3D printing adventures

I recently shelled out around $900 and bought myself a Prusa i3 3D printer kit for rapid prototyping. Unfortunately, I spent quite some time getting the ‘calibration’ working.

The RepRap wiki was very helpful in helping to calibrate. However, I was quite lucky and the supplier where I got my kit from actually provided me with some pre-calculated numbers so I cut down on about one third of calibration needed.

After some tweaking with acceleration and steps/mm adjustments for the Z-axis, I finally got my test cubes to print properly.

However, after a while, I noticed a lot of my prints were falling apart. Eventually, the print quality just dropped to downright unacceptable.

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Notice how the layers don’t seem to stick together? The infill didn’t seem to be ‘infilling’ either. The whole thing seemed like a delicate honeycomb. Most of the time, I was able to crush and rip it apart fairly easily.

Let’s take a look at what the printer is actually doing.

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As you can see, the extruder isn’t providing enough material.

At this point, I suspected a few things. Firstly, it’s obvious that there’s not enough material or that material is being extruded unevenly.

Of course, the first thing I did was head to the Print Troubleshooting page of the RepRap wiki and to the Google-mobile. Both suggested that my prints are turning out badly due to material contamination but I ruled this out initially since the rolls of filament were close to brand new.

Next, I suspected the Z-axis steps/mm calibration may be out of whack. Could it be that the Z-axis is moving up faster in reality than slic3r is expecting it to? Maybe not enough material is being deposited due to this discrepancy.

Something told me at the back of my head that this was unlikely since for a day or two, I was getting pretty good prints before this started happening and I didn’t touch the calibration settings at all. Nevertheless, I did waste a few days attempting to ‘recalibrate’ the Z-axis to no avail.

Maybe it was just a PLA thing? I took out a roll of ABS and fed it to the machine and printed a test object. Hey, presto! Apart from some dragging and oozing, the test object turned out okay! Unfortunately, the second print showed the same symptoms as PLA so I ruled material out.

Now, I started suspecting the extruder. Perhaps the plastic isn’t being heated to the correct temperature making it hard to extrude (and hence, the rest of the printer moves too fast for the extruder to keep up). I wasted a day heating up PLA to different temperatures with very little difference.

At this point, I was pretty frustrated and took a break from it for a few days.

When I finally decided to give it another crack, I suspected the extruder again. Maybe the E-steps/mm calibration was out (again, unlikely since the first few prints worked). No matter how I measured, the calibration was spot on (the supplier had it calibrated pretty precisely).

This whole time, I was on Google searching and reading about similar problems – none which matched mine exactly.

Alright, at this point, I decided it was time to take the material contamination possibility seriously. The room where I’m printing in can get quite humid so I suspect the filament may have gone dud quicker than expected. Baked both rolls of filament in the oven at 60 degrees and monitored the oven temperature very closely to make sure I didn’t deform the PLA plastic. I left them to bake for about 4 hours.

When I tried another print with the baked filament, I had the same problem. With both materials. Dammit. I then, took another break and came back a couple days later to have a look again.

Anyway, I still suspected the extruder. I tried a test print while gently pushing the filament into the feeder. And, what do you know? The layers started giving me clean lines for the first time in about two weeks!

So finally, I figured for some reason, it wasn’t extruding enough material. I didn’t think I made any build mistakes.

Although the extruder design appeared to be a custom one, it was simple enough to work out how it worked and I couldn’t see any problems.

My next suspect was the hot end. Could it be clogged? I tried to clean it out by heating the PLA to 190 degrees, letting it cool to about 40 degrees, then heating it to about 80 degrees and sharply pulling the filament out. That was supposed to pull out any bits of gunk. I actually did this a couple of times before trying another test print.

Again, no cigar. Dammit.

It wasn’t until I was casually browsing the supplier’s documentation for the printer that I had an epiphany. I noticed that the cog for pushing the filament through always needed cleaning. What if it wasn’t meant to be like that?

A quick Google told me that if the cogs needed constant cleaning, there was something wrong.

I looked at the extruder design again.

IMG_20140723_121558

 

Maybe the ball bearing wasn’t pushing the filament hard enough onto the cog? Maybe that’s why the filament wasn’t being pushed though.

I added an extra bolt before the spring so the bearing pushes harder against the filament and fired another test print.

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Hey, success!

Now, it’s definitely not a perfect print, there’s still inconsistencies to be fixed and fine tuning to do but it was over 9000 times better than the craptastic prints I was getting before!

At the very least now, I have the option of printing out and trying other, more standard extruder designs now.

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