How to Inject Silicone Molds

How to Inject Silicone Molds

·      Often castings of an object are made by injecting material into a mold. The mold may be made up of two or more pieces, which are closed before injection begins. The main benefits of this process are reduced seam lines in the product as well as allowing you to use only as much casting material as you need with little waste. When injecting material into a closed silicone mold, it is essential to take several steps to insure that the casting comes out right. If your mold was designed for this purpose with the holes already in place, begin at Step 6. 

1

Determine the best injection point in your mold. Ideally, this should be a place that is not easily seen on the cast, such as the back or bottom. Mark the point with a marker.

2

Determine the highest points in the cast. Mark these with the marker.

3

Drill a hole in the silicone at the injection point. The drill bit should be the same diameter as the tip of the syringe. Use an extremely sharp drill bit to prevent the rubber from grabbing onto the bit. It's a good idea to have a friend hold the mold in place just in case the bit grabs the silicone; otherwise the entire mold will spin and could cause injuries.

4

Drill small holes in the highest points. Use the smallest bit you have for these as they are simply to allow air to escape as you inject the casting material.

5

Mark the holes in the mold shell and drill it out as well.

6

Apply a thin coat of silicone mold release or hand soap to the entire inner mold surface with a paintbrush. Allow it to dry and buff out the excess with a paper towel.

7

Close the mold and strap or clamp it shut tightly.

8

Mix the casting material according to its instructions.

9

Pour the casting material into the syringe.

10

Insert the tip of the syringe into the injection hole and inject the casting material.

11

Allow the casting material to run out of the air release holes for a few seconds before plugging each one with a bit of clay. This allows any air bubbles in the casting material to escape the mold.

12

Once the mold is filled, remove the syringe and plug the injection hole with clay.

13

Allow the casting material to cure and dry.

14

Remove the cast from the mold.

15

Remove the knobs left by the holes with a razor blade and sandpaper if needed.

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How to Make a Silicone Mold

Silicone molds are most often used in projects that require resin or other plastic casting, and can be seen in the creation of toys, collectible figurines, props, model parts and other small plastic casting projects. Silicone rubber is usually preferred because it can be used with many materials and it does not stick to itself or other objects, negating the need for a mold release agent or a separating wall during the molding process. The most common type of silicone mold is the two-part mold, which creates a seamless end product.

Instructions

1

Build a molding box for the model object you would like to make copies from. For smaller objects, make your box walls from Legos, and roll out a flat piece of modeling clay for the bottom of the box. For larger objects, build the box walls and bottom from sturdy cardboard or wood. Make sure that the box gives your model a clearance of at least 1/4 inch on all sides.

2

Mix together half a batch of silicone RTV rubber and catalyst, following the packaging directions for the brand of rubber you have. Make sure that the catalyst is completely blended into the rubber, creating a pale version of the catalyst's color.

3

Mark the halfway point on your molding box with a pencil or marker. Pour the batch of silicone rubber into the molding box, and stop at this halfway mark.

4

Press the model object into the siliconerubber until it is half covered and does not touch the sides of the molding box. Let this half of the mold cure, or dry, overnight or for 12 hours.

5

Mix together the rest of the silicone RTV rubber, and pour it into the molding box, covering the model object completely. Let the rubber cure overnight.

6

Take the molding box apart and separate the mold halves, removing the model object. Fit the mold halves back together and secure them with rubber bands.

7

Carve a pouring hole in the top of the mold at the joining line with a razor blade or utility knife. Cut the hole deep enough to penetrate through the rubber and reach the inside cavity.

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What Is Die Cast Molding?

The die casting method is used to manufacture things like toy cars.

Used in a variety of industrial, commercial and consumer products, die cast parts can be found in many common items like cars and toys. Created by placing molten metal into pressurized steel molds the die cast pieces can be very complex, and because of the reliability of the technology, identical parts can be manufactured with great accuracy.

