Excessive Stringing With A Dual Gear Clone Extruder
Dual gear extruders are one of the most versatile and reliable options for budget to mid-range 3D printers. It's dual gear, bi-directional, and works equally well in bowden or direct-drive configurations. It's so popular that a plethora of ridiculously cheap clones are available via AliExpress, Amazon and eBay.
As always, with cheapskate copies the quality control on the clones can leave a bit to be desired but, it is normally only in the assembly process. They are still markedly better than any of the bright red aluminium pieces of tat that seem to abound!
Unfortunately, there are a lot of Facebook group members who install dual gear extruders and then suffer a lot of stringing. Normally, stringing can be corrected by retraction tuning but nothing seems to help these people.
I suffered a similar issue. Bearing in mind that I have 10 printers with exactly the same hot end assemblies and extruders, it seemed kind of odd that one of my printers had a stupidly high level of stringing. I normally run all of these printers on the same slicer profile without an issue but I was beginning to have to meddle with this particular one to make it print properly. There was nothing wrong with extrusion so you wouldn't assume the extruder was at fault. I was looking more at incorrect temperatures or some other issue that was causing the strings.
My printers are tools to do a job and this particular one wasn't performing.
Ridiculously, I even ordered a glass bed for it in the mad assumption that it was radiating more heat than the spring steel/PEI bed it was currently using (the only difference between the other printers).
Then, I had a revelation. What if the extruder couldn't retract effectively? When the extruders arrive, they are basically assembled. I'd never really taken one apart to inspect the insides as you just tend to mount them. Taking the thing apart revealed the issue. The grub screw on one of the extruder gears wasn't tight! This was allowing the extruder gear to 'slop' between the extremes of the flat on the extruder motor shaft, probably removing 1.5 to 2mm of retraction (and making it delayed).
Take a look at the 'before and after' images below.
You can see there is a massive difference.
That grub screw literally took a quarter turn to tighten and unless the extruder assembly was dismantled, everything appeared as it should be.
I've learned a lesson here. I made the assumption that even manufacturers in the Far East are capable of doing up a screw.
Apparently not!
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