How to make a mold out of plastic. Casting plastic parts at home

Small parts of models are usually made of plastic or metal by machining. However, when a lot of them are required, it is better to cast parts from plastic in plaster molds.

Plastic can be prepared from AKR-7 acrylate powder mixed with a solvent to a doughy state. Both necessary components are available in denture sets.

If the part is symmetrical and has a simple configuration, such as an anchor, a wheel or a lifebuoy, then it is more convenient to make the form collapsible, from two halves that can be used repeatedly.

When forming, metal or plastic casting models are pressed into the gypsum that has not yet hardened to the plane of symmetry (partition) and allowed to harden. The second half of the mold is poured, after wetting the lower part with a mild soapy solution to facilitate the separation of the halves. The upper part of the mold should have a through hole: a diameter of 3-4 mm for filling with plastic and exiting its excess during polymerization. Having taken out the casting model and folded both halves, they are pulled together with twine or rubber - and the mold is ready.

Rice. 1. Collapsible mold for casting:
1 - the base of the form; 2 - upper half; 3 - mounting rod (wood); 4 - plastic model; 5 - cardboard box.
For the manufacture of a part of a complex configuration, a mold consisting of three or more parts is required. Here it is better to use the method used in precision casting - according to the investment model.

Rice. 2. Non-collapsible mold for casting:
1 - plaster casting; 2 - paraffin model; 3 - mounting rod (wood); 4 - cardboard box.

In this case, the form will be one-piece, that is, disposable. The model for its production is made of paraffin, poured with a solution of gypsum, providing in the uppermost part a cylindrical or conical hole with a diameter of 3-5 mm widening upwards - a sprue. After 30-40 minutes, the frozen gypsum mold is immersed in a vessel with cold water with the sprue up and boiled until the casting model is completely melted. Paraffin, being lighter, is displaced from the mold by water and floats to the surface. Then, without removing the form, the water is cooled and a layer of solidified paraffin is removed from its surface. To remove its residues from the mold, heating should be repeated.

Thanks to this method, we obtain a cavity in plaster that accurately reproduces the shape of the part. If fasteners are desired inside the future part, then they should be inserted into the paraffin casting model so that they do not move during melting. For example, if you want to have a metal nut in the part, then it is placed with a protruding bolt and everything is poured with plaster. Then the free end of the bolt will be in the thickness of the gypsum and, after melting the paraffin, will hold the nut in the right place.
With a non-separable form, plastic is prepared in glassware, bringing it to the consistency of liquid sour cream. After mixing the mass with a glass rod, pour it through the sprue hole into the mold. The preparation of the polymer and the filling of the mold are carried out without delay, since the mass thickens quickly. At the time of pouring, the mold must be moistened from the inside, otherwise the surface of the finished part will turn out to be rough and porous.

The filled form is kept at room temperature for 15-30 minutes until the rubber-like thickening of the mass. After that, it is compacted through the sprue hole with a glass or wooden stick. The compacted surface of the mass should not reach the upper edge of the mold by 3-5 mm, since acrylate expands during polymerization.

The sprue hole is covered with moistened cellophane and plywood trim and tightened with a clamp. Then the form together with the clamp is immersed in a pan with water at room temperature and brought to a boil by gradual heating for 30-40 minutes. It should not be violent and lasts at least 45 minutes. After that, the heating stops, and the form is kept in the pan for another 15-20 minutes. To obtain a better casting, a slow complete cooling of the mold to room temperature is necessary.

Plastic has long and firmly entered our lives. Plastic containers, toys, dishes, packaging and even pipes - all this is very widely used in everyday life. Therefore, the demand for them is quite high. Molding of plastic products is one of the promising niches of Russian business. With proper organization of production and marketing, this can make very good money.

Where should you start?

The first thing to do before organizing production is to choose which groups of goods you will produce. Much depends on your specific capabilities. For example, if it is possible to agree on the supply of containers for packaging semi-finished products, you should start with it. This will give a good start to the production process. Later, if necessary, it will be possible to expand and engage in the production of other product groups.

