Wednesday, August 7, 2019

So You Want to Buy a 3D Printer? - Part 2

In our last adventure I was dealing with a clog, after having taken apart the print head to replace the fan and try to figure out why it wasn't printing as it should.

I left it with the clog and me looking at taking more advanced measures.

I did continue.

The first thing I did was take a piece of piano wire, heat it up, and jam it down the filament path to try to gather up any filament boogers. This is kind of like a cold pull except that it will gather up a different kind of debris. Larger pieces will stick to the wire and be pulled out since it's smaller than the diameter of the tube. I got out some gunk so that looked promising.

Another run of cleaning filament dashed those hopes.

I did a couple more passes of piano wire - cleaning filament before deciding there wasn't anything that was going to get pulled out.

It was back to cold pulls, hoping that the adventure with piano wire had at least moved around whatever was clogging the nozzle.

Two cold pulls later and it was still not working. I was on the verge of taking it apart so I could get to the nozzle more directly.

Now when I do a cold pull I like to make sure I know what's going on. Typically you heat it up to 265, run the filament (or push it down) until it comes out the nozzle, then cool to around 180-190 and pull it back out. I tend to set the temperature for the cool down rather than try to catch it at the right time. I set it to 190 and it works.

This wasn't working.

The next time I set it to 185 when I was going to pull it back out. And I found a chunk of something in the end of the cleaning filament. This is good. This is what you want. Cleaning filament is undyed nylon so it's kind of a translucent cream and you can tell if it gathers up anything in the process.

THIS time the cleaning filament ran nice and clean. It was the thick, smooth extrusion that I needed.

The moral of the story here? That sometimes you have to just keep at it and you'll get it working again. A clog can always be fixed, even if that fix is putting on a new nozzle. This time I could use the standard methods (with the extra kick of piano wire) to clean it out and continue.

Why piano wire? Because it's hardened wire and can stand up to heating and abuse. This stuff is really tough. You need special nippers because it will chip regular ones. It's serious stuff and very handy if you're going to be using it for various things. But if not then I recommend skipping it because while the wire isn't expensive at the hobby store the nippers are.

Let's go onto another thing that happens - twisted filament.

Almost all the time if your filament gets twisted it's user error. You can never let the end of the filament go unsecured. If you do there's every chance it's going to slip under a winding and then you get twisted filament. That will bind up at some point and do something as simple as break or as nasty as pull the filament roll around and screw up your alignment.

There are rare times when you get twists on the roll and they aren't user error. I've had it happen. I've seen the pictures of it from other brands. We honestly don't know how it happens at the factory since it should never be able to happen but it does.

Untwisting filament is kind of an exercise in patience. You can't just unroll it to the twist, untangle it, and roll it back up. That darn twist will keep sliding behind what you're unrolling. There's plenty of instructions on how to do it but I'll simplify here.

Keeping a grip on the end of the filament you back roll it to loosen up the windings. You keep doing that until you've got a nice amount of filament loose, hopefully with your tangle in there somewhere, then slide the whole mess over the side of the spool. It is a mess at this point. And I have yet to do it where there aren't windings on the spool that didn't get pulled off so I need to repeat a couple of times until it's just one piece being unwound. It's not pretty.

Then there's the fun of winding it back onto the spool. Filament is wound while it's still hot and it keeps the curve of the spool. And it's springy. So it's all over the place as you're trying to figure out how to get through the twists and hopefully deal with the tangle. I know most filament is cheap enough that I could cut off the part I've pulled off the spool and I have done that when it kinks or just gets too frustrating. But I like a challenge. Sometimes.

Ok. Clog is cleared! Filament twist gone! Ready to print, right?

Nope. The broken filament in the print head means it won't let me load new filament.

This one worked with the easy fix. Heat it up to cleaning temps, let the filament ooze out and soften, run some cleaning filament until the old stuff is gone. Then lower the temperature and load the new filament.

Except it didn't seem to want to load.

Being patient fixed that one. The load process built into the firmware has it doing a ram (fast load) for a bit then slower as it builds the pressure on the nozzle. The motor wasn't moving filament on the ram. But it was moving on the slower one. So I kept saying the filament wasn't loaded (it wasn't) so the process would continue to push out at the slow speed. Eventually the leftover cleaning filament came out (that could have been part of the issue) and the new filament was in this neat little spiral before extruding clean.

While the spiral looks cool it's not cool. It means there's .. a clog. This time just letting the filament run cleaned it up and I've got the printer going again.

So there's a whole bunch of little annoyances that happen with far more frequency than any of us like. There's far worse ones but clogged filament is pretty much an expected thing no matter how clean you try to keep your nozzle.

I'll detail the next problem when it happens. Because one will happen.

No comments:

Post a Comment