T3P3 Kossel Mini Kit

Assembly Instructions -

Chapter 20 - Test Printing

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Think3DPrint3D Ltd


2001 Install and Run Slic3r

Slic3r is the software used to produce G-code print files from the STL files produced by CAD programs.You should download the latest version of Slic3r from http://slic3r.org/download/. If you are running Linux you should also read the installation instructions on the Github Slic3r page linked to from the Slic3 download page. The 32 and 64-bit Windows versions of Slic3r current at the time of writing are also stored on the uSD card supplied with your kit.

These installation and start-up instructions are written for the Windows version. Unzip the appropriate version of Slic3r (32 or 64-bit) to a folder of your choice. There is no installer script, and the GUI version of Slic3r is run by clicking on slic3r.exe.

When you run it for the first time, the Configuration Wizard will open.

You should cancel this and instead import the Kossel_draft.ini  configuration file from wherever you backed up the uSD card on your hard drive,  using File/Load Config.

NOTE: Early kits were shipped with the configuration file T3P3_KM_default_PLA_config.ini  and you can use this file for test slicing instead. Please email us if you would like copies of the three current Slic3r configuration files Kossel_draft.ini, Kossel_medium.ini, and Kossel_fine.ini.

After loading the config.ini file, Slic3r will open in Simple mode. You can stay with this for now, but in the longer term you will need to change to  Expert mode, so may prefer to do so right away. Choose File>Preferences and select Expert in the drop-down box.

You will now have to restart Slic3r and then import the Kossel_draft.ini  or T3P3_KM_default_PLA_config.ini again.

In either case, if you are new to 3D printing, this would be a good point to review the first four sections of the Slic3r online manual for an overview of the main features and settings.

2002 Prepare Printbed

The mirror glass printbed needs to be prepared to help the first layer of molten PLA to stick well. The most common preparation methods are to spray it with hairspray, cover it with Scotch Blue painters’ tape or apply a thin layer of a PVA-based adhesive like a Pritt or UHU stick. We have tried all 3 and concluded that a Pritt adhesive stick works as well as Scotch blue tape and is much easier to apply, so we have provided a tube of Pritt stick in the kit and suggest you start with it. Some of our customers have had better results with blue tape lightly wiped with alcohol (methylated spirits or isopropyl) before printing.  You may wish to try these options if you have adhesion problems with the Pritt stick.

Apply the glue stick thinly and evenly onto the cold glass mirror plate.


You can do this with the glass already on the printer. Try to keep the application thin and even.


2003 Print Test Object

The sample filament we provide has an effective diameter of 1.75 mm +/- 0.05mm. The default Slic3r settings assume 1.75 mm which is close enough for now, but when you start buying your own filament, you should check the diameter with digital calipers. Ensure the filament is measured directly across, straightened out of its natural curve. Make at least 2 measurements at 90 degrees and take the average. Enter the measured diameter in Slic3r.

Open Slic3r and select the Plater tab.

Locate the 30mm-hollow-box.stl  file in the Test_objects folder (in Slic3r folder for early kits) which was on the uSD card supplied with the kit. Drag and drop it onto the grid of the Plater tab in Slic3r.

Before exporting it as Gcode, double-check that Print, Filament and Print Settings are all set to the Kossel_draft.ini  or T3P3_KM_default_PLA_config.ini  that you loaded. This is a good habit to get into once you build up a selection of different saved settings.

Click on Export G-code and the program will ask you where to save it and under what filename. The default is the same filename as the .stl file, in the same folder - in this case 30mm-hollow-box.gcode. Later on when printing from SD card you will change the save location to the card, and may want to add descriptors to the filename such as Black-175-200C-30mm-hollow-box.gcode to identify filament colour, diameter and print temperature, as well as the object.

Open Pronterface, connect to the printer, power it on and set the hot-end to 200C. Click on Load file, navigate to 30mm-hollow-box.gcode and select it.

Pronterface will load it and then report some information about it in the right-hand pane.

It’s worth looking at this to check the size of the print, how much filament you will need, and how long Pronterface expects it to take:

Loaded E:\T3P3-Kossel-Mini-Manual-and-Software\Slic3r\30mm-hollow-box.gcode, 1525 lines

776.641145706 mm of filament used in this print

The print goes:

- from -22.43 mm to 22.43 mm in X and is 44.86 mm wide

- from -22.43 mm to 22.43 mm in Y and is 44.86 mm deep

- from 0.00 mm to 30.10 mm in Z and is 30.10 mm high

Estimated duration: 0:20:54

Once the hot-end temperature reaches the set-point, click on Print. The printer will Home itself, run the Auto-bed-level procedure using the Z-probe, and pause briefly after retracting the probe to confirm the hot-end is up to temperature. Pronterface will show the results of the auto-bed-levelling:

[The following pictures still show a print bed covered in blue painter’s tape - please ignore this].

You should always watch the beginning of the print to confirm that all goes well. This is particularly important when starting to print with a new and untried filament which may behave differently. Occasionally the border around the print may become detached and get in the way of the print.

Once the print is well under way you can leave it and get on with other things.


When the print finishes, the printer will home itself.

Carefully remove the print from the printbed. The 30mm hollow box test print should come off quite easily, but for large flat objects you may need to use a knife blade or similar to lift one corner. A sharp chisel, used very carefully, can be ideal.

If you have vernier calipers you should now measure the 30mm box and confirm that it is close to 30mm in all 3 dimensions. With the Marlin settings provided, it should be accurate to within + 0.2mm. Fine-tuning to achieve even better accuracy is beyond the scope of this manual, but help with this is available on the web - for example the blog by minow.

You can now go on to slice, print and measure the other test object, 5mm_Calibration_Steps.stl.

If all has gone well so far, it only remains to tidy up the printer, attach the LCD controller and start printing other objects!