RepRap software tweaking manual

Tweaking Manual

This page is under construction.

This is a suggested method to help you get up and running quickly.

Test .stl's are attached at the bottom of this page.

Suggested values, in brackets, are for extruding Capa through a nozzle diameter of 0.4 mm with the 12V GM3 Solarbotics extruder motor run through a 13:38 gearbox .

Warning: You need to open and close an STL file in the software before the preference changes take effect.

Heating the extruder

You will need the extruder exerciser for this section (Tools -> Extruder Exerciser).

• For Capa, 130 °C is a good start.
• Always allow a few minutes after the thermocouple has registered the target temperature before extruding. This ensure that the entire nozzle has acclimatised.

Measure the virgin filament section

Because of die swell your filament will solidify slightly fatter than the diameter of the nozzle orifice. Knowing the final diameter important to give you an idea of subsequent parameters.

• Pick a suitable extruder motor speed (210).
• Heat the extruder.
• Extrude a purge section over thin air.
• Cut the filament (by scraping an edge across the orifice) and dispose the purge.
• Collect ~2 cm of clean filament. Any longer and the weight of the filament will start to stretch it and distort the section.
• Allow to cool.
• Using callipers measure the diameter of the filament at the tip closest to where the purge was severed - this end will be least stretched by it's own weight . Be sure not to push too hard with the callipers to ensure fair readings.
• Record the diameter.

Measure the deposited filament section

When the filament is laid down onto the bed its own weight will distort its profile while it is molten. The nozzle needs to be run over the bed at with a good 2-3 mm clearance to ensure that the nozzle is not squashing the deposited filament . It also needs to run at the correct speed: too fast, and the filament will be under tension, too slow and the filament will be compressed.

• Set the following preferences (File -> Preferences):
• Extruder0_ExtrusionTemp (130)
• Extruder0_ExtrusionSpeed (210) //Speed of the extruder motor
• Extruder0_XYSpeed (247) //Max speed of nozzle in XY plane
• Extruder0_OutlineSpeed (0.17)
• Print the border of the widebar.stl (simply 'Build -> Cancel' during the last border segment).
• Allow to print cool.
• Tip: move the nozzle away using the stepper exerciser and then, while you're measuring up print, you can keep the extruder nozzle hot using the extruder exerciser.
• Measure the border filament section, again with callipers, and compare with the virgin section. If the border section is smaller then the filament is under tension (increase the extruder motor speed, or reduce the nozzle XY speed). Conversely, if the border section is bigger then the filament is under compression (reduce the extruder motor speed, or increase the nozzle XY speed).
• Repeat the print until satisfied (this may take several attempts).
• When you are happy with the parameter ratios, clean the nozzle and then turn the extruder off and allow to cool.

Adjust the z=0

Move the nozzle out over the bed. By adjusting the z-flag and homing the bed using the stepper exerciser you can set the datum position for the bed.

The software (at time of writing) prints its first layer at z=0. Using the filament from the previous test adjust the z=0 height so that the filament can freely slide under the nozzle.

Test your setting by printing the widebar.stl border again. Use the callipers to make sure that the nozzle is not deforming the profile of the segment by being too close to the bed.

Setting the curve speed

Due to minor pauses between segments, a piece of code has been added to reduce the impact of filament dumping during pauses. This code comes into play for short segments, and applies to the radii of most profiles. The code speeds the nozzle up during the short segment.

• Set the preference: Extruder0_ShortSpeed (0.8)
• Print the borders of the circles.stl
• Measure the average profile, repeat until satisfied that the average section of the short segments are close to that of the normal segments.

Setting the infill

Now you're confident about your segment sections, it's time to get that into the preferences and checked by printing a :

• Set the preferences:
• Extruder0_ExtrusionInfillWidth (0.55)
• Extruder0_ExtrusionHeight (0.5)
• Extruder0_ExtrusionSize (0.55)
• Extruder0_InfillSpeed (0.17 - initially same as OutlineSpeed)
• Test this out by printing the entire first layer of the widebar.stl
• Adjust preferences until satisfied with the result

Checking layer bonding

Perhaps most important of all is ensuring that your layers are close enough to bond together. But at the same time they must not be too close otherwise deposition will quickly get messy. It is essential therefore that the Extruder0_ExtrusionHeight preference is correct.

• Print the whole of the 10mm-cube.stl
• Adjust the Extruder0_ExtrusionHeight parameter accordingly.

Pay particular attention to the heights of the infill segments compared with the height of the border segments. These should be level. If not, go back to the previous section to adjust your infill settings accordingly.

-- Main.EdSells - 25 Jan 2008