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.

Chrome Vs. Nickel Plating

Chrome and nickel are metals used to plate machine parts, such as rollers and cylinders, with a scratch-resistant surface that protects them from wear and tear. They are also used on bathroom and kitchen fixtures.

1.                            Chrome

Chrome comes in standard and hard versions. It is applied in varying thicknesses according to the required purpose. Thinner coatings are used on objects that are not exposed to much abrasion. Thicker coatings offer more protection from abrasion and corrosion. If a machine part is frequently exposed to water, experts at Phoenix Electroplating recommend an undercoat of nickel plating, as chrome is porous.

Nickel

Nickel is used to prevent corrosion, particularly when applied prior to chrome plating on objects. It is also hard-wearing and is widely used on machine parts in the oil and gas industry, the automotive industry, in making molds for plastics and in food processing machines.

Bathroom and Kitchen Fixtures

According to Rejuvenation, suppliers of home fixtures, nickel was the standard finish for kitchen and bathroom fixtures made from the 1800s until the 1930s. Chrome then overtook nickel in popularity. Nickel is warmer in appearance and creates a more authentic, antique look, but Rejuvenation says the two finishes blend harmoniously in one room.

How to Clean Chrome Plated Plastic

Any chrome surfaces actually consist of an extremely thin layer of chrome plated onto another material. Regardless of what that other material is, from plastic to steel to aluminum, this chrome plated is what needs to be addressed when the time comes to clean it. You can always buy a special chrome cleaner, but there are several items in your home that work just as well and are far less expensive.

1.                            Toothpaste Method

1

Spread a thin layer of toothpaste on the surface of the chrome plating. Use the opaque white toothpaste, not one of the gel varieties.

2

Rub the toothpaste-covered chrome plating with a soft, clean cloth in small circular and swirling patterns. There is no need to apply a lot of force.

3

Take a fresh cloth and wipe away the toothpaste, revealing a shining, clean surface.

2.                            Vinegar Method

4

Pour undiluted distilled white vinegar into a spray bottle.

5

Spray the surface of the chrome plating with the undiluted vinegar.

6

Wipe down the surface with a clean cloth.

3.                            Baby Oil Method

7

Dampen a portion of a soft cloth with baby oil.

8

Rub the baby oil into the chrome plating in the same manner as you did with the toothpaste.

9

Wipe off excess baby oil with a fresh cloth or a still fresh portion of the same cloth.

10

Wipe down the newly cleaned area with soapy water to remove any greasy feeling from the baby oil, if desired.

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How to Chrome Plastic Parts

How to Chrome Plastic Parts

1

Take the part down to the bare plastic. You can do this by etching the parts with strong chromic acid, according to Atlas Chrome. This will give you a basic surface to begin working on.

2

Repair any cracks or splits in the plastic part. You can do this by using epoxy glue purchased at your local auto supply store.

3

Dip the plastic parts with silver so that that they will conduct electricity.

4

Layer a conventional plating process such as copper, nickel or chrome onto the plastic parts in several layers. You will most likely need to lightly sand and buff the plastic parts prior this process as well.

5

Apply the chrome plating to the plastic parts for the final revamp. Do this by soaking them in a chrome plating solution for about five minutes

How to Make a Two Part Mold

There are several different ways to make molds. The most common mold types are one-part and two-part molds, with the complex three-part molds used a little less often. One part molds are best suited to flat-backed designs, as they typically require one side of the mold to be completely open at all times. Two part molds are used for most other projects, as they can be taken apart to retrieve a cast object. Three part molds are like two part molds, but have an added inner piece that makes the casting hollow.

Instructions

1

Coat your model with mold release, so that the mold material does not stick to the model.

2

Create an open-top box that will hold your liquid mold material. You can make the box out of pieces of thick cardboard or even wood, although cardboard will be easier to take apart later. Make sure that the box is at least 1/4 inch bigger than the model in all dimensions.

3

Seal the corners, edges and bottom of the box with modeling clay, so that none of the mold material leaks out of the box.

4

Mix together a batch of your mold-making material. Typically, two-part molds are made from either plaster or rubber. Make sure to take the appropriate safety precautions for the material you have chosen.

5

Pour the mold material into the box. Stop pouring once the box is half-filled. Discard the rest of the mixture.

6

Let the mold material sit for several minutes to firm up slightly. When the material is ready, press the model into it so that half of the model has sunken into the material. Let the other half of the model sit above the surface.

7

Let the mold material harden completely. If you have used plaster or rubber, this will set in 12 hours.

8

Coat the top of the mold, which has the model sticking out of it, with mold release. This will make the mold easier to separate later.

9

Make another batch of your mold material. Pour the material into the box, covering the model completely. Fill the box.

10

Let the mold material harden completely. When the material has hardened, take the box apart.

11

Pull each side of the mold apart and remove the model from the inside. Fit the mold back together.

12

Tie the mold together with rubber bands or cording. Carve a hole in the mold, at the seam, that reaches the inside cavity. Use this hole to pour your casting material.

What Is the Blow Molding Process?

Blow molding is used to produce plastic bottles.

Blow molding is a method for making a variety of hollow plastic products. Molten plastic is extruded, in a tube shape, from a die, then a mold closes around it. The plastic is then inflated.

History

Blow molding first appeared late in the 1800s, but modern polyethylene bottle production did not commence until the early 1940s.

Types

The blow molding process can take four forms: reheat and blow molding, injection blow molding, stretch blow molding and extrusion blow molding. The machinery can vary significantly, though the major difference tends to be the point of plastic inflation.

Uses

The various processes are used to create a range of products, including bleach and milk bottles. Stretch blow molding is used in the production of PET (Polyethylene terephthalate) bottles, which are widely employed for carbonated beverages.

Plastics

The plastics used in the various blow molding processes can include HDPE (high density polyethylene), LDPE (low density polyethylene), PP (polypropylene), and PVC (polyvinyl chloride).

Disadvantages of Blow Molding

Blow molding is the process in which hollow, plastic containers are made. Air is blown into molds to form items such as thermoplastic bottles, tubing and milk jugs. While blow molding allows companies to manufacture high volumes of plastic containers, which are significantly cheaper than glass, there are a few disadvantages to the process. Some disadvantages include environmental hazards and a significant dependence on petroleum.

Environmental Disadvantages

Plastic products made by the process of blow molding aren't biodegradable, which presents an obvious environmental hazard, especially when empty containers find their way to landfills. When disposed of in landfills, plastic products are buried and remain in the earth forever. Their oil-based material then becomes part of the soil and runs the risk of threatening plant life, animals and groundwater.

Dependence on Petroleum

Aside from the gasoline industry, plastic manufacturers depend on millions of gallons of petroleum in their quest to produce blow-molded products. Because oil is the most important agent in thermoplastics and blow molding is becoming more streamlined and automated, the process plays an ongoing threat on a diminishing world oil supply.

Process and Material Limitations

Although blow molding has been automated and can produce mass quantities of products, the process is largely limited to hollow forms. These forms are delicate and contain various thicknesses which must be precise, which often results in wasted material in the process of arriving at containers with proper dimensions and specifications. In some cases, thermoplastic is stretched to save on material, which can lead to substandard containers.

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