No response from motor at slow speeds. Heat issue?

[CarlofET]

Hi all -

Just getting going with my brand new DIY CNC machine and having a blast doing it. I had an issue today, though, that had me a little frustrated.

I have one of the electronics kits from cncrouterparts.com - the 4 axis kit (two motors driving X) with the gecko g540.

After playing with it for a while today, suddenly I noticed that while jogging the motors in mach3 with the arrow keys on the keyboard, the y axis was slow to respond. I would hold down the button and watch the y values count up and only after several seconds the motor would start turning. If I turned the velocity up it would respond right on. When running a program, the rapid movements were fine while the cutting movements didn't go anywhere.

I was doing some troubleshooting, switching around cables, etc. and noticed that whenever I would plug the thing back in it would work fine for about as long as it had been disconnected. After leaving it for an hour or so powered off it worked fine the rest of the day.

The motors and controller get pretty hot after being powered on for a few hours. The controller is pretty much too hot to hold your finger on. Could heat be the culprit? Why on the Y axis, which moves the least amount in the programs I've been running, and not either of the X axis motors or the Z?

Thanks in advance for your insight. I don't think I could have taken on this project without the amazing amount of info posted here already.

[CarveOne]

My guess is that the G540 is going into thermal shutdown. Try adding a fan or providing better heat sinking of the G540 assembly by mounting it to a metal plate or extruded heat sink of some kind.

It's normal for the motors to get hot while running for hours but I think the G540 has idle current reduction, like the G203V) that should help during long periods of inactivity.

CarveOne

[zeeway]

My machine went through similar issues. I kept reading about all the effortless builds, and was beginning to think I was the red headed step child who couldn't do anything right. But hallelujah - my machine is now fixed - although I still cross my fingers as I say that.

I have the gecko 540 and the 380 oz in motors from CNCrouterparts.com, also. However I only use three axes, with only one motor on the x axis.

I suspected the gecko 540 was overheating, and losing steps. Mariss said in a post that the gecko 540 would simply shut down if it got overheated. I went ahead and put a dual fan setup (from a home theater) blowing over it, and that helped it stay cooler. I also noticed that a company in Australia is selling a similar fan for use with gecko's. The gecko still gets warm to the touch - but not blazing hot like it used to. This seemed to help the problem - or maybe it was my imagination....

And by the way, stepper motors do run very warmly - you can touch them, but you wouldn't want to linger there.

On top of losing steps, my Z axis began to chatter and not move at all - found (with Ahren's help) that was a bad DB9 connector on one the motors that allowed two of the pins to retract and lose contact.

I was still losing steps...so I rebuilt my z axis and rechecked to make sure there was no binding anywhere. I also suspected that electrical noise from my router cable was getting in the signal wires to the motors - nope, that wasn't it.

I tried a new parallel port card in my Dell 2.8 MGHZ computer - couldn't get the dang thing to work. Still don't know why.

So a couple of weeks ago, suspecting it was my computer not putting out enough signal in a reliable stream through the parallel port, I finally bit the bullet and ordered a SmoothStepper board from Warp9...http://www.warp9td.com. The short story is that it works - no more lost steps, or DRO's showing motion while the axis stays stationary. The challenge is that the documentation that comes with the SmoothStepper is sketchy - you have to read a lot of posts to figure out what to do. If I had it to do over again I would suggest you buy the board from soigeneris dot com. They seem to have a good support setup, and the owner (?) Jeff Birt is active on the boards.

I put the SmoothStepper board in my control box - it attaches to the computer through a USB cable. The board connects through a special ribbon cable and gender changer to the parallel port on the gecko.

If you are interested in this approach suggest you read a lot of posts here:
http://www.machsupport.com/forum/ind...oard,65.0.html. Warp9 also has a forum, which you may find useful.

If you are unwilling to go the SmoothStepper route, I suggest you try another computer with strong output through the parallel port.

Good Luck.

[jsheerin]

I had a similar problem and it turned out that my parallel port could not source enough current to drive the G540. For some reason I never entirely figured out, this only showed up at low speeds, or it showed up most reliably at low speeds. See this thread, especially towards the end:
http://www.cnczone.com/forums/showthread.php?t=75784
I fixed this with a pci dual parallel port card. I bought two cards. The Rosewill card worked for me, but the other did not (can't remember the type). I couldn't get it installed - the chip it used was the same so it probably would have worked if I could have gotten the drivers to work.

[CarlofET]

Thanks for the replies already everyone. The input is quite helpful.

