Prusa i3, consistently bad prints

Hello everyone, been lurking here for months to get advice on printing issues, but I feel the need to make a post.

I've been trying to set up my prusa i3, which I built from a kit, for months now. Every time I think I calibrate it and get all the settings correctly, a new issue pops up.

First issue is I can't get the bed to temperature, so maybe the bed resistor is broken (I have a glass plate on it). It won't go past 70 degrees celsius, and I'm aiming for 100. This means ABS or anything other than PLA is out of the question. I've resorted to using blue masking tape for PLA but I hate it, as it's difficult to get the prints off the table. My room isn't particularly cold, but maybe the glass just won't reach that kind of temperature.

Second issue is with print quality. It's really bad. I'm attaching a picture of PLA prints that I had to cancel because they were so bad. I was printing with Slic3r settings at 200 degrees celsius and VERY slow speed. And you can see for yourself how it turns out... For some reason the fan didn't run for this print, but it makes little difference (I know it's too far from the nozzle, but any closer and it would collide with the print). I've tried a series of different temperatures and two different filaments. I've never managed to get a good print out of my printer, and it's very disappointing. Motor voltages are set to 0.4V.

Honestly, I'm regretting getting a Prusa i3 kit. There are so many out of the box/plug and play printers out on the market now at an affordable price, I'm starting to wonder why I'm still trying to fix this thing. Please convince me otherwise. I really want a printer that will run fine and give me nice results without having to spend an hour experimenting and calibrating before every print, it's starting to get me depressed... Appreciate any help.

First and foremost, it looks like you need to increase your retraction length. This will help with the strings and blobs.
Secondly, reduce the print temperature. 185 is OK. When you're printing slowly, a high temperature will not allow layers to cool properly, giving you a melty look.
Third, make sure you've calibrated e-steps per mm. It looks like you're over extruding.
Fourth, if you haven't done this already, run through the calibration steps on the reprap wiki [reprap.org]

Stick with it - once you get it running right, you'll want to start hacking it.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

hello. Don't give up, that Prusa will give you just as good of a print as any of those box printers. Post your firmware settings so all of the gurus out there can take a look. Have you tried a different roll of filament? Maybe you have a bad batch. Is that extruder fan blowing on your heatbed while your trying to heat it up? I put cardboard on top of my glass to speed up the heating process. That Prusa is a proven design so there is no reason think it will never work for you. 200 for PLA seems high. I'm guessing your firmware settings might be to blame.

change temps
try hi or lower

mess with retraction

can you extrude say 100mm of filament and its consistent ?
First thing i do , heat my printer up, Extrude a bunch of filament to make sure nothing is slipping or jamming and have free flow of hot molten filament.


My guess if you are having these issues you will have it on other printers unless its like one of those machines that has Low to hi quality settings,
Believe me its well worth getting this thing operational.. keep on going with it, It took me a year to get good consistent reliable results.. im into my 3 year of printing and i can tell you its worth learning about all issue because you can effectively troubleshoot your issues and fix stuff quickly... no so easy on those ready to go machines..

Best of luck, keep on going you wont regret it eventually...

Wht size is your power supply? You may be under powered.

Sorry for the late reply! Been busy IRL...

Thanks everyone for the encouragements. I've kept trying. I had already changed filament in the first picture. I switched to printing at 195 degrees celsius with the bed around 70 degrees (won't go higher) and things are much better, but not quite there yet. Speaking of bed temperature, my power supply is 12V, I bought it along with the kit. Here's a pic:




I also got the fan installed with a new fan housing, and it might be a little better with it. I reset my Slic3r setting to default and went from there. Much better. But for some reason I can't print more than a certain height before the print looks melty again and loses accuracy. Here's a couple of pictures, tried to print different kinds of spin tops found on Thingiverse:








Also notice the fan housing being inaccurate near the top (same problem).

Printing under a certain z height seems to be fine though, as is shown by the OK lego piece below:




Could it be that my motors start drifting after a while? That the extruder motor starts going too fast? Would an e-step calibration fix this? I'm using the default vanilla Marlin firmware with Pronterface to control my printer.


Thanks in advance. Best forum I've visited ever!

since your parts look good below a certian Z height, I'd look at the stiffness of your printer. Does it wobble more as you get higher up on the Z?

I haven't really noticed any difference in wobbling as it gets higher. But there's more blobbing from the extruder. If it continues I'll have a look at step calibration.

Notice the printing gets messy where the printing is quicker per layer, like the top there, that means you need to set in the cooling section to slow down (5mm/s) when the layer time is less than 23seconds. What is happening is the hot filament is laying down a new layer before the previous layer has properly cooled so it just gets hotter and hotter and give you that look.

the spin tops you printed look like they need a cooling fan (a big fan blowing over the whole printer, directed at the print plate, just needs to be a weak or set to slow speed). have you tried putting a fan on it?
it can make the world of difference for that type of print.

Edited 1 time(s). Last edit at 12/07/2014 08:45PM by nechaus.

the lego looks pretty good

Quote
nechaus
the spin tops you printed look like they need a cooling fan (a big fan blowing over the whole printer, directed at the print plate, just needs to be a weak or set to slow speed). have you tried putting a fan on it?
it can make the world of difference for that type of print.

I have a cooling fan attached to the extruder. I've increased the minimum fan speed in Slic3r and I've changed the minimum speed as tmorris9 said. I'll try again with the spintop.

yeah i can see that, nice job, but still try a big fan.. its worth trying quickly

all these test will stick in your mind, you will soon look at prints and think, oh i can do this to fix that... it will all come natural to you

Well, I've tried some more (a lot more). It's always the same. I've set full fan speed, a range of different temperatures. Now half my roll of filament is spent and nearly all prints have failed. For some reason, they ALWAYS fail after a certain z height. Why? No idea. I would change filament, but this is the second filament I've tried, and it's better than the last one.

The nozzle starts oozing a lot of filament, always around the same z. The printer vibrates more around that z height, mostly because the nozzle starts crashing into the completely jagged previous layer. I keep monitoring temperatures but I see no drift, temperature is always around 185 degrees. I'd appreciate any help.