Mendel Working Again

Two more cartridge heaters arrived and I fitted one. This time there were no failures. The printer is now fitted with a new 0.3mm nozzle and is printing nicely. I had to change the nozzle size from 0.7mm which I had set to try to get the blocked nozzle working. The 0.3mm is smaller than the original one (the 0.5mm was out of stock), and seems to provide better results than the 0.5mm, but is slower. I have managed for the first time to print out one of the small gears for the extruder, which I never managed with the 0.5mm. 

I've also put the nut that holds the bed on to the carriage back in, which means it doesn't wobble, and so should have even better results.

Mendel

The replacement for the cartridge heater arrived yesterday and I fitted it this morning. Unbelievably it also failed in the same way. I cut the heater open and it seems to be a problem where the heater element joins the connecting wire. The element is 3R, the join is open circuit. So maybe it isn't anything I'm doing...

More Mendel Problems

The problems continue... The new hot end parts arrived, and were fine, but i couldn't get the old heater resistor out of the heater block. So i ordered a new cartridge heater, which is the replacement for the resistor. I fitted that this morning and wired it up. heating up the hot end, I saw the temperature reach 150C or so then drop back. Measuring the cartridge heater found it to be 350k, so essentially open circuit. I'll have to get a replacement...

Looks like the new Duet electronics that are on the Fisher printer can be retro fitted to the mendel, so I'll see how that goes and maybe do a retro fit later. That'll solve the problems I'm having installing host software on older hardware.

Mendel 3D Printer Problems

My Mendel 3D printer has been working fine for a while, apart from an over temperature moment when a thermistor went open circuit. Recently, though, I've wondered if the platform stepper belt was a bit loose. As things were still being printed I didn't worry too much. The printer is in a box that has filament reel holders and so didn't flex too much when I moved it about. Now I have a new workshop and a dedicated place for the printer to live, I moved it to it's new home. I haven't had time to start it up recently, but yesterday I decided to run it up and install the software on a new control PC. After powering on I popped to the other workshop room for something and when I came back noticed that there was a 'hot PLA' smell. Not good. Here we go again I thought, thermistor problem. Power off, multimeter out to check the thermistor resistance. The problem was obvious when I started to probe the thermistor screw contacts: the wires to the thermistor had fallen out. Not good. The second wire down in this picture was hanging out:

This meant that the thermistor was open circuit and the control electronics seem to always be performing the PID (even when hot end is off) and with the open circuit it drives to max temperature. Which is quite hot.

I reconnected the thermistor wires and started again. No smell this time.
All started off quite well and I tried printing a badge holder. No luck. Twice I got a mis-alignment of later layers, like this:

Platform stepper belt I thought. Turns out I was right, and I have now found out where the M3 nut I found came from. The stepper belt connection blocks are under the bed and I hadn't noticed that one had fallen off. As the connector block has a tooth that engages with the belt teeth, it looks like it had only jumped a tooth or two. 

After removing the bed and re-tightening the connector blocks it looks like the printing is much better, no misaligned layers yet, and a much tidier print. It's working more like I remember from just after I built it.