Filament clogging in the heat-break - Solved

[Adrian_S]

TL;DR Too great a retraction distance during slow printing can cause filament jams in the heat-break tube

I got my Hictop 3DP11 running again a few weeks back while waiting for a part to cure a problem on my TronXY Crux 1. The Hictop is excellent with PLA, sort of copes with ABS and PETG, but now I have the TronXY mended I just use the Hictop for PLA.

I switched to some ECO PLA from 3DJake that is excellent but does need a higher temperature than typical PLA, I ended up printing at 210 nozzle temp and 60 bed, and it was Ok, apart from a few wisps of stringing inside when movements of more than half an inch were called for, but I was happy cleaning that off.

I started printing some bigger items yesterday and increased the retraction distance from 2.5 to 4.5 mm, then as there was still some stringing, to 6.5 mm. What then began to happen was intermittent failure to extrude, sometimes just a weakened layer or two, but sometimes a total failure to extrude after some of the print.

What I found was the filament was stuck in the heat-break tube, and I couldn't clear it by pushing down, I had to use a nozzle-cleaner with the temperature at 250 and push the cleaning wire slowly upwards from the nozzle, until the contents of the heat-break tube softened and could be pushed up with the wire.

Going back to a retraction distance of 2.5 mm completely cured this problem.

I think I now understand why it happened, and why it was more likely to happen when printing things with several items on the print bed or single items but with large distances between different extrusion points.

I have a stock 3DP11, the only changes are a fan for cooling the motherboard, ball-bearings between the threaded rods and stepper shafts, and a circular part-cooler duct. I print slowly, 30mm/s mostly, and limit travel speed to 60 mm/s and at the start of each print use the Control -> Motion page to reduce acceleration to 500 and XY Jerk to 1. With very short movements between extrusion points nothing really happens, but if there is quite a hop from one item to the adjacent item several centimeters away, there is enough time for the hot retracted filament to cool and stick to the cooler part of the heat-break. With a much shorter retraction length, the part of the heat-break that the retracted filament is in contact with is still hot enough for there to be no cooling effect.

Not something I would have expected first but with hindsight I suppose it makes sense.

Hopefully this will help somebody else wondering why they're getting clogged heat-breaks. Most of the Reddit posts I found on this were way too complicated to help me.

[Roberts_Clif]

I built this simple Enclosure pictured below and believed that my 3DP11 and 3DP12 print ABS almost to perfection.

I 3D Printed in ABS most of the Parts for my MPCNC

Though I had problems with bed warping at temps above 96C I never had problems printing any model with the settings below
Nozzle 232C
Med 96C
Enclosure 38C

I have a few post on making this MYCNC posted on this forum simply search "MPCNC"

[Adrian_S]

I built an enclosure for my TronXY Crux, and within three weeks I had the filament runout detector fail. It could be coincidence, or, it could be the elevated temperature in the enclosure caused a failure? The specs for the TronXY suggested over 30 C was getting marginal for the motherboard.

I looked at how to enclose the build space on the Hictop without including the power supply or motherboard inside the heated chamber and it was looking very fiddly, so after I found the TronXY prints ABS in the open with no problems I just switched to that.

Personally I think the Hictop bed and carriage is too flimsy, and so the bed tends to bend a little as you tighten the levelling screws or as you heat it up. I plan to replace the steel carriage plate with some 1/8 aluminium plate to see if the extra rigidity improves things. If it does, I'll have another look at printing ABS on it when I need something large.

That's a very neat CNC, maybe you should add some sub-forums here for the 1610-3018 series and home-brewed machines? There's a lot of commonality with the 3D-printers.

[Roberts_Clif]

I created a controller case with fan shown in this link

Well looked for STL filse could not find reposted
Attaching here base and Cover