First resin castings from a few tile tools; a few lumps and bumps and air bubbles but these will be better on the second and third pull and the tools are clean.
20 Star Wars Death Star silicone rubber tile tools are ready to cast resin in to; let production begin!
The casting of the Hawk engine bell cleaned up really quite well; the main bell was made round / circular; the inside hollowed out previously but the "fuel" inlet ribbed section was difficult to work with; some of the ribs were missing in places, had air bubbles trapped in them but generally the ribbed section was not circular.
A replacement part was turned from model board; the ribs made a bit thicker and rounded off (to cast more easily later). The original casting had the ribbed section cut off with the new part fixed in place with some cyanoacrylate.
Three tools (in some old pots); 1 is the Hawk Main Engine Bell and the other 2 are for the 44" Eagle Transporter, the 3d printed masters for the passenger pod and walkway VTOLS.
Some 3d Printed parts for the engine section; the test fitting to the painted brass frame in the first photo.
Two cylinders are required; one (used twice) needs the grooves to clear the frame tubes. I will produce silicone tools for these.
The engine bell has been tooled and split (see my fun stop motion); good resins have been produced. The one image shows the tool in production after degassing in my vacuum tank.
Just a bit of fun splitting the silicone tool for making 44" Eagle Transporter Engine Bells.
I have been on the Facebook War Gaming Trade and Sell page, see the comments for a deal on a bundle set of buildings here or give me a shout via the contact button.
I have put together a Sci-Fi Building set; suitable for 6mm scale gaming. Message me if interested, £24 with UK free post. Will post overseas.
A note of caution; avoid standard Selotape and ensure everything (part / tools / hands / bench etc) is impeccably clean. RTV silicones react badly with many substances including the adhesive on the back of most Selotape type products; magic tape is safe. Isopropanol Alcohol is a best bet to clean parts
but in this case the part was not my own and being unsure of the materials used strong washing liquid and water was trusted to ensure the silicone wouldn’t react.
2.Runners and Risers
The runners and risers need to be set out with some thought. Visualising the flow of a liquid though something that is currently solid but will become a cavity can be a challenge.
In this case the part is set fairly flat; the item will be cast without vacuum by my friend. Being flat will help lift air bubbles of the “A” face. The A face is in this case a face! The A face will often be the lower surfaces of the mould.
The runner; resin goes in here, is a piece of 6mm rod and the risers; air and resin flow out here, are some 2x2mm plastic off cuts.
The runner is often best placed at one side of the part and the risers
at the opposite side. This part being fairly flat in the mould gave three “high” spots; these would trap air and need risers. The feed in placed centrally between these risers makes good sense – imagine poring a thick liquid on to a flat surface, a circular puddle is formed. The runner at centre will flow out equally within reason to the risers. At centre the part has a boss and rib feature for connection to the body of the figure; these make good flow features and give further reasoning to the runner position.
If the part were to be vacuum cast; I would have lifted the chin and
have used a single riser.
3. Set the tool
4. Mixing and Degassing
5. Pour and degas
Hollow parts need care also; these might tend to float, a balance between pour outside and inside is necessary.
The issue with moving the pour point around is over-layering the silicone; trapping more air between layers and the need to degas further.
I always degas again, this can be more difficult as the tool boxing / shape might not be as tall as the first
degassing pot. It will be harder to achieve full vacuum without overflowing the box; the box is lower just to keep the runners and risers short.
6. wait and cut open
When happy full cure is achieved; remove the box and trim the outside edges of the block. Remove the runner and risers.
Have a good look at the split line (that black edge has some meaning now). Check the tape is still attached to the master.
Initial cutting of tool should be a wavy (but smooth) single cut all the way around the four outer edges of the block. This cut should be one scalpel blade deep and can be (just about) seen in the photo.
The test run will clean the mould out fully. In this case no air bubbles on the A face and minimal on the B face – very good considering run with out vacuum assist.