[helpmeout]

I have a desktop engraver that has the nema 17 stepper motors.I have set-up the controlers with about 1.5 amps,and it does OK. The Z axis is using a dremel for my engraver.The problem is the holding power does not seem to be strong enough to keep the dremel raised,it will often drop to the bottom of the axis.

My question is should I increase the current to that stepper,and may be it will hold that dremel where its supposed to be at.Im using Geko 201's so i can set the current up a little.The voltage is at 32 volts and they dont get very hot.

Or should I change the Z axis stepper to a Nema 23 that I can increase the current enough that the holding power will stop it from dropping suddenly.

[ger21]

Does it drop during movement, or by itself wen it's not moving?
WHat's the rated current for the motor?

[helpmeout]

As far as I can tell it only drops after it travels to the spot where it needs to lower the bit to start engraving,and when it stops to raise the z-axis to move to another area.I forgot to say it is on a pully and timing belt type of travel system but it does not seem that the timming belt is slipping or the pulley is sliping on the stepper motor shaft. Im afraid to start engraving with it until this is corrected.Ive never done any engraving with it yet,was setting it up to start engraving and this started.If I have too Ill remove the timming belt system on this z axis and convert it to a lead screw,and if I need too will use a nema 23 for z axis stepper....the nema 17 I think is rated at 2.0 amps it has about 75 oz of torque I think this might not be enough to keep that small dremels weight on the z axises mount,

Im trying to find something that is very light for a spindle for this axis.....also when I shut the computer and the power down it will not hold at the position where powered off it drops, so this nema 17 I think is too small for its.....

[awerby]

The Dremel doesn't weigh much; it seems strange that even your small motor can't hold it up. But is there a screw involved in your Z axis, or is it riding directly on the belt? Usually, the belt turns a pulley attached to a screw, which confers a certain mechanical advantage, giving it more resistance to back-driving. If the weight is directly on the motor, then the holding torque of the motor has to be more than the weight of the spindle assembly. Are you giving the motor its full 2 amps? If it's getting less, then torque will be reduced.

[ger21]

Try reducing your acceleration and velocity by 50%.

[helpmeout]

OK Ill try that and see what happens,and Ill recheck the pulley and timming belt also could be I missed something.I do know from the time I got it if the z axis was up with the dremel was mounted as soon as you shut off the power the dremel bit would crash into the table.The only soulition to that problem would be is to either replace the z axis motor with a nema 23 that has more holding power,Or change the belt system on the z axis to a leadscrew set-up. when I power down that small of a motor justs free-wheels.Havent broken any bits yet because I caught this problem early on.....

[ger21]

If you are direct driving a belt, than that's the problem. You need some type of reduction to give you some mechanical advantage.

[helpmeout]

I think your right,about that,Found out this is a zinbot I wonder if all of there z axis of that model has the same problem

[george4657]

According to the manual:
"AUTO CURRENT REDUCTION: The G201 reduces motor phase current to 33% of the set value when the motor is stopped. If enabled, this reduction occurs 1 second after the last step pulse is sent to the drive. Auto current reduction can be enabled or disabled."

If this is enabled power is reduced when stopped so be sure this is disabled.

Even a nema23 motor will have very little holding power when turned off.

[helpmeout]

Ive had these geckos for a good number of years,and I just learned something new about them today with your post.The information was there but I missed it.but how do you enable or disable that feature.Ihave an input named reset that I dont have hooked up to any thing not to ground or to high (is it 5 volts ) is that where the connection is made at..If not where.....

[george4657]

You can find the manual at G201 REV-16 | GeckoDrive
There are jumpers inside.

[ger21]

I would not disable the current reduction. Even with the holding torque reduced to 33% while not spinning, it will still have more torque than when it is spinning. If it can't hold the Z axis with the current reduction, the motor is way too small.

[helpmeout]

After reading Georges reply I readup on the manuel and from what it looks like even tho pin 7 is not grounded which causes the current to the windings to be shut off,they are anyways.I must open the cover and jumper If im not mistaken pin 1&5 that will allow the windings to have current at 100% which z axis needs.that should correct the problem. Ill know more after I try it and reply back....

[helpmeout]

I have a small nema 23,with a small amount of rework on the z axis motor mount,Will be my next step.I think the nema 17 that is on it is the largest torque-size (is that correct torque-size) Oz-inches,I can get....