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IndustryArena Forum > CNC Electronics > Stepper Motors / Drives > Jogs fine, MDI and G code fails
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  1. #1
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    Jogs fine, MDI and G code fails

    I built a CNC router. I has dual 1232 oz.-in. stepper motors driving the Y axis. It has a 270 oz.-in. stepper motor driving the X axis and another like it driving the Z axis. The Y axis is driven by s-wrapped HTD belts, and both the X and Z have ball screws. The stepper drivers are 2 DM860H models for my Y drives and DM542T models for my X and Z. My motion controller is a C94 Multifunction CNC board with a UC300ETH from cnc4pc.com. I have 3 power supplies. A 60VDC for the Y axis, a 36VDC for the X and Z axis and a 24vdc for the controller board. I am using UCCNC software to then control the CNC router. I am able to jog all axes with no problem and never loosing a step. The Y axis moves as it should when giving it MDI commands as well. The problem is the X and Z do not move when given an MDI command. They will make a noise and move a fraction of an inch and then stop, while the DRO continues to advance to the number that was entered. I had originally blamed the issue on bad drivers, (X and Z both had TB6600 drivers which I replaced with the DM542T models) but basically no change. Any help or direction would be great.

    X & Z axis stepper motors - 57BYGH627
    X & Z axis drivers - DM542T
    X & Z axis power supply - 36VCD 11 A

    Y axis stepper motors - WT86STH118-6004A
    Y axis drivers - DM542T
    Y axis power supply - 60 VCD 10 A 600W

  2. #2
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    Apr 2004
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    Re: Jogs fine, MDI and G code fails

    Why did you give the Y axis 60v but the X and Z only 36v? It sounds like those motors, with 3.5mH inductance, would like 60v as well, and the drivers could handle it. What happens when you switch over the leads from the axis that works to one that doesn't? (Turn everything off and let the caps drain first, before disconnecting anything).
    Andrew Werby
    Website

  3. #3
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    Re: Jogs fine, MDI and G code fails

    The motor on the 60vdc power supply are nema 34 and they have different drivers. I see I made a typo in the bottom of my post. The drivers on the Y axis are actually DM860H not DM542T. I used the larger motors because they have to move the gantry which is quite heavy. I think my problem is the nema 23 motors that I purchased are rated at under 5 volts I am looking at purchasing motors rated at 24-48 VDC as a solution.

    I have also done more trials to see what is going on. It seems if I set my acceleration and velocity way down 5in/min^2 and 40 in/min. I am able to get it to take MDI and G-code. But it moves like molasses.

  4. #4
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    Re: Jogs fine, MDI and G code fails

    The nameplate voltage ratings on stepper motors don't tell you how much DC voltage to supply them with; I'm not really sure what they refer to. The inductance is a better guide to their power requirements. A formula that's more helpful is 32 times the square root of the inductance - that gives you the optimal DC voltage to get best performance at the top of the motor's speed range. If the motors have 3.5mH inductance, that comes to right around 60 volts.

    The fact that the motors you've had trouble with perform better with lower acceleration and velocity is a clue that they're not getting enough voltage. Before switching them out, try changing the power supply to give them 60 volts (assuming the drivers can handle that). You should be able to test this by switching the 60v power cables from the motor that works well to one that's been giving you problems and then trying the MDI commands.
    Andrew Werby
    Website

  5. #5
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    Re: Jogs fine, MDI and G code fails

    Will an undersized PS also cause the motor to get hotter than normal? The motor seems be be hotter than I would expect it to be. I don't have a way to measure it. I'm able to touch it but it is very warm.

    These are my stepper drivers. They are rated up to 50VDC.
    https://www.amazon.com/dp/B06Y5VPSFN...roduct_details
    So I can't go above a 50VDC power supply. I will try to come up with a 48VDC PS for testing.

    This is the main Stepper motor in question. https://www.ebay.com/itm/312737898308

    Thank you for your help!

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