Greg's Hinged Accessible Extruder strength

I see this extruder is becoming popular: [www.thingiverse.com]

Long before lever designs started to appear I made one of my own. The lever was much thicker than the hinges on Greg's but I found it wasn't strong enough and it failed after a few weeks of use. I increased the thickness twice before abandoning the idea.

I use the original version of Wade's with my beefed up bracket: [www.thingiverse.com]. I print that 100% and the forces on it compress it rather than trying to de-laminate it like the do Greg's. Even so they tend to crack after about 6 months continuous use.

I am wondering how Greg's can possibly be strong enough. Perhaps I use a lot more force on my idler than anybody else but I need it to extrude ABS at a reasonable rate.

Has anybody had one fail? I would appreciate comments from people who use one, particularly to print ABS. Are my fears unfounded?

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[www.hydraraptor.blogspot.com]

I can't comment on printing with ABS, however I use that hinged extruder printed in PLA to print PLA. I haven't had any cracking issues. I do not have to tighten the idler very much to get excellent grip on PLA. My hobbed bolt has some very sharp threads. I have only put a few pounds of PLA through the hinged extruder though, before that I used a regular Wade's.

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nophead Wrote:
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> Has anybody had one fail? I would appreciate
> comments from people who use one, particularly to
> print ABS. Are my fears unfounded?

I have used the same extruder body and hinged pressure block (but my version has a little lever on top) for the last 3 months. Made out of PLA with just 30% infill. I has processed 6kg of material (mostly 3mm PLA / about 1 kg of ABS).
I use just one sprung bolt for PLA and 2 for ABS, both are done up almost as much as they can go, just before the spring is fully compressed.

I can't see any problems with it, the body of the extruder is ABS, and it has an M3 bolt as the hinge, I did initially wonder about using sections of PTFE tube as a 'bearing' for the M3 bolt but it does not seem to need it.

Maybe your heated chamber is accelerating de-lamination?

I have always wondered, how much material do you use in 6 months?

Best Regards,

Rich.

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[richrap.blogspot.com]

It could be an issue with the printed parts. I have found a wide variation in strength between similar parts, particularly when loaded. I only work in ABS and print my parts slow with double walls. Mechanically the parts are very good at 35% fill, but I have had delamination problems when trying to up the print speed.

It would be interesting to see whether this affects the mechanical strength of the part. I imaging fast printing reduces the nozzle dwell and therefore the heat spread into the lower layers. This could affect inter layer bonding with the printed layer cold bonded to the lower layers (This is a well known phenomena in metal called "hot forging" used by blacksmiths and is not as strong as weldingwhich melts the substrate material).

To solve your cracking issue, perhaps you could try a larger hobbed bolt? A larger surface area pushing the filament should reduce slipping no?

I've been considering this to speed up my extruder, because i have very soft filament that tends to just strip if i tighten the idler much at all. However I opted to buy a new .35 mm extruder instead, and my new 1.5 mm filament is much firmer.

I was worried that the hinge wouldnt be strong enough, but none of my hinges have failed so far. I did have one idler fail, but I think it had a print flaw and it wasnt the hinge that broke, it delaminated down the middle. If the hinge wasnt strong enough, the next upgrade would have been a ball and socket style hinge so that the idler is in compression instead of tension (and no screw would be needed). My experience is wholly in PLA though. ABS may have quite different mechanical properties.

I think the main difference is that ABS needs more force to push it, but is much softer, so it needs a lot of force on the idler to make the teeth sink deeper into the filament.

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[www.hydraraptor.blogspot.com]

I've also had a hinged idler de-laminate near the middle. In my case, I was printing at a lower temperature and had frequent de-lamination issues.

Once I raised my extrusion temperature these issues have entirely disappeared, and while I'll admit that I haven't likely run the volume through my machine that you would in a 6 month period, I made a point to over tighten to try and make it fail. So far, so good.

As for the extrusion rate... I've pushed this setup to 100mm/s while printing 0.2mm layers with a WOT of 3, through a 0.45mm nozzle without issue.

I also made a laser cut one for Huxley Seedling using Springs to pull the Clamp It worked on my first build ok but finding good springs caused me to abandon this design for ABS..

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I saw the following post and it reminded me of this thread (that I'm posting to now):

[numbersixreprap.blogspot.com]

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--Jeff Keegan (Just Another RepRap blog)

Hi guys!
Firstly, thanks to Jeff (post above) for pointing this thread out to me (via a note to my blog). I can't keep up with all the posts and this one is well burried.

Anyway, I do feel the need to make clear that while I did manage to break Gregs "Hinged Idler", (Sorry Greg! ) I don't think it was any fault with the design. The Idler in question was one of my first printed items and the print quality was patchy. The final straw for the poor component was the excessive squeeze I gave it! The pressure applied was well in excess of normal operating conditions. It took me 5 min to find all the pieces, since I had the long bolts removed at the time!

As with others, I can only speak of my experience with printing PLA through Gregs Extruder design. But I do hope to try some ABS at some point in the future. I'm not yet printing much at 'high' speed. Generally I chug along at 40mm/sec. I have the hinged idler held against the hobbed bolt with moderate pressure. I have reasonably strong springs on it, but could close the bolts another 3mm (estimate) if I needed to, before the springs would be fully compressed.

I'm printing with 1.75mm filament through a .35mm exit hole in the nozzle, at relatively slow speeds. I expect that won't have significant back-pressure in comparison to trying to push 3mm filament through a .5mm nozzle for example, at higher speeds. I'm sure someone will do the maths. I'm as happy to do a quick experiment sometimes.

I have toyed with the idea of a Idler design that would be in compression rather than tension, but I read above that Greg also entertained such an option, but hasn't felt the need.

Nophead - not sure what else to add that might help answer your opening question on this post. I appreciate the characteristics of ABS seem to require greater idler pressure in order to achieve traction, but that aside, are there any characteristics when hot, that would make the ABS more difficult to move through the hot-end/exit point?
Are you generally using 3mm filament, and what nozzle hole? (just good to have some technical detail relating to your experience).

Regards for now,
NumberSix

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[numbersixreprap.blogspot.com]

I was having a tremendous amount of trouble with part strength, and eventually tracked it down to a bug in sfact. Under certain circumstances, it was retracting more than it was replacing. This would happen more often in the infill, but sometimes also exhibited as gaps in the exterior shell.

Updating to the latest sfact daily, and switching to the "Olddimension" module resulted in much stronger parts, so if you haven't updated sfact recently (the last couple of weeks or so), you should.