[Metal Casting Part 2] For the Sunday mechanic who loves to make his own parts, who loves to work on parts, if he could make his own casting parts, it would be great fun! Who wouldn't think so? For us at Motomechanic, it's the same. I have tried to make this dream come true with white metal casting. In this part 2 of our metal casting series, I will try to unmould the master parts and melt and pour the white metal.
Challenge with white metal for metal accessories
The characteristic of white metal is that it melts with heat and has a low melting point. When repairing wiring or connecting wires, the soldering iron is used to melt the solder and fix the copper core wire in one piece, which can be thought of as almost the same image. The composition of white metal is tin (tin) as the main component and contains antimony, lead, and copper. Depending on the subtle differences in the concentration ratio, the shine, bending and cutting characteristics of the finished product will differ, so which specification is best depends on the part to be made.
White metal is known as a flexible and easy to work metal. The personal production of accessories such as handmade rings, necklaces and brooches is now a very popular hobby. White metal is also widely used as a material for handmade accessories, and the heat-resistant silicon rubber mold-making material used here is one of the products used by users who make handmade accessories. I searched on the internet for "handmade accessories white metal" and bought white metal materials by mail order while surfing the net further from there.
White powder is mold release agent, talc for FRP craft
The white powder used as a mold release agent is called talc, which is used as a filler when making molds for FRP work. According to Mr. Yoshinori Itabashi, the technical advisor of Motomechanic magazine and the owner of Model Create Maxi, who practiced this white metal casting, "You can use wheat flour or potato starch as a mold release agent instead of talc. In short, it is important that the powder is in powder form. Talc, by the way, is used to increase the bulk of resin in making FRP parts. When talc and AEROSIL® powder are mixed with polyresin, they can be used as putty when molding FRP parts.
I smeared talc over and over to make the brown heat-resistant silicon mold this white, and used a dry brush to spread it deep into the grooves of the mold. Seeing such a situation, I asked Mr. Itabashi, "Is it OK to use blackboard chalk powder? I asked Mr. Itabashi, "Is it safe to use blackboard chalk powder?" He replied that it was perfectly safe. It is true that chalk and wax stone, which is used to draw pictures on the ground, are derived from minerals and can be said to be the same as talc in classification, although their hardness is different.
The heat-resistant silicon mold, which has become white with talc powder, is placed in a high-temperature dryer (CV Junior by CARVEK) to warm it up thoroughly. By heating the heat-resistant silicon mold itself, the temperature difference between the molten white metal and the mold is reduced. When the temperature difference is reduced, the white metal can be easily poured into the mold. On the other hand, if the temperature difference between the melted white metal and the silicon mold is too large and cools down at once, it becomes difficult to reproduce the shape as the master.If you look at the top image, you can see that the edges of the letters are rounded.This is the result. It seems that the white metal melted by the temperature difference cooled down at once, and it became such a finish.
The CV Junior, a CARVEK high temperature dryer, is designed to look like a two-story toaster oven for the kitchen. The main feature is the flexibility of temperature and timer settings. The maximum temperature is over 200 degrees Celsius, and the maximum timer time is one hour. Continuous operation is also possible, so it can be used in a wide variety of situations. It is said to be used for small stained glass and ceramics. Of course, it is also ideal for baking and drying paint for small motorcycle parts. A simple thermometer is included to provide analog feedback of the temperature setting. This time, the temperature is set to the highest (over 200℃). The temperature is rising now.
Melts in a stainless steel pot with a cassette stove!
This time, I bought JIS standard 2, 4, 6 and 8 kinds of white metal. We tried simple casting with each material and enjoyed it. I judged that JIS standard type 2 white metal was suitable for making emblem. I put the white metal into a stainless steel pot (purchased at a 100-yen shop) and heated it on a cassette stove. Probably when the temperature exceeds 200 degrees, the white metal begins to melt like butter. The adjustment of the heat power is done by the up and down movement of the pot. It seems that it is not good to make the temperature too high.