If there are no developments, then you should start with consumer products:

• buckets;
• flower pots;
• seedling containers;
• packaging.

Choosing the right room

Injection molding of plastics does not impose strict requirements on production conditions. But, despite this, the premises should be located away from residential areas, it is best if it is located in an industrial area. At the same time, a number of conditions and fire safety requirements must also be observed. At the same time, from 50 to 200 square meters will be required for the production workshop itself. m. Also about 80 square meters. m will go under the warehouse. Plastic products, although light, are quite voluminous.

Recruitment

The success of the enterprise depends on how well the selection of personnel is carried out. In total, from 6 to 10 people may be required to work in a small production workshop. The most important of them will, of course, be a technologist. It is his selection that should be given the closest attention. It is not worth saving on his salary, the salary of a good specialist should be at least 30,000 rubles.

The main types of raw materials for plastic injection

For plastic injection molding, polymers in granules are used. The use of one or another of them depends on its physico-chemical properties. In terms of resistance to temperature, all solid polymers are divided into the following groups:

1. Thermoplastic. Under the influence of temperature, they have the ability to easily move from a solid state to a plastic one and vice versa. They are very easy to recycle.
2. Thermosetting. They have high strength and thermal stability. They are based on various synthetic resins. To give certain properties, special additives and fillers are introduced into their composition.
3. Styrofoam. They are characterized by excellent heat and sound insulation. They are made from synthetic polymers, the role of the filler in them is played by a gaseous medium.

You can buy plastic for molding in companies specializing in the sale of polymers. Usually you can buy raw materials from them, not only domestic, but imported. The average price for high-density polyethylene at the moment is about 35 rubles. per kilogram, polypropylene from 40 rubles. and higher.

Basic casting technology

There are three main plastic injection molding technologies:

1. Extrusion or injection molding. One of the most popular technologies. Of its shortcomings, it is worth noting the high cost of injection molding machines; also, for the competent organization of the technological process, special education is required.
2. Blown. Used for making hollow products. For example, polyethylene bottles and other containers. The essence of this technology is that the polymer is first heated to a certain temperature and then blown onto a cooled mold.
3. Thermoforming. This technology involves the use of compressed air or pressing. Most often, this method is used to make disposable tableware and food packaging.

injection molding technology

Plastic injection molding technology includes the following production processes:

1. Loading raw materials into a vacuum loader. The raw material used may be in the form of granules, powders or tablets.
2. Supply of raw materials to the hopper of the injection molding machine.
3. Heat. The heated surface of the screw located in the hopper melts the polymers and, if necessary, mixes them with fillers.
4. Pour the plastic into the mold. Under the action of an axial force, the molten polymers are extruded into a mold.

The advantages of this type of casting include the following:

1. High quality products.
2. High performance.
3. The casting process can be fully automated.

Types of plastic injection

The manufacture of plastic products by injection molding can be carried out in several ways:

1. Injection. One of the most common casting methods. It is characterized by a short-term injection of molten polymer. During it, a certain pressure is created in the working chamber of the casting machine, after which the plasticized polymer is injected.
2. Injection-press. This method is used in the production of products with a large surface. It requires special molds with moving parts.
3. Injection gas. During such casting, the force of compressed gas is additionally used, which compresses the plastic in the mold.
4. Intrusive. The easiest casting option. Used for casting the simplest products with a minimum number of surfaces.

In addition to the above methods, there are more complex types of casting:

1. Sandwich. During it, two types of plastics are used. This method allows the production of goods with an outer coating.
2. Co-injection. Used for the manufacture of multilayer products. For it, a nozzle of complex design will need to be installed on an injection molding machine. This method makes it possible to produce products with mixed colors.
3. Casting in multi-component molds. This method allows the production of products with a clear color distinction. Of its features, it should be noted the possibility of producing products with adjacent parts of different densities.
4. Casting in rotary molds. With this method it is possible to produce two-component products. During it, the main blank is first cast, which then moves to another mold, where the second layer of polymer is applied. This method is the least productive of all of the above.

