Dual Y-Drive causing a lot of heat!

raynelang
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Dual Y-Drive causing a lot of heat!

Post by raynelang » Thu Jul 11, 2013 11:50 am

Hello,

I just got my Shapeoko moving around last night. I have the dual y-axis drive upgrade and am using the gtbl v4 controller with nema 17 motors. Both Y axis motors are plugged into the same controller.

The X and Z axis move nice but when I move the Y axis, even 5mm, the IC on the controller gets so hot I can't even touch it. Right now the trim pot for this axis is set to about 50%. Using a BIG fan I was able to keep the IC at a warm-hot state when moving the Y axis but I am worried that when I start cutting with the CNC that the controller is going to melt. Any suggestion for cooling this sucker or did I maybe do something wrong? (my belts could be too tight which could be making the motors work too hard?)
ShapeOko #1726

WillAdams
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Re: Dual Y-Drive causing a lot of heat!

Post by WillAdams » Thu Jul 11, 2013 12:00 pm

My machine wouldn't even move reliably until I added a fan --- cooling seems to be a requirement, but I don't think that there's that much difference between just moving the machine and cutting (if one's spindle isn't _too_ heavy).
Shapeoko 3XL #0006 w/Makita RT0701 Router w/0.125″ and ¼″ Elaire precision collets
Nomad 883 Pro #596 (bamboo)

jasonharper
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Re: Dual Y-Drive causing a lot of heat!

Post by jasonharper » Thu Jul 11, 2013 5:55 pm

I suspect that hooking the windings of the two motors in series rather than parallel would work better for driving two motors off of the same controller channel - the current drawn (which is what's heating up the chip) would be the same as a single motor. Twice the voltage is required, but assuming that you're using the recommended 24V+ power supply, voltage shouldn't be the limiting factor.

(I haven't actually tried this - I'm going for the drive shaft rather than the dual motor upgrade, primarily to avoid having to deal with this problem.)
ShapeOko #1743F, double X axis, 5mm Y drive shaft, DW660 spindle

cvoinescu
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Re: Dual Y-Drive causing a lot of heat!

Post by cvoinescu » Thu Jul 11, 2013 6:05 pm

Stepper motors need about the same amount of power when stationary and when moving, so more or faster movement won't make it worse. You can reduce the current a little, if you're concerned, but the drivers have excellent thermal protection and are almost impossible to destroy by overheating. However, if they get too hot and thermal protection shuts them down, your workpiece will be ruined, and there's a chance your endmill will break too -- so you don't want to get there. Good airflow above and below the board should keep it from overheating. It's normal for the chip to get very hot -- it probably burns skin before it goes into thermal shutdown, so be careful when probing it with your fingers.

Jasonharper is right: connecting the motors in series will give you more current through each motor with less driver heating, but you'll lose some of the benefits of a 24 V power supply (vs. 12 V). Your maximum speed on the Y axis will be lower, but your low-speed torque will improve substantially.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

raynelang
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Location: Ontario, Canada

Re: Dual Y-Drive causing a lot of heat!

Post by raynelang » Fri Jul 12, 2013 2:44 pm

I really like the idea of trying to connect them in series. I have minimal experience with steppers so i'm not entirely sure how you would go about connecting them in series. My 'coil' wire pairs are black+green and red+blue. Would it be correct to wire the motors in this way:

TerminalA -> black1 -> (mtr1) -> green1 -> black2 -> (mtr2) -> green2 -> TerminalA
Y-Driver ->
TerminalB -> blue1 -> (mtr1) -> red1 -> blue2 -> (mtr2) -> red2 -> TerminalB

Also... adding a big fan to help cool the controller helped a LOT, thanks!
ShapeOko #1726

cvoinescu
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Re: Dual Y-Drive causing a lot of heat!

Post by cvoinescu » Fri Jul 12, 2013 3:42 pm

You've got it, except you need one motor to turn the other way, so swap, say, blue and red for the second motor:

TerminalB -> blue1 -> (mtr1) -> red1 -> red2 -> (mtr2) -> blue2 -> TerminalB

Keep the other pair as you have it, do not swap both, or your motor will change direction twice (that is, it'll stay the same).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

wisof
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Re: Dual Y-Drive causing a lot of heat!

Post by wisof » Fri Jul 26, 2013 10:36 am

Anyone care to make a better graphic for this? I am trying to do the same, but not sure I have it correct. Image I can make (a much better) graphic, once I have the right connections...

cvoinescu
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Re: Dual Y-Drive causing a lot of heat!

Post by cvoinescu » Fri Jul 26, 2013 11:23 am

Wisof, your connections are wrong. You connected the coils across the two H-bridges of the driver, which is never the right thing to do. No matter how you wire the motors, all connections should be between pins 1 and 2 of the driver, and, separately, between pins 3 and 4. There should be no connection between 1 or 2 on one hand, and 3 or 4 on the other hand.

Check out this posts of mine where I give a crude (but correct) diagram. There are many permutations that work; that is just one of them. Half of them have both motors spinning in the same direction, half in opposite directions (which is what you need for dual Y, so my example does that). Here is a discussion about the merits of series vs. parallel vs. separate drivers (it's about Marlin and RAMPS, but some of the points still apply).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

wisof
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Re: Dual Y-Drive causing a lot of heat!

Post by wisof » Fri Jul 26, 2013 12:04 pm

Thanks for the link! Excellent.
Image something more like this...

cvoinescu
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Re: Dual Y-Drive causing a lot of heat!

Post by cvoinescu » Fri Jul 26, 2013 1:24 pm

Yes, it just needs cleaning up -- way too many intersecting lines for a schematic. :)

Like this (showing both parallel and series, wired for motors turning in opposite directions).
Steppers Parallel and Series 2.png
Steppers Parallel and Series 2.png (3.16 KiB) Viewed 9276 times
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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