Print Bulging

I'm hoping you guys have seen something like this before. So I have been printing for a little while now with mild success, nothing too crazy. I have a kickstarter beta printer with a heated bed, and I run Repetier w/ slic3r. Here is what happened leading up to my problems:

• Receive new PLA filament from Robo (had been out for about two weeks)
• Updated Repetier to latest version.
• Ran a few prints which turned out worse than previous prints
  • The layers all of a sudden seemed very thin so I started messing with my z0 position and also decreased the temperature
• Things seemed better and then I switched filament, still PLA, different color
  • Print quality was considerably worse
  • Lowered temp again got a little better
• I decided to make a test block with some different features to see if I could narrow down the inconsistencies (attached images)
  • The group of 3 prints had a solid infill
  • The group of 3 prints had a honeycomb infill

You can see that the plastic is bulging out from the side on these prints. The difference between the two sets is, the bulging is worse with the solid infill. Note that at this point my temp is now back up around 190-200c.

In the top view of the solid infill the plastic on the top layer of the larger square surface is smeared around. In watching the printer run it seems like whenever it's printing solid infill, the extrusion nozzle is dragging through the filament previously laid down.

I'm really stuck on what to do. I saw a post that said to check the extrusion ratio by marking 110 mm up on the filament from a benchmark and extruding 100 mm and measuring after. The results were good. I'm not sure what setting I could have accidentally changed to cause this.

Any thoughts?

 

Does a 15mm cal cube print out at 15mm?

Does your printer have a cover on the bottom, with smooth rods that run all the way to the top of the lid?

 

-Mike -

The bottom of the printer does not have a cover, and the smooth rods do not run all the way to the top. I printed a 15mm cube, the actual measurements were:

x = 14.97-15.02 mm
y = 15.07-15.12 mm
z = 15.37-15.42 mm

 

I marked a line 110 mm up the filament, extruded 100 mm of filament, and then re-measured. The distance after was fairly close to 10 mm, I'm not certain how accurate my test was, it was difficult to get a caliper in there to measure. I might try again and see what results I get.

If it was off, I don't think it would have been more than 2 mm over-extrusion. Could a 2 mm over-extrusion, over a 100 mm span throw my prints off that much?

 

2mm * pi * (1.75mm/2)^2 is 4.81mm^3 which is a decent amount of volume error.

100mm is 240.5mm^3 so that's a 2% error

 

Mike & Mark - I re-tested to see if I was in fact over extruding. I took the cover off of the printer to get a more accurate measurement up the filament. I ran this test twice with different measuring out different lengths of filament, and both times the results were exactly where they should be, so over-extruding is not the issue.

Ziggy - I did consider the fact that I updated the software to be the source of the problem. However I did have the most recent version before the update, It had only been installed on this pc for a few weeks.

After I tested the extrusion ratio, I adjusted some of the speeds to slow down the printing. Since this is a small part, the slow speeds should have helped. The results were essentially a step backwards, the bulging is still evident and the print did not turn out straight at all. The concerning part is that features on this part that previously printed fine, are now way off. Pictures attached.

I will probably give Cura a try today and let you know the results.

 

Note: I am having failures when trying to upload my images.

Mark - I'm not saying that a better slicer wouldn't help, but I'm thinking that is not the cause of my problems. I did try using Cura, some of the settings were quite different from Slic3r, and had different failures.

When using slic3r the material was "bulging" out the side of the print. Now with Cura it's like the filament is being "dragged" around by the nozzle. The key thing to note here is the failures with both slicers seem to be at the same spot in the print. This is leading me to think I have a mechanical issue rather than software/slicer issue.

I then tried to print a different part, 1/2" hex shape. I had one semi successful print in Cura. As I was watching the next print, I noticed the carriage (correct term?) that rides on the nut on the Z-rods was bobbing up and down during the print. I stopped the print and messed with the carriage, which kind of fell into the correct position. I tried the print again but had no gains in print quality.

I'll also note that the raft and infill with Cura have been turning out terribly, but this just relate back to the main problem.

Will post the pictures at a later date if I can get them to upload.

 

I'm not able to upload anything to the forum right now. It is a small test, so it shouldn't be a problem to get the part to you. I could get the part to you in an email, send me a PM with your email address if that's okay. Thanks.