Dual Z nema 17's overheating

I'm rebuilding a printer for a friend, it's a Tevo Tarantula. If you ever hear the words Tevo & Tarantula mentioned in the same breath do yourself a favour and head for the nearest exit. II could really go off on a tangent here but I'll leave it at that.

I's got an MKS Base V1.4 board with dual Z nema 17's, one is attached the Z driver and the other one is running from E1. They are driving the gantry through lead screws. They sync up and run excellent but they run really hot on a large print where there isn't much movement on the Z axis.

I understand this is a normal phenomenon for a stepper holding a load in a static position but do they really need to be on while they aren't driving the lead screw, will the gantry work back downward from vibration etc if they are off?

Is there a way to set their state when the Z axis isn't being driven?

I'm running Marlin 2.0 bugfix but it's a pre rolled version (Jim Browns Easy config) so I haven't dug into much except to reverse the Z axis direction and enable the stepper on E1.

Edited 1 time(s). Last edit at 02/03/2019 05:31AM by Shreks donkey.

... maybe you can reduce the set current for the drivers, so they won't skip steps but stay cooler?

Some drivers supports reducing current while paused or have a special "sleep" mode, where the current is drastically lowered (but not complete off), and instantly rised with next step ...

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Viktor
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Reducing the current was my first thought too and I have dialled it back a bit on both drivers but it still seems the same. I didn't want to go too far down that route in case I went too far on one side and it started losing steps, they were out of sync and skipping steps when I first got it & I'm sure it caused some minor psychological damage trying to figure out what was happening.

I'm not sure if this board (MKS Base V1.4) can be put into a sleep mode for drivers but I'll look into it. The firmware is a cut down tailored piece of work (quite well done though) , everything seems to be dumped into the configuration.h and configuration_adv.h. It's a slick setup but not so user friendly in some respects.

I'll dig my way through it Tomorrow and see what I can find.

Thanks for the reply @VDX

That board should be able to run smoothieware. All config in one text file. Why would you mess around with Marlin?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

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the_digital_dentist
That board should be able to run smoothieware. All config in one text file. Why would you mess around with Marlin?

DD, are you thinking of the MKS Sbase? That can run Smoothieware and RepRapFirmware. The MKS Base (without the S) is an 8-bit board.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Oh! You're right. Never mind...

It looks like that board has on-board drivers, but still uses pots to set the motor current. In that case, try turning the current down until the motors skip steps, then turn it back up a little until they stop skipping.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I played around quite a bit with these stepper drivers over the last week and they just don't want to run the steppers at a reasonable temp without missing steps.

I have them on separate drivers Z and E1, if I make a split cable and run them both from the same driver will that halve their operating current and enable them to run cooler?

Edited 2 time(s). Last edit at 02/12/2019 04:37AM by Shreks donkey.

That machine normally runs with a single Z axis motor and screw. Adding a second motor should reduce the load on the first motor, unless the second motor set-up isn't done right.
Post a few pictures of the machine, especially the modification that adds the second Z axis motor and screw.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Yeah it did have a single Z axis motor when my mate got it, it was a top mount setup on a flimsy acrylic plate. He set it up with dual Z steppers mounted on the bottom with brackets from thingiverse printed from PLA but the brackets he printed melted from the heat of the steppers and they were softening up and distorting every time the machine ran. So I ditched the printed brackets and ordered some metal brackets which should arrive in a few days.

It wasn't the load on the motors causing the issue it was the holding current when they weren't moving causing the issues during long prints. Some of the prints he was doing were big flat things where there was almost no Z movement , so the steppers were sitting for ages just holding the load on each layer. For thinner taller prints the motors ran colder than most of the steppers I've got on my printers.

He had two different lead screws in it when he dropped it off and they had a slightly different pitch which caused quite a few headaches until I decided to pull them both out and compare them.

The machine is in pieces right now so I can't really show you any pics. When I get the parts and get it all back together I'll post a few pics.

I'll be glad to see the end of the bloody thing to be honest, if it were mine I would have salvaged what I could off it and built my own RepRap with the parts.

Edited 1 time(s). Last edit at 02/12/2019 04:46PM by Shreks donkey.