Choosing the right equipment

After deciding on organizational issues and choosing a room, you can proceed to the selection and purchase of equipment. It is represented by models of both domestic and imported production. The advantage of the former is most often only the price. Imported equipment, although it is much more expensive, but it is much better and more reliable.

When organizing production, you will need the following equipment for plastic injection:

Injection molding machine

It is an injection molding machine designed for the manufacture of piece products. or extruders - this is the most used type of equipment, with the help of them more than 2/3 of all plastic products in the world are produced. Regardless of the model, each plastic injection machine necessarily consists of the following structural units:

1. Injection. It melts and feeds plastic.
2. Closings. He is responsible for closing and diluting the mold during the casting process.
3. The drive responsible for the operation of all moving parts.

All currently existing extruders according to the type of mechanism that creates pressure can be classified into the following types:

1. Single-worm. Their main advantage is the simplicity of design and the small size of the material chamber.
2. Two-worm. Differ in better hashing by polymer and the improved production characteristics.
3. Worm-piston.
4. Piston.

Also, depending on the location of the press part, the following types of injection molding machines are distinguished:

• horizontal;
• corner with vertical press;
• vertical;
• angular with a horizontal press.

The price for such units ranges from 200 thousand rubles for used ones to 1-2 million rubles. for new ones.

Press forms

Molds for plastic injection are the main type of equipment for injection molding machines. For the production of each product, its own individual form is made. The principle of its work is very simple. The injection molding machine injects molten plastic into the mould. After it cools, it opens the mold and pushes the finished product out of it. Plastic injection molds can be made from various steel grades. This affects the number of their production cycles. It can range from 100,000 to 1 million.

Vacuum raw material loader

Vacuum autoloaders of polymeric raw materials are a type of peripheral equipment that can significantly speed up and facilitate the process of supplying polymeric materials to the loading hoppers of injection molding machines. According to their design features, they can be divided into vertical and separate models. The first ones perform standard functions, the second ones are used when transporting polymers over long distances.

Refrigeration unit

Refrigeration units or otherwise chillers are used to cool water in the production of plastics under pressure. They can significantly reduce the duration of the production cycle.

All of the above equipment is used for casting in mass production. But what if you don't need thousands of identical products? The way out of this situation is small-scale molding of plastics at home.

Home plastic molding

Do-it-yourself plastic injection at home is a kind of industrial option for the manufacture of plastic products. It allows you to make any not very large products. For example, such as:

• various caps and caps;
• corps;
• toys;
• cubes;
• dishes;
• souvenirs.

Equipment for small batch casting

Small-scale casting does not require the purchase of expensive equipment. For a small workshop, it will be enough to purchase the following:

1. Desktop manual machine for molding plastics.
2. The forming part of the mold.
3. Silicone for molds.
4. Two-component plastic.

Tabletop casting machine is a kind of foundry equipment used for small batch production. He can carry out his work both with the help of single and multi-seat forms. To install such a machine, an ordinary desktop of a small area is quite enough, the main thing is that it is stable.

At the moment, there are modifications of machines with an electromechanical drive. They are more reliable and easier to maintain. Some of the advanced models of such units are even equipped with an automatic clamping unit. A manual casting machine allows you to produce an average of 10 to 15 products per hour.

Self-made silicone molds

Molds for plastic injection at home can be made independently. To do this, you first have to prepare a sample model. Its production can be ordered from the owner of the 3D printer.

1. Using a wide brush, carefully coat the sample with a thin layer of silicone.
2. We place it in a pre-prepared formwork.
3. We fill the entire volume of the formwork with silicone.
4. We are waiting for 7-8 hours until the silicone completely hardens.
5. We make a cut shape.

Your first mold is ready, now you can start hand casting.

