And at the last, a solution

Tonight was incredibly frustrating RepRapping. I was trying to print one of Prusa's newest design X end idler with push fit connectors. This thing is kind of rough on the printer for various reasons I won't get into, suffice it to say that it shakes the table when printing.

I aborted two attempts at it last night and 5 tonight. The layers just were not stacking up. This means that the printer was skipping steps in both X and Y axes. I tried everything I could think of including replacing the motor drivers, retuning the drive current, changing the way the software was laying out the part, and a few other things. No luck at all.

In a final desperate act, I switched back to the older firmware. Bingo, problem solved. After describing the events to folks on IRC, it turns out that the default acceleration and jerk settings on the firmware are probably a bit too hight for my printer and it's driving the motors against inertia just a little too hard. For tonight I'm letting it finish up the print with the old firmware but I'm going to try reducing acceleration on the newer firmware, because the new firmware is SO much nicer - the old "Sprinter" firmware starts and stops at the ends of every line segment as it goes and that shakes the hell out of the printer.

I was having very dark thoughts about DIY 3D printing along about 9:30 this evening, but after putting the old firmware back on it's in the middle of a beautiful print with perfect bridges, and all is well again.

This is clearly the root cause of a lot of trouble I've been having over the last week or more, so I'm glad to have the actual cause finally isolated.

And Stephen Fry has a new miniseries about language that I'm watching so it's all good.