Die Cast History

The mid-1800's saw the development and use of pressure-injected die casting, but the technology was limited for the first 20 years to the production of printer's type and the use of tin and lead. By the end of the 1800's other shapes and parts, like phonographs, began to be produced using alloys like zinc, aluminum and magnesium. These, as well as magnesium and copper, remain popular die casting metals today.

Types of Die Cast Methods

There are two predominant methods of commercial die casting. The hot chamber and cold chamber methods both utilize injection systems, but in different ways. The hot system is used for metals with low melting points such zinc, copper and lead. The injection system itself is immersed in a bath of molten metal where it then fills with the liquefied metal. The cold chamber method is used for metals with higher melting points like aluminum. A manual or automatic ladle pours the molten metal into a cylindrical sleeve and is then sealed under pressure to cool.

Die Cast Advantages

The die casting technique is more useful than other production methods because it creates durable, identical materials and parts in more shapes and types than what is capable by other manufacturing processes. The accuracy of the die casting process, as well as the strength and easy assembly of its finished products, makes it an efficient commercial manufacturing method that is valuable in a wide range of industries.

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Injection Blow Molding Basics

Injection blow molding is a manufacturing process that combines the accuracy of injection molding with the minimal waste and rapid processing of blow molding. Injection blow molding can be used with plastics and is generally used to make hollow shapes such as bottles. The manufacturing process is more expensive than other blow molding techniques, so larger containers are generally fabricated using extrusion blow molding. The final products of injection blow molding have no seams, and can be glass clear.

Injection Blow Molding Process

The injection blow molding process has three phases: Injection of the material into the preform mold; blowing of the preform, or parison, into the product mold; and ejection of the product from the machine. A commonly used machine configuration is a three-stage blow molding machine, which rotates through 120 inches for each phase of the process. In the injection phase, molten plastic or glass is injected into the preform mold over a core pin, which forms the interior of the parison and finishes the interior of the neck. At this point, the neck of the container is fully formed. The parison is removed from the mold and inserted into the blow mold. The parison is inflated inside the blow mold by pressurized air. After a cooling period, the product is ejected from the machine, tested for leaks, and moved to another station for labeling or finishing.

Designing for the Injection Blow Molding Process

Designing products to be fabricated using injection blow molding includes selecting a thermoplastic resin for the product application, designing the mold geometry to take into account material shrinkage during cooling, calculating the right amount of material to be injected and choosing the right pressure to inflate the parison in the mold. Tolerances in the core rod and preform mold design are critical so that the core rod sits exactly in the center of the mold and the resulting parison has constant wall thickness prior to blowing.

Products Fabricated Using the Injection Blow Molding Process

Injection blow molding is used to create hollow products such as bottles, and is generally only used for small containers such as medicine bottles or single-serve beverage containers. The injection phase of the process can create a neck with very fine tolerances, with designs such as screw threads or threads for childproof caps. Unlike standard injection molding, undercuts can be incorporated into an injection blow molded design for some products, such as mascara bottles.

How to Clean Chromed Plastic on Vehicles

·                               Chromed plastic is found on many locations of a vehicle such as grills, door handles and body mouldings. It becomes water spotted, can be discolored from acid rain or covered in bug residue. Using a glass cleaner to remove these contaminants is the safest way to clean the plastic without harming the adjacent painted areas. This process can be repeated as needed. However, since the glass cleaner dries to a spotless finish, usually no further cleaning is necessary. 

Instructions

1

Mix a bucket of soapy water using dish detergent and water as if preparing to hand-wash a car. Use the mixture with a kitchen sponge to clean the moulding of all road film and grime. Dry when complete with a chamois or kitchen-type towel.

2

Apply glass cleaner such as Windex to a kitchen towel or directly onto chrome and scrub chromed area with the kitchen towel. Chrome does not scratch easily, so use moderate pressure to scrub stains.

3

Repeat as necessary. Due to the majority of stains, such as tree sap or acid rain spots, being water-based contaminants, a water-based cleaner such as Windex is the best for cleaning. Although glass cleaner should remove all stains, rubbing compound with a terry cloth rag and elbow grease may be used for removing more difficult stains such as dried bird droppings or bug residue.