My printer is a RepRapPro Mendel.

My printer is a RepRapPro Mendel.

I’m experiencing an issue on top surfaces and line-infill with my printer, and I’ve been having a lot of trouble diagnosing the problem. Here are some pictures of it happening when trying to print the top layer on a honeycomb pattern at 15% infill, which hopefully will not be too blurry.

I can’t quite figure out how to describe the issue, which means I’m having trouble searching for solutions. Basically, if I use line infill, the infill will start out looking great, but toward the top will just look like a giant mess (blobs, ooze, and eventually the lines just won’t get deposited at all). You can also see that if I use a patterned infill, the first top layer to get laid across it won’t adhere properly either. Ooze blobs will form at certain intersections related to the pattern. Depending on how many/large they are, the print head will then get stuck on them as it travels to do the next layer, forcing me to cancel the print.

This is cheap filament from eBay (I originally was using white PLA from Faberdashery which worked very well. This new filament required I lay down blue painters tape to get it to stick to my glass bed at all, after days of troubleshooting and tweaking). I wouldn’t be surprised to find out the cheap filament is the problem,

What kind of test prints / calibration might I be able to do to compensate for this, or at least provide more useful information when asking for help?

Looks like the plastic is having trouble getting through the extruder. It’s odd that the infill would be ok and the top is a problem. Do you run them at very different speeds? (i.e. is your infill slower than your solid layer speed?) It may also be (normal) differences in the filament. Have you tried running your extruder at a higher temperature?

I feel like I’ve tried everything. I currently have the top solid infill set to be substantially slower than the regular infill. It’s been a while since I had it set to be an equal or greater value to my regular infill. I’ll add this to the top of my list of things to try.

I have tried higher temperatures. I’ve run the temperature gambit from 190-215 while troubleshooting my original sticking issue, and currently have it set near the upper end of that range.

Set the top solid infill speed to match your perimeter speed, since they look ok. Then try increasing the infill percentage --it may just be that you can’t bridge the gaps smoothly. Alternatively, if your layer height is on the small side, you might try increasing it, so as to lay down a thicker bead of plastic. It might simply be that your plastic isn’t strong enough to withstand the tension of bridging the gaps in the infill. Finally, and perhaps counterintuitively, try running the extruder about 5C colder. That might also help the bead hold together better.

Your extruder may also be overheating when you print slowly. That might explain why things work great to start with, and then fail after a while. Running at a higher speed cools the extruder with the filament itself. Hopefully one of these ideas will help you. :slight_smile:

I’ve been beating my head against this for a while now and I’m afraid I’m still not making much headway on it.

By the looks of it, my filament is simply continuing to create blobs instead of stretching to span gaps properly. I’ve tried bringing infill speeds down low and high, and I’ve tried no huge success.

The problem is most visible when doing just regular old line or rectilinear infill. Occasionally, the printhead will lay down a line of plastic and it won’t stay put to the previous layer - it will instead kind of skip along and create a series of arcs pointing upwards, sticking at the point where the lower level crossed over.

When it comes time to do top solid infill, these tiny bumps will have turned themselves into full blobs that will completely upset the look.

Changing my top solid infill to be concentric helps a bit, but there will still be large holes and blobs in my top surfaces. They’ll be a mess, even when just printing a regular 20mm calibration cube.

I’ve just ordered some new filament from sainsmart, which I’m hoping will be substantially better than this eBay filament and fix the problem, but I’m not too optimistic about this - no one else seems to think that bad-quality filament could be the problem. I’ve varied my filament diameter between 1.6-1.75 in Slic3r to varying degrees of improvement, but there’s no point at which the problem clears up completely.

Couple thoughts - First, I’m sure you’ve calibrated for filament diameter, but wanted to mention that just to be thorough. Second, you mentioned that this filament does not stick well – usually, that’s a sign that it’s still not hot enough – depending on your nozzle, the actual temperature at the tip can be quite a bit lower than the temperature at the sensor, so you might be able to crank it up even more. While PLA generally runs well in the 180-220 range, I’ve had occasions to need to crank it up higher than that (at least with blacks). (Hopefully, it’s just the color of your filament, but if you are actually running natural PLA, that golden color means you are running too hot) Your nozzle might also have some problems regulating temperature if you have a lot of travels in between feeds. Also, when there is a lot of travel, you could be oozing (which is made worse at higher temps). One trick that has worked well for me on my ToM is to stick a room fan – (a Vornado on medium in my case) to blow into the print area. Have you printed a good sized calibration square, at 100% fill, as well as doing the sparse infill? It would be good to look at that more carefully first.