DIY plastic parts. Molding plastics into silicone is an affordable small-scale production at home. How to make a casting mold

Let's compare the methods on the example of one product. We calculated the cost of manufacturing a plastic case with dimensions of 165 mm ⅹ 95 mm ⅹ 75 mm using different methods.

Injection of plastic into both silicone molds and molds starts with designing a 3D model product in CAD programs (SolidWorks, AutoCAD, FreeCAD).

Picture. Development of a 3D model in AutoCAD.

If the future product has no predecessors and analogues, a 3D model is developed based only on the requirements of the technical specifications.

If the product is not unique, references are used in the design - reference samples of the product.

After creating a 3D model digitally, we proceed to making a prototype. It will help evaluate the functionality of the developed product. At the prototyping stages, design changes do not entail significant costs.

A prototype of a plastic product is made on a 3D printer.

Picture. Creation of a prototype on a 3D printer.

The product from the 3D printer has a layered surface. If the customer is satisfied with this type of quality, the rest of a modest edition is printed on the printer and goes through the grinding procedure.

If the requirements are higher or it is necessary to obtain a larger volume of products at the output, we use the methods of molding plastics into molds. Consider separately small-scale and large-scale production.

Small-scale production: injection of plastics into silicone

For small scale production, use . To create a master model, a 3D printed prototype is treated with varnish and sanded to obtain a smooth surface.

The master model is half-immersed in a clay base and filled with a mixture of silicone and hardener. The filled form is left in the chamber for degassing and solidification for 24 hours.

As a result, we get half of the silicone mold for casting.

Then we repeat the process and get the second half. We connect two elements of the form, using a frame for rigidity. Fill the silicone mold with polyurethane, leave it in the chamber.

Depending on the type of plastic, the curing time is from 4 to 24 hours.

High-volume production: plastic injection molding

In large-scale production, the most resource-intensive stage is manufacturing from metal. Molds are durable and make it possible to obtain products with high detailing accuracy.

Picture. Metal mold for plastic casting.

In the injection molding process, plastics are fed into an injection molding machine where they are melted, homogenized and injected into a mold under high pressure. First, the material hardens near the cold walls, then - inside the body of the casting.

After cooling, the mold opens, the product goes to the final processing stage, and the mold goes to a new casting cycle. The cycle is completed by the final processing of the part: cutting off the sprue, milling, applying a soft-touch coating.

Material overview for plastic injection molding

Consider the types of materials that are used for casting.

For 3D printing As a rule, thermoplastics or composite materials based on them are used. The most popular types: polyactide, polyvinyl alcohol, nylon, metal simulants.

For silicone mold casting polyurethanes are used that can withstand temperatures from -60 ° C to +80 ° C.
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Pavel Cherepnin talked about such a cool thing as a thermoforming box. It allows you to melt plastic at home, make various parts and shapes from any plastic waste, such as a canister or a plastic bottle, at home.

So, this time another useful device is a box for thermoforming plastic. With the help of such a box, we can make any shape from plastic. Making masks out of plastic. cases for any equipment, boxes with molds for tools, in general, any plastic part or toy that we wish. We are limited only by the size of the frame. But even this can be overcome by making a larger thermoforming box. the principle is this. The main part of the device is a sealed box in which a grate is installed instead of the upper side, we connect a vacuum cleaner to the wall of the box, which pumps out air from the inside, thereby attracting plastic to the grate. The plastic sheet is fixed between two frames. It is advisable to use plywood and not chipboard, as I did. I took the plastic itself from plastic cans and bottles. Made two frames. One large size for canisters and one smaller size for bottles. We heat the plastic in the oven to about 120 degrees, so that it becomes plastic. Then we put the form on the grate, turn on the vacuum cleaner and press the frame with the heated plastic to the box. The air will draw in the plastic and give it the shape of the workpiece.

You can use specialized plastic, such as ABS plastic or polycarbonate. The forms are strong, for example, I made a mask from a canister. And a bottle of detergent. Let's try to mold a “smiley” out of it. It turns out also pretty cool, you can use and make a lamp, an iron man helmet. Let's make it out of cement. Let's try. Perfectly molded, excellent models are obtained in the home workshop. You can do whatever your imagination allows.

