Rotational casting is easy but how do you do it when the casting needs to have solid parts?
00.00 Good morning! My first "How Would I Cast This?" video. Casting challenges explained.
00:47 How do you hollow cast a piece with solid parts?
01:37 Polishing plastic on a buffing wheel.
02:28 Seal up any openings in hollow models with clay or wax.
02:53 Preparing you model for molding is everything!
03:29 Waxing a wooden sprue and installing it in the model. No vents needed.
04:25 Blue sprue wax has many uses, including sealing wood and filleting joints.
04:50 The Foredom Wax Carver is one of my most important tools.
06:00 Using a rubber spacer to hold the model away from the bottom of the mold case.
07:35 Pouring the rubber into the mold cases.
10:20 The temperature in your shop greatly affects curing time in both rubber and resin. The hotter it is the faster stuff sets!
10:55 Cutting the molds open.
11:10 Cutting open a radial mold.
12:25 Checking the molds for flaws and bubbles.
12:40 Use scissors to trim mold flash.
12:50 You don't need tools or devices to help you cut open molds.
14:16 Mixing resin. Equal parts of A and B resin.
14:48 Mixing small amounts of resin is trickier than large batches because you must measure very accurately or the ratio will be off.
15:20 Pouring the resin. You need go fast because the heat makes resin go off quick. I pour the solid sections of the mold first, before rotating the hollow body of the casting.
16:07 Slush casting a mold is just like rotational casting except you do it by hand without using a machine. making a rigid holder from cardboard helps prevent mold distortion as you slush cast it.
17:35 Pouring the hollow body of the casting which is mounted unto a small rotational machine.
17:50 Rotating the mold.
18:35 Hand rotating allows you to control how the resin coats the walls of the mold.
18:47 Watching your witness cup and drips tell you the state of the resin inside the mold.
19:40 De-molding the slush cast part. Checking it for flaws.
20:27 It is common to catch bubbles in the fine surface details of a rotocast part. You may have to brush the resin into the details prior to rotating the part.
20:49 The first shot out of a mold tells you what problems you may need to fix to produce perfect castings.
20:55 The resin from the witness cup tells me that the part in the rotator is ready to come out.
21:03 Removing the mold from the machine. Lots of small rubber bands are better than a couple of big strong ones because they distribute the holding pressure evenly over the mold. This is less likely to distort the mold.
21:50 I built a small cardboard cradle to help prevent distortion from the rubber bands.
22:20 Popping out the plug and evaluating the casting.
23:45 Cutting open the castings on the band saw to see how they look. You can learn a lot from cutting open your first casting.
25:21 Hit that LIKE button, be sure to ask questions or comment and thanks for watching!