Problem with steppers

[mrcodewiz]

I have a CNCd X2 with all Keling stuff - 425 oz steppers, 4030 drivers, C10 BOB, and 24 Volt power supply.

I just installed a 4th driver and stepper for a 4th axis project I am working on and I upgraded the power supply to 36V while I was at it. I run all of the steppers at 1/4 steps.

I used to only run the X and Y at 45 IPM rapids and the Z at 20 IPM. I can now run the Z at 50 and the X and Y at 75 but not all at once. I can run the X back and forth all by itself or the same for Y or Z and it runs just fine with out missing steps. However, if I am holding down the Z and doing a rapid then at the same time I start doing a rapid with the X, the Z will stop and sound like it is stuck. It doesn't do it every time but it does it most of the time and I can duplicate the behavior on the X by having it do a rapid and then attempting to start one of the other axis in a rapid or changing direction while doing a rapid on one of the other axes.

Am I just expecting too much? Should I change the steps to 1/2 (will it make a difference)? Is 36V just not enough of a change to expect more than 5 more IPM rapids from each axis (it doesn't do it at 30 for Z and 50 for X and Y) or could it be something else?

[MrWild]

How many amps do the steppers draw? How many amps is the PS. Did you wire your drives in a daisy chain or star pattern. Daisy chain is where you wire one after another so one power line goes freom drive to drive, while star has each drive having it's own power wire leading to a central point. If daisy chained, the single wire cannot give enough amps for all then drives down line.

For total amperage needed from your PS, add up all motor amperage, then multiply by .66. Say each motor needs 3A. Withn four motors, that comes to 12A. Now multiply 12A by .66 and you get 7.92 amps needed. Round it up to 8 amps. Anything less and even if the drives are wired inn a star orientation, you will still be deficient in power to drive multiple drives at once.

Now for the ringer. It is doubtful you will ever run four drives at once. Most likely just three. If the Kelling drives will take 48v., I'd go with the 48v 7.2A power supply.

[mrcodewiz]

How many amps do the steppers draw? How many amps is the PS. Did you wire your drives in a daisy chain or star pattern. Daisy chain is where you wire one after another so one power line goes freom drive to drive, while star has each drive having it's own power wire leading to a central point. If daisy chained, the single wire cannot give enough amps for all then drives down line.

For total amperage needed from your PS, add up all motor amperage, then multiply by .66. Say each motor needs 3A. Withn four motors, that comes to 12A. Now multiply 12A by .66 and you get 7.92 amps needed. Round it up to 8 amps. Anything less and even if the drives are wired inn a star orientation, you will still be deficient in power to drive multiple drives at once.

Now for the ringer. It is doubtful you will ever run four drives at once. Most likely just three. If the Kelling drives will take 48v., I'd go with the 48v 7.2A power supply.

Each driver has its own leads to the PS. The power supply is 36V, 8.8 Amps and I turned the pot up so it is more like 39.5 volts. I wired them up bipolar so looking at the specs, it looks like 2.8A - multiplied by 3 (I took the 4th off for now) is 5.5 so that seem ok. I don't think I ever noticed this with the old power supply - it does it with only 2 axis running is the odd thing. It doesn't even take 3 letalone 4.

[mrcodewiz]

I thought maybe my gibs were too tight but I can completely loosen the Z gibs and I get the same effect. Rapid down with Z, Start rapiding with X and Z freezes. My rapids are not much more than they were with the 24V PS. Maybe the new power supply just doesn't have as much of an effect as I thought it would and I am stuck with < 50 IPM rapids on the XY and < 25 on the Z?

[cnczoner]

Sounds like a low-supply-current issue to me. Isn't the 2.8A per phase? So you'd need 2.8 x 2 x .67 = 3.73A per motor. If you upgraded the PS, then you probably have the older 24V PS -- try separating a couple motors off to that PS for now, just to have extra current capacity for now.

Cheers,
-Neil.

[mrcodewiz]

I didn't even think of that! I will give that a shot tonight and see how it runs. Would having the driver for the 4th axis wired up to the power supply be a contributing factor even if I am not running the 4th axis?

[cnczoner]

I would think so if you have the motor attached, as the drive will be held in one of the 4 microstepping states. Max torque on steppers is holding torque -- when the motor is stationary. Some examples here (next to the pics of the motors).

But current draw should be minimal if the stepper is not connected.

Might be an interesting exercise to hook up an ammeter to the power supply output, and add one driver/motor at a time to the system to see how the current adds up. Keep the motors stationary.

Also note that if you're using a linear power supply, the output voltage drops as current goes up. If you using one of those pre-made enclosed switching power supplies, they often don't deliver as much current as they claim.

Cheers,
-Neil.