Wiring an 8 wire Nema to 4 core CY cable to an AM882

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24-02-2020
Desertboy

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by JAZZCNC

Your asking for trouble running at the drives Max voltage. You will damage them at some point if your running at high feeds and happen to catch the mains at a peak the back EMF will fry them.!

They will run like a grumpy bear at 2 x turn them up to 8x and they will run much smoother, you'll lose a little torque but will run much nicer.

I'll try that in a minute, thanks.

PSU test's at 72v without load ~68v with load with home supply when I try it at work I get 78v without load and around 70v with load, it's a Toroidal transformer.

That really confused me originally but power is far from clean.

When Maplins went bankrupt they were half price so I bought 2 both 1kva.
24-02-2020
AndyUK

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by JAZZCNC

Andy, just want to clear something up just in case you or others think the drives current rating is a must not exceed the limit or will break.! . . . They are not limited to 4.2a you can actually run them higher and you won't damage them. It's not recommended because you will over time shorten their life because they will run hotter and the gains will be limited so not worth doing. But you won't kill them running a little higher current.

I was aware that going slightly over would just lead to more cooling requirements, but didn't realize they were quite so lenient.

Let's explore this a bit though; those 4nm Nema23s from CNC4YOU just have "current" listed in the datasheet as 4A. Now is that likely to be a peak or RMS current suggestion?

My EM806 drivers, essentially the same as Desertboy's, have a current table with Peak and RMS, what settings would you use for these motors?

I'm kinda surprised we're talking about this machine being able to reach 20m/min, I'm stalling at half that!
24-02-2020
Desertboy

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by AndyUK

I was aware that going slightly over would just lead to more cooling requirements, but didn't realize they were quite so lenient.

Let's explore this a bit though; those 4nm Nema23s from CNC4YOU just have "current" listed in the datasheet as 4A. Now is that likely to be a peak or RMS current suggestion?

My EM806 drivers, essentially the same as Desertboy's, have a current table with Peak and RMS, what settings would you use for these motors?

I'm kinda surprised we're talking about this machine being able to reach 20m/min, I'm stalling at half that!

They should have an autotune function like the AM882's have a look in the manual, I used it with my first motors and it really did seem to work.
24-02-2020
AndyUK

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by Desertboy

They should have an autotune function like the AM882's have a look in the manual, I used it with my first motors and it really did seem to work.

It's something that I've not done yet but is on my list. Does it suggest a current setting for you?
24-02-2020
JAZZCNC

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by AndyUK

Let's explore this a bit though; those 4nm Nema23s from CNC4YOU just have "current" listed in the datasheet as 4A. Now is that likely to be a peak or RMS current suggestion?

My EM806 drivers, essentially the same as Desertboy's, have a current table with Peak and RMS, what settings would you use for these motors?

Most data sheets nearly always quote peak ratings, so if doesn't state RMS always go with peak.

Quote:

Originally Posted by AndyUK

I'm kinda surprised we're talking about this machine being able to reach 20m/min, I'm stalling at half that!

Couple of reason why he'll be getting that speed. If he really is because 2000rpm is high for a stepper.? (Have you checked the machines moving correct distance.? If steps Per is wrong you'll get false reading)

#1 He's only running at 400 Ms so will have more torque but the motors will be running very rough.
# 2 He's running well above 70vdc and close to 80V
24-02-2020
JAZZCNC

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by AndyUK

It's something that I've not done yet but is on my list. Does it suggest a current setting for you?

No, it doesn't, you still have to set the current using the Dip switches or can connect to drives and use software to set them more accurately in 0.1a increments.

The autotune can make a big difference and it's certainly something you should do. Do your motors Hiss or squeal.? . . . If so they will stop after Autotune
24-02-2020
AndyUK

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by JAZZCNC

No, it doesn't, you still have to set the current using the Dip switches or can connect to drives and use software to set them more accurately in 0.1a increments.

The autotune can make a big difference and it's certainly something you should do. Do your motors Hiss or squeal.? . . . If so they will stop after Autotune

Yeah there's a strange hiss and squealing that changes pitch even when the notes aren't doing anything. I just assumed it was the drivers being weird...!

Yeah definitely something I will look at over the weekend.
26-02-2020
AndyUK

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Tuned my all my motors last night and manually set the currents using Protuner. Much happier machine now, the X axis has gone from stalling at 8m/min to being able to do 15m/min without flinching. The Y can do 20m/min, but I've set both X and Y back down to 10m/min for general use.

Still getting some quiet hissing and squealing, although it seems to be emanating from the motor drivers not the motors themselves. Is this something I need to keep an eye on?
26-02-2020
JAZZCNC

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by AndyUK

Still getting some quiet hissing and squealing, although it seems to be emanating from the motor drivers not the motors themselves. Is this something I need to keep an eye on?

Nothing to worry about it's quite normal to get quiet hiss, often it only happens when stood still and it's the recirc circuit lowering the current.

Surprising isn't it how much difference the tuning makes..:thumsup:
27-02-2020
Desertboy

Re: Wiring an 8 wire Nema to 4 core CY cable to an AM882

Quote:

Originally Posted by JAZZCNC

Most data sheets nearly always quote peak ratings, so if doesn't state RMS always go with peak.

Couple of reason why he'll be getting that speed. If he really is because 2000rpm is high for a stepper.? (Have you checked the machines moving correct distance.? If steps Per is wrong you'll get false reading)

#1 He's only running at 400 Ms so will have more torque but the motors will be running very rough.
# 2 He's running well above 70vdc and close to 80V

I'm running at 68-70v with load from the stepper a couple of volts higher without, the steps are setup right dimensions spot on, 1:1 coupling on all axis, now I turned on 8 microsteps it faults at 20m/min but dialed back to 15m/min and it's very happy and does seems smoother.

I have the cutting speed set to 8m/min seems to make nice parts 2mm cuts, might try it at 10m/min.

Only doing wood if I ever do aluminium I'll dial the speed right back and only cut to the sides on the machine where it's strongest.

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