Steppers Stalling

**nikos8** · 11-18-2018, 07:52 AM

Hello to all.

I'm having some issues with my x-axis steppers. The x-axis is 48". The gantry weighs approximately 135 lbs. It has hiwin 30mm linear slides and 1605 ballsrews with two 420oz nema 23 steppers. The Hiwin linear slides were a recent upgrade to the machine. The driver is a gecko g540 with a 48v 12 amp power supply.

The problem I am having is that the steppers start making a grinding noise and skip steps at anything above 55 ipm. With the old linear slides I could cut closer to 90 ipm. I checked the PS and it is putting out 49.2v.

I know the ballscrews are a limitation to the speed and the Hiwin slides are on the tighter side so there is a need for more torque to move the gantry.

I need more speed out of the machine. It's just too slow the way it is right now. What can I change to make it cut faster without a problem? I'm not looking to cut at 300 ipm but I would like to be able to cut at 100 ipm - 150 ipm.

Nick

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**ger21** · 11-18-2018, 08:16 AM

1610 ballscrews and/or new drives that can run at a higher voltage.

What are the specs on the motors? (Current and Inductance?)

1610 ballscrews will definitely be faster, but you still may be underpowered.

**nikos8** · 11-18-2018, 08:21 AM

The g450 is rated to 50v but limits the amperage to 3.5, The steppers are 4.2 a with inductance at 3.0 mh. I was looking for drivers that can handle more voltage, closer to 80v or switching out the ballscrews with something different. I'm not too happy with the 1605 at that length. What would be a better choice?

**wizard** · 11-18-2018, 08:25 AM

I'd check for mechanical binding first! Disconnect the lead screws and get a feel for how the gantry slides along the rails. Reconnect the leadscrews with the motors disconnected and get a feel for how the gantry drives my hand. In either case the movement should be smooth and bind free. If not alignment is required.

You didn't mention what you upgraded from (or I missed it) but those rails will not be forgiving at all when it comes to misalignment. Different bearing systems have a greater tolerance to misalignment, twist and other ills. Profile rails though really need to be mounted on a common plain and precisely parallel to each other. Often an upgrade can be a significant struggle as the old frame might not be up to the task.

I'm hoping that you have the electronics / software set up properly for the steppers. This means a proper current setting. One big actually huge mistake people make is setting the stepper currents below the stepper rating in the mistaken belief that the steppers are running too hot. Setup the amps to run the steppers at the motors rated current operating point. Also the CNC software parameters setup correctly for your machine.

**ger21** · 11-18-2018, 08:34 AM

I'd probably go with 2010 or 2525 ballscrews. But 2525 would probably require new Nema 34 steppers.

You could go with G201X Drives. I'd go for 400-600oz Nema 34's, with a current rating of around 6 amps. Smaller motor with 2010 screws, larger motor with 2525.

**nikos8** · 11-18-2018, 08:35 AM

Originally the machine had bearing blocks from cncrouterparts which ran on 1/4 aluminum. As far as binding, the gantry moves smoothly from end to end with no binding or more effort anywhere throughout the entire range of travel. It is tighter than the previous "rails" however. All the electronics and software has been setup properly, checked and rechecked. I cannot reach the full amperage of the steppers since the g540 limits the amps to 3.5.

**ger21** · 11-18-2018, 08:37 AM

Gecko is developing a new G570, similar to a G540 but with 7 amps, and more features.

https://www.cnczone.com/forums/gecko...-software.html

**nikos8** · 11-18-2018, 08:46 AM

Originally Posted by ger21

Gecko is developing a new G570, similar to a G540 but with 7 amps, and more features.

https://www.cnczone.com/forums/gecko...-software.html

That looks interesting. Voltage is still at 50v however.

**wizard** · 11-18-2018, 04:51 PM

The inability to reach full current from the drives will be a killer. It means your motors will ever develop full torque.

At this point I wouldn’t throw the motors away. The slow lead screws are another matter but I wouldn’t bother with them until I had proper drivers. I might seriously consider a driver that runs from AC line voltage instead of looking for a high voltage power supply of around 80 VDC. You need fairly high voltage due to motor inductance so drivers powered from line are a good option. Whatever you do make sure you have current head room if you consider a motor upgrade.

I suspect that low current and high inductance are working against you here. Note that the calculated max voltage for your motor inductance is around 56 volts. Running the motors at 48 VDC would be very possible, if at slightly lower performance, if the drivers where capable of delivering proper current. 7 or 8 thenths of an Amp doesn’t sound like a lot but it is a significant percentage of the motors rated current.

Originally Posted by nikos8

Originally the machine had bearing blocks from cncrouterparts which ran on 1/4 aluminum. As far as binding, the gantry moves smoothly from end to end with no binding or more effort anywhere throughout the entire range of travel. It is tighter than the previous "rails" however. All the electronics and software has been setup properly, checked and rechecked. I cannot reach the full amperage of the steppers since the g540 limits the amps to 3.5.

**wizard** · 11-18-2018, 05:16 PM

Gerry

Thanks for the heads up. This new hardware sounds very interesting. I’m sure many here will be interested.

Originally Posted by ger21

Gecko is developing a new G570, similar to a G540 but with 7 amps, and more features.

https://www.cnczone.com/forums/gecko...-software.html

**joeavaerage** · 11-18-2018, 07:51 PM

Hi,
if you want high speed with genuine authority you may have to consider AC servos.
DMM have carved out a good reputation for performance, quality and cost.

DMM | AC SERVO DRIVE | AC SERVO MOTOR | ROTARY ENCODER

Craig

**nikos8** · 11-19-2018, 08:15 AM

Originally Posted by wizard

The inability to reach full current from the drives will be a killer. It means your motors will ever develop full torque.

At this point I wouldn’t throw the motors away. The slow lead screws are another matter but I wouldn’t bother with them until I had proper drivers. I might seriously consider a driver that runs from AC line voltage instead of looking for a high voltage power supply of around 80 VDC. You need fairly high voltage due to motor inductance so drivers powered from line are a good option. Whatever you do make sure you have current head room if you consider a motor upgrade.

I suspect that low current and high inductance are working against you here. Note that the calculated max voltage for your motor inductance is around 56 volts. Running the motors at 48 VDC would be very possible, if at slightly lower performance, if the drivers where capable of delivering proper current. 7 or 8 thenths of an Amp doesn’t sound like a lot but it is a significant percentage of the motors rated current.

I know that that the G540 limits the amps to 3.5A and my motors can run to 4.2A and that torque falls off proportionately. I ordered G201X drives that can handle more voltage and amperage and can handle a motor upgrade. But I think that the ball screws are what's really holding me back at this point. Running a stepper at 500-600 rpm to reach the speeds I want, I don't know if the torque will be enough with the current motors.

**joeavaerage** · 11-19-2018, 12:37 PM

Hi,
may I suggest having a look at the Leadshine website, they have pretty thorough specs for their stuff. I have attached one from their 34 size stepper range.
Note that torque does fall off, at 70V it is still about 2/3 of stall torque at 500 rpm.

Leadshine Technology - Home

Craig