Oswestry Works

Locomotive works diorama in 4mm

Tag: 1:1 mix

Pushing the envelope with a B9 resin mix

GWR 9000 Class Top Feed test print

After what was in retrospect disappointing results with Spot HT – through my own ineptitude I must add, I went back to the tried and tested  1:1 mix of B9 Creator Red and Cherry resin.  This isn’t to say one is any better than the other, but with little life left in the layer of PDMS silicone before it needs replacement I didn’t have the leeway to experiment further with Spot HT.

This last batch of prints has been more experimentation with what level of detail is possible.  Second time round I reduced the size of the whistles and the steam heating cock to be a more prototypical size, even more challenging for the printer.  After quite a few false starts (left the projector lens cap on, build table not calibrated properly, not enough resin, ultrasonic died), I finally got a successful batch of prints of the highest detail so far.

This feels like uncharted territory because I’ve not wanted to let myself believe that it was capable of this kind of detail, until I’d seen it with my own eyes, coming out of my own printer.  I firstly revisited the design of the top feed for the Dukedog, the previous version not having a recess for the pipework.  This was designed to fit 20 swg copper wire, but the printed hole is slightly tight. It was a good exercise to see how well the resin could be worked with and the small hole could be opened up easily twiddling with a small drill bit.  This top feed will end up on 9014.

The whistles came out almost perfectly, considering that some of the detail in the design was under 0.25mm it would be impossible to see with out a macro lens or magnification.  Once cured these fine parts are quite robust, they aren’t indestructible but they did handle tweezers and finger tips, positioning them and trimming away traces of Tacky Wax under a magnifying glass!  It’s the detail presented on these that has really left me speechless.

GWR Standard whistles and mounting bracket test print

GWR Standard whistles and mounting bracket 30 micron xyz print

The beauty of this resin is it’s use to complement traditional materials, in this case matching up the whistles and mount with a Comet whistle shield etch and two strands of 36 swg copper wire to represent the whistle pipework.  The whistle print stood up to the finicky task of glueing everything together well, with impatient tweezer nibs looming, third hands full, trying not to drown the details out in glue.  This is the kind of detail I was hoping to attain after a few abortive attempts last year.

So with that done I think I’m out of excuses as to why 5726 can’t be finally painted and have its correct numbers fitted!

5726 with new whistle assembly

Comet Whistle Shield Etch, 36 SWG copper wire and 3D printed whistle and bracket assembly

5726 with new whistle assembly

5726 with new whistle assembly

B9 Creator first print

After a week or so of tinkering I’ve had my first successful print from the B9 Creator v1.2 HD.  This model is capable of 30 micron xy axis, though with quite a small build area at that resolution of 57.6 mm (2.67″) x 32.4 mm (1.28″) x 203.2 mm (8.0″).   By tilting your 3D model you can however print slightly larger objects.

Supports being added in the B9C software
In September I’d had Tebee’s Welshpool & Llanfair Beyer Peacock & Co 0-6-0T printed on a Statasys Objet Eden 260V, at 200 micron xy and 16 micron z.  I figured this print would set a bar to measure against once I’d got the B9 operational.  So far, with a little more tweaking I think the B9 comes out better with less striping and improved detail, the material is also much tougher.
P1170400P1170401

Some jewellers on the B9 Creator forums have been having good results with a 1:1 mix of the B9 Red and Cherry resins, so that is the material I’ve started out with at 30 micron XY and Z.  Over Christmas I’ll be trying the same print with pure Cherry and Spot-HT.  It’s been quite a learning curve to get something productive, mainly because a UV filter hadn’t been removed from the projector assembly which meant to get anything to print I had to use much higher exposure times.  Thankfully B9C support were able to quickly identify the issue and from that point onwards I’ve been able to print using default settings.  I think I’ll try for longer settle times on the next print as I think these will help to reduce some traces of lines in the print where the resin has been curing as its still settling.

P1170405

A steep learning curve…

The last few days I’ve been trying to get some test prints out of the B9 Creator I bought back in September.  To say its been a challenge is an understatement, however the support and help I’ve received from the B9 community has helped me progress from tomato soup to something physical.

The B9 Creator uses a DLP projector to cure a photopolymer (light initiated) resin.  The 3D print is sliced in the desired Z axis size, in my case 30 microns, each slice is then projected into the resin through a ‘window’ in the bottom of the resin vat.  The z axis build table steps up out of the resin as each layer is cured.  Once I’ve worked out how to calibrate properly and the optimum settings have been fathomed, it should be capable of some pretty mind blowing results.

However, at this point my first prints were a complete failure – nothing curing in the resin at all, nothing floating around.  Experimenting with higher exposure settings resulted in some layers appearing, but they’d detached themselves from the build table and were floating around in the vat.

After some more hair pulling I’d realised I’d calibrated the build table wrong, then retried with the higher exposure settings and voilà! Something was created, just visible on the base of the build table under the excess resin.   There are a number of post print steps that need to be carried out, removing the print from the build table, cleaning with 70% isopropanol, putting into an ultrasonic bath and curing in a UV oven.

Once I have some decent prints to share I’ll explain a little more of the process, in the mean time here is my catalogue of errors!