Safety attention!

Please note that the wizard is working in violation of safety regulations. Do not deviate from the rules of TB, take care of your health when melting hot plastic!

Making the box body

First you need to make the body of the box. Of course, you can take ready-made, for example, from old furniture. But certain dimensions were required for the manufacture of masks, parts for cars, we had to do it from scratch.

Used old boards. I found in the garden, along the street, literally rubbish and garbage that is lying around and no one needs it. I had to cut, remove all unnecessary parts, protruding ends, bumps, so that the boards were even and of the same height and width. The size was made according to the face, a cast of cement was taken and a box was made on it. It is necessary to make masks. Therefore, I focused on the largest sizes that may be required. I sawed everything with a circular saw, perhaps with a jigsaw, but working with a saw is much more convenient and faster. Got a frame. A groove had to be made along the top of each board, it needs to be placed with a grate. Grille for conducting air into the box. A vacuum cleaner is connected to the box itself, and creates a vacuum or, more simply, a vacuum inside the box, and attracts plastic. I made cuts along the edges of each board from the ends, smeared it with glue with a glue gun and stuck all the details to each other. Got a box. Then I fixed all the corners with self-tapping screws. After fixing it turned out to be strong, screws and glue hold it just tightly. You have to make the bottom.

Found chipboard from furniture. Let's draw the bottom. Let's cut off the excess. Chipboard is difficult to cut - a dense material. The box for melting and shaping the plastic is ready.

Making a lattice

I took what was in the garden, you can take any lattice. We will cut everything to size so that there is nothing superfluous, according to the internal grooves that we made in advance. Well, the grille fits perfectly, but so far it is not fixed by anything, so I will fasten it with the same self-tapping screws. Four is enough. You don’t need special strength, and in the future you don’t need to remove the grate, you don’t need to make a super mount. Fine. Everything is attached. You can move on to the next step. You need to make a frame for the plastic on top. There is a perfect piece of chipboard, just cut it in half and the frame is ready.

Now you need to cut a hole in each frame from above. Let's draw a square without exact measurements. Cut with a circular saw or electric jigsaw. The frame is ready.

How to mold plastic parts at home?

Casting is, in fact, a way of copying or replicating a sample from which a mold has been removed. That is, if you need one detail, what's the point of making a shape? True, sometimes it seems to be a simpler option: make a sample from some pliable material, remove the mold from it and fill it with metal. Well, in a jeweler's shop they do waxing, a plaster mold, a casting.

Specifically, molding plastic at home is a technology that can be useful to modellers. It is difficult to name something else, although if you are inclined to do things with your own hands, then knowledge of casting techniques will come up somewhere and come in handy.

In this article, only one type of casting is considered - casting resin into a silicone mold. At the exit, you have an epoxy part.

So, the first thing that is done is the master model. Here you have all the cards in your hands, only you yourself know what it is more convenient for you to make it from. It can be plastic and wood, metal and even paper, even clay, or what plasticine has replaced for children now, everything depends on the detail and your skills. But! When you finish working on the detail, it must be smeared with a release agent, the tree can be pre-soaked with wax diluted with PVA or drying oil.

Mold making materials

The mold is made from silicone. This is a liquid material that polymerizes in air, sometimes with the participation of catalysts. Silicones are divided into filling and coating. Everything is clear here: the first ones assume that you put the part in a flask and poured silicone on top like cucumbers with marinade, and coating is when you apply layer after layer with a brush, like embalmers, bandages on a mummy.

Two important physical characteristics of silicones that affect shape formation are elongation and toughness. The first refers to the polymerized state, the second to the liquid. The elongation factor is how much an object can be stretched without breaking. Suitable for molding plastic at home are those with an elongation coefficient of 200% or more (yes, at least 1300%). It affects the number of castings, the higher the KU, the more copies will come out of this form. Although 700-800% is enough for the eyes, it gives from 30 to 80+ castings, which also depends on the complexity of the master model itself.

Viscosity affects the quality of the flow around the model, the filling of depressions. The lower the viscosity, the better the flow. Therefore, 3000 centipoise is a rubicon between casting and coating silicones.

