I have to do something now that I wish I didn’t have to, but I feel it’s necessary. Recently, I bought 4 rolls of Sunlu brand filament from Amazon: 3 rolls of regular PLA and 1 roll of wood PLA. I bought the red to do the 2 Nintendo Switch game pack holders I posted about on Saturday. I also wanted to print a new photo infinity backdrop holder I found on Thingiverse and decided to use the silver filament I ordered.
Things did not go well.
First, I found I had to use a much higher nozzle temperature compared to the other PLA filaments I’ve used. That in itself is not a terrible thing, but it is something I noted. In fairness, the package does say to use temps between 200C and 230C. I found 218C worked relatively well for laying down filament.
Second, I had real problems with shrinkage, leading to deformation of the models and causing them pop loose from the print bed. I have used 4 or 5 brands of PLA to date and have not experienced this issue with any of them. I took photos to illustrate this issue:
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This image needs a little explanation. The print with the tweezers was printed first. Note how a number of the lines of filament did not adhere well, as shown by the tweezers underneath 1 of the lines. Also notice that I had to put a brim around the print. This was because, during a previous attempt to print all parts of this model, many of the ends lifted off the print bed. In all cases the glass print bed plate was coated with Magigoo.
I fixed the layer adhesion issue by slowing the print speed down to 40mm/sec overall, with a first layer speed of 15mm/sec and inner/outer wall speed of 25mm/sec. However, even this didn’t fix all the layer adhesion issues:
I managed to fix this with a little superglue, but it should not have happened in the first place IMHO.
Slowing down did not help with the lack of bed adhesion and shrinkage (I believe is causing the poor bed adhesion). The model without tweezers was printed after the one with tweezers. In Cura I simply multiplied the existing model, rotated it around to fit more tightly to the existing, then deleted the first model from the layout. The printing itself went not too badly overall, although the Sunlu prints seem to be more brittle than other PLAs I’ve used. The real issue is the shrinkage, as shown by the closest end of the left-hand model, where it lifted from the bed and moved to the left.
Looking at the model lifted from the bed got me thinking about something I’d noticed when printing the Nintendo Switch trays: that is, I had noticed that 1 corner of at least 1 of the trays had curled up a little bit from the bed. I didn’t really think much about it at the time, but the backdrop model made me wonder. I now suspect the trays didn’t lift up more only because they had such a huge percentage of their mass directly in contact with the print bed. IOW, the huge contact area overrode the effects of shrinkage.
(continued in next post)