Originally Posted by CarveOne My guess is that the G540 is going into thermal shutdown. Try adding a fan or providing better heat sinking of the G540 assembly by mounting it to a metal plate or extruded heat sink of some kind. It's normal for the motors to get hot while running for hours but I think the G540 has idle current reduction, like the G203V) that should help during long periods of inactivity. CarveOne

Do you think I would expect to see a problem in just one axis if it's a heat problem with the G540? I would expect it to just all stop working if it's shutting down, but obviously I have little experience in the matter. Either way I'll be doing what I can to reduce the heat on this thing.

Originally Posted by zeeway I suspected the gecko 540 was overheating, and losing steps. Mariss said in a post that the gecko 540 would simply shut down if it got overheated. I went ahead and put a dual fan setup (from a home theater) blowing over it, and that helped it stay cooler. I also noticed that a company in Australia is selling a similar fan for use with gecko's. The gecko still gets warm to the touch - but not blazing hot like it used to. This seemed to help the problem - or maybe it was my imagination.... And by the way, stepper motors do run very warmly - you can touch them, but you wouldn't want to linger there. On top of losing steps, my Z axis began to chatter and not move at all - found (with Ahren's help) that was a bad DB9 connector on one the motors that allowed two of the pins to retract and lose contact. I was still losing steps...so I rebuilt my z axis and rechecked to make sure there was no binding anywhere. I also suspected that electrical noise from my router cable was getting in the signal wires to the motors - nope, that wasn't it. I tried a new parallel port card in my Dell 2.8 MGHZ computer - couldn't get the dang thing to work. Still don't know why. So a couple of weeks ago, suspecting it was my computer not putting out enough signal in a reliable stream through the parallel port, I finally bit the bullet and ordered a SmoothStepper board from Warp9...http://www.warp9td.com. The short story is that it works - no more lost steps, or DRO's showing motion while the axis stays stationary. The challenge is that the documentation that comes with the SmoothStepper is sketchy - you have to read a lot of posts to figure out what to do. If I had it to do over again I would suggest you buy the board from soigeneris dot com. They seem to have a good support setup, and the owner (?) Jeff Birt is active on the boards. I put the SmoothStepper board in my control box - it attaches to the computer through a USB cable. The board connects through a special ribbon cable and gender changer to the parallel port on the gecko. If you are interested in this approach suggest you read a lot of posts here: http://www.machsupport.com/forum/ind...oard,65.0.html. Warp9 also has a forum, which you may find useful. If you are unwilling to go the SmoothStepper route, I suggest you try another computer with strong output through the parallel port. Good Luck.

I will definitely keep this in mind, as the signal sounds like it might be the problem. I'd really like to get the setup I have working, but if it gives me too much of a hassle I'll know I have this as a backup.

Originally Posted by jsheerin I had a similar problem and it turned out that my parallel port could not source enough current to drive the G540. For some reason I never entirely figured out, this only showed up at low speeds, or it showed up most reliably at low speeds. See this thread, especially towards the end: http://www.cnczone.com/forums/showthread.php?t=75784 I fixed this with a pci dual parallel port card. I bought two cards. The Rosewill card worked for me, but the other did not (can't remember the type). I couldn't get it installed - the chip it used was the same so it probably would have worked if I could have gotten the drivers to work.

That link describes a situation very similar to mine. I'd better do some investigation of the parallel port. The computer I'm using is brand new, fresh install of XP, and uses an add-on parallel PCI card as there isn't one on board. As such, I don't know how to check EPP mode.

This is the card I bought: http://www.newegg.com/Product/Produc...Tpk=15-104-211

I e-mailed Ahren and he gave me some things to check as well. I'll investigate today and write back if I make any progress.

Thanks again to everyone for your help!

[CarveOne]

The G540 has four of the G251 boards in it. Any one of those four boards could be shutting down due to binding on one motor more so than the others. The G251 board has the same circuit as the G203V except that they have a lower output current spec. The thermal shut down apparently does not automatically re-enable after the board cools down. You have to power down the G540 and power it up again.

Keeping the G540 cooler will let it run longer at a temperature that is lower than the preset shut down temperature of the G251 boards.

If your parallel port card is outputting signals that are very near or below the acceptable voltage input required by the G540 then that may be why it stops working sometimes and then starts working again. I have seen recommendations for the Rosewill cards but there are no guarantees since the makers of these boards will change designs and use different parts based on what is available cheaper. Fortunately the boards are low cost. When you find one that works well, buy a couple of spare boards for future builds.

CarveOne