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Author Topic: Can't raise feedrate past 50 in./min. without messing up... suggestions?  (Read 9067 times)

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Well I need some help. Right now all four of my geckos have 68k ohms resistors which puts the current above 4 amps.  The motors on my CNC machine(http://www.kelinginc.net/KL23H51-24-8B.pdf have a max amps rating of 3.4A in bipolar parallel(which I don't know if mine are hooked up this way?). So should if I were to replace the resistors on the Geckos with 45k ohms resistors(which would put the current just under 3.4 amps), would I be able to go with higher feed rates?  Or should I invest in bigger motors that can take the 7 amps possible with no resistors?
« Last Edit: March 09, 2012, 05:11:11 PM by mp2008 »
Bump... sorry, would like to get this figured out quick, losing money.

Offline BR549

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What is the power supply VOLTAGE to the drives That more than anything will set the max speed of the motor. What are your motors rated for?

(;-) TP
What is the power supply VOLTAGE to the drives That more than anything will set the max speed of the motor. What are your motors rated for?

(;-) TP
I didn't set it up so I'd have to test it to know the Voltage.  My motors specs are in the link in my post at the top of this page.

Offline BR549

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I would check your voltage then contact the motor manf and find out what the maxium voltage the motors can safely run . The Geckos can handle up to 80 volts but i would  give it a small safety and just use up to 70-75 volts.

AMPS in general give you torque and VOLTs give you speed.

(;-) TP

Offline RICH

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Can you give some info on your machine?
For a CNC router your usualy interested in fast feedrates so you won't burn the wood with the router bit. Stepper motors are somewhat limited in how fast they can rotate.
At  higher motor rpm's you have less torque so even if the torque requirements for moving the axis are low  you still need enough to take care of the machining and reserve just for the sake of reliability.  The higher feedrates are achieved by using multi start screws or gearing. So have a look at comparable machines and make note of components used along with feedrates achieved. You need to look at the whole system and what you want to do with it. There are plenty of post's about routers and certainly worth some searching.

RICH


Can you give some info on your machine?
For a CNC router your usualy interested in fast feedrates so you won't burn the wood with the router bit. Stepper motors are somewhat limited in how fast they can rotate.
At  higher motor rpm's you have less torque so even if the torque requirements for moving the axis are low  you still need enough to take care of the machining and reserve just for the sake of reliability.  The higher feedrates are achieved by using multi start screws or gearing. So have a look at comparable machines and make note of components used along with feedrates achieved. You need to look at the whole system and what you want to do with it. There are plenty of post's about routers and certainly worth some searching.

RICH



Machine:
Travel: X-24",Y-36",Z-5"
X & Y Axis uses precision ground cnc linear rails.
Z Axis uses 2 linear bearings on .75 DIA 440 hardened Stainless Steel Round Bars.
X, Y, & Z Axis Stainless Steel Acme Lead Screws
Anti-backlash Acetal Nut on X, Y, & Z.
Uses 2 paired motors(Y & A axis-one on each side of table) to run the Y axis.


Right now my Geckos have 55 Volts running to them and Idk what my motors max Voltage spec is or how to find it.

Offline RICH

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I just think you need different motors since the ones you have are 160 in oz motors. Have a look at the motors on Kelings site
and you will find some 360 to 500 in oz that can be run at 3 amps and should be able to almost triple your speed.
Review the motor curves to compare if they list a curve for the motor.

RICH
I just think you need different motors since the ones you have are 160 in oz motors. Have a look at the motors on Kelings site
and you will find some 360 to 500 in oz that can be run at 3 amps and should be able to almost triple your speed.
Review the motor curves to compare if they list a curve for the motor.

RICH

I had a feeling all along these motors were my problem.  I've been to their website and found the biggest 8-wire NEMA 23 stepper motor:

2:        NEMA 23 BIPOLAR STEPPER MOTOR 425  oz-in
KL23H286-20-8B (1/4” shaft with a flat)   Specification  or Specification Price: $49
425 oz In. Hybrid Motor
1.8° /200 Steps Per Rev.
2.8 Amps Current Per Phase ( Bipolar Parallel)
8-wire  Bi-polar or unipolar,  NEMA 23 Frame

Compared to the ones I have now:

5:   NEMA 23  BIPOLAR STEPPER MOTOR  156 oz-in KL23H251-24-8B ( ¼” dual shaft with a flat) $26.95
Specification , Torque-Speed-Curve
156 oz In. Hybrid Motor
1.8° /200 Steps Per Rev.
3.4 Amps Current Per Phase ( Bipolar Parallel)
8-wire  Bi-polar or unipolar,  NEMA 23 Frame

Do you think the bigger motor listed above would be enough to make the machine as fast as I need it(150-200 in/min)?  

Thanks for the help,
Mike
« Last Edit: March 13, 2012, 03:20:06 AM by mp2008 »

Offline RICH

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Mike,
What is the max Kernel Speed you can use?
What are your steps per unit?
Post a pic of your machine.

RICH