Printing

Introduction

The eMAKER Huxley is being sold as a complete printing solution, as such the eMAKER host software comes with pre-tuned print settings for PLA and ABS filament. We encourage people to play with and put forward improvements to the print settings, but would advise starting with the provided print profiles and working from there.

Warming up the printer

The standard Huxley print profiles include a start-up routine which will prepare the printer before the print starts. This routine does not, however, include a command to wait for the heatbed to reach the desired temperature.   This is because it can take up to 20 minutes for the heatbed to reach the target temperature for ABS printing.  It would be quite disconcerting for the printer to sit apparently idle and for it to suddenly start after all that time.

So before starting a print, you will need to heat the bed to a suitable temperature for printing.  Choose:

• 95C for PLA
• 140C for ABS

On the Huxley printer, the headbed temperature is measured on the underside of the build surface, so do not be alarmed if these temperatures seem higher than you might be accustomed to.

Preparing a file to print

Your 3D model will need to be processed into a format which the printer understands. This is known as a G-Code file (print commands are G-Codes, see this reference).  The conversion to G-Code is performed using a tool called “Skeinforge” which takes a 3D model in STL format, slices it into layers and determines the path that the print head will follow to build your object.  Skeinforge has a plethora of configuration settings to control the conversion process.  Rather than have to have to set these yourself, you can use one of the predefined “Profiles” which are tuned for your eMaker Huxley for various materials (e.g. PLA and ABS).

Choose a profile by navigating to the Skeinforge->Profiles menu.  If no profiles are visible, select Skeinforge->Open Skeinforge, and select a profile from the “Profile Selection:” drop-down menu.  You should select “Huxley-PLA-05-03″ if you’re printing with PLA, or “Huxley-ABS-05-03″ if you’re printing with ABS.  Once you’ve selected the profile you want, you can close Skeinforge by selecting File->Quit.  The Printer Interface software will conveniently remember your selection and will make the profile you selected available in the Skeinforge->Profile menu for quick selection as shown below.

Now that you’ve selected a profile, you’re ready to convert your 3D model into G-Code.  The 3D model will need to be in the STL file format.  Click on “Load file” and select an STL file to process it. You will see progress of this process in the log window.  Once the conversion is complete, Skeinforge will save the converted G-Code file into the same location as the original STL file.   Once complete, the log will indicate how much filament will be used to print the model.

If you’ve already generated G-Code for your model, you can save time by loading the pre-processed G-Code file instead of doing the conversion again.  Note, however, that if you change materials or Skeinforge profiles or settings, you should re-generate the G-Code file.

Now you’re ready to either print direct form USB or copy the file to the MicroSD card in the machine.  If printing from USB, you will need to load the processed file since the software currently only automatically loads .gcode files and the eMAKER Huxley print profiles output .pla and .abs files.

It is recommended, however, to print from the MicroSD for a number of reasons. When printing from USB, the print can be adversely affected by the host PC giving the printer a low priority over other running applications, slowing down the stream of commands. Also, the USB connection appears to be quite sensitive to AC noise on the power cable to the host PC.

To print from the SD card, copy the file to the card.  You can do this through the printer interface with the SD card in the printer, but it is much quicker to insert the card into the host PC and copy the file.  If you copy the file on your computer, make sure you press the “INIT SD” button in the Printer Interface software after the is re-inserted into the printer.

Starting a print

To begin a print, you need to select the file you wish to print. Either from the “Load file” button to print direct from USB, or from the “SD Print” button.

Once the print starts, the machine will go through the following startup routine:

1. The printer moves all 3 motion axes in a negative direction to find X, Y, and Z zero positions.
2. The nozzle is heated to the relevant extrusion temperature (set in the Skeinforge “Temperature” plugin).
3. Once the extrusion temperature has been reached, the machine will print an outline before printing the component(s) to ensure the melt chamber behind the nozzle is primed.

When not required to move, the Z motors are automatically de-activated. This can be a useful feature as it allows the Z height to be tweaked and the X axis to be leveled whilst the outline is being printed. Simply rotate the Z couplings by hand to get a good first layer (filament slightly squished). If you have moved the two couplings in unison to adjust the Z height, you will need to adjust the Z offset in the firmware before the next print, otherwise you will end up having to tweak the Z height manually at the start of each print.

To adjust the Z height in firmware, send the command M203 Z<value> from the Pronterface software, where<value> is the amount in millimeters by which you wish to adjust the Z height.  If the first layer is too close to the bed, you need to effectively move the bed down, so <value> will be negative. If the nozzle is too far from the bed during the first layer, <value> should be positive to raise the bed.  Adjustments may be made in the range from -1.28mm to +1.27mm.  Note that the Z height adjustment is stored in non-volatile memory on the printer so your printer will remember this setting even if you remove power.

Tuning your printer

The Skeinforge print profiles are tuned based on an assumption as  to how much plastic is fed into the extruder for a given number of steps of the extruder drive motor. A critical parameter affecting the quality of the prints is how accurately Skeinforge knows the volume of plastic it is feeding into the extruder. In practice, this will vary slightly from machine to machine. This is due primarily to the actual filament diameter, and to variations in the effective diameter of the hobbed stud (a smaller diameter hobbed stud will require a higher number of steps for a given extruded volume and vice versa).

Setting filament diameter

The filament diameter should be measured (with a vernier caliper, micrometer or other precision tool) and the value entered in the Skeinforge “Dimension” plugin.

Setting E steps per mm

The E steps/mm parameter is set in the printer firmware.  The E steps/mm setting can be adjusted without uploading new firmware, by sending the command M92 E<value>, where <value> is the new E steps/mm value. By default the firmware has this set to 980. When this value is tuned, the top surface fill will have virtually no gaps between lines of extruded filament, and no extra plastic at the ends of the lines as shown in these prints:

If the E steps/mm is set too low, a gap will separate the fill lines as shown here:

Testing to determine a good value for E steps/mm

You will have to do some experimentation to determine a good value for E steps/mm for your printer.  A good test piece for this exercise is a 3mm high 30x30mm square.

Once you are happy with your E steps/mm value, you can edit your firmware as per these instructions.  Please update your firmware even if you don’t need to change this setting; new versions come out regularly for fixing bugs (like the bug where an unplugged/failed thermistor means the heater goes to full power)!

Profiles

Printing with different plastic may require modified print profiles. Have a look at this page for details, and if your plastic isn’t listed, please add to the table once you have worked out the best settings.

Changing Filament

1. Heat the nozzle to operating temperature.
2. Reverse filament until it comes out of the extruder drive (about 380mm). You can do this at 600mm/min.
3. Send the command M84 to turn the motors off. Feed the new filament in by hand.
4. Drive/feed the filament to just before the hot end.
5. Command the filament at 200mm/min until it squirts out of the nozzle. You may need to hold the Bowden tube straight for the filament to go down into the hot end easily.