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Print misalignment
#1
The other day I fired up my daVinci to print out a toy for my daughter - here is the Thingiverse link http://www.thingiverse.com/thing:452651. I was printing out four of the decagonal shaped number rings in one go, using slic3r 1.1.7 to generate the gcode. It started out fine, as you can see in the photo below. After making sure it was printing fine, I went of to do some other things around the house. Came back a couple of hours later expecting it to be nearly finished, to find this mess:



Another view out of the printer:



At first I thought perhaps the gcode file had corrupted on the way to the printer - slic3r took a very long time to slice the job, and it took a long time to send to the printer. The gcode was ~14M in size, so not mammoth but it didn't feel right. So, recently I had made a mod to the printer, putting in an external SD card reader in the bottom of the print chamber with the ribbon cable going into the back where the SD card reader sits. The original SD card has been moved to the new reader. So I pulled it out and checked the original gcode file with the offline_print.gcode file - apart from an extra CR/LF at the very bottom of the offline_print file, they were identical.

Scratched my head, thought that maybe the file was too big for the poor printer, so sliced up a single ring and tried again. It got further and was working fine. I walked out of the room to go grab some lunch, came back maybe 20 minutes later to this:






Bugger me if it hadn't happened again. I watched it for a while, and as I was about to abort the job, a very loud clunk from the carriage and it appeared stop mid-move and skip teeth on the belt. I checked belt tension and all looked ok. Then I noticed it.

The clear tube that goes through the rubber grommet between the cartridge chamber and print chamber had pulled out of the grommet and was sitting right on the print head. The filament was rubbing on the grommet, which was putting so much drag on the filament it was pulling the print head off course.

I've seen the tube pull out before but never had this happen. After putting the tube back in the grommet, all good again, although I'm not sure if there's been any damage to the belts or pulleys. It seems to be going fine but who knows?

Anybody else experienced this before? Something to look out for.

Cheers,

Pete[Image: 20141109_095211s.jpg][Image: 20141109_095240s.jpg][Image: 20141109_120320.jpg][Image: 20141109_124302s.jpg]
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#2
I'm glad you posted this as i was just about to myself. I have a davinci duo. Recently installed repetier using cura slicer. I thought that this new install might be a problem but wondered if my x axis was slipping.
i have the exact same problem as you. Ive tried different objects, but for the last 3 attempts they are slewed like yours. I will try tightening my belt and look at the feed as you did.
i hope others who experience this can chime in too.



I wonder if this happens when (if) the PC goes to sleep mode. I'll keep a closer eye on it.[Image: 20141110_062803.jpg]
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#3
Not sure if yours is the exact same problem - it looks similar, but mine is Y axis, offset towards the rear of the print chamber - direct pull or drag from the print filament has stopped the print head from moving towards the front of the printer, with enough force to make the belt skip on the pulley.

Yours on the other hand is X axis, offset towards the right. Not sure if drag from the filament would cause the print head to be pulled to the right, if anything I would bet it would stop it from going to the right, therefore your print job would be offset towards the left.

Did you check the plastic tube in the grommet?

As for the PC going to sleep - by the time the print job starts (with the bed raising), the file has long since been transferred fully to the printer and it's being printed from the SD card. The host PC can sleep, shut down or whatever without affecting the print job. At least, I've put mine to sleep before without it affecting the print.... your mileage may vary Smile

Cheers,

Pete
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#4
I tightened the X axis. It seems many people notice the x axis is less tight on these machines. Now is as tight as the Y & Z.
I reprinted yesterday and came out a success - except that damn gear. Everytime it prints there appears a low spot in the teeth. I've just reinstalled the stock firmware and printed the gear - it turned out near perfect.
I'm not sure if the gcode is transferred to the printer using repetier - I havent tested this yet.
Im not sure which plastic tube you are referring to - the one on the chassis feeding from the cartridges, or the one leading into the hot end?
I am not using the cartridges, and am feeding from two spools on top of the printer. It may well have jammed in my absence.
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#5
Sorry I musn't have taken notice of the fact you are running repetier. Yes, I mean the tube between the cartrdige slot and the print chamber, centre back, not the one in the top of the hot end.

I've found it difficult to get a good position for feeding filament from outside the printer cabinet. I've got some large spools that I sit on roller-bearing supports on top of the printer, that move quite freely, but what I find is when the head moves back against the feed direction, filament tends to unwind from the spool, and then gets caught in the rollers causing feed problems. I tried a couple of different ways, one where the filament was coming from the top of the spool down through the slot in the printer's lid. This seemed to work but I found it placed a lot of drag on the print head, causing poor print quality and lots of clunking noises. Changing to a bottom feed worked better but as I said it tends to unwind in certain situations. I thought of drilling a small hole in the back of the printer lid, in line with the tube between the cartridge slot and print chamber, and feed the filament through there so it's for all intents and purposes the same as feeding from a cartridge. But I have been reluctant, as it's an obvious mod that can't be reversed. All my other mods can be reversed in case it needs to go back for warranty. Sounds like the subject of another post.....

Cheers,

Pete
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#6
Well, I was going to proudly write that my simple setup i have with 2 spools hanging off a air purifier on top of the printer worked great. However last night the filament unreveled and jammed as you mentioned. I have temporarily taped a guard stick along the spools to prevent the filament from falling off.
I thought as well to feed the filaments thorugh the back into the stock guides. I don't care much about voiding the warranty - if parts fail I'll just buy then cheaply, and possibly upgrade the printer in the process.
I havent yet sized if two spools can be hung where the cartridges currently sit. I'll do that if space permits.
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