Trouble printing at normal speed

I have a Prusa i2 built from the kit available on mixshop.com,and was to get some pretty nice prints (PLA, 190°C) with the default firmware and settings. I then calibrated my extrusion length, and began calibrating as per the reprap calibration guide. Everything was going fine, until midway through a print of a fan duct. (Pictured) have since cleaned my extruder, and taken great care to perfectly level my print bed, but for some reason I can't get prints to work at the default speeds. At 10mm/s the prints come out nicely, but any higher speed that that after the first few layers the filament stops adhering to the layers. I suspect that something is wrong with my hot end, but I haven't been able to think of what the problem might be. Anyone else had this problem before?

My pics are too large to post here, so I linked to- [imgur.com]

Are you using a cooling fan? If so, you probably need to put some kapton tape around your hot end as an insulator. The fan may be cooling your hot end down enough to mess up the print.

Otherwise, I would try increasing your extrusion multiplier - 5-7% should help. It looks like there wasn't enough filament being put down on that print that messed up.

What program are you using to print? If you have the ability to adjust your print speed while printing, you can start at 10mm/s and increase it to see what speed causes the issues to start and if there is a specific area that the print begins to fail at.

In my experience, PLA not sticking is generally either from improper temperature - too hot or not enough time to cool before the next layer - or speeds that are too high.

A cooling fan can help the 2nd problem, but as I noted above, be sure to insulate your hot end.

It looks to me like a fan is not being used to cool the print. i see defects along the outer walls that indicate filament was not cooled enough before next layer, also the thinning of the print begins even before the top narrower part of the print. it is likely that the print is sagging down. this issue needs to be addressed before further troubleshooting.

What i would guess is that with warmer temps outside, your prints are going to start to fail without cooling if pla is used.

install a cooling fan if possible, but be sure to insulate the hot end, you would be suprised with just 1 wrap around with kapton tape how much heat remains on heater block. If no kapton is available then get some plumbers ptfe tape and wrap that arround.

IMHO

Edited 1 time(s). Last edit at 05/31/2013 08:30PM by jamesdanielv.

Thanks for the input!

1) I am not using a cooling fan, have been working on printing that part for a while, but my hot end is covered in kapton tape.

2) I am using Slicer, with repetier as the interface. I adjusted the speed from the default 30 mm/s to 10 mm/s to try to get a good print

3) I may not be at the right temperature, but I have not been able to get to that stage of calibration. I was almost to printing the 50 mm tower when my prints started to fail.


-Thanks

another thing that may help that print is to print 2 or 4 copies of it at a time. this will allow the layers to cool before the next layer is placed because the time it takes to finish a z layer is longer. slowing print down below 10m/s can cause oozing. it may take more feedstock, but it will help.

Also, try seeing if your printing temp is correct, and try to use the misprinted fan duct to get the second one to print better?

Ok, I actually have a 200mm fan that I can mount to the frame with zip ties and see if that helps. I have the Lm8uu carriage with fan mount, but my fan doesn't fit. I'll try that out. Thanks guys.

I was wondering if maybe my filament is bad? It seems like there is a wide deviation between how much is extruded per layer.

Ok, so i figured out the problem. My extruder had worked loose of its screws, and my heated bed thermistor was loose as well. A few washers adn some kapton tape later and I am getting the best print quality to date. Thanks for the help!