Tuesday, April 28, 2015

Latest Issue: Extruder Not Extruding

We let a print run all night and woke up to a giant mass of angel hair ABS. After a doctor's visit, some errands, and lunch, my husband decided that he really needed to try his hand out at printing some female stormtroopers. This all resulted in nothing. No, really, nothing. Prusa, our Makerfarm 8" Prusa i3, was refusing to extrude. There are a variety of reasons why this can happen, so let's explore some of those reasons:
  • Tension on the filament clamp spring(s) too strong
  • Tension on the filament clamp spring(s) too weak
  • Tension on the filament itself (ie. Not unwinding/feeding freely)
  • Extruder motor malfunction
  • Hotend not hot enough
  • Hotend too hot
Each of these situations can and will cause issues with extrusion, however we've missed one insidious possible cause of error: the hotend nozzle being too close to the print bed. Betcha didn't think of that one! The reason why this is such a pain in the ass is because with the way I troubleshoot, I generally go through the above checklist first before checking the nozzle to bed distance. This is a problem is because it doesn't allow the filament to freely escape the nozzle, which results in the hobbed bolt chewing up the filament, the nozzle grinding the print bed, and a lack of extrusion. The solution to this problem is to recalibrate your Z-stop and to make sure your print bed and X-carriage are level. If you've already calibrated everything else, and you are definitely too close to the print bed, you more than likely only need to recalibrate the Z-stop.

Sunday, April 26, 2015

Misadventures with the Prusa i3

The Prusa i3's nozzle had come loose and we had determined this by the fact that hot filament was oozing out of the top of the nozzle. To remedy the situation, the hotend needed to be removed and soaked in acetone. This also meant that the thermistor had to be reattached. This created a new problem: by screwing in the hotend tighter than it had previously been inserted, the hotend was higher up off the heated bed. This meant that the extruder had to be closer to the hotbed on the z-axis, so low, that it was jumping on and off the couplers that attach the z-motors to the threaded rods. Okay, "easy" fix, raise the heated bed off of the build plate using our adjustable spring loaded screws that we had added in a previous upgrade. Oh, wait, while installing that upgrade my husband had destroyed one of the screw holes partially by impatience and partially by Makerfarm's optimistically tight tolerances. Welp, guess I had made it a whole month without going to Home Depot.


Went to Home Depot for a piece of plywood, hoping for the smallest piece available as we only needed at 8" x 8" section for the build plate. They were out of 2' x 2' x 0.5" pine boards, so I delegated the task of tracking down a store associate to said husband. Here's a neat tip, if Home Depot is out of a particular size package of goods, they'll generally give you an upgrade for the lesser price. In this case, no 2' x 2' x 0.5" pine plywood, but they did have 2' x 4' x 0.5" pine plywood AND 2' x 4' x 0.5" birch plywood. We requested that they cut the larger board in half for us, but their saw was down for repair, so they were nice enough to give us the $17.50 piece of birch for the price of the small pine board ($7.14). Keep that one in the back of your head, you'll thank me later.

It should also be noted that after going through half a gallon of acetone (yay, ABS!), we finally decided to supersize it and move up to the much cheaper gallon can of (industrial solvent) acetone. The gallon cans cost like $4.25 a quart, whereas the quart sized cans cost nearly $8/each.

After escaping Home Depot (and forgetting to get the Dremel, d'oh), we made our way back home where my husband was impeded by the childhood top on the acetone. He eventually gave up and passed it off to me. Obviously I couldn't do it either, and thought, "hey, I should pop this plastic sleeve off the top and see if I can open the can that way," but did not for fear of breaking this thing that I kinda wanted to return. So no go on the acetone. Off to the return pile.

Back to the repairs: My husband got to work on cutting down a new buildplate. "This should be easy," he thought. "Just put in some new screw holes and it'll be good to go!" Oh, wait, the y-idler is tenoned to a laser cut mortise in the buildplate... Hand drill probably not going to work. After rifling through the workshop for 5 minutes, he found a chisel, and proceeded to fix one the world's most advanced manufacturing tools with a Bronze Age tool. With some wood working skills and the new Dremel (which we remembered on the return trip, hooray!) he transferred the hole template from the old buildplate to the new one. Then he was kind enough to reassemble the printer, leaving me with the joyous task of recalibration.


See my enthusiasm there? If not, you can see it here: Calibrating a Prusa i3.

Two weeks after determining the nozzle issue, a calibration cube printed out perfectly.

Calibrating a Prusa i3

Hopefully you're reading this before you scratch the shit out of your buildplate.
  • Level your X-carriage using a clinometer (free Android app, Clinometer) to level out the thing properly. You *could* use a bubble level, but those aren't accurate or precise enough.  
    • Always make sure to
      • Remove your phone case.
      • Calibrate the clinometer app.
      • Rotate the phone 180 degrees to mitigate the zeroing error that is inevitably leftover even after you've calibrated your phone. The object in question is actually level when you have the same reading after rotating the phone 180 degrees.
  • Level out your buildplate.
    • If you have a spring loaded assembly, which you should, you'll need to adjust the bolts in each corner. Follow this tutorial for further information.
      • Want to hack your own springloaded assembly, but can't find the springs anywhere? Use the springs out of a set of the SAME unused clicky pens. You want the spring coefficients to all match up.
      • Locknuts are your friend with these spring loaded assemblies, especially if you don't want to have to level out your buildplate every single print.
    • If you have a fixed bolt assembly, you'll need to add/remove washers/spacers until the bed is level. 
  • Calibrate your endstops.
    • Z-stop: you'll need to bring the nozzle of the hotend down such that it is close enough to the bed such that you can run a sheet of paper under it. The paper should be snug; you want some drag on it. Then you will need to screw and unscrew the Z-stop bolt until you hear the telltale "click" of the endstop. Screw and unscrew it until you get that bolt as close as possible to the exact moment you hear the click when going down.
  • Check your filament situation
    • Make sure the hobbed bolt is clean and free of dust and debris.
    • Don't forget to add filament.
  • Check your wires, make sure nothing came undone while moving the printer around.