Paint Table Sunday 11 September 2022

 I have made progress on the figures you saw on my workbench last Saturday. Not as much as I'd have liked because, you guessed it, I managed to distract myself...again. There's actually not much left to do on these - paint the base, add the camo dots, paint the metals and a couple of details and varnish them. They should be done before Wednesday.

3D Printing

The distraction

In my last post I mentioned that I plan, at some point, to print a full sized (OK, scaled down a bit to fit on my printer) Judge Dredd helmet. Well, I decided to do a test print of a half-size helmet to see how it would look. I opted to print it upside down as that would require much less support material.

I spent ages trying to get the support material off, but what remains seems to be permanently fused. So, I decided to do some more tests prints on even smaller versions to hone in my support settings. I thought I had them honed in, and printed another half-size helmet:

Better, but still an awful lot of fused material - I think the extra weight compared to the smaller tests was the problem. Cue a few more tests before I decided to see how well it would print in the normal orientation rather than upside down:

Left - printed without dome support
Right - printed with some dome support

The one printed with some dome support (support angle threshold set at 70 degrees) came out very clean where the support was, but around it there was some sagging - I think I need to set the threshold at 60 degrees. Or just not worry as  it won't be seen...

Of course, the lesson here is that I could have just printed the helmet upright and the material wasted on supports would have been much less than what I ended up using on all the test pieces! Now I just have to hope that, when I finally print it, the scaled down version will fit my head. If it doesn't it will just have to be an ornament.

Traveller Ships

With all that going on, I also managed to print another three 1:270 scale Traveller ships - an Armed Packet, another Type S Scout/Courier and a Vargr Corsair.

While printing these (and the helmets) I noticed that I was getting a lot of bad stringing. I knew that one possible cause was a worn out nozzle (replacing the current one was already on my to-do list) so I bit the bullet and replaced it. I also decided to replace the PTFE tube inside the heat break - I'm glad I did, as it highlighted a problem I hadn't been aware of:

It seems that the PTFE tube inside the hot end was slightly too short and there had been a small gap between the end and the nozzle. Over time, that had filled up with filament which had burned and crept up inside the hot end. Getting the white PTFE tube out was a job and a half and I knew I'd have to ream out the bore. After about an hour of twisting increasing sizes of drill bits I'd got all of the caked material out and the new PTFE (blue "Capricorn" high temp stuff) could go all the way through. With that done, I was able to fit the new nozzle.

However, I was still getting really bad stringing. I've spent several hours yesterday and today printing out small test pieces to see if changing my retraction settings might help. I got variable results. I finally concluded that it must be a problem with the filament - I suspect it might not be as dry as it should be. So, I switched out the grey for a new spool of purple and ran a test print to compare against a similar print I'd done on Saturday with the grey:

It's definitely an issue with the grey filament. I'm going to buy a filament dryer to see if that helps as I like the grey for prints as it's good for taking photographs of models.