The main types of silicones for mold making

There are a lot of silicones for making molds, the most common of them are discussed below:

1. Mold Star 15,16,30. This series of silicones cures very well at room temperature. Can be used to produce molds with very good detail. Chemically sensitive to latex and sulfur. The number in the classification means the hardness index. They have a two-component base, which is mixed immediately before pouring.
2. Rebound 25, 40. Used to create molds using the "patch" method. The silicone is simply applied to the sample with a brush. Can be used in combination with various plasticizers and modifiers. They are two-component formulations.
3. Sorta Clear 18, 37, 40. Translucent silicones, well suited for creating cut shapes. They can also be used in conjunction with various additives and set accelerators.

Main characteristics of two-component plastics

Liquid two-component plastics are quite widely used in small-scale casting. There are quite a few brands of such polymers. Their main difference is the density and hardness of the finished product. Also, depending on the additives, they can have a different texture and color. After mixing the components that make up the polymer, an accelerated process of solidification or otherwise polymerization begins, which usually lasts no more than 10 minutes.

The use of liquid plastics makes it possible to implement a variety of design solutions. Also, such polymers are very often used to create prototypes and models in design development.

Products made of liquid plastic are in no way inferior to analogues of industrial production. They are just as strong, beautiful and durable. In addition, the market for liquid polymers is constantly expanding and improving, which makes it possible to acquire more and more advanced samples.

Technology of molding into silicone molds

For silicone molds, you will also need to purchase a special liquid plastic for casting. It does not require preheating and freezes perfectly at room temperature. Molding plastic into silicone molds is as follows:

1. The casting mold is thoroughly cleaned of dust and other contaminants.
2. Both halves of the form are firmly fixed with rubber bands, adhesive tape or any other available materials.
3. Two-component plastic for molding is diluted in the tank. Both of its components should be stirred very carefully. In this case, you need to act as quickly as possible. After a few minutes, the plastic begins to set. At this stage, a dye is added to give a certain color to the composition.
4. The thoroughly mixed mixture is poured into the mold in a thin stream. It must necessarily fill even the channel for casting. After the degassing process, the volume of the material will decrease somewhat.
5. Wait for the curing of the product. Usually it takes no more than 10-15 minutes.

Molded plastic allows you to create a small amount of original author's products with your own hands.

Casting technology using a manual machine

Casting methods using a manual machine are somewhat similar to production ones. The process itself looks like this:

1. Installation of injection nozzle on the machine.
2. Applying a layer of silicone to the mold surface.
3. Installing the form on the unit.
4. Stirring and heating of polymers with a screw.
5. Casting.
6. Cooling.
7. Disassembly of the mold and extraction of the finished product.

The tabletop injection molding press is ideal for small production environments. It is highly versatile. It can carry out casting of products practically from any types of polymers. To increase productivity, a plastic injection press should be equipped with several similar molds at once. This allows you to organize an almost uninterrupted production process.

Also, additionally finished products can be fastened together using a special welding extruder. This allows you to significantly expand the injection molding business by producing more complex products.

Plastic scrap can be found everywhere. Old broken things constantly appear at home, the street is full of bottles and packages. A lover of doing something may have the idea to collect it all, grind it up and melt it into something of value.

A beginner "caster" should not do this, since each type of plastic has only its own inherent properties, so it would have to be melted at different temperatures. In addition, in production, parts are usually cast in special installations where high pressure is maintained.

Even if you manage to pick up pieces of plastic of the same kind and crush them, melting will result in bubbles. So it's best to go to the hardware store and buy liquid plastic, from which the parts are no less durable than the factory ones. Epoxy can also replace plastic. You will also need:
- silicone;
- large capacity;
- .

If you still decide to make something out of plastic scrap, do not do it indoors. Plastic fumes are toxic.

Making a shape

For casting in several plastic parts, you will need a model. You can make it from anything. Suitable for you:
- plasticine;
- gypsum;
- wood;
- paper and many other materials.

