Oops! or AHA Moment?

[rsterne]

After printing my stock today, I decided I would do a pair of test coupons with the dried IEMAI PETG-CF filament to see if there was any difference.... I loaded the G-code for the 240C X & Y coupons and printed them.... Part way through I thought "Oh, no, I still have the 0.6mm nozzle in place"!!!.... The G-code is written for a 0.4mm, of course.... So, I looked at the partially printed coupons, and they were GORGEOUS!.... Here is a pic of them when complete....



The layer lines were less obvious than when printed with the 0.4mm nozzle, and the top surfaces of the prints were smoother than anything I have ever seen before.... Has anyone here ever used a 0.6mm nozzle with a 0.4mm G-code?.... Thinking about it, the printer is extruding filament as if the nozzle is 0.4mm, it doesn't know that a 0.6mm is fitted.... So, the layer height is 0.25mm and the wall thickness is 0.4mm, and the extruder should be pushing out the correct volume of filament for that, just through a 0.6mm nozzle.... All I can say is they look great!....

I ran the coupons through my tensile testing, and compared to the 240C ones printed with the 0.4mm nozzle, the horizontal (X-axis) ended up 28% stronger (~8000 psi) with the 0.6mm nozzle, but the vertical (Z-axis) coupon was only half as strong!.... When you look at the broken ends of the vertical coupon, you can clearly see the layer lines (typical in a weak layer-to-layer bonding), as if more temperature was required.... Both coupons were more like they had been printed at 220C instead of 240.... I wonder if somehow the low flow through the larger nozzle is having that effect?....

Anyway, if I find out anything else interesting, I'll post it....

Bob

[Back_Roads]

 Wow they almost look injection molded!

[Airnut]

Humm.... Makes me wonder how the CF would print if the g-code was changed to .6 and temp increased?

[rsterne]

Check out the stock I did.... https://www.gatewaytoairguns.org/GTA/index.php?topic=211683.0 .... It was 0.6 wall thickness and 0.4mm layer height....

I retested with the 0.4mm settings (0.6mm nozzle) at 250C and the strength in both X and Z went DOWN about 5%.... 

I think the very poor strength in Z is due to the 0.2mm layer thickness (at 33%) being much less than the 60% minimum suggested for CF filled filament.... I will be retesting at 0.4mm thickness and 0.6mm wall at 240C (the middle of the suggested range)....

Bob

[rsterne]

I retested the IEMAI PETG-CF today, still with the 0.6mm nozzle, but with a wall thickness of 0.6mm and a layer height of 0.38mm.... That is just over 60% of the nozzle diameter, and chosen to get 8 full layers in the 3mm thickness of the horizontal (X-axis) coupon.... It gave the greatest yield (tensile) strength I have achieved with this filament, at just over 8500 psi.... However, the vertical (Z-axis) was quite poor, at only 2700 psi.... An examination of the broken ends showed that the X coupon was a rough, ragged break, and you could see most of the individual printed lines, and they did not all break flush with each other.... To me, that means that the CF strands are quite well aligned with the lines.... The Z coupon, however, had only 4 "walls" per side (8 total), with distinct gaps between them, and where there should have been a "dot" in the center, only a hole.... The total area of print lines was significant less than when you print with a 0.4mm nozzle, which has 6 "walls" per side, plus a large "dot" in the center, so a total of over 13 lines of 0.4mm wide in the 5.6mm square test section.... That works out to a sum of line (in X or Y) of (8 x 0.6) = 4.8mm for the 0.6mm nozzle, but (13+ x 0.4) = over 5.2mm for the 0.4mm nozzle.... I think that solves the question of why the bigger nozzle was weaker for layer adhesion....

The fact remains, however, that the horizontal coupon printed with the 0.6mm nozzle was over 40% stronger than the one printed with the 0.4mm nozzle, both printed at 240C.... The coupon printed with the 0.4mm nozzle was actually stronger when printed at 220C, so I should probably do a 0.6mm one at that temperature to check....

Bob

[rsterne]

I tested the 0.6mm nozzle with a 0.6mm wall and 0.38mm layer thickness at 220C.... Although with the 0.4mm nozzle, that temperature was the strongest, with the larger nozzle that did no happen, it was about 5% weaker than at 240C.... So, the 0.6mm nozzle is great for X, not good for Z....

Bob