Surface Finish

Help with printing with specific plastic filaments.
Post Reply
Gilz
Posts: 4
Joined: Fri Jan 19, 2018 6:57 am

Surface Finish

Post by Gilz » Wed Nov 14, 2018 7:21 pm

I have a Lulzbot Mini (type 1, no LCD), and it works well, but I find I am unable to get a good surf finish. The top ends up looking rather like an old vinyl 78 record (except the lines are not curved!). This occurs with both ABS and PLA, but considerably worse with the ABS. I have adjusted the extrusion temp from 200 to 240C, but don't see any difference. I have dried the filament in the oven over night at 80C. Still no difference. Any suggestions? Thanks?

Galadriel
Aleph Objects | LulzBot
Posts: 258
Joined: Mon Sep 25, 2017 10:23 am

Re: Surface Finish

Post by Galadriel » Thu Nov 15, 2018 2:04 pm

Could you post some photos of the results of your print? Troubleshooting surface quality issues without a visual example can get tricky because of differences in terminology, getting a look at exactly what you are seeing really helps to clear that up.

Gilz
Posts: 4
Joined: Fri Jan 19, 2018 6:57 am

Re: Surface Finish

Post by Gilz » Thu Nov 15, 2018 7:37 pm

Thanks for your reply. Here are a couple of photos: (Can only get 1 photo to attach!), but they are much the same.
Attachments
IMG_0142.JPG

kcchen_00
Posts: 1635
Joined: Thu Feb 19, 2015 12:42 am

Re: Surface Finish

Post by kcchen_00 » Thu Nov 15, 2018 10:18 pm

More pictures may help... but that looks like overextrusion. Try reducing the flow rate to 95-97%.

Gilz
Posts: 4
Joined: Fri Jan 19, 2018 6:57 am

Re: Surface Finish

Post by Gilz » Fri Nov 16, 2018 2:40 pm

Thank you I will try reducing the extrusion rate.
Meanwhile here is another photo:
Attachments
IMG_0144.JPG

kcchen_00
Posts: 1635
Joined: Thu Feb 19, 2015 12:42 am

Re: Surface Finish

Post by kcchen_00 » Fri Nov 16, 2018 3:08 pm

Hmm... I'm still trying to figure out what that diagonal seam might be... It looks like the nozzle dragging across the surface, but that typically produces a straight line (well, more straight line).

Turn the fan on to help set the plastic, if its not on already. I like 8-20% for ABS (past 4 layers @ .3 Layer height), if PLA it should on.

Hopefully its just a bit of overextrusion.

Gilz
Posts: 4
Joined: Fri Jan 19, 2018 6:57 am

Re: Surface Finish

Post by Gilz » Fri Nov 16, 2018 6:09 pm

I tried various Flow %ages (extrusion rates): 100%, 95%, 90% & 85%. 90% clearly gave the best (flattest) result, both visually and by feel. I also tried 105% for the initial layer, but eventually went back to using 100%. (Changing two parameters at once is always folly). I have tried photographing the differences, but that doesn't really show how great the improvement is. Visually the change from 100% to 90% flow rate made a big difference....but it is still not perfect! I will hold to 90% for the moment and adjust other parameters (one at a time) to see how far I can go. I will try adjusting the fan rate and layer height too. Thanks for all your help. I appreciate it. I will keep trying and should I eventually achieve a gorgeous smooth ABS surface, I will definitely let the forum know!
Attachments
image.png
image.png (739 Bytes) Viewed 97 times

kcchen_00
Posts: 1635
Joined: Thu Feb 19, 2015 12:42 am

Re: Surface Finish

Post by kcchen_00 » Sat Nov 17, 2018 1:55 am

Glad it helped.

Reducing the flow rate too much can affect the layer adhesion and reduce the strength of the project - increasing extrusion temps by a degree or two can help. It can also affect dimensional accuracy (smaller dimension). I like to stay near 95% as a minimum.

Post Reply