There's a Global Shortage of Toilet Paper

There's a Global Shortage of Toilet Paper

But more importantly there appears to be a global shortage of PLA. I've been printing a fair few things recently and thought it'd be a good idea to stock upon PLA filament. Unfortunately I found that lots of suppliers were out of stock and the price had risen to about double what I last paid. I managed to buy some PLA at a higher price than my last purchase, so I have some in stock.
I had a look around and found that PETG was an odour free plastic (not biodegradable though) that seemed to be similar to PLA. More importantly it was available. I bought some as a sample.

My fisher 3D printer doesn't have a heated bed. This hasn't caused me any problems with PLA other than a slight warp on some larger prints. The bed has Buildtak (BuildTak?) on it which is a very nice surface. PETG seems to need a heated bed according to the internet. Anyway, the PETG arrived and I had a go at printing with it using my normal PLA settings and no heated bed (I've ordered some parts but they won't arrive for ages).

First, the robot that came with the printer:

He didn't print very well, in fact his foot half fell off, but it wasn't a total disaster. I then realised that the file was an STL that was on the SD card and it has a print temperature of 200C. I don't print PLA at that temperature, for some reason all my printers work best at 220C. PETG seems to have a slightly higher print temperature than PLA. I tried a couple of my smaller parts with PETG at my PLA temperature: 220C:

That's a dehydrator knob and a thicknesser latch thingy and both printed fine. No problems at all.

The layers look very similar to the PLA versions. The part does seem to have a little more flex in it compared to PLA.

My Panasonic lens fix was a success until I dropped it again, I then printed another part and fitted it, but it was a slightly different design and had a hole in it which caused too much flex for the contacts on the lens to reliably engage with the camera. It finally got to the pint where I couldn't use th elens, so I decided to fix the problem. I altered the model and printed a new part in PLA and an identical one in PETG. Of course, it's white not black as that was the PETG colour I bought:

The PETG part seems to be a bit more 'slippery' and this is useful on a lens mount, so the PETG part is better than the PLA one in this respect.

The PLA part doesn't seem to be quite as tidy as the PETG, but the difference in colour doesn't help the PLA.

The lens is now working with the PETG part, which is what I wanted. It looks like PETG is going to work for me in the same way I use PLA. Excellent.

The Failures of 3D Printing

Not 3D printing in general, but the 3D printed parts that were no good, for whatever reason, when I was building my prototype can transformer. The finished article is here:

and makes things like this:

When I was building the prototype I printed many parts, a lot of which didn't work. This is normal for my builds, but this time I kept the failures. It was surprising how many there were:

The histogram of failure

I laid them out grouping the same part, so you can see which bits I had trouble with. The X carriage, for instance, is there as four failed parts, and the Z carriage is there in a form that isn't in the final machine. There are some gears in the picture (a lot of gears, in fact) which are also not in the final machine. I started off driving the Y axis using gears as they 3D print well. They have a lot of backlash, however, and just didn't work well enough. The final machine uses MXL belts.

The biggest failure is the part that engages with the top of the can and has to grab the can well enough to stop it moving as the Y axis rotates. They are the two rows of circular objects just down from the top. I had a lot of trouble with that poart and still don't have it perfect. In the end I made a common base for the part and screw inserts of different shapes in to it. This means I don't waste (any more) plastic and time printing the main body.

Most parts are failures for mechanical design reasons, the printer itself is very reliable now and I only had one or two print failures and they tend to be operator error in some form anyway.

The reason for black and white is that I have two printers, one set up for black and one for white. I found they print slightly different sized objects, so having different colours was useful as I knew which printer had printed what.

Fisher Problem and Fix

The friend's problem with his Fisher printer has probably been fixed. The problem was a snag of the filament when the angle of the Bowden tube was anything other than vertical. The filament enter the heatsink in the hot end through a pneumatic fitting on his printer. neither of mine have that arrangement, so I haven't seen that problem. I made an aluminium tube that helped to hold the Bowden tube vertical, but it didn't quite fix the problem. Some support from the RepRap people and a design for a bracket was sent and printed. This does seem to have fixed the problem, except maybe when the effector is at the top of its travel.

The final arrangement is here:

It's difficult to see how the tube can be anything other than vertical, with all this encouragement...

New Printer

When I looked on the RepRapPro site for a new heater and nozzle for the Mendel, I saw that they had a beta version of their new Fisher delta printer at a reasonable price. So I bought a kit.

It's much smaller than the mendel and has lots of new features.

It also has green printed parts:

The packaging of the kit is compact and neat

The printer itself has several laser cut parts, so this printer can't make all the parts for itself, as the mendel can (except for the standard off the shelf parts like motors).

Being a delta printer it prints in a completely different way. It has auto bed probing too, which is really nice.

It prints nicely too, and doesn't suffer from the bed wobble that my mendel does. The print head mounting and linkages mean that the nozzle is the only part that moves and it is very firmly located at all times.

Due to the compact construction there's a tight fit for wiring inside the case, which has caused the odd problem, apart from that it's great.