illuminarti

There's really not that much wrong with your printer if you can extrude at 7-8mm^3/s.

That's awesome Ian... it sounds like the new job is worth the minor hassles to begin with. Mine too :-) Good luck sorting everything out, and we look forward to having you back in the fold when you can.

Or indeed just turn off 'enable combing' in Cura's advanced preferences.

I think it's most likely a coincidence Didier, because nothing should have changed about what happens when you do an abort. But let me know if you see it again.

Are you sure? When you first start a print, the 'Tune' menu is going to show the nozzle temp as 0, while it heats up the bed. Only when the bed is mostly heated does it turn on the nozzle heater. This is to avoid leaving the head sitting hot for a long time and cooking the filament inside.

I totally agree, Rick. The issue is just to try and find the sweet spot of the 'right amount' of priming. If you're only retracting 8mm manually, then the initial fast prime of 20mm is going to be too much, and *might* cause grinding on some newer printers with the weaker extruder springs, depending on the tension setting. Fortunately that doesn't seem to be the case for you. Theoretically, the best approach if you're priming manually as well would be to retract the full 20, and then have a longer slow prime built into the firmware (or, indeed, just be able to tell the firmware to not make any assumptions about priming, and do it all manually, if that's your thing). Being able to manually set the prime distance would be a big help in the printer GUI would be a good start.

The robot is actually quite tricky to print: it's small and has overhangs. To get the best results, you need to slow down the print, cool down the temp, and allow adequate time for cooling of the plastic. For best results, print two robots at once - so the freshly laid plastic on one can be cooling while the other prints. I highly recommend turning off quickprint, and start learning the detailed settings; you're unlikely to get good results on anything just using those - the full settings will give you far more control.

I think it's basically just the sound of the individual steps. So long as the motor, knurled sleeve, and filament all keep moving forwards - and it looks like they are - then it shouldn't be a problem.

That's really awesome, Mark. Thanks for sharing!

I configured the firmware to perform the priming in two parts; firstly it quickly undoes the 20mm end-of-print retraction, then it more slowly extrudes about 5mm of filament to properly get the flow started. We might want to increase that a bit - especially if the head has leaked any while it has been heating/cooling. I think the 'extra' priming amount should be made user configurable in the GUI. Bear in mind, however, that one of the purposes of the skirt is to provide a chance for the head to finish priming, so I don't see it as necessarily a problem if it's patchy at the start. Also, I would avoid priming the head manually - or at least increase the retraction distance to about 20mm, since that's what the printer is going to undo when it starts.

The double pulley is, indeed a single piece.

You need to loosen the grub screws on the pulleys on the rod that runs through the sliding block, so that you can slide that rod out of the sliding block. Then loosen the pulleys on the two rods that run at right angles, and slide those rods out partially, so that you can take off the pulleys that the belt goes around. Then open up the sliding block carefully, and replace the belt and/or spring. Then reassemble everything in reverse order. The assembly manual may help: https://github.com/Ultimaker/Ultimaker2/blob/master/um2%20assembly%20manual%20V1.1%20_english.pdf Where abouts are you located?

Some things to try: 1) Install the firmware I posted above 2) Adjust the extruder tension spring - If you're carving semi-circular divots out of the plastic, you probably need more tension; if you're just kind of flattening it out, then go for less tension. 3) Print the extrusion test piece to get a feel for the capacity of your extruder 4) Consider using less retractions, and printing slower/hotter. 5) Alternative feeders such as Robert's may be helpful.

Do you have a plugin enabled in Cura? A pause at height or 'Change Filament' one, perhaps? Look at the plugins tab.

Mineral oil is also good for restoring the surface finish on sanded PLA.

Grinding during the print is probably down to the tension on the extruder being not quite right; either too much or too little. Once the print is underway, the firmware should just do whatever the gcode asks of it. It's probably the combination/spacing of retractions that's causing issues; you need to get to the point that once too much is asked of it, the motor slips backwards (avoiding damaging the filament), rather than being able to keep moving forwards against stationary filament, and grinding it away.

Yay! I'm glad it's working well for you. I really need to try that extruder design. Which one is that?

Aaron - great way to maximize available space, storing your toothbrush in your printer like that!

Compared to the cost of the printer, and the time taken for prints, even expensive filament is the cheapest part of the equation. As Shurik says, buy good quality filament and you'll save a lot of time and money in the long run, and get better results while you are at it. Cheap filaments can have contaminants, and highly variable composition and diameter - all of which can cause prints to fail and/or damage the printer, wasting money in the long run.

I generally print it at 230/60, with a thin film of glue stick (spread with a wet paper towel).

Yes, but for different reasons. The worst offender was a bug that was introduced on April 23, when code was added to raise the print bed before starting to extrude, but without properly reseting the E coordinate. But even prior to that it was trying to extrude too much, too fast during the start up. Back then, the extruding and the raising of the bed all happened in one movement anyway, but still too fast.

I hunted around and I saw some references to retractions at tool change, but not actually in the T-code handler. I agree that it's not symmetric right now, and needs some work. But for the simple single extruder case, the changes I made should help - and for multi-extruder, they shouldn't make things any worse :-)

Ok, my initial testing seems to be working ok, so I'll post the hex file if anyone else wants to take a look. This is the current 14.06.1 Ultimaker² firmware with some fixes: 1) The e-coordinate wasn't fully reset to zero at the start of prints. As a result, during the bed raising at the start, the extruder could be advanced very rapidly, causing grinding. 2) The extruder was then primed for 30mm at 10mm/s. That's too fast, especially if the head is already primed. So I put in a slower recovery of 20mm (to make up for the retraction that should be happening at the end of the print), followed by an even slower 'true priming'. The speeds are configurable in configuration.h 3) The '20mm at the end' retraction actually wasn't happening when prints finished normally. Only when aborted, or when filament was loaded. (I held on to the filament during a bunch of back-to-back quick prints to check whether it happened - it never did). So I changed that so that the 20mm at the end did happen. 4) The G10/G11 'retracted' state wasn't getting reset at the start of a print. As a result, if you already finished one print with a retraction, then the first retraction of the next print (e.g., at the end of the skirt) didn't happen, because the machine thinks it's already retracted. And then at the start of the object proper, the corresponding de-retraction fires, dumping plastic out of the already primed nozzle. 5) I changed the default bed temp for PLA to 60º, because that's well overdue to be changed. You can see the details of what was changed here: https://github.com/illuminarti/SecretMarlin/commit/24a692b02157e1ebae00d773d6c39c8eaebbdbb2 The hex file is available here: https://www.dropbox.com/s/1i6ha8em51h61bo/Marlin_grind_fix_test.hex Let me know how it works for you.

No, the 1/7th factor is because normal gcode expresses e coords in linear mm, whereas UltiGcode expresses it in cubic mm. The priming code is in a conditional which only gets called if there are 'material' headers in the gcode file. I don't know if Cura adds those to regular gcode, but normally one wouldn't.

Yes, the priming doesn't happening using raw gcodes, so it's less of an issue. However, there is another bug which causes random harmful extrusion during the bed raising part, which also causes grinding. I've fixed up the bugs and am testing a fix this evening. I'll post a hex file here later for anyone who wants to try it out. I was having repeated problems with grinding across several different printers, and they're all behaving much better with the new firmware.