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I have just finished setting up my printer for dual material printing, and I was having a problem with the extruders failing to extrude properly. At first I though it was an issue with the temperature, but as I bug tested I eventually found it to be an issue with the steppers not turning properly. Strangely, when I wasn't printing they worked fine. After extensive hair pulling, I finally narrowed it down to a heat problem, where the Ramb0 was overheating, causing the extruder stepper drivers to act strange (a sort of half-step motion instead of a full step while extruding, similar in appearance to what happens when filament jams). After pointing a small tabletop fan at the Ramb0, my problem has disappeared.

Anyone else experienced this? or other related problems due to heat?

This issue is pretty pronounced on Pololu drivers that have too much current through them, I ruined a few in my early days with a Sanguinololu controller on an H-1 never had issues with the RAMBo that was on the MAX I built for work, or even the on on the RapMan that's driving NEMA 23s.

pyrophreek wrote:I have just finished setting up my printer for dual material printing, and I was having a problem with the extruders failing to extrude properly. At first I though it was an issue with the temperature, but as I bug tested I eventually found it to be an issue with the steppers not turning properly. Strangely, when I wasn't printing they worked fine. After extensive hair pulling, I finally narrowed it down to a heat problem, where the Ramb0 was overheating, causing the extruder stepper drivers to act strange (a sort of half-step motion instead of a full step while extruding, similar in appearance to what happens when filament jams). After pointing a small tabletop fan at the Ramb0, my problem has disappeared.

Anyone else experienced this? or other related problems due to heat?

It's a common problem many users have placed an internal fan blowing on the Rambo driver chips.

I would never run a rambo board without a fan blowing on the driver chips.
You have to keep them cool or you will have strange behavior.
I think the driver cuts out to protect itself.
When your extruder 'skips' backwards (not grinding filament) that is driver chip overheating.
I have had this problem on my MAX.
The Orion does it to if I push it very hard, me thinks maybe I need to add a fan to it?
but where? it is so jam packed inside?

Extruder skipping has more to do with the stepper motors inability to overcome the head pressure in the hot end. The reverse motion you're seeing is the result of the spring force created by the filament in the bowden tube bouncing back. Try slowing down your print speed or increasing the hot end temp a bit.

g.

but the stepper motor "instability" is caused by the driver chip overheating and shutting off, right?

yes, the back spin is caused by the bowden tube back pressure spring, I get that.

bvandiepenbos wrote:I would never run a rambo board without a fan blowing on the driver chips.
You have to keep them cool or you will have strange behavior.
I think the driver cuts out to protect itself.
When your extruder 'skips' backwards (not grinding filament) that is driver chip overheating.
I have had this problem on my MAX.
The Orion does it to if I push it very hard, me thinks maybe I need to add a fan to it?
but where? it is so jam packed inside?

Insert 3' tube, put a blow-hard on other end of tube (my wife is looking for work), problem is solved.

I mounted a 50 mm to the back door of the Rambo using the cutouts they provide and wired it to the 12v output on the board so it's constantly on. Fixed my overheating problems. The other "work around" solution is opening the doors to simply allow the Rambo the ability to breathe better, but that requires longer wires for a couple of things and a messy look of a door flapping in the breeze.