trimmers in electronic box

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artohautala
Posts: 13
Joined: Sat May 17, 2014 3:19 pm

trimmers in electronic box

Post by artohautala » Fri Jan 23, 2015 5:21 pm

HI ,
any idea how to really set those trimmers in electronic box ?
in manual there is only picture of they positions
but how trimmers affects to step motors ... or other things ...
can you tell me pls...
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-arto-

satoer
Posts: 436
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Location: Netherlands

Post by satoer » Fri Jan 23, 2015 10:15 pm

It’s the power to the stepper motors.
More power = Stronger turning power of the stepper motor. But as a result: also hotter stepper motor and hotter stepper motor controller (even risk on overheating)
Less power = Weaker turning of the stepper motor, this results in cooler stepper motor and cooler motor controller. But you risk skipping steps (and if it's even skipping one step, the whole print becomes misaligned).
So, you need to find the perfect sweet spot.

If the stepper motor stops suddenly for a second or more: Overheating stepper motor drivers => Adjust less power to the stepper motors.
If the stepper skips steps: Stepper motor's need more power => Adjust more power to the stepper motors.

The trimmer positions in the manual are usually a good starting point. If the steppermotor skips steps there are also other reasons why this can happen. Like a too tight belt or too much pressure on the filament spring.
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Dreide
Posts: 176
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Location: Lausanne, Switzerland

Post by Dreide » Fri Jan 23, 2015 10:19 pm

The trimmers are used to adjust the currents of the stepper motors.
See also http://forum.felixprinters.com/viewtopic.php?f=11&t=949.
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kerog
Posts: 117
Joined: Mon Jun 09, 2014 1:54 am

Post by kerog » Sun Jan 25, 2015 7:58 am

Every once in a while, it looks like I get a single instance of a wrong stepping. This results in subsequent layers of the print being shifted over, sometimes by as much as a centimeter. I've only seen it happen on the first few layers of a print, though, and it only happens *very* occasionally. I think this is what the Make reviewers were seeing. The belt tightening explanation doesn't make any sense to me, but I'm not sure this does either. Does anyone have a clearer description of symptoms from specific belt or stepper potentiometer issues? Seems like either of those would result in more consistent issues than what I'm seeing.

Typical example enclosed.
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Dreide
Posts: 176
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Location: Lausanne, Switzerland

Post by Dreide » Sun Jan 25, 2015 10:24 am

kerog wrote:I've only seen it happen on the first few layers of a print, though, and it only happens *very* occasionally.
During the first few layers the risk of losing steps might be somewhat higher because if the print bed is a bit closer to the nozzle than specified in the slicer (plus perhaps Z offset in the firmware settings), you will get over-extrusion. This not only creates a bit more drag on the extruder while extruding but also pushes some material higher than the nozzle as the material cannot go anywhere else. If the nozzle runs into such surplus material while traveling to a new location, additional force is needed to keep the extruder moving. You can tell the slicer by how much the extruder should be lifted when traveling. A few layers into the print and depending on several factors, the surplus material from the first layer will eventually have no effect anymore - at the latest when infill is sparse, surplus material has other ways to go than just up. In your case it looks like you might have over-extrusion in the first place though; but anyway, the motors should be strong enough to cope with this, especially if the part is small and the material is still warm and soft when the nozzle runs into surplus material.
kerog wrote:The belt tightening explanation doesn't make any sense to me, but I'm not sure this does either. Does anyone have a clearer description of symptoms from specific belt or stepper potentiometer issues? Seems like either of those would result in more consistent issues than what I'm seeing.
The tighter the belt the more force is needed to move the X carriage (or the bed in case of Y). And the more power the motor gets the more force (torque) it can develop - normally at least. But as satoer said, higher power also means more stress on the electronics and the motor, let alone the motor becoming noisier.
Another phenomenon that might play a role here is that the force needed to bend the belt around the pulley (and the counter bearing) depends on how the belt was bent before. If you don't use the printer for a while and then manually move the X carriage, you will notice that it moves easier close to the position it was resting all the time before. The same happens if you only print small parts and always at the same position on the print bed. The effect is the stronger the higher the belt tension is, and it needs a while before the belt gets "used" to the current position range. So again something that will be more prominent in the beginning of a print.
Last but not least, there is the pulley issue. If the pulley can slip on the motor axis, this will cause torque peaks as well. So it is good practice to check the pulley set screw then and when.

Especially abrupt force changes will be problematic for a stepper motor, and once one step is lost further such steps are likely to follow. I don't think that any of the issues will cause consistent symptoms as there are just too many factors that play a role. And you cannot conclude from steps being lost just in the beginning of a print that this is primarily caused by a problem that occurs more likely at the beginning of a print as well. It could just be that this problem, which usually might be well tolerated, is the straw that breaks the camel's back.
Felix 2.0->3.0dual * Repetier (host+firmware) * KISSlicer Pro, Simplify3D * Cubify Design

kerog
Posts: 117
Joined: Mon Jun 09, 2014 1:54 am

Post by kerog » Sun Jan 25, 2015 8:18 pm

Thanks for the detailed explanation!

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