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Author Topic: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?  (Read 21345 times)

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #30 on: October 12, 2012, 11:31:25 AM »
Those steppers will work, but their performance, particularly in terms of rapid speed, will far well short of stellar.  Those motors are VERY high inductance, which, on it's own, severely limits top speed.  Further aggravating the problem is the fact that the power supply, at only 60V, is WELL below the ~150V required to get the best performance those motors are capable of.  My guess is you'll probably be limited to rapid speeds well under 100 IPM.

Though the drivers allow micro-stepping up to 256X, this is essentially useless.  You'll want to use the 8X, or at most 16X setting, to keep your pulse rates reasonable.

Regards,
Ray L.

Yes,  after making the adaptors I tested the maximum speed and I don't get more than 420 RPM on the steppers, so I guess the only thing one can do here is changing the pitch on the ballscrews or accept the speed that they are cabable of right...  Maybe 3 new controllers will improve on things ?

All the best to you guys.....

Leif

Changing the screws will likely not help, since faster screws will require more torque at ALL speeds.  High voltage controllers *might* help, and might not.  Your problem, as pointed out earlier, is those very high inductance motors.  Replace them, and you should get dramatically improved performance.

Regards,
Ray L.
Regards,
Ray L.

Offline BR549

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #31 on: October 12, 2012, 07:37:43 PM »
HOW fast do you think you need to go ? That would be about 84IPM ?

Just a thought, (;-) TP

Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #32 on: October 13, 2012, 12:39:28 PM »
Hi,

Id like to go from one end of the table to the other in about ten seconds, in rapid,  but i m beginning to understand that Ill need servos for this kind of performance ......

Leif
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Offline BR549

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #33 on: October 13, 2012, 12:53:23 PM »
Hopefully you realize that BP kneemills were never designed to go that fast. You end up wearing out the machine in a hurry or possibly twisting the ball screws.  Certainly you cannot cut that fast with a 1 1/2 hp slow spindle.

Sometimes you have to step back and think about what you are trying to do.

Just a thought, (;-) TP
Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #34 on: October 13, 2012, 12:59:55 PM »
You are right TP .... Maybe I just expext to much after looking at those Utube videos shoving Japanese CNC machines :-)

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 #35 on: October 13, 2012, 01:57:49 PM »
All depends if its a retrofitted manual or a CNC from the start. Not sure what the Servo Driven BP's do but my Beaver Mill was 8m/min rapids.
Hood
Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #36 on: October 14, 2012, 06:47:34 AM »
Quite impressive speed ......1/3 of that would be nice on my oldie....

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 #37 on: October 14, 2012, 07:26:23 AM »
Rapids are very nice to have but not when its at the expense of acceleration. With a servo system you can  have both, with a stepper you cant, certainly not on a Bridgeport sized machine.
On my Bridgeport when I had steppers I could get over 2500mm/min( 100IPM) but the max acceleration with it was 40mm/s. I reduced the rapids to 2200mm/min and I could increase the acceleration to , if I recall, 120mm/s. There was a huge difference in machining time as acceleration is much more important for that.
I fitted servos to the same machine and could get 6000mm/min rapids and 1000mm/s, could have got a lot more if I had fitted active shunts but 6m/min is plenty for the wee table of the Bridgeport series 1.



Hood

Offline BR549

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Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #38 on: October 14, 2012, 10:35:32 AM »
I have an old BP series 1 cnc. With the old stepper it maxed out about 85 IPM.  Cutting was in the 20-30 IPM range.  I put a set of 1kw ac servos on the girl. It would almost jump off the ground moving so fast .

STILL only cut in the 20-30 IPM range. It could move scary fast for an open machine. You could literally dance it across the floor

Point is it still is HP/RPM limited for high speed work so in reality it was a waste of resources to do the conversion based on work output and cost.  BUT she was my baby for many years so cost be darned.

IF FAST rapids are your time saver then it is time to look for a better CAM system(;-) IT needs to spend more time cutting than ZOOMING around the table.

I would try what you have first THEN after you have mastered the process look into FASTER.

Re: How much stepper power do a 1-1/2 HP Bridgeport need to do a good job ?
« Reply #39 on: October 14, 2012, 12:18:02 PM »
Well  BR549.....lots of good sense in those words, Ill stay with the steppers for now and see how they work and forget about the speed for now.  I know the Hp decides how deep and fast one can cut. but every little movement takes time as you know.. :-)

Thanks for sharing your first-hand experiences Hood  :-)

Leif
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