When a 3D print really counts - My Wade’s block cracked on my Mendel90, I had only a few chances to print a new one before it was too late. Fortunately my 3rd attempt was a success.
Green is good.
OK, so as a noob, this makes me ask about the strength of these parts. I’ve seen a bunch of people suggest that the first thing you should do is to print spare parts. That makes sense, but is it because failures are frequent?, or was yours just a weak layer or something?
Nice job @Robert_Wozniak
@Chet_Wyatt the way I see it besides having spares should something go wrong, it also gives you good practice at printing real use items and not just calibration cubes/etc when you’re first getting everything dialed in
yup, that makes sense too, you can only use so many cats ;), but I’m still curious about the frequency of failures.
That makes sense too, I would think fatigue would be more of a concern.
I’ve printed several spare parts, but this one was very complex, so I avoided it previously. My first two attempts were in ABS, but due to the thickness, they began to warp. The final print was PLA, at 0.2mm layering. I’m definatly going to continue printing the rest of my spare parts.
I think my failure was due partly to design and partly due to abuse. In the design, the part is very thin right where the pinch roller pin rests against the block. This is where the crack began. This dimension is set by the diameter of the hobbed bolt bearing, and the pinch roller diameter relative to the hobbed bolt. The abuse is due to my experimenting with urethane TPE flexible materials. The flexible filament has tremendous traction against the hobbed bolt, and also occasionally gets kinked up in the feed to the hotend. Because it’s flexible/compressible, I think it’s storing energy, which is reacted by the hobbed bolt, and ultimately by the wades block.
On this particular failure, the crack was cross grain. The original part, probably could have been printed with a higher fill density, and more than one perimeter layer. The green replacement part was printed with 2 perimeters, and 75% honeycomb fill density.
Overall though the quality of nopheads printed parts suppliied with the Mendel90 kit are superb.
@Robert_Wozniak In my printing experience, and I may be wrong on this, the number of perimeters is more important than the infill percentage when it comes to strength. Higher printing temperatures (as long as you’re below the point where the filament is thermally degrading) also contributes to greater strength through better layer adhesion.
When I print for strength I usually go for at least 4 perimeters and bump my temperature up by 5 to 7 degrees.
Also, pushing extrusion up to 102% should also lend more strength, although you have to be careful with that or you may end up with bad dimensional fidelity.
@Stephen_Baird Thanks for those great printing tips…You bring up a good point, while there are a myriad of settings to adjust, most of the time we are worrying about the finish quality. But there are other qualities to consider, that in some cases are more important.
I’m confused on the first photo what piece is missing? as on the green one (photo) there is something bolted to this broken piece. Also could this damage not been caused by over tightening the bolt?
In the first photo, the idler block is removed. I removed it to check if the hobbed bolt needed cleaning. This first exposed the crack.