Silicone molds are used for casting standard products. Silicone is a budget-friendly and convenient material for these purposes: it can withstand heavy loads and temperature differences, and is compatible with many materials. The production of silicone molds is carried out using a simple technology, which is characterized by low technological requirements.
The main goal when making a mold is to suit the future process. It must meet production requirements in terms of: shape, technology used, material characteristics.
Production stages
The production technology consists of several stages:
- preparing the model if necessary. At this stage, an analysis of the future technological process is carried out and a material for the matrix is selected - a filling compound for molds;
- the prototype completely reproduces the shape of the future model, taking into account the location of fasteners, protrusions, and sprues. Technological grooves and holes are also displayed;
- the next step is the preparation of formwork and embeds. The formwork needs to be covered with sealant and the prototype fixed. If necessary, the outside of the model is coated with a separation compound;
- Next, the material for filling is prepared. Silicone is mixed with the addition of special compounds. Then degassing is performed by vacuuming;
- The next step is to directly pour the silicone into the mold. The process is carried out under vacuum conditions so that there are no air bubbles left in the future form;
- Then polymerization or hardening of the material occurs. Depending on the additives used and the thickness, it lasts from a day to a week;
- Next, the resulting product is cleaned, followed by drying.
Types of silicone
When making molds, the following types of silicone are used, which are selected depending on needs:
- anti-allergenic;
- resistant to temperature changes;
- especially durable (for example, tin-based silicone paste) and others.
Supplements
Additives are used to impart certain technological properties to the form. They are selected depending on the final goal. If it is necessary to add color to the form, a pigmented additive is used. There are also compositions that:
- contain a hardener and help accelerate the hardening process;
- increase the viscosity of the material, which allows it to be applied to the model with a brush;
- increase the strength of the material and others.
The main requirements for production are the provision of ventilation and the presence of protective rubber gloves on the hands of the worker.
Brief background. We were faced with a task: to produce a certain number of rubber buttons for car keys according to the sample. We tried to print them on a 3D printer from rubber filament, but we were not happy with the quality. It was then that the idea came to reverse the silicone casting technology. What came of it, read under the cut.
A lot of photos.
Technology overview
Plastic injection molding
Not quite rubber, but the essence is the same: a special machine - an injection molding machine (TPA) - brings the raw material (2) to the melting temperature and through the output die (3) injects the melt into the mold (4.6). Typically, thermoplastics are used as feedstocks.
Pros: manufacturability, high speed of product production, widest range of materials, high final quality, highest degree of detail. Disadvantages: this also includes manufacturability, unreasonably high cost for home use, high energy consumption, payback only on large runs.
Casting in silicone molds
The technology is simple and elegant; anyone who wants to learn more can follow the links in the title, but here I will give a brief description. The master model is placed in a bath and filled with liquid silicone mixture, after some time the silicone hardens. The result is cut up anyhow and the master model is taken out of it. Due to its physical properties, silicone immediately takes its original shape with hollowness in the form of a master model, into which anything that hardens should be poured. Anything that has hardened is removed in the same way as the master model. Pros: simplicity, low cost, repeatability. Cons: not everything is so simple, there are bubbles in the product, in some places the process is quite lengthy, a limited range of materials, dirt - then you walk around and stick to everything.
So, let's go! After practicing a little on cats, it was decided to make a matrix not based on silicone, but on the same plastics that are poured into these same silicones. The principle here is the same: we mix the two components of thermoset with each other and pour them into the finished matrix until curing. There are a number of reasons why I decided not to use silicone as a matrix. Firstly, even when using a large amount of separating lubricant, it was not always possible to properly tear the model off the matrix; several pieces had to be thrown out. Secondly, silicone matrices quickly become unusable, especially if they are boiled to speed up the polymerization process. Thirdly, silicone still deforms, especially if you squeeze out air bubbles manually and not with a compressor. Fourthly, I had a lot of plastic and little silicone, however, after several unsuccessful attempts to manage to pour the mixture into the matrix before it polymerized, the situation changed to the opposite. And fifthly, I just wanted it to be “like in a factory.” A classic mold consists of a die (usually the lower part) and a punch (usually the upper, pressure-creating part). I decided to start by making a matrix into which the master model will be “poured.” I immediately apologize for possible hidden advertising on business cards, I tried to remove all the sweat, initially the goal was not to post here. As you can see, the part itself is small, which means laminated business cards can be used as formwork. Lamination, in addition to an aesthetically smooth surface, allows you to do without the use of a separating agent. Based on previous experience, I decided that the model would not just lie with its back on the business card, but on a small plasticine elevation. As a result, the product will be, as it were, recessed in the bath, which will provide an additional opportunity to avoid bubbles.
I glued it to the plasticine with superglue, otherwise it won’t stick. The tub is inside out. We seal the holes. Result To press the punch, I decided to “pour” four pins into the matrix along the edges. The bottom line is this: the back of the buttons, the one that is glued to the plasticine bath, has a counterpart for the punch, to which it will be pressed. Accordingly, we will “pour” thread into this same part.
In the photo, part of the thread is covered with a tube, this is the counter part of the punch. Since it is very difficult to visualize the parallelism of the pins, on another business card I made holes in the same places and assembled something like this frame: As you can see, the threaded ends face the inside of the matrix .
The result with the formwork will already look like this: As the direct material for pouring, I used what the seller recommended with the words: “Holds 120 Celsius and hardens in three minutes.” Actually, this is a cardboard box with two jars of yellow and blue, half a liter each. The liquid in the jars is transparent, one thinner than the other. Well, that is, the contents of the blue jar are thicker, and the contents of the yellow jar have a yellowish tint. After polymerization, the composition loses its transparency and becomes, I don’t even know how to put it otherwise, but gently white. The chemical composition is not really known, on the yellow one it says: 4,4′-Methylenebis (phenyl isocyanate) and a warning about urgent and inexorable death in the most terrible agony, if anything happens. But the blue jar tells us that “No hazardous ingridients”, but there is still a WARNING on it. One way or another, the children of the Soviet Union cannot be intimidated by such trifles, which means we will work with what we have.
Actually, photo of the cans: The whole thing needs to be mixed in a one to one ratio, which is damn convenient, unlike silicone, into which you need to pour 3-4% of the catalyst. Go and measure when the final product weighs half a gram!
Educational page
So, let's go!If you mix different contents from all four jars (yellow, blue, silicone and silicone catalyst) in any proportions, then absolutely nothing will happen. Because the phases of liquids do not coincide and they do not mix. But if we mix everything together, and in the right proportions, we get an indistinct mass, similar to very fragile polyurethane foam.
We prepare the proportions: Mