Lessons in Rapid Prototyping and Design

Never before did I realise what a huge difference software and firmware can make to 3D-print quality.

Not long after setting my reprap up again in its new home, I found it having problems moving in the Z-axis, where the motors would refuse to move half the time, which after describing it on IRC people helped me figure out that the controller was telling the motors to accelerate too fast.
The acceleration that had been implemented in June 2011 Sprinter firmware still caused a significant amount of 'jerkiness' in axis movements. By updating to the latest version for June 2012, not only did more appropriate acceleration, adjusted by a predictive 'look-ahead' buffer, improve this current problem, but it also cut out a vibration problem that broke my Y-axis last year, by pausing at the end of each move for a few ms, when making very short successive movements in order to draw a narrow zig-zag fill line. This helps because in most stepper-motor use there is no feedback control mechanism - the idea being to move a set number of steps then lock in place and hope for the best, which in reality can result in nasty vibrations. By stopping for a moment, the transient vibrations resulting from overshoot can settle, so there is less chance of them feeding into some resonant frequency and shaking the printer to bits.

Illustration of overshoot, via Wikimedia Commons.

In the new firmware a minimum temperature is now set by default, which might have prevented another previous incident that I had with over-heating when a thermistor connection broke.

Replacing Small Parts by Rapid-Prototyping

Since getting back to the city I've been on a small spree of trying to find little things that I could replace or redesign using 3D printing, whenever there was a moment to spare.

Firstly, for a long time I'd been meaning to make replacement parts for a very humble purpose, the male buckle clips on a couple of Highlander rucksacks I have that had mostly lost their teeth after many years of fatigue when packing and unpacking heavy luggage, while the rest of the nylon construction remains as functional as the day I got it.

The buckles used here, with 'Rock Lockster' imprinted along the T-shaped guide, lasted for probably a few thousand clip-unclip cycles over the course of several years before teeth started to break off all the clips. The replacement I made is shown clipped in.