Approximate plastic usage.

[rewolff 0]

Hi,

How can I estimate the amount of plastic a model will use?

I'm trying to print the standard test-cube 20mm.

During the whole process, the gear moves (almost) 5 teeth. As the big wheel has 50 teeth, my feedroller will move 1/10th of a rotation. A full rotation would advance the plastic by 8 * PI = 24 mm, so a tenth of that is 2.4mm.

So, the models is being printed with 2.4 mm worth of plastic. If I remember the formulas correctly the area of the 3mm plastic is a little over 6 mm^2. Times 2.4 means about 15 mm^3 worth of plastic.

Is that correct for the 20mm cube? I don't think so. Total area of the cube is 6 * 20 * 20 = 2400 mm^2. This would make the walls of the cube about 6 micron thick. That's beyond the capabilities of the ultimaker I believe... :-)

So.... Why is there a scaling problem in the feedrate of the plastic feeder?

[frodeheg 0]

There are some jumpers on the ultimaker pcb that set the speed of the motor. Have you checked that the jumpers have the right settings? (sorry I am not with my ultimaker now, so I don't know the correct setting, but it is probably on the wiki somewhere.)

[rewolff 0]

Thanks for your answer, but the jumpers are set correctly at the factory.

The problem turned out to be that the recommended slicer, in all variants, experimental or not output too little material feed movement.

I tried "slic3r" and suddenly it started printing!

During my second "testprint", of the 20mm cube, the print suddenly stopped.

Shortly thereafter, the thermocouple disconnected from the little PCB on top of the extruder head.

Shortly thereafter, the head overheated and started smoking.

It turns out that the head had become clogged, and that the material feed was pushing the pipe backwards instead of the material forward. This resulted in the pipe pulling on the thermocouple wire and then disconnecting it. The software SHOULD detect this and not continue to heat the head without any temperature feedback.

Anyway, the bowden tube slides easily through the plastic fitting, so it will no longer work. I'm waiting for feedback from Ultimaker about what they are going to do about it.....

[Daid 306]

The software SHOULD detect this and not continue to heat the head without any temperature feedback.

If you disconnect the thermocouple board then any recent version of Marlin (installed by RepG34 or Cura) will shut off the heater instantly.

If you disconnect the yellow/red wires from the thermocouple board, then it's a different story. Because then the thermocouple board returns the temperature of the thermocouple board, instead of the thermocouple. This is room temperature, which is a valid temperature. There have been some experiments with detecting if the heater really works. But there where false positives (and thus failed prints because of this feature), so it's not enabled.

Cura has a first run wizard, which checks if your heater+temperature sensor function correctly. This is protection against improper assembly.

The bowden tube connection in the printer head is IMHO, the worst part of the machine. I actually have 2 of the white clips on my machine to ensure it stays in place. If this tube moves, even a mm, then you will have problems. Usually it's plugging problems, and not overheating problems.

[rewolff 0]

If you disconnect the yellow/red wires from the thermocouple board, then it's a different story. Because then the thermocouple board returns the temperature of the thermocouple board, instead of the thermocouple. This is room temperature, which is a valid temperature.

The thermocouple has a very low impedance, right? What would a 10k pullup resistor on the positive side of the thermocouple do?

I'm hoping for: when disconnected, the pin of the thermocouple-sensor-chip will go high and the chip will return "max temp". This would result in the heater being turned off without any modifications.

Is there really an AD595 chip in the thermocouple module? It's an expensive chip!

[update]

[rewolff 0]

OK. The original problem in this thread was caused by a mismatch in the "units" of the material feed assembly. You can set them with a G-code command. The setting can be saved to eeprom. Apparently there are two settings for this parameter in existance and getting them mixed up doesn't work.

If the software needs to extrude 1mm^3 of plastic, it could send "G1 E1". The firmware then translates that to X steps of the stepper motor and everything is fine. Everything also works when the units are not mm^3 of plastic but mm-of-filament. Then in this case, only about 0.16 mm of filament would be needed. So the G-code could be G1 E0.16, which with the proper scaling in the firmware could work out to exactly the same X steps of the stepper motor.

Mix these up and it doesn't work.

In practise I switched to slic3r who had things setup correctly.

[rooiejoris 5]

I really like your explanation!

Solution from my point of view:

In the gcode:

Use M92 E28 for 'old' slicers

Use M92 E865'8888 (you should calibrate this value!) for new (volumetric) slicers.

[rewolff 0]

A few days ago, for me the "just use XXX in the G-code" wasn't as easy as you think it is. You have to know how.....

For reference:

- You can add G-code in the G-code tab of replicatorg before hitting "build".

(don't forget to switch to the G-code window before hitting build for a second run, because otherwise it will automatically regenerate the G-code).

- You can add G-code in the G-code-> edit slicing profiles -> -> custom G-code -> start G-code.

[update] Still not easy to do.....

I've gotten models to build using slic3r, so now I know the basics are working, I decided to go back to the "recommended" (or at least default) slicer. Turns out the "edit profile" is completely different. But by default they should at least do SOMETHING.

Apparently skeinforge 4.0 and skeinforge 5.0 are "old" slicers, because I needed M92 E28 and not the E866.

After pressing "build" the platform moves down 35mm, some plastic is extruded.... and then nothing. What am I doing wrong????

[Daid 306]

Have you tried Cura instead of RepG/Skeinforge? It should be less painless according to it's users.

[rewolff 0]

I have now. I'm NEVER going back. Never!

:-)