Multi-part printing issues

I have been chugging along for a few weeks now and I have mostly been printing just one part at a time. I recently wanted to print out some link-lock pieces for a new cooling system I'm working on. When I print just 1 link it comes out great. There is no cleanup needed and it is strong and perfect. When I try to print multiple links in the same print the result is a hot mess. The individual pieces crumble apart, they have weird artifacts around them as if the printer cannot find the same location twice.

I have messed with the retraction rate but am having difficulty because this is a delta printer with a bowden extruder. I feel like maybe its not retracting accurately. When I tell it to air extrude 10MM and measure the output it is 10MM. I have been using Slic3r and Repieter-Host for printing. The printer is running Marlin.

Suggestions?

Looks like you need to activate retraction. This will suck back a bit of filament before traveling and then push it back prior to extruding after the move. I'm at work right now and so cannot look at slic3r to determine where the setting is, but it shouldn't be too difficult to find. Just turn it on initially. The default settings are probably a good place to start.

Start with 3mm of retraction and see if that makes a change

I initially thought the same thing about retraction. I was using 3mm and I don't remember what it was in that print, maybe 1.5MM. There was no change to the output. I have been thinking about it more and I'm wondering if its something to do with the bowden style extruder. Its an airtripper v3 and I am using 2MM ID PTFE tube with it. I wonder if its specifically due to the length and pressure between the filament and the hot end. Its a hotends.com hotend of the latest flavor.

The thing that really perplexes me is that the PLA is not bonding to itself in multi-part prints. Even if I have zero retraction and even bigger stringers between parts shouldn't the resultant parts still be just as solid as the single part? They would just be more connected.

Quote
thefuzzbl


When I tell it to air extrude 10MM and measure the output it is 10MM. I have been using Slic3r and Repieter-Host for printing. The printer is running Marlin.

Suggestions?

To measure the extrusion accurately you need to check it from the top of the the extruder, not the nozzle i.e. mark the filament,say 50mm above the entry point of the extruder and set repetier to extrude 50mm. The mark should stop at the entry point. If not, you need to re-calibrate.

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That definitely looks like a retraction issue. If you aren't retracting enough (or fast enough), the heated plastic oozes out of the hot end causing stringers everywhere. Then, when the next printed line starts, there is not enough plastic left in the nozzle and a gap is left in the print.

Many people have run 1.75mm bowden setups successfully with very little oozing, so it is definitely possible.

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Okay - Progress! I have been messing with retraction speed and length and I think I have made a huge improvement. Now I'm seeing a new issue. Perhaps it was present before, I dont know because I couldn't see it with all the extra PLA. It seems like the printer does not know how to make a circle when jumping between parts. When it jumps to the other part it starts the circle outside where it needs to be. It then makes its passes on that layer in the correct spot. It keeps doing that for the whole print.

Ideas?

Well, I've been messing with it all evening. I have it to where most of the non cirleness is gone however there is still some between the parts on the printer. They are not just filament strings, it looks like the layer is starting away from the part then the radius closes and corrects itself. The parts are still quite weak though. I can crush them in my hand and the layers just peel apart. When I print just one of these pieces it is super solid. No chance I could crush it in my fingers.

Is your hotend loose?

The hotend feels pretty solid. Also remember, when printing just 1 part it is perfect. The parts are solid and strong with no weirdness.

What do you have as you acceleration values for X and Y. This is probably not it, but perhaps those values are too high?? If the values are too high, the firmware would think the head had arrived prior to it actually doing so; it would then prematurely start extruding. Sounds wild, but I'm just throwing ideas out there.

More updates! I've been working on this issue still and I'm still stuck with it. I tried printing part of my new cooling setup and had the same problem but this time on the same part. It happened on all the pieces that come out of the mail body. Its disappointing because the main body of the part turned out really good. The extruder even crossed over the part and it put all the layers down great.

There should actually be three nozzles coming off the mail body, one came off right away.

Another issue that came up is that the infill is not going all the way to the perimeter wall. I checked the picture guide on the reprap wiki and it suggests checking for friction in the PLA. There is not any friction there, its super easy to unroll it and it feeds right into the printer.

Is this possibly a slic3r error? I'm using the 1.0.0RC2 from inside repieter-host. For this print I saved it to an SD card and ran it from the printer. I have tried using just slic3r but it does not allow me to rotate the part into the correct position.

Are your belts tight? Are your pulleys tight on the motor shafts?

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Belts are tight, pullies rotate smoothly and are secure. Everything else, simple 1 part with no extensions, prints great. I just noticed that there is a slic3r forum. I'm going to repost this there. Thanks for the support so far, its helpful to know that its not just me that is stumped.

Try a different slicer. Sometimes Slic3r does weird things.

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Finally an update! I had a lot going on with work and life so I have not been able to look into this further. I have started using Cura, which is way nicer than repieter in my opinion as it does it all in one package. I'm still having the exact same issue though. Is it a bug in Marlin? Is there a setting I'm missing?

Also to note, I wondered if I was getting a vibration and that was the problem. I have taken steps to significantly upgrade the stiffness of the printer top to bottom. I do not think there is any vibration that is caused by the printer stiffness anymore.