Update: a re-design, reducing heat escape and a weird problem

I haven't updated for a few days as I've been busy with other things. However, I've not been ignoring the problem completely. 

My next priority is to redesign the orientation of the X-axis cable chain as I described in my last post. Clearly I should have done it that way initially and I'm now kicking myself for deciding against it and going with the seemingly more simple path that I did. Having said that, it shouldn't be too arduous to redesign it and replace the parts. I just need to find a little time.

As part of my ongoing testing, the printer developed a very weird problem. Ironically, I had just completed a very good tuning of bed level and managed to print a very good example of the test print I designed. 

The very next day I tried to print another quite wide print and the right-hand side of the print just disappeared, almost as if the bed level had risen sharply on that side. I rechecked the level numerous times and everything seemed OK.

I decided that the next thing was to remove the bed completely. This is something which I needed to do anyway as I wanted to fit the insulation pad which I had received quite some time ago.

I first stuck some kapton tape over the exposed thermistor and wiring connections.

It was then an easy exercise to fit the foil-covered foam sheet to the base

I then pierced the four mounting holes for the bed levelling screws and was able to re-fit the bed.

Early testing has been very postive. The bed does seem to heat more quickly. Of more significance is that it seems to cool noticeably more slowly, which is very helpful when I'm carrying out more than one print. Previously the bed would drop very quickly from print temperature and take a long time before it was then ready for the next.

Next, I re-assembled the bed, relevelled and tested again.

The same problem was present, despite the fact that it was now certain that the bed was flat. So, I set about determining why the right side of the bed wouldn't print. It's worth saying that I'd already checked that it wasn't greasy and had cleaned it assiduously. 

After watching the first layer print very closely, I finally noticed that the extruder stepper actually started stuttering on the right side of the bed and started behaving correctly again as it returned to the left. 

Having a suspicion as to what was wrong, I replaced the stepper motor cable with another and, surely enough, the print was fine. It appears as if the slight flexing of the stepper cable was enough to affect its connection to the motor. The failing one was one of the shielded ones which I'd created and it looks as if the crimping to the JST PH connector on the motor wasn't good. It had tested fine for quite some time, but clearly something had adversely affected it.

So, I plan to reterminate that end of the cable and re-test. I would really like to stick with the shielded cables, but perhaps the choice of cable, or maybe the connectors will prove to be unwise.

I plan to report back again soon.

Thanks for reading!

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