it (duh!) by not allowing the shaft to turn. In that case you will draw the peak current of 26.62 amps. You can't run the motor very long like this without burning it up. When stalled and drawing it's peak current the motor will generate it's Stall Torque figure (cause it's stalled-again duh). This is NOT the 200 oz-in value! Torque is proportional to current. So if it's 200 oz-in at 8.22 amps, it will be (26.62A/8.22A)*200 oz-in or just about 650 oz-in at stall. Granted, you can't do it for too long, but if the mill hangs up on something while running at a low torque, it will load up and "push through" the tough spot at a higher torque and then return to whatever low value it was at originally. Also the ability to generate the high torques will give great accelleration.

You will not be able to directly couple the motor to your screw. Instead you'll use some amount of speed reduction. Say you want 200 inch per minute rapid speeds. For every inch of travel your 4 tpi screw needs 4 rotations. So to go 200 inches in one minute is 800 revolutions of the screw-800 rpm. But say your motor can hit 3200 rpm. That's four times too fast, so use 4:1 speed reduction via toothed pulleys. Guess what? A four to one speed reduction also gives a four times increase in torque at the screw! So your motor looks like an 800 oz-in motor when idling along at it's continuous rating and, if pushed, looks like a (650 oz-in * 4) 2600 oz-in behemoth.

Good motor? Great motor. Go for it!

Evodyne

[walter]

Wait a minute...I know that face! It`s the Terminator head from 2004 IMTS Show in Chicago! I`ve seen it on Wire EDM floor .


But anyway...

Thanks for quick reply. First I thought the motors might be NEMA 23 so I planned to use them with Gecko 320/340 on smaller router. Then I realized it`s NEMA 42 & and a lot more more torque. The price is right so it got me thinking...
I could use the motors for small and larger router projects. So right know I`m wondering if Geckos can handle this motor, Gecko is 80V max. Can you comment on that?

Thanks again.

[Evodyne]

Originally Posted by walter Wait a minute...I know that face! It`s the Terminator head from 2004 IMTS Show in Chicago! I`ve seen it on Wire EDM floor .

No, unfortunately a farm accident involving a combine left me severely disfigured. I actually look just like the picture.

But anyway... Thanks for quick reply. First I thought the motors might be NEMA 23 so I planned to use them with Gecko 320/340 on smaller router. Then I realized it`s NEMA 42 & and a lot more more torque. The price is right so it got me thinking... I could use the motors for small and larger router projects. So right know I`m wondering if Geckos can handle this motor, Gecko is 80V max. Can you comment on that? Thanks again.

Sure man! Voltage is essentially top speed. So if you run lower you go slower. Do you have the rest of the specs? You can figure out the top speed at 80 or 75 VDC. The specs are available from Baldor's web site if you do a bit of poking around. Once you pick a voltage (lets say 75 VDC), it defines the torque, speed, and current curves you'll run at. Those are nice motors-you can derate a bit and still have plenty of power. Or look at Rutex drives-you can hit 100 VDC with them. How many of these puppies have you got?

Evodyne

[walter]

Yeah, I would use 75 VDC max with Geckos. Good enough for me. Just wanted to know if Geckos are suitable before I write the check. Price would be around $250 a piece (shipped). I`m not sure.

I`d limit work to 60 ipm and rapids to 150 ipm. Don`t need speed- just enough torque to move 100 pounds and ability to work 24/7


If you`re positive about Geckos(320/340) then I guess my only question is about motor power consumption and cabling- do I need to hunt for original cables with 16 pin connectors? Any way around that?

Thanks for all your help.

[Evodyne]

Walter,

I've used the stepping motor Geckos and I love them. I'll be in the market for some servo drives from them soon myself.

I've been looking for a simple/fast/cheap way around those connectors myself. I've got several other motors, so for me the answer is simple: I'm going to sell off my Baldors. Mine actually are NEMA 23's-they are rated at 80 oz-in vs. the 200 oz-in ones you have. Your probably better off to bite the bullet and get the right connectors-once you make them up they ought to be just about bulletproof.

Evodyne

[Mariss Freimanis]

The motor will work with our drives but the encoder may be a problem:

1) 1000-line. This will give 4,000 steps per revolution. Your motor is rated at 4,500 RPM at 100VDC; at 72VDC you'll get 3,240 RPM or 54 revs per second. It will take 216,000 steps per second to get that speed.

2) Encoder power. Our drives can supply only 50mA to power the encoder. This works very nicely with US Digital encoders. Your encoder is probably going to draw a lot more current at 5VDC.

Both are good reasons to replace the encoder. A good resolution would be a 200-line encoder. This would allow full speed with Mach3 and the G320 can power it directly. Otherwise it is a very nice motor; calculations show 480 Watts of power (2/3 HP) at 72VDC. That is about two to three times the power you can get from a step motor.

Mariss

[Evodyne]

Mariss,

Is there an advantage to replacing the encoder to a lower count unit vs. going to a G-340 with the step multiplying enabled? Intuitively to me the two choices seem to get you to the same place.

Evodyne

[walter]

Thanks a lot for your help, much appreciated.

I`ll still use Geckos, not sure about servo motors though. Baldor 1000 line differential encoder needs 80 mA - Mariss was right. I`ll investigate new encoders and mounting options or abandon closed loop system altogether and go with Gecko stepping drives. I`m getting very impatient

Cheers

[Evodyne]

Walter,

You can always power the encoder from a separate supply and feed the A and B outputs to the Gecko.

Evo

[walter]

Originally Posted by Evodyne Walter, You can always power the encoder from a separate supply and feed the A and B outputs to the Gecko. Evo

Which ones? I`ve got AB and A(-) B(-).

Here`s the whole list :

channel A
channel A-
channel B-
channel B
channel Z
channel Z-
(brake)
+5vdc
COMMON
(brake)
encoder shield
tach shield
tach ccw+
motor ccm-
tach ccw-
motor ccw+




EDIT: Never mind. 1000 line encoder is no good. Just read about Mach software 45000 steps limit. This equals to 165 ipm max. Not bad for $250, but somewhat limiting.

Thanks anyway. Appreciate the help!

[Evodyne]

Walter,

Ignore Z's, A(-) and B(-)

From the G-3xx manual....

STEP 1: ENCODER HOOK-UP

The encoder must be at minimum a 25 line-count digital quadrature encoder and must operate on a single +5VDC power supply. If the encoder supply current is more than 50 mA, use an external +5VDC supply. It may have an INDEX output, which will not be used. If it has differential outputs, use only the “+” phase outputs. IMPORTANT: Connect a 470-ohm resistor from TERM. 6 to TERM. 7 if an external power supply is used for the encoder.

(TERM. 6) ENC- Connect the encoder power supply ground to this terminal.
(TERM. 7) ENC+ Connect the encoder +5VDC to this terminal
(TERM. 8) PHASE A Connect the encoder phase “A” to this terminal
(TERM. 9) PHASE B Connect the encoder phase “B” to this terminal

Evodyne