The completely melted white metal was poured into a sufficiently warmed heat-resistant silicon mold. At this time, the silicon mold was heated at 200°C for more than 30 minutes. If the melted white metal (commonly called "Yuyu") overflowed and flowed out from the mold, it would cause burns, so the work proceeded on the CV Junior standard aluminum tray. The temperature was too high to touch with bare hands, so we wore leather gloves to work safely. The DIY metal casting was done by trial and error. For this Kawasaki emblem, JIS type 2 white metal was a good match. The two types, which are mainly composed of tin, shine well when polished and seem to have good followability in bending.
When it cools, demold it! Let's finish with a flat file!
The burrs around the perimeter of the empreme and the surrounding area should be shaved off with a flat file to finish. Immediately after pouring the white metal into the emblem, I pushed the aluminum plate which I made holes in two places. The white metal flowed into the hole by pushing from the top of the melting white metal, and two protrusions were made on the back side of the emblem. Because the melting point of the aluminum plate and the white metal is completely different, this kind of work became possible.
After roughly finishing with a flat file, I primed the surface with a transparent primer to improve adhesion. Next, I prepared a semi-gloss black urethane paint and sprayed the surface and perimeter with a thin layer of paint. It's exciting to imagine the finished product after all this work!
When the paint was completely dry, I scraped the surface and tried to make the word "Kawasaki" stand out. I put sandpaper on a small polisher buff and scraped only the surface of the letters. It is a very good finish. After polishing with polisher, I made hairline finish with sandpaper.
- Point 1: Choose a white metal material that is compatible with the parts you make or want to reprint.
- Point 2: Heat the heat-resistant silicon mold before pouring the white metal. If the mold is cold, the melted white metal will not flow smoothly.
- Point 3: By manufacturing aluminum press plates that match the dimensions of the rubber mold, the finish of the product will be improved.
Some of the private tents that are exhibited at various events and garage sales sell handmade accessories. One of the most popular materials used for handmade accessories is white metal. Not all of the products are made of white metal, but the color, luster, and shine of these accessories are probably made of white metal. Some of them were very similar in color.
What kind of material does he use to make the mold? I didn't ask for details, so I don't know, but he makes a blank by pouring heated and melted metal (probably white metal) into a base mold, and then asserts his unique individuality by engraving. As I have heard in the past, "If you engrave metal from white metal, you can make unique accessories, and such accessories are very popular! It is true that white metal is the best choice to express your favorite design, because it is easy to engrave and process.
As a matter of fact, have you ever heard of engine parts made of light metals in the same family as white metals? Crank metal, which is well known as an engine part, is exactly the same. Crank metal is used as a bearing metal in the journal part of crankshaft and big end part of connecting rod.
The white metal we used this time is commercially available white metal made by JIS (Japanese Industrial Standards) formula, but there seems to be a difference in the formula of metal components and manufacturing method from the material for engine parts. Such "recipe differences" are the trade secrets of each manufacturer. By lubricating with engine oil while maintaining a moderate clearance, sliding resistance becomes extremely low, and excellent wear resistance is also a characteristic of white metal materials.
In making this emblem, we purchased several kinds of white metal materials of JIS standard. We used a stainless steel pot and a gas stove which we bought at a 100-yen shop to heat-melt the white metal in our own way. We repeated the test by changing the pouring procedure, but the white metal of JIS standard 2 seemed to be the best material for the emblem which we made this time. Before pouring the emblem into the mold, I heated the mold to 200 degrees Celsius and poured the melted white metal into the mold. When pouring into the heat-resistant silicon mold at room temperature, the edge of each character did not appear and the character looked like it was round and beveled.
We, the Sunday mechanics, have little know-how and there were many things that did not work as we expected, but we could enjoy the DIY metal casting (white metal casting) with repeated trial and error. We would like to enjoy white metal casting with a different approach in some other occasion.
In cooperation with Model Create Maxi
