OhmEye

I posted this on a Google group recently and thought I’d repost it on my own blog:

I have been converted to an evil and lazy extrusion calibration anarchist. I no longer believe in measuring filament diameter or how much filament is pulled in, or adjusting the filament settings when slicing. All that painstaking effort is in the hope that if it’s done carefully enough that the calculations will result in the correct extrusion rate without needing any additional tweaking. I was abducted by aliens (or at least an Australian) and brainwashed to avoid all the extra work and skip all the measurement and mathematical masturbation by just watching the extrusion rate during a print and adjusting it until it’s correct. ↓ Read more…

This is an example of a typical and simple home repair solution when a 3D printer is available. Instead of replacing an inexpensive small mirror or attempting to recover and glue the broken pins that attach the mirror to its stand, I decided to add a thin frame piece to the mirror with new pins. With just 3 measurements and less than 20 minutes of work I had a file ready to print, and the solution seems to work well. I probably spent as much time producing this photo gallery as I did doing the work itself. 🙂 My point in posting this is to show a typical example of just one of many ways I find myself using a 3D printer in applications in our home. It didn’t take long after learning some basic design tools to find myself discovering ways to use 3D printed parts to solve mundane household needs.

So although my MendelMax 2 beta2 has only minor Z wobble visible in the prints as long as the leadscrews are not constrained at the bottom by bearings, I wanted to completely eliminate the wobble from appearing at the nozzle. I also prefer constrained leadscrews, I think the bearings help support the weight of the X axis and result in slightly more precise Z movement by taking weight off the flexible motor couplers. I designed a simple part to mount to the leadscrew nuts to support the X axis without being directly connected, so that any XY movement just slides harmlessly against the bottom of the Z arms and they only move in the Z directions. Files are in http://ohmeye.com/download/mendelmax/

I often see confusion by people in IRC about how to disable and enable endstops so that accidentally sending a home command (G28) doesn’t cause their printer to crash an axis past it’s physical range. G28 is a command that moves an axis until it triggers an endstop switch placed at the end of the axis. When the switch triggers, the position is set to either MIN or MAX for the axis, depending on which direction homing is set to use. Homing to the MIN endstop is by far the most common method, so G28 moves the axis in the negative direction looking for an endstop and stops when it triggers it and sets the current position to zero. If you don’t have an endstop installed, it will never trigger it and try to go farther than it can, and various bad things can happen, what I call “crashing” the axis. To avoid this, if you do not have hardware endstops for the G28 command to use, you can disable endstops completely in the firmware. ↓ Read more…