Steam Train Whistle

Summary: My first print with custom settings. Use the pause function to correct minor errors during a print.

Since before I got my 3D printer, I have wanted to print this steam train whistle from Thingiverse. I thought it would be cool to print something functional, even if its only function is making noise!

first try

My first attempt didn't turn out so well because the filament feeder was skipping.

second try

I tried again after "fixing" the problem only to have the feeder start skipping again and ruin another print. I was feeling cocky after a successful print so I had upped the printer speed to 80 mm/s. That's still a conservative speed for the UM2 but maybe that was the reason for the skipping?  Rather than repeat the print at 50 mm/s, I ended up disassembling the filament feeder and performing an Atomic Clean on the print head. While feeding the filament back into the bowden tube I noticed that unless the curve of the filament matched the curve of the tube, the filament would bind firmly in the tube. The deep pits in the filament from the feeder probably didn't help either. So I cut off any filament that had been through the feeder already, made sure the filament was uncoiling cleanly and following the curve of the bowden tube, and fed it back into the filament feeder.

stray filament

Bingo, that did the trick. The PLA seemed to be flowing smoothly so I set up the whistle print again, this time at 50 mm/s. About a third of the way through the print I noticed a piece of PLA had been pulled out of place and was sticking up in the middle of the whistle chamber. I was worried that this might affect the sound of the whistle so I paused the print. To pause a print, just go to tune < pause printing with the navigation button on the printer. A pause also moves the print head out of the way. With the print paused I was able to cut off the piece of stray filament. Hit "unpause" and the print picks up where it left off with no visible sign of the interruption.

third time's a charm

About an hour later the print finished. I didn't hear or see the feeder skip once during the entire print. The whistle looks great and sounds just as good. And it is loud. The kids should love it...my wife will hate it.

I used the full settings and made some adjustments as recommended by the whistle designer. The final print settings were as follows.

220°C
0.25 mm layer height
0.75 mm bottom/top layer
25% infill
0.8 shell
0.3 mm initial layer
50 mm/s print speed
all other settings were default

Don't Over-tighten the Material Feeder!!!

this is what happens when feeder tension is too high

Summary: Over-tightening the material feeder will cause the filament to slip and will lead to under extrusion.

Yesterday morning I made the nice print pictured above with the normal quality settings. That evening I tried to make some more prints. They did not look good.

Multirotor helicopter foot.  WTF!

The picture above was the result of a normal quality print. Looks like under extrusion again. I was already printing at 220°C so I didn't think temperature was the issue. It was a model that I designed from scratch so I thought maybe the problem was with my model. I downloaded a popular whistle model from Thingiverse and tried again. This time I used the full settings so I could change the layer height, number of layers, and infill as directed.

not even close

As it was printing I could hear some clicking coming from the material feeder as the knurled wheel slipped on the filament. I thought the tension on the material feeder might not be high enough so I tightened it until the indicator was on the center line. No improvement. I canceled the print after about 30 minutes; the layers were a mess.

reducing resistance on spool

I thought the nozzle might be clogged but before I tore it down I decided to check the UM forum again and search the under extrusion posts. I noticed that under extrusion can occur when the coils on the filament spool have trouble unwinding. This seemed particularly common with Ultimate-Blue PLA as it seems stiffer than some other brands. So I removed the spool, unwound a bunch of coils, and tried to straighten the filament as best I could. Then I tried printing the multirotor foot again.

proper tension setting on the feeder

With the machine back facing me, I noticed the material feeder slipping about every 5 seconds. With the better view I could see how too much tension (rather than not enough) could lead to the slipping I was seeing. So I backed off the tension until the slipping stopped. The material started feeding just fine, no more slipping.

that's better

The foot printed perfectly. Thinking back, I believe the first thing I did to combat under extrusion was increase the tension on the material feeder when I should have been increasing the temperature. Keep in mind there are two different versions of the material feeder for the UM2. There is an older version which apparently had some problems and needs to be adjusted to about the middle setting. And there is the new version which I have which likes to be set towards the top. This setting is much more critical than I expected and I wonder how many under extrusion problems are a result of improper tension on the material feeder. Check this first as it can save you the trouble of cleaning your print head!