My statistically-invalid strength test.

[rsilvers]

I just compared 0.3mm layers to 0.1mm layers. 0.3mm was very weak for layer bonding. The parts would pull apart a lot easier than PLA in the layer direction, and so rendered PC pointless. 0.1mm layers had strong bonding. I am not sure where the sweet spot is, but err toward thinner layers. At some point I should compare 0.1, 0.15, 0.20, 0.25.

I did a quick comparison of 0.3mm at 40 and 60 mm/sec, and could not notice a difference in layer bonding.

If only someone had a pull machine and a lot of time.

[rsilvers]

I have had some issues with Polycarbonate not being very strong with layer bonding. It seems to be stronger with thinner layers, so I wanted to do Z-strength test.

I printed hexagonal rods and filled a bucket with water while supporting the bucket from the rods. When the rod broke, I turned off the water, and weighed it. The two strongest were the MakerGear PLA and the ColorFabb PLA-PHA. Both not only supported the bucket with 48 lbs of water in it, but I could even bounce it up and down. When doing so, the MakerGear broke. I was not able to break the PLA-PHA at all until I used pliers. I made up guesstimated weights for those, but the real value is probably higher for both. The lesson here is, if you want to print a part that will be stressed in a way that will try to separate layers, then PLA is king. If you want a part that pulls on the material, then PC is best, followed by PolyMax.

[jimc]

just out of curiosity, when you are printing petg, what temp are you running the hot end?


ahh yes it would help if i actually read the graph

[rsilvers]

250C

[rsilvers]

I didn't know what to expect going in, but my respect for PLA went up. And PETG did very well, so that is still on my short list. ABS has moved down as it offers almost nothing over PETG but has several things that are worse. And PC doing doing well is a letdown but maybe 290C is not hot enough?

[jimc]

what i find odd is the layer bonding with the pet. both colorfabb xt, esun and a couple other i have tried the layer bonding was so crazy that there was pretty much no layers whatsoever. if i make a 2mm thick bar i cannot break petg along its layer lines. i can take a razor knife and try to split the layers but the test bar will crack irregular like im breaking a piece of plexiglass. the layers are almost non existent. i print it at 255. the only time i see layers break is when i drop down to 235. did you change your thermistor table to #5? very interesting test though. thanks rob for putting the time in.

[rsilvers]

These were rods, and they broke. Whether or not it was on a layer, I am not sure. I didn't expect this outcome and was surprised.

But I could work on finding the best bonding temp of each material. I could compare PETG at 250, 255, and 260 and then retest PC at 300 and 315.

[lem]

Wow. Wish I could hold up 60 lbs of water with two fingers.

[rsilvers]

I held both sides and I had my knees under my wrists, but yes, it was hard.

[rsilvers]

I redid PETG at 60mm/sec at 255 and 260C. There was no significant difference. They were 29 and 31 lbs.