Make a model of the part to be cast. Lubricate it with lithol or other lubricant. After that, make a shape. Silicone molds are becoming more and more popular. This is understandable, it is easy and convenient to work with this material, but several circumstances must be taken into account. Firstly, there are two types of silicone, pouring and coating. Secondly, each species has its own elongation coefficient and its own viscosity. As for the first parameter, silicone with a coefficient of 200% is suitable for plastic injection.

Pay attention to the viscosity coefficient. The smaller it is, the more accurate the shape will be. This is especially important if you are going to work with potting silicone. Consider also the polymerization time. If you have casting silicone, place the master model in a flask (it can be made of steel or, for example, bronze) and fill with silicone. Gently apply the coating material with a brush, taking into account all the irregularities. Let the silicone harden and then remove the master model.

The flask is a metal container. It should be slightly larger than the master model.

Pour detail

The casting process largely depends on what exactly you are making the part from. Polyester resins and liquid plastics are great because you don't have to melt anything, but they differ in viscosity and pot life. These parameters are indicated in the specifications. Treat the mold with lubricant and fill it with liquid plastic as directed in the instructions. Give

Plastic is a universal material. It has found wide application in the manufacture of various components and parts in both industrial and household appliances. Products from it are used in the design of interiors of residential premises and offices.

A variety of material, called liquid plastic, allows you to create a wide variety of shapes and sizes of crafts. This makes it possible to implement original design solutions. How to make liquid plastic at home?

Materials for manufacturing

To make liquid plastic with your own hands, you need to prepare the following:

• glass or metal container;
• acetone;
• Styrofoam.

In this case, the amount of acetone used depends on the desired volume of the finished product.

If you want to make liquid plastic with your own hands, the recipe for its preparation will be based on dissolving foam in acetone. To do this, use It is a packaging container for various household and electronic equipment.

How to make liquid plastic with your own hands

Step by step recipe the preparation of the named material looks like this:

1. Open the container with acetone and pour the liquid into the glass container so that its level from the bottom is approximately 1 cm.
2. Polystyrene foam must be broken into many small pieces, each of which will be easily placed under the thickness of the solvent.
3. Do-it-yourself liquid plastic can be made by dropping each piece into a container and waiting for it to completely dissolve.
4. Styrofoam should be added to the container until it stops melting. Then you need to wait 5-10 minutes for the unused acetone to evaporate.
5. After that, a viscous mass is formed at the bottom of the container, which can be used to produce a variety of products.

Knowing how to make liquid plastic, remember that the complete hardening of the mass lasts 20-30 hours. Therefore, the manufactured part cannot be removed from the mold during this period of time.

The substance should be applied with a small rubber spatula. The movements must be smooth. Liquid plastic must be stretched on the surface to be treated. If it is used to fill gaps, it is better to use brushes with a hard bristle in the work. They need to "push" the mixture into the gaps. After the plastic has hardened, it is recommended to apply another layer of the substance.

The described tool has long been sold ready-made. It only needs to be heated in a water bath or in special equipment. Also, a building hair dryer is often used for this.

As a rule, liquid plastic is produced in dense packages. Its terms and conditions of storage are strict. The temperature in the room where it is located should not fall below 15 degrees. Otherwise, the tool will lose performance:

• viscosity;
• elasticity;
• hardness after hardening;
• practicality;
• durability.

The cost of liquid plastic is quite high. That is why it is better to do it yourself.

Precautionary measures

Acetone is a very dangerous liquid that has an extremely negative effect on the human body. Therefore, do-it-yourself liquid plastic is allowed to be made only with strict observance of the following precautions:

1. Before working with acetone, you must carefully study the instructions for its use. It is listed on the container label.
2. Special sealed goggles should be used. They will protect your eyes in case of drops and fumes of liquid. Working without them can cause serious eye injury.
3. Acetone is toxic and should only be used in a well ventilated area. In this case, it is necessary to use respiratory protection equipment.
4. It is highly flammable. Therefore, do-it-yourself liquid plastic is made away from sources of open fire. Smoking is strictly prohibited during work.
5. Residues of acetone must not be drained into the sewerage system.
6. At the end of the process, as well as after pouring the finished plastic into molds, you must thoroughly wash your hands.

