Tuesday, January 7, 2014

Safety First- Remotely Monitoring and Killing Your Jobs on the Cheap

I am always nervous about leaving my printer printing when I leave the house because I have these visions about it suddenly bursting into flames. I have wired a lot of things for 120 V but until I can get a UL certification on my home built printer I am never going to be perfectly comfortable with my wiring job. This culminated last weekend when I had a date with my fiancĂ© that I had to leave for but the print wouldn't be finished for another few hours. I wanted a way to remotely monitor the job and kill the power to everything at the end.  Unfortunately, I did not have it and the fear of the unknown sat in the back of my mind the whole night until I finally got home and saw that everything had finished normally.

For those wondering, there is a way in the G-code to cut the power to everything after the print finishes but I like redundancies. Here is what I add in Slic3r under the Custom G-code section:
G1 X12.0 F4000
G1 Y170 F4000
M104 S0- Set the extruder temperature to 0
M140 S0- Set the bed temperature to 0
M84- Turn off idle hold on the motors

To prevent this nervousness from happening again I wanted a way to remotely monitor and cut the power to everything if something happened. I had seen a lot of great work done with Octoprint and a webcam but since wiring a kill switch there required additional wiring and a relay that I was going to have to do myself (and thus was not UL certified), I wanted a commercial option. I went with a wifi enabled WeMo switch that the printer plugs into and you can control it remotely from your iPhone. This works even over 3G/LTE so you do not need to be in the same network.
WeMo wifi enabled switch.

The web interface is pretty slick too. You can turn off the printer manually or there are additional rules so you can have it turn on/off to correspond with the time of day, when the sunrises, or other rules. I bet this could help with workflow if someone wanted to have a printer turn on and automatically warm up the heat bed before you got up but that is far more use than I have for my printer at the moment.
WeMo iphone interface.

The next logical piece is adding the webcam functionality. Although the idea of using Octoprint to automatically slice and then submit jobs is pretty amazing, I didn't feel like forking over the $90 for the hardware and instead went for the less expensive iCam program on my iphone ($5). It works by streaming your webcam over to the iCam servers and then you can connect to it on your iPhone or Android device.
Mac OS X interface for streaming the progress of your printer.

iPhone interface for monitoring the print.

Together these work pretty well and I'd recommend it to anyone who wants a cheaper plug and play option to monitor their prints.

Experimenting with Taulman 618 Nylon

Most of my experience on this Mendel Max has been with PLA. I have calibrated things well enough that I can pretty much press print, walk away and be reasonably sure that my print will come out perfectly. For those who have the same printer that I do, my firmware might be a good place to start if you have issues. Unfortunately, the downside with PLA is that it can be prone to cracking under stress and I have some parts that I want to print which need extra durability. I purchased some Taulman 618 Nylon because I thought that this might the perfect material to print with that could take a beating.

To start, I read Richrap's article on Nylon and he states that Garolite is the material of choice for printing on. Unfortunately being in the US, it was difficult to track down. The only place I found it was McMaster Carr but I had read some bad reports about it not being flat in the Reprap forums so I decided instead to use cardboard from a cereal box. I taped it down with simple painter's tape and let it print a test cube.
Printing a test cube with Nylon 618.

I heated the hot end to 330 °C and did not bother warming the bed. I had read that it is important to dry the Taulman 618 before use and although I did see constant steam emanating from the hot end while printing, it did not appear to affect the print much. After finishing the cube, I noticed slight curling at one of the corners of the cube but it was in the same spot that I had not taped down the cardboard well so that should be an easy fix going forward. The Nylon bound so strongly that upon pulling on the cube, it actually tore up part of the cardboard!
Damages from pulling up the test cube. Note the slight curling in the upper left of the cube.

Getting a reasonable print the first time using Nylon was a surprise itself, but I was even more shocked when I stress tested the block. The fill density is 0.3 so it is mostly air on the inside but even after compressing the box with a monkey wrench as hard as I could, I barely made a dent in the block.
This stuff is strong!

The rigidity of the nylon also surprised me greatly. I had heard that 618 Nylon was quite flexible so it didn't surprise me that I couldn't crack the block but I found that even deforming it was a challenge. Due to this strength, I would have no hesitations in the future using this Nylon for something like an extruder gear. After considerably more work I was able to split the block in two at the small crack you see in the above image. The thin top part could be folded in half but it required a wrench. There was no cracking or irreversible damage and the bottom part shows how hollow the part actually is.

The two halves of the block after pulling it apart still show remarkable durability. 

Now that I have a general idea of how to print Nylon, I am excited to see how future prints will work out. Has anyone found any really good uses for it?