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Author Topic: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?  (Read 21206 times)

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I got a  Model BR2J Vertical Milling Machine with  1 - 1/2 HP  that my dad left me, I was advised not to use the 3 steppers (1.8 degree - 1600 OZ/inch )  that I have, due to lack of power. Can this be right, the motors really look quite impressive with a little over 12 pounds each.  I really would like to hear what the more successive combinations have out there ?

Leif

« Last Edit: September 19, 2012, 03:41:16 PM by Gropper »
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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #1 on: September 19, 2012, 03:58:07 PM »
1600 oz-in should be more than adequate for a BP.  That won't be enough to move the knee without retaining the bevel gear drive, and adding another 4:1 or greater belt reducer.  But it should be quite adequate for X, Y and quill.

Regards,
Ray L.
Regards,
Ray L.
Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #2 on: September 19, 2012, 04:20:26 PM »
successful combinations .... not successive combinations.... could that be the spell checker ...probably not  .  Thanks to Ray for the fast reply,  Ill start make the stepper mounts then, and set the thing in motion HUH......
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Offline olf20

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #3 on: September 19, 2012, 07:43:07 PM »
I used 1200 oz in stepper on my 9 x 54 Knee Mill. It does not
have ball screws yet. My power supply is 72 Volts with Gecko
201's. Not a rocket ship but very stable.
olf20 / Bob
Mach3, Atlas Knee Mill, 4th Axis, VcarvePro, ESS, Super PID.
Been Heating with corn since 1998
Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #4 on: September 20, 2012, 04:19:21 AM »
Hi,

Well...do you think the ”reduced” speed was due to lack of torque or just too few impulses per minute from the controlling soft / hardware Bob ?  Maybe you used micro stepping in some form which can really reduce speed a lot.  Can you give an estimate on the table speed in feet per minute with those 1200 OZ/in

Leif
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Offline Hood

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #5 on: September 20, 2012, 05:02:05 AM »
Steppers are not fast on this type of machine when you compare to servos. It will be however fast enough for most, the downside to me of steppers is the low acceleration when compared to servos.
Ok what I had, on the first mill I did, a manual Bridgeport converted to CNC, was 916 ozin steppers geared 2:1, I then got the CNC Bridgeport and used the same steppers but it already had 2.5:1 reduction so I kept that.
Both of these had more than enough torque and rapids achieved were 2500mm/min  @ 40mm/s accel or 2200mm/min @ 100mm/s. I settled on the latter as accel is much more important than rapids. If you have servos of the correct size then you can have both for example I can get in excess of 6000mm/min @ 800mm/s acceleration. So steppers are fine for most but doesnt matter what size you will nt get lightning rapids or acceleration.

Hood
Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #6 on: September 20, 2012, 05:56:45 AM »
Hood,

I only intend to use the mill for smaller items ( 5x5x10 inches ) so the speeds you indicate are  fine…. Anyway I can se the servos is necessary for professional use when time matters.  Ill give those 1600 OZ/in steppers a chance now that they are at hand my friend. Did you get a huge improvement in accuracy with the second machine  ( Bridgeport CNC )  I guess it had real ball spindles  ?

Leif
« Last Edit: September 20, 2012, 06:07:40 AM by Gropper »
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Offline olf20

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #7 on: September 20, 2012, 07:03:53 AM »
I'm don't know the ft / min but the motors were 1:1 via timing belt.
I'm not getting much speed from the motors (rpm low) so I
purchase pulleys to give me a 2:1 reduction.
I talked to several vendors and posted on here on the forum
before the conversion and all agreeded that the 1200 would
do the job. I'm not dissatisfied with the setup just fine tuning.
I have not had a chance to install them yet due to building a
new building and moving our business.
Hope to get back to this soon.
olf20 / Bob
Mach3, Atlas Knee Mill, 4th Axis, VcarvePro, ESS, Super PID.
Been Heating with corn since 1998

Offline Hood

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #8 on: September 20, 2012, 07:07:11 AM »
Both mills had balscrews as I fitted them to the manual mill when I retrofitted it.

BTW you do want to use microstepping, Gecko say 10 is optimum.
Hood
Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #9 on: September 20, 2012, 10:36:13 AM »
Hi,

I don't really know if Ill microstep the BP  Hood, Ill lose speed and who knows.... Probably also a bit of torque, and that ain't good in this setup, but Ill try it if the resolution is to coarse.

I'm looking forward to hear about your project olf20

All the Best
Leif
« Last Edit: September 20, 2012, 10:50:40 AM by Gropper »
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