Tag Archives: reprappro

Setting Up Megatronics

Steps per mm

Possibly the most exciting thing for me when building a 3D printer is the electronics. I have built 2 kits (a Huxley from eMaker and a Mendel from RepRapPro) and am now building my own design. Until any printer gets attached to its electronics it is a mere metal doorstop. What I wanted to write up about was how I calculated the steps per millimetre for the DSF.

While in my usual ‘I’m bored lets search the net’ mood, I stumbled across the excellent RepRap Calculator3 ┬áby Josef Prusa. If you are building a printer from scratch this will greatly simplify figuring out what number the steps per millimetres should be.

Like many of the printers out there my DSF uses belts for the X and Y axis’ (T5) and a lead screw for the Z (M5). For the belt drives all I needed to change was the belt preset to 5mm – or the T5 belt. The pulley I was using was already 8 teeth and 1/16th stepping. As a result this would give me 80 steps per millimetre or a 0.0125mm resolution.

The Z axis uses an M5 threaded rod as its drive so again all I needed to change was the preset to M5. This means a step of 4000 steps per millimetre or 0.00025mm resolution. Obviously that is much finer then any of the prints I would ever do, the finest I have done was 0.1mm/layer. In reality I could set the stepper to full steps and still retain a resolution of 0.004mm.

So thanks to the calculators I have a 80 steps/mm for X and Y and 4000 for Z. Ignore the 800 for the extruder above. I have not yet got an extruder so that is just place holding!

One last thing; I have limited the feedrate of the Z axis to a low 2mm per second. Any faster and the motors stall. I need to oil the threaded rod to try and get some extra speed out of it, but I am not holding my breath.

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Simple Cooling Fan for RepRapPro Mendel

Simple but very effective

At the school I work at we have a RRP Mendel. I was trying to print some students work but it kept failing. Eventually I discovered that the problem was down to curling from some overhangs on one piece. As the part had 45degree angle and only 5mm thick, the printer was catching on the curled ands and eventually cause the printer to miss some steps. I needed a way of cooling the plastic faster.

I then found an 80mm computer case fan that was being recycled. As I needed to get the part printed I simply cable-tied the fan onto the smooth rods of the X-Axis. Amazingly these are about 80mm apart and the fan fitted beautifully behind the X-Axis endstop. Now I was able to get the print to finish and have a great look as well.

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Filed under Musings