Problem with gaps between strings of material

Hi everybody

My problem is that whenever I print a solid layer or a perimeter often the layer is solid near the edge of the object (where the nozzle movement slows down) but in the middle of the object (where the nozzle movement speeds up) there is gaps between the lines of material. It is like the extruder can't keep up the pace of extruding material.
The same problem occurs when printing perimeters, the perimeters does not touch each other.

I have lowered the speed of perimeter to 20 mm/s without any improvements.

I am printing on a Prusa I3 with a Gregs extruder, J-head 0,5 mm.

See attached pictures for examples of the problem.

Any ideas for resolving the problem?

Extrusion width might be wrong, for 0.5mm nozzle should be close or at 0.6
Check also if you really have set your nozzle right size in your slicer.

Edited 1 time(s). Last edit at 10/19/2014 12:19PM by ggherbaz.

Hi ggherbaz

Thanks for the answer

My nozzle diameter is set to 0,5 mm in Slic3r, but I have set "extrusion width" to "0" which should mean that Slic3r calculate a width on its own.
I will try to force it to 0.6 mm widths.

You may need to used a higher extrusion factor or higher extruder steps/mm setting. Possible also a slightly higher extruder temperature to get the plastic flowing faster. If it's mostly a problem on the first layer, then it could also mean that at Z=0 the nozzle is significantly above the bed instead of just touching it.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Hi dc42

Thanks for the answer.

I will try to see if what you mentions will solve the problem.

Before trying to compensate for extrusion width. The root of the problem is more likely that you have not put in the exact filament diameter. You must measure the filament (every single roll you get) using a caliper and put that into the slicer. There will be a difference in print quality if you have say 2.90mm and the actual filament is 2.85mm.

I found this out the hard by setting mine up once then never measuring new rolls. Once I started measuring new rolls and inputing the proper diameter my prints got much better.

Although I agreed with tmorris9 about the importance of measuring your filament, unless you have huge differences like with t-glase or nylon, an small difference will not create the issues seen on the pictures. If like you said your nozzle size and extrusion with are right like they are, I will agreed more with dc42 about the problem been in steps per mm of the extruder.

The only thing that puzzles me is the fact that you are over extruding in the perimeters. You said that you slow down your perimeter speed, but what about your infill speed?

Edited 1 time(s). Last edit at 10/20/2014 05:45PM by ggherbaz.

There's a checklist of things you should check:


- check if you have the correct setup of the filament extrusion length, including fine tuning by caliper measuring.
- additionally, you might try artificially setup a smaller nozzle size in Slicer
- check if you have enough power in your extruder stepper
- check if you have the right filament setup in slicer.


In the end, the way I see it (that is, "visual analysis"), you're not extruding enough filament!

Hi

The solution to this problem was to calibrate the steps/mm on the extruder.
It was, as some of you mentioned, calibrated to only about 90% of the correct value, so my printer wasn't extruding enough material.

Thank you all for the helping responses.

/Stensig