Derby Makers

The heart of Derby's Maker community

Our RepRap Mendel 90

I’ll try and flesh this out as we go along, but here’s the story of our 3D printer and how to get started if you want to use it.

The printer is a RepRap Mendel 90 designed by Nophead. The story of how the Silk Mill came to be in possession of the printer is in Glyn’s write up of our trip to Sheffield’s Festival of the Mind here. There are various pieces of software required to be able to create the digital models and prepare them for printing, then with which to drive the printer.  In fact, there are many software packages that will do each of these but I will only list those here that we were given with the printer or that I use – not because these are the best but because I’m new to all this and sticking with what works, for now.



I use Sketchup – its free and easy to use and can be downloaded here.  To be able to create printable models Sketchup needs a plugin to export .stl files – this being a standard format for 3D model files for printing.

The plugin is available here – download the file and drop it in the plugins folder, usually C:\Program Files (x86)\Google\Google SketchUp 8\Plugins.

There is also a plugin for importing .stl files to Sketchup here.  Note the link for downloading the file is a little way down the page, just above the comments section – not the big download button at the top which is an advert for something else completely.

When drawing in Sketchup make sure you have set the dimensions of your drawing to millimetres or inches, then when exporting to the .stl format pick the same dimensions – this will help to ensure the print is the size you want it.


A relatively new one to me, but it came in very useful when trying to prepare some of my initial models for printing.  Any holes, gaps or reversed faces in the model will cause problems for the slicing program.

netfabb Studio Basic is a free program that will check the .stl for any problems.  It can be found here. When you run the program, open the .stl file you exported from Sketchup (Project -> Open).  If you get a hazard warning triangle below and to the right of the image then there are things to fix.  Click the red cross on the toolbar to bring up the repair tool, click the ‘Automatic Repair’ button, select ‘Default Repair’ and click ‘Execute’.  Then click the ‘Apply Repair’ button then ‘Yes’ to remove the old part.  Then click Part -> Export Part -> as STL to save the file back to disc.

You may get an extra errors warning here with the option to repair them – click ‘repair’ then ‘Export’ and this bit is done.


Skeinforge seems to be Nophead’s slicing engine of choice, probably because it is highly configurable.  Unfortunately it’s not that easy to understand.  Fortunately we don’t really need to, as the hard work has already been done in the shape of the config file we have (provided by Nophead).

Firstly get the application:- 50_reprap_python_beanshell (zip file).  Installation requires some supporting bits and pieces (such as Python), so follow the guide in the wiki (here) to get it installed.

The config file is in this zip file (skeinforge) and unzip it into C:\users\your user name\.skeingforge (note the ‘.’ at the beginning of the folder name).  This config defines all the settings skeinforge will use to ‘slice’ the model in to the layers the printer needs to lay down so that the outside of the print is as smooth as the printer can make it and the inside uses the minimum of plastic while still retaining the strength.

This photo shows the internal lattice of quite a large solid copy of our logo I printed – I stopped the print before the top layers were printed as I ran out of time.


Printrun is a simple interface for driving the printer with.  Download and install to the directions here.

To be continued…..

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