Is there a way to improve the quality of flat top layers ?

[BiMNrd 11]

Hello guys, I am printing with a 0.8 AA core and I find that the top layers are not coming out as nicely. There is quite a bit of "lifted" plastic or markings of the start and end points.

the smaller the part, the more this can be seen. 

 

I am wondering if there a setting in CURA and will allow me to mitigate this.  

Could it be a mixture of retraction (add more - currently at 5mm) and top/bottom layer speed? 

 

example below part size is 1" x 1.75"

 

[stu_le_brew 42]

you could try the option in Cura (under Shell coomand) of "Enable Ironing"

 

 

[DrCeeVee 19]

I've noticed this issue on some of my prints (Tough PLA). It happens when a top layer is small, narrow, or has a shape that forces the printer to do many small zig-zag movements to fill the inner area of the layer. The start/end points of those zig-zag material deposits tend to rise slightly, thus giving the layer a rough/bumpy feel when you touch it and run your finger over it.

 

I don't mind so much about this, as it can be corrected by gently sanding the layer, but would like to hear of a solution. One thing that comes to mind is forcing the printer to fill the surface layers by using the longest possible fill lines (i.e., instead of filling a long and narrow area by doing many small zig-zag fills along the short dimension, it should do a few long fills along the long dimension of the area). I don't know if there is a parameter in Cura that can do this.

 

Another thing I've heard is the "ironing" technique, where the hot print head just passes on top of the top layer, barely touching it, and extruding very little material, thus "ironing" the layer with its hot metal end, shaving any bumps and filling any gaps with material. Cura can do it, by ticking "Enable Ironing" in "Shell". I haven't had the chance to try it, as my brand-new Ultimaker S5 is still at the reseller for inspection due to some problems it had when delivered to us. Will know more when I print some test parts.

 

I think it's worth trying the "ironing" technique on one of the small parts in your photo and report back to us what you get, so that the community can also benefit from your experience.

[AndersK 59]

Ironing will solve that for you. The default flow for ironing is 10% which for some materials is too much, also depending on what brand you use.

 

Start with about 4%. Increase if you still see a pattern and reduce if you get blobs.

[BiMNrd 11]

I tired ironing, doesnt work as well for ABS.  looks like a melted piece of plasic fyi.  

 

[DrCeeVee 19]

I've never used ABS, and based on what I've been reading, it seems to be a difficult material to print... Can't you use something like Tough PLA? The few test prints I've tried with my Ultimaker S5 were very strong and sturdy. Couldn't break them with my bare hands.

 

If ironing doesn't work, I would try gently sanding the piece by placing a fine sandpaper on a flat surface.

Edited February 8, 2020 by DrCeeVee
Capitalized material name.

[BiMNrd 11]

no, and no.  Another ABS printer I have produce great results, a colleagues produces greats result. This is not an ABS issue its a slicer issue. An no, I dont have time to sand plus sanding usually damages the part. 

 

I am looking for a technical solution, its a $5K printer!

[BiMNrd 11]

I tried to see if I could change retraction settings PER PART and apparently that is a global parameter that cant be changed. I am going run another test a report

[DrCeeVee 19]

@BiMNrd:

 

I know that this will not solve your problem, but it would be very useful and helpful to the community if you could post photos of a side-by-side comparison of a print using ABS on the Ultimaker vs. your other printer, to see the differences in quality and layer flatness as it relates to your problem.

 

Don't do it if it's too difficult for you. I'm just curious to see the differences in quality between the two printers.

[BiMNrd 11]

I will post later on. I do have a several trials. learned a ton the past two days.

[geert_2 558]

I believe the effect you see is overextrusion, due to the printer slowing down at the corners or ends, but the nozzle pressure is still up and takes some time to dissipate by leaking away. This gets more visible when printing lots of small segments.

 

Printing slower and cooler helps, but does not eliminate the effect. But for me it is no problem.

 

I haven't tried features like "coasting" (if I remember the name correctly, stopping to extrude just before a corner, so that pressure has time to drop). Maybe this might help? But if you overdo it, it might cause gaps at the start of the next segment. So try just a little bit.

 

[BiMNrd 11]

I read about that before. It may be something worth trying. 

[arverbo 0]

@BiMNrd diddid you solve the problem? I have the exact same issue.