Print fan error and cycling on/off constantly  

Re: Print fan error and cycling on/off constantly

Is this normal for the print fan to cycle on and off constantly through the print? I have a 75 hour print job. It's annoying but if normal so be it. I would assume it would just adjust the RPM as needed to maintain temps vs. on/off cycles.

could be, depending on the model and slicing settings used but if its throwing an error then its a wiring issue. the blower fan, more than any other parts, seems to have delicate wires and more than a few of them have failed.

check the einsy board connector, check that the wires aren't pinched by ties on the hotend itself, and if nothing looks out of place i'd try their live chat. usually much faster to get a response that way.

Re: Print fan error and cycling on/off constantly

The issue was the common one with the i3 MK3 print fan when printing a large object. The print fan wire is not strong and when the extruder goes the limits of the bed it bends and breaks the wire internally. I removed the protective wrap and I could feel the print fan flexing too easy at one point. I cut the wire and removed that short section and spliced them together again and now it works.

Thanks for this youtuber that had a great video and has a nice part you can print on thingiverse to help prevent this which I'll be installing.

I have spare fans on the way but the difficulty with communicating with Prusa has been troubling. I never see live chat online and my emails go days in getting answered, if even getting an answer. They need to separate the INFO emails to a support channel for current customers needing assistance.

The fan on/off is not normal, my guess is 1 of the 3 wires was broken but the fan was getting power. So prusa was able to start/stop the fan to manage the temp but not manage the fan properly if the sensor was intact.

Problem solved, good lesson learned.

P.S. I tried the youtuber's thingiverse "thing" to put on the cables and that does not work for me (TPU printed) as the i3 keeps reporting crashes with it installed.

Re: Print fan error and cycling on/off constantly

it is so easy to rewire things like 3 and 4 wire fans if you have a broken wire just splice in new wire (use fine strand wire high flex silicone insulated sort and use crimp splices and heat shrink tubing for strain relief not soldered and the replacement will outlast the fan itself... If you can build a printer kit you can rewire things like fans... Admittedly it was easier back when every small town had a radio shack store to do this sort of thing when I had fatigue failure in the heater wiring in the efector whip on y Delta printer i fabricated a strain relief in the repaired high flex area with about 5 different sizes of heat shrink tube with each larger tube a little bit shorter,,, that was over 4 years ago and it has not failed again.

I can understand the feeling of "why did not Prusa do something" like this with these vulnerable fan and thermistor wiring?! I expect it os down to the incidence of failure (Prusa runs some 300 MK3 printers 24/7 in their printer farm making the parts needed for production at 6000 printers a month so they know the rate at which things fail and how often a printer in the farm needs to be overhauled. and they know the warranty claims the support department sees each month and the cost of repairing (or in the case of these fans replacing them) is less then specifying the high flex micro strand wiring for them from their supplier which at a guess would be just 50 cents a kit.... or $3,000 a month increase in parts costs. volume manufacturing is all about juggling these sorts of trade offs.

Re: Print fan error and cycling on/off constantly

...
Problem solved, good lesson learned.
...

The correct cable placement/guidance is crucial. In the video you've posted, you can see it's done inaccurate that's why he has a bending at this spot.
I did the same mistake on my MK2. Because of this I had to rewire FAN cables twice. It took some time until I realized what's wrong.
With my next printer MK3 I paid attention to this during the assembly. My cables are flexing very nice and even in all directions at max length. Will try to say: It can work with the provided equipment many hours. But it's also very easy to assemble it wrong and get the first broken cable very fast.

Besides of that: All cables which you bend will break over time. The only difference is after how many hours, depending how strong you bend them.

Re: Print fan error and cycling on/off constantly

...
Problem solved, good lesson learned.
...

The correct cable placement/guidance is crucial. In the video you've posted, you can see it's done inaccurate that's why he has a bending at this spot.
I did the same mistake on my MK2. Because of this I had to rewire FAN cables twice. It took some time until I realized what's wrong.
With my next printer MK3 I paid attention to this during the assembly. My cables are flexing very nice and even in all directions at max length. Will try to say: It can work with the provided equipment many hours. But it's also very easy to assemble it wrong and get the first broken cable very fast.

Besides of that: All cables which you bend will break over time. The only difference is after how many hours, depending how strong you bend them.

FYI - I bought this i3 MK3 "assembled" from Prusa ($200 additional)

Re: Print fan error and cycling on/off constantly

FYI - I bought this i3 MK3 "assembled" from Prusa ($200 additional)

I know what you mean. But the company is growing so fast. I'm pretty sure they have many new guys assembling it. Don't expect superior build quality only because it was done in-house.