Missing/Uneven Perimeters!

Hello!

I've been having a problem with my prints from my Prusa I3(with bowden extruder) coming out with wavy or missing perimeters. The infill seems to print just fine. I know it is not the extruder because it was doing it before I had to replace it due to bad filament(ugh!). The X and Y axis rods seem to be stright although I don't really know how to check that very well; the Z-axis uses the metal spring connectors on the motors so I wouldn't think thats it. The printer is flat on a stable desk and doesn't vibrate anymore than it did when I bought it. Been using this I3 since September 2015.

I have checked the belts, leveled everything that I can, cleaned the machine, put new lubricant on the rods, tried different filaments, layer heights, speeds, made infills print before perimeters, temps, cooling settings, tried different retraction settings and layer percentages..

I have not checked the belt bearings for the X and Y axis, could that be a problem?

Anything would be helpful and of course I'm willing to check something that I have already tried.

Thanks!

try your retraction i would try doing some retraction test prints

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I had a similar issue, which turned out to be a loose y belt clamp, which allowed the bed to have a little play. The y would drift a tiny bit back and forth every pass leading to walls that looked like yours.

What speeds are you printing at, maybe try slowing the outer perimeter a bit.

Hi guys,

I'll try some more retraction settings with test peices and I'll check to see if my bed or extruder carriage have any play in the belt clamps, haven't checked that. Right now my speeds are:

Perimeters: 35mm/s (external at 90%)
Small Perimeters : 25mm/s
Infill: 55mm/s
Solid Infill: 55mm/s
Top Solid Infill: 45mm/s
Travel: 130mm/s
First Layer: 80%

Thanks for responding!

So far here is what I got. I tried to loosen the printer filament before I started the test print and that seemed to help a little. The printer was releveled and that didn't help. Neither did increasing the perimeter thinkness. Should I try increasing flow rate?

I'll have wait to do retraction testing as I am out of time for now.

Looks like an extruder issue to me. The corners seem fairly well aligned its just the under extruded layers that look bad. So it makes me think the position control is OK.
Check the spring tension on your pressure wheel. Try increasing it. If there is no adjuster put a washer underneath the spring. Someone on here reported they had a tension spring that was "set" overly compressed and had to stretch it to get good pressure. Also check the hobbed bolt/gear on the extruder is tight and that the pressure wheel can move enough to maintain pressure on the filament.

Quote
MCcarman
Looks like an extruder issue to me. The corners seem fairly well aligned its just the under extruded layers that look bad. So it makes me think the position control is OK.
Check the spring tension on your pressure wheel. Try increasing it. If there is no adjuster put a washer underneath the spring. Someone on here reported they had a tension spring that was "set" overly compressed and had to stretch it to get good pressure. Also check the hobbed bolt/gear on the extruder is tight and that the pressure wheel can move enough to maintain pressure on the filament.

That sounds like it could just work. I'll try it as soon as I can.

Thanks!

I've adjusted the extruder motor so it bites the plastic a little harder and checked that everything on the bowden cable is nice and tight as well as the feed bearing and gear. It seemed to help a little more but I am still not sure why it has small gaps. Do you guys think I should try adjust the z-axis stepping?

I know this is a bit old, but I am at work and don't feel like working, so now I'm browsing.
I notice with the uneven layers, that thinner layers appear fairly regularly. Every fifth layer or so. This looks to me like a problem with the hobbed bolt. If there is a bit of filament plastic stuck in a few teeth in the hobbed bolt, when it comes those teeth's turn to grip the filament and push it into the extruder, they don't get a good grip and they slip, until the next clean teeth come around and they get everything going again. So at those times, the filament briefly stops moving and the amount of extruded plastic briefly drops. So watch your extruder gear rotate and see if its position coincides with those thinner layers. Or better still, open up the extruder and inspect the hobbed bolt (flip open the pressure lever and push the filament out of the way to get a look). Get in there with a needle or something and scrape the plastic out from between the teeth.
It might be that you are extruding too fast some times (infill maybe) and the filament can't ooze out fast enough, Or your hotend needs to be a bit hotter so the plastic flows better...

And if you find (or have found) the answer, let us know so that others with the same problem looking here will also get the help they need.

Thanks for in input, the printer is still having the problem so I'll try your suggestions out as soon as I can.

I'll post what I find!

Thanks.

Yay! I removed the extruder gear, cleaned out the dust and refitted it back onto the motor. I rechecked the settings and set them to the default settings for my printer then saved and printed. As you can see from the picture, the .25mm prints came out like they should. I tested both of my PLA spools (Hatchbox and eSun) and both did well. Ignore the messy first layers, it was one of my settings. However, after I configured my printer for an ABS test print, my power supply died! (*INTERNAL SCREAMS*) So, I guess thats the next thing to work on. lol.

Thanks! to blabbersnitch and to everyone else that responded. All of it is great advice!