Print jumps 7mm in Y direction after initial layers

[Drone]

My guess is that the Y motor also has more work to do. Anyone know how the weight of the Y bed, heater, glass, and rolling hardware compares to the X-carriage and extruder parts? Plus, as the print grows, the weight that the Y-motor needs to move around keeps going up...

All very good points Printbus. Keeping that in mind it might make sense to look at the part being printed and the orientation it is being printed in. If the part is much narrower in x than y, for the same reason it might make sense to reorient the print to put the longer direction on the x axis.

[printbus]

All very good points Printbus. Keeping that in mind it might make sense to look at the part being printed and the orientation it is being printed in. If the part is much narrower in x than y, for the same reason it might make sense to reorient the print to put the longer direction on the x axis.

I was going to argue that it wouldn't make any difference, but I see your point. Putting the bulk of the print in the X axis would minimize how much movement is required in the Y direction. Interesting thought.

OME - We're just offering you ideas on what could be causing your Y axis issue. You certainly have the right to discard any of the suggestions that are provided.

[Roxy]

My guess is that the Y motor also has more work to do. Anyone know how the weight of the Y bed, heater, glass, and rolling hardware compares to the X-carriage and extruder parts? Plus, as the print grows, the weight that the Y-motor needs to move around keeps going up...

Agreed... There are a couple of corner cases. Like what if the Slicer was pretty much just generating GCode that moved the X Axis. But in general the X & Y movement are going to be similar. The difference is the Y motor is moving much more weight. That is going to factor directly into how much energy is being pumped into the Y motor.

[old man emu]

OME - We're just offering you ideas on what could be causing your Y axis issue. You certainly have the right to discard any of the suggestions that are provided.

No problem with that. This is a discussion, after all. We hope to reach a conclusion that explains the situation.

As to the Mass that the steppers are moving, if you discount the parts common to both X & Y axis units, such as the linear bearings, idler bearings and components, you have to compare the weights of items being moved.

As an approximation, I'd say that the print board and heater on the Y axis are the same as the extruder gear assembly including the hobbed bolt on the X axis. The extra weights are the extruder itself, its cooling fan and the biggy, the extruder stepper motor. A NEMA 17 weighs approximately 11 oz (~300 gm). So, I'd say that the X-axis stepper has to do more Work ( Mass x Acceleration x Distance) than the Y axis.

Drone might have hit on a factor. Originally I had the object sliced so that its length in the X axis direction was greater than in the Y axis direction. I had an unrelated issue with that print (uneven bed), so I re-sliced so that the object was longer in the Y direction than the X direction. That meant that the Y axis stepper had more work to do, and that's when the jump happened.

What I am not satisfied with is that after the jump, the print continued with all subsequent Y positions offset exactly 7 mm from the pre-jump Y positions. The extrusions after the jump were as neat as those before it.

I'm going to run another print tonight to see if room temperature was a factor. It's cooler tonight than on the afternoon that I encountered the problem.

Old Man Emu

[old man emu]

UPDATE:

I did the prints last night - it's nearly 8:30 am as I write this, you sleepy heads - and the jump did not happen. The ambient room temperature was 21C.

I think I might put my money on "Overheated Y Stepper" to win the Reason Stakes and bring a fan when the temperature out in the field is over 30C.

OME

[Drone]

Glad to hear you got it figured out EMU! Now you need to implement a long term solution. A 9c differential in ambient temp must mean you are running on the ragged edge between a successful and unsuccessful print even at 21c ambient. So get a cooling solution, new motor, or another method to make sure you don't waste time on unsuccessful prints due to overheating issues. Long prints that fail partway into a print suck and definitely require a remedy to eliminate.

[gmay3]

UPDATE:

I did the prints last night - it's nearly 8:30 am as I write this, you sleepy heads - and the jump did not happen. The ambient room temperature was 21C.

I think I might put my money on "Overheated Y Stepper" to win the Reason Stakes and bring a fan when the temperature out in the field is over 30C.

OME

Great news OME! I also put my money on "Overheated Y Stepper", as this was the direct cause of my problems as well. Then I put my money on 3 new stepper motors that printbus suggested . Here's the Amazon link below:

http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

[gmay3]

Just wanted to give an update. I have received the 3 new Kysan motors and replaced the y, x, and extruder motors. No modification to the stepper driver pots was needed (the 0.39V measurement thing). I did need to solder on an extension to the wires for the x motor, but Colin included them with our printer kits which was fantastic!

Over all they seem much higher in quality compared to the motors shipped with the 8" i3v. There is less resistance when I turn the shaft on the kysan motors compared to the old ones when both motors are unplugged. Most importantly, they were even cooler to the touch than the old z motors were at the end of the print. They are quieter and emit some musical tones instead of of a low rumble/sawing through wood sound when printing.

Very satisfied with these new guys! A big thanks to ya printbus!

[printbus]

I concur on the quality assessment, but I didn't want to push things more than I already had earlier. Just a reminder that the Kysans are wired with 22 gauge wire rather than 26 - I view that as significant in itself. Good to hear yours are also quieter, since I thought my extruder was running quieter now as well. All these reasons could be why Kysans are frequently recommended.

Guess I now want to bump more of these higher on the wish list for motors other than the extruder.

FOLLOWUP POST: To those that have the i3v-10 and i3v-12, remember that gmay3 and I are discussing replacements for an earlier motor Colin was using in the i3v-8 kits.

[AbuMaia]

And possibly in the i3 8 kits as well. I'm nearly convinced to upgrade my motors too.