[sledhead306]

Hey I have been fooling with my g0704 that I converted to ball screw and used a cnc kit from https://www.omc-stepperonline.com/cn...0h-34hs46.html . I have the kernnal speed at 45000 and can't seem to get more than 125 imp on and of my axis without stalling. The drivers are set to 1/8 steps. I am running power supplies on 120v . Any suggestions?

[109jb]

Your motors are too big and too high inductance. The G0704 runs great on 570 oz-in steppers and a big reason for that is because the 570 oz-in motors are only 2.2mH. Your motors are 11 mH. This gives them gobs of low speed torque, but no top end.

[sledhead306]

Your motors are too big and too high inductance. The G0704 runs great on 570 oz-in steppers and a big reason for that is because the 570 oz-in motors are only 2.2mH. Your motors are 11 mH. This gives them gobs of low speed torque, but no top end.

2.2 mh? I'm not familiar with that

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[Fastest1]

What are you using for a computer and OS? What happens if you 1/4 step? Can you gain the speed you desire?

[sledhead306]

What are you using for a computer and OS? What happens if you 1/4 step? Can you gain the speed you desire?

I have tried 1/8 1/4 1/2. Still no luck. I am running a bare bones p5k deluxe mother board with a 2.2 ghz amd processor. 4 gb of ram on Windows xp. I have an aftermarket card for the lpt port. Not sure of the brand.

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[datac]

Any new mill will need quite a bit of scrutiny and patience with gib adjustment during an adequate break in time, especially these imports. Based on my own experience with the same mill, it would seem to me machines running over 125ipm early on may not have the gibs tight enough, or the user spent a lot of time lapping or exercising the machine before use.

That said, running with the crowd thinking anyone needs more than 125ipm on a small MILL with only 8x16 inch work area is beyond me. If you have fine detailed, high speed work, you might be just using the wrong machine.

Mine was setup and tested with 125 or 150ipm maximums, but I have since set it back to 100 max and even that seems overkill for the size and quality of this machine. Don't waste any time competing in the "speed races".... just focus on accuracy which is enough of a challenge with this particular mill.

[109jb]

What is the power supply output for the stepper drivers?

[sledhead306]

What is the power supply output for the stepper drivers?

I believe is it 60vdc but I'd have to get a closer look I think I tagged the kit I bought

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[jalessi]

I agree with John (109jb). Did you review the torque curve of the motors you are using? At 125 IPM most likely you are spinning the motors over 600 RPM, the torque drop off is a understatement. Are your steppers directly driving the ballscrews or are pulleys also part of the RPM equation? See attached image:

Your motors are too big and too high inductance. The G0704 runs great on 570 oz-in steppers and a big reason for that is because the 570 oz-in motors are only 2.2mH. Your motors are 11 mH. This gives them gobs of low speed torque, but no top end.

[109jb]

I believe is it 60vdc but I'd have to get a closer look I think I tagged the kit I bought

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At 60V and 11mH inductance you are at the limit of what the motors can do.

The inductance of the motor has a strong affect on the torque drop off. In layman's terms, the inductance is a measure of how fast the coils can be fed the current. Think of a common garden hose. The flow rate is like the current and the voltage is like the water pressure. If you have a small diameter hose (High inductance), you need to increase the pressure to get the same amount of flow compared to a large diameter hose (Low inductance).

To calculate the ideal voltage to use, the formula is 32 * sqrt(inductance) For a 11mH motor the ideal voltage is 106V compared to 48V for a 2.2mH motor. There are 570 oz-in NEMA 23 motors that are commonly used for G0704 conversions that have 2.2mH inductance and most people run them right at their ideal of 48V. So, the motor is happy and the torque stays higher longer as rpm increases. When you use a high inductance motor even at their ideal voltage the torque drops off faster due to the inductance preventing the motor coild from getting the power the motor wants. Lower the voltage below ideal and it gets worse and consequently torque drops off even faster.

So, what can you do for this?

1. Leave it alone and live with what the currently installed motors, drivers, and power supplies can do.
2. Increase the voltage going to the drivers by replacing the power supplies. However, you are likely limited by the voltage the stepper drivers are rated for.
3. Replace the motors with lower inductance motors. Going to lower inductance motors, even if they have a lower 0 rpm torque rating, can improve the performance. However, lowering inductance while keeping the torque the same means increased current required, so again you have to check what your power supplies and drivers can handle.

[109jb]

Here is the torque curve for the 570 oz-in motors I mentioned.

Attachment 380366

[sledhead306]

I get what you are saying. After some research and picking my own brain I think I'm going to order some 570 oz motors and try that. I am doing a y extension at the moment so won't get to find out for a while.

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[Fastest1]

You got no change in speed between a 1/8 and 1/4 stepping?
Something is wrong then.

Have you calculated the theoretical distance traveled per step?
Many of us start out misunderstanding this and going for super high resolution not based in reality.
Btw, a G0704 can go much faster than 125ipm and never use a kernel speed of 45,000


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[sledhead306]

You got no change in speed between a 1/8 and 1/4 stepping?
Something is wrong then.

Have you calculated the theoretical distance traveled per step?
Many of us start out misunderstanding this and going for super high resolution not based in reality.
Btw, a G0704 can go much faster than 125ipm and never use a kernel speed of 45,000


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I found it would just stall if I tried to get anything faster by Changing my steps. I tried all the kernnal speed options. What kernnal speed do you recommend

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[109jb]

Microstep vs. Full Step Torque | GeckoDrive

[Fastest1]

I found it would just stall if I tried to get anything faster by Changing my steps. I tried all the kernnal speed options. What kernnal speed do you recommend

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25,000. Mach even recommends it. If speed is the real criteria, maybe a Smoothstepper, Acorn or UCNC?

[DJEkim33]

Any new mill will need quite a bit of scrutiny and patience with gib adjustment during an adequate break in time, especially these imports. Based on my own experience with the same mill, it would seem to me machines running over 125ipm early on may not have the gibs tight enough, or the user spent a lot of time lapping or exercising the machine before use.

That said, running with the crowd thinking anyone needs more than 125ipm on a small MILL with only 8x16 inch work area is beyond me. If you have fine detailed, high speed work, you might be just using the wrong machine.

Mine was setup and tested with 125 or 150ipm maximums, but I have since set it back to 100 max and even that seems overkill for the size and quality of this machine. Don't waste any time competing in the "speed races".... just focus on accuracy which is enough of a challenge with this particular mill.

I was able to get over 350 ipm at an acceleration of 30 in/s sq out of my setup and have since turned everything down to max at 90 ipm at 20 in/s sq. There is no need other than bragging rights on a G0704 to go over that. I found the machine deflects at higher speeds and thus looses accuracy. I would spend more time, energy and money on improving accuracy and rigidity of the machine before worrying about speed.

[eldata]

There is no need other than bragging rights on a G0704 to go over that

Titans of CNC disagree,

https://www.youtube.com/watch?v=2fuYj4trEGg

[CL_MotoTech]

Lol, yes that video applied directly to those with G0704's. The video didn't even come off as an advertisement, truly educational.

[eldata]

The post was meant to be comic relief. Chill out, why so uptight? Next time I'll add an emoji so you're on the right page.