Monthly Archives: March 2011

Printing

Print Quality Progression

The secret is Skeinforge!

So far I had steered clear of Skeinforge because it seemed quite advanced and complicated, but my general aim today was to improve the print resolution, and my particular goal is to print a replacement Mendel pulley. These are sufficiently intricate, and also small enough to print quickly. The difference between the results yielded from the repsnapper gcode generator and Skeinforge is pretty big, which comes as no great surprise really, and I was pretty happy with the results.

The two videos from Prusa helped get me started working with the tools, and his initial Skeinforge settings seemed to produce good results.  Of course there is still a lot of tweaking to do – but progress has been made!

 

Printing

Print Quality Regression

Sadly today’s results were a step backwards.  Something is causing the diameter of the extruded filament to be inconsistent (blockage? slippage? feed problem?).

From left to right: Yesterday’s calibration piece; Today AM; Today PM

Print Quality Degradation

Extruder Printing

Improved Calibration of Extruder

After finding the Extruder Steps Calculation Spreadsheet on the brokentoaster blog I calibrated the extruder to produce better results.  The important thing it seems is to measure everything on your own gear, and don’t take it for granted that the default settings will just do.

My gear ratio is 3.55 (not 5); the extruded filament diameter is more like 0.9 mm (not 0.5, although I will measure this again tomorrow); the Pinch Wheel Diameter (PWD) is 6.7 mm (not 8) and the steps per revolution is 3200 (after taking into account the 1/16 microstep setting).  Consequently, the E_STEPS_PER_MM comes out at 48.5 according to the spreadsheet, a much higher value than the original setting of 22 in the Tonokip firmware I am using.  The initial results seem much better.  Still much room for improvement – but I was able to print a (rough) replacement end-stop holder, after my Z axis holder broke from over-zealous tightening last night.

Hopefully I will find time to formulate the process I went through and add it to the wiki, or add to an existing page if it already exists.  I think these calibration steps, together with getting the right firmware/host combination, is a potential sticking point for newcomers, and providing clear directions and help would really help.

Printing

First Print Attempt

The extruder is still not pushing enough it seems, and this test mini-mug was printed largely with the help of gravity, but I’m happy to have something produced so soon after starting the Mendel build!

And the obligatory first video.

I was worried the printer might be too loud but i’m quite happy with the sound level, and I find the “tune” it makes whilst printing is actually quite soothing!

Extruder

Makeshift PLA Feeder

Two spare skateboard wheels
+ smooth rod from an old printer
+ spare shelf parts
= Makeshift PLA Feeder!

Frame Hot End

Calibrating the Top Plate

Uncategorized

Testing the Extruder and Hot End

Time to learn about temperatures, motor speeds and material science!

Documentation

Alternative Front Covers

Whilst putting the visual guide together I created a few images for the front cover, some of which I thought looked quite good.

Hot End

Constructing the Hot End

This Hot End looks too neat and pretty, so I guess it won’t last long. I suspect the red front wire connection will melt once it gets too full temperature, but i’ll give it a go tomorrow.

I also successfully got the test setup to heat up to 200°C and manually fed some PLA through.

Attaching the nozzle and insulator

Attaching the nozzle and insulator

Crimping the NiChrome wire

Crimping the NiChrome wire

Attaching the NiChrome to the nozzle

Attaching the NiChrome to the nozzle

Attaching the thermistor to the nozzle

Attaching the thermistor to the nozzle

Close up of the completed Hot End

Close up of the completed Hot End

3D Modelling Documentation

Prusa Mendel Visual Instructions

Whilst building my Prusa Mendel I started playing with Google SketchUp, and when I came across a model of the Mendel it inspired me to set myself a goal of interpreting the Prusa build steps in the same style as a Lego or Meccano instruction manual.  This was also partly prompted by the call to arms in the reprap.org Community Portal to produce documentation that lowers the (already quite low) barrier to entry even further.

 

The front page

The front page

The original instructions on the wiki are already clear and easy to follow, so the text from each step is simply copied verbatim.  This document is deemed to be a supplement to them, and perhaps will help people with less, or no, mechanical background grasp what is involved in building a reprap, or stop a few mistakes from being made during a build (as I did – embarrassingly having to rebuild the front rods a couple of times due to misreading the diagram – which, of course, now seem clear with hindsight :))  Regardless, I had fun putting it together and learnt a but about SketchUp (and the Mendel) in the process.

A sample of the content

A sample of the content

 

The guide is available in PDF format and in several sizes from the start page: Prusa Mendel Visual Instructions.  The document was put together in Microsoft Publisher and this, together with the SketchUp model I created, is available as a github project for people to fork and use as they wish.  There is also an issue tracker to take bugs and suggestions.