Edit:
The bulging problem disclosed here looks very similar to what I am experiencing.
Post:
I have a Mini 1 purchased in 2018 and used semi-regularly since, not sure of the manufacture date. The printer communicates with Cura LE over USB. No screen, no MicroSD. The printer is fairly well maintained, clean, dialled in, lubricated.
The case fan for cooling the RAMBo board (I believe v1.3) no longer spins without assistance, in the form of poking a (non-conductive) spudger through the case to set the fan spinning. When the system is idle and the fan isn’t running I can hear a faint intermittent but frequent electronic buzzing/squeaking noise which might correspond to a PWM signal.
I’ve performed a fairly solid diagnosis that correlates either:
- Overheating of the RAMBo board;
- The fan not spinning,
- or both.
Particularly, I have ruled out the host computer and USB cable.
With transient loss of print fidelity, typically manifesting as what I suppose is either:
- Overextrusion.
- Dropped commands or failed hot end moves.
I strongly suspect the latter. This loss of fidelity is in the form of layers which are wider than expected, which produces a print which is ribbed in the x,y plane with unacceptable dimensions. I attribute this to a missed z-step. In such prints the hot-end retraction at the end of the print is anomalous, pausing for a fraction of a second at about 1 second intervals. Unfortunately I don’t presently have any examples to take a photo of.
If I set the fan running manually by pushing it with the spudger, I get basically ideal prints.
I have popped the case and run the fan up to 24 V DC and it seems okay. I think the minimum voltage for spinning up unassisted was about 5 V.
I request assistance and advice in diagnosing what is going on here. I have read other threads and discussions on Lulzbot specifically and RAMBo more generally, and suspect 5 diagnoses/courses of action:
- Fan is dying, replace fan (need to know precise model).
- Fan is dying, increase PWM duty cycle in firmware or G-code (how?).
- Fan power MOSFET is damaged (replace MOSFET).
- Fan power MOSFET is damaged (replace RAMBo).
- Fan power MOSFET is damaged (patch fan directly into PSU and purchase hearing protection).
Assume I have:
- Amateur to intermediate electronics skills.
- Amateur to intermediate microcontroller programming proficiency.
- Strong Linux proficiency and a Linux box.
- An oscilloscope, multimeter, bench PSU, soldering iron.
- Very limited SMD desoldering and reflow capabilities (specifically a Miniware MHP30 hotplate).
Thank you in advance to anyone who takes the time to lend their expertise.