Applications of liquid plastic in finishing

For decoration, the product has been used for a long time. After its application, an elastic film appears on the treated surface. It is highly waterproof and UV resistant. The material protected by such a film is not afraid of exposure to aggressive detergents. The smooth surface has a pleasant sheen and retains its characteristics for many years.

Liquid plastic in window works

Most of the newly installed plastic windows in the connection area have gaps. To exclude such a phenomenon, all parts of the window structure that are interconnected are treated with the described substance. After drying, it creates an elastic sealed film on the surface. Do-it-yourself application of liquid plastic on windows is possible after making the material according to the above method.

Means in anti-corrosion treatment

Liquid plastic is also characterized by a high degree of adhesion to the treated metal surface. This property of the substance began to be used in the anti-corrosion treatment of steel. Liquid plastic is applied to the surface without prior priming. It dries out after a few hours. After that, a film is formed on the surface, which will protect the material from rust.

The manufacture of products by casting, taking into account modern materials, has become quite affordable, quite simple and low-cost. Consider the option of using polyurethane for pouring and silicone for creating a mold.

It will take

For work, we will use quite affordable and inexpensive materials and products:

• silicone "ELASTOLUX-M" for mold making;
• silicone "ELASTOFORM" for the manufacture of the substrate;
• a separator based on kerosene or petroleum jelly;
• oppression for the form with a total weight of 1 kg;
• cast polyurethane "UNIKAST 9" (base, part A);
• hardener (part B);
• precision scales;
• plastic glass.

Technology of casting polyurethane products into silicone molds

First of all, you need to print a master model with a gating system on a 3D printer. Or take a finished part that needs to be repeated, glue toothpicks as sprues. It will be needed to make a reusable silicone mold.

For it we use silicone, characterized by high elasticity and sufficient strength. For a base substrate with a thickness of 10-15 mm, a less expensive two-component silicone of the ELASTOFORM type is suitable.

Made silicone mold.

How is the casting process

We put the silicone mold on the substrate. If it will be used repeatedly, then we periodically lubricate it with a separator based on kerosene or petroleum jelly.

From above, we press down the silicone mold with a dispersed load (oppression) weighing up to one kilogram. In order for the casting material to be poured neatly and quickly, we make a paper funnel. After that, we can assume that the mold is prepared for casting.

For pouring, we take the cheapest cast polyurethane "UNIKAST 9" (part A) and hardener (part B), which we mix in a ratio of 1: 0.6.

For high-quality mixing, you need a precision scale and a plastic cup. You can add a dye of any color to the base, which is sold separately. For 1 kg of polyurethane, 90-100 drops of dye are needed.

Pour 22 grams of liquid polyurethane and 13.2 grams of hardener into a cup on the scales and stir thoroughly for 30 seconds, no more, since it will already begin to harden. When stirring, we will feel that the glass is heating up, which means the polymerization process has begun. The mixture is ready to pour.
Pour the mix without interruption until liquid polyurethane comes out of the sprues. Primary hardening will take about two minutes, and full - 10-15 minutes, but it is better to hold the pour in the form of 20-30 minutes.

After half an hour, we begin to remove the polyurethane casting from the silicone mold.

We first break off a paper funnel with excess polyurethane frozen in it, then the excess that protruded from the sprues, along with the “legs”. This will make it easier for us to remove the molded product from the mold.

In addition, the silicone mold is very flexible, which also makes it easy to remove the casting from it without any difficulty.

It remains to slightly process the holes, break off or cut off the sprues and drill holes with a drill. After that, the cast product practically does not differ from the master mold.

Comparison between injection molding and 3D printing

Casting compared to 3D printing is a fast process. To print such a box on a 3D printer, it will take 4.0-4.5 hours. In this case, the 3D model often turns out to be defective and everything must be started all over again. The casting process takes a maximum of 30 minutes. The next point is cheapness. Casting is more than 3 times cheaper than 3D printing.