In addition, attention should be paid to the working time and polymerization time. The working time is the interval until the viscosity corresponds to the declared one and the silicone has not begun to thicken, and the polymerization time is the interval during which this silicone has fully acquired the property of elongation and corresponds to the declared KU.

Purely technically, silicones are one-component, ready-to-use and require mixing with a hardener.

Casting materials

These can be epoxy and polyester resins, liquid plastics, etc. The most important characteristics include lifetime and viscosity. Viscosity-fluidity, as you remember, affects the filling of the model, and the lifetime is the time that the material retains the indicated viscosity.

Polyester resins and some liquid plastics have the lowest viscosity (80-300 cps), which is somewhere between water and growth. oil

Life time choose those materials for which it is not less than 3-5 minutes.

There are several technologies for molding and molding plastic. But the fact is that each grade and type of plastic has its own characteristics, yield strength, solidification temperature, boiling point, and so on. Without these characteristics, it will be difficult for you to create something at home, since you can either simply not melt the plastic or burn it. if the characteristics are known or by the method of scientific poke you can try this: chop the plastic, that is, extrude, after which the extrudate is placed in a mold and baked at the melting temperature of your polymer grade, but no more, since it can catch fire or darken.

The following resources may help you:

http://igrushka.kz/vip71/shpfor.php

Now there are HDPE and HDPE pipes, tights and many other materials, I tried a sea of ​​pouring methods, you can pour small molds by hand, but they should be on the one hand, for more molds you need a press and almost copying a production machine.

Casting plastic parts at home is quite difficult, but although this is all relative, perhaps for someone this is not at all a difficult procedure. But pouring from recycled materials is already a more capacious procedure, and quite toxic, harmful to our health, which I do not advise doing. There are other casting methods where you do not need to use recyclable materials and harm your health. I advise you to read the articles Plastic molding at home and Plastic molding at home and Casting at home

Wish you luck.

It is better not to melt - it will burn. It is necessary to cut into cubes-granules and bake under pressure in the form. How is it done in production? But this requires the right equipment.

Each plastic has its own technical parameters that are not known to you if you take recycled materials. I recommend taking granulated ABS plastic from suppliers of raw materials (it is not expensive) with the declared characteristics. Then make the correct mold and an extruder that will heat the plastic granules to a state of fluidity (according to its technical parameters) and extrude into a hot mold.

There is plastic in the form of plasticine, you mold the desired part and load it into the oven for about five minutes and it is all hardened and ready to use.

I didn't know about this until a friend showed me. I've tried it myself and it's easy. On with coca, I remember it is sold in art stores.

At the moment, there are already many technologies for molding plastic parts, they mainly consist in mixing two or more components, a technology similar to epoxy resin. The main thing is to have a shape, mix the ingredients and pour. My friend does interesting things this way, but he doesn’t tell his technology yet. (

Yes, about plastic. In general, as far as I know, conditionally plastics are those that can be melted, and those that, when heated, will burn, smoke and char. So, if the plastic stretches and sticks, then it can be processed. An example is plastic bags (I think someone else remembers homemade covers for textbooks that were made with an iron). I have never been able to pour plastic at home. However, some details can be made (we made crafts from pens and other junk (designers, glass from flashlights) using a burner). You melt with a heated sting and then shape it with your hands or with tongs. They were also soldered with a burner. Why couldn't it pour? Seriously, in production (I had an internship), most products are created by special injection molding machines and extruders. Due to the chemical and physical properties of various plastics, it is difficult to install something like this at home. Although theoretically, I thought to do it in the following way - pour plastic crumb into a mold and then heat it in boiling water, shaking it from time to time (so that there are no air bubbles). I heard that they used to cast spoons, but it seems like the men worked with celluloid, and not with modern plastics.

I remember my first unsuccessful experience of trying to mold a plastic part at home. I warmed up pieces of plastic in a mold in the oven and already at this stage I realized that without special equipment that creates pressure during casting, nothing would come of my undertaking. Bubbles form in the heated plastic! Therefore, it is better to use other materials or methods.