What do you suppose is causing this build issue?

[roykirk]

I'm looking for some thoughts on what might be causing these build errors. These were taken on two separate Creators at the same time. Not sure if it's a design error or something off with the Creators? I first encountered this issue when printing at 50/75, 50c heated bed, .25 layer height, 1.75 PLA filament, 3 shells, 10% infill. I thought maybe I was going too fast so I decreased both machines down to 30/75 but the same issue resulted (these photos were from the 30/75 attempt). If I let these run long enough, the upper layers eventually "straighten" themselves out, but with such mistakes in the lower layers I end up with a model that has bumps and rough edges everywhere. Although I had bed leveling issues with the second creator, both machines seem to be leveling out quite well right now. Some other particulars -

- both models designed in Sketchup
- both models checked for errors in netfabb and meshmixer. neither utility found errors
- both models prepped for printing in Makerware. Makerware preview shows a perfectly built model on all layers
- raft on both models built with a different colored PLA

The only thing I haven't tried yet is to use an infrared thermal gun (as curious ardvark recommended) to check for the accuracy of the bed temp. But these errors seem to be clear glitches in the g-code because they're causing the extruders to not keep a straight line in these particular areas. If I keep having this issue, I may try Rep G for g-code to see if I get the same issue.




photo 2.jpgphoto 1.jpg

[jimc]

The problem is is putting down some type of interface layer so that the raft can be easily removed. Some slicers will put a larger "z" gap between the raft and the model so the two dont completely bond to each other. With the extrusions not sticking they arent staying where they are supposed to and being pulled around. One issue is your layer height. Assuming you have a .4 nozzle, your layer height of .25 is max for a normally printed layer and if the slicer is increasing the layer height for that one layer so it doesnt bond to the raft then you are going to have issues. Look at the extrusions. They are completely round. This should not be. Extruded plastic needs to be flat. The sides of each extrusion line should just touch the next. Lower the layer height to .15 but really you should get rid of the raft and use a brim. I have never been a raft person. Make your part bond solid to the bed and if you need more adhesion then use a brim feature or add some mouse ears to the model to hold to hold it down.

[roykirk]

Wow, what an excellent lesson. Thanks! I'm going to give it a try at .15 without a raft and see what happens. I'm also not a raft person, but I'd recently gone back to them reluctantly because I'd been having problems with edges pulling up. The rafts seemed to have been fixing that so I'd been staying with them for now. I'll give it a go without and see what happens.

[roykirk]

Very much indebted to you, jimc, it worked perfect. I also upped my bed temp to 60c (IR thermometer showed I was running about 5c cooler than setting), and got in to Skeinforge and tweaked all first layer settings to 40% (they were all set at 90%). Perfect prints almost finished on both printers.

[curious aardvark]

okay - how are you changing the first layer settings ???

[jimc]

awesome! glad it worked out

[roykirk]

okay - how are you changing the first layer settings ???

See above. I seem to have figured it out with jimc's help. I'd never gotten in to the Skeinforge settings, but once in there I figured out how to change the first layer settings. As I said in a previous thread, I'm a "if it ain't broke, don't fix it," sort of guy, so I'd never had the need to tweak slicer settings until now. All sorts of stuff in there.

[Default]

I agree with jimc's suggestions, glad they worked. I find using a brim with no raft results in a way better surface finish; and you don't need to clean the part. Another point is make sure that your print bed is leveled (specifically at the are which you'll be printing).

okay - how are you changing the first layer settings ???

If you're using Slic3r, you can adjust the first layer temperature and speed settings under filament settings and print settings > speed.

[roykirk]

Sorry, curious aardvark, I may have misunderstood your question. I'm using Replicator G, so I'm changing my Skeinforge settings for the first layer using "edit slicer." First layer controls are contained under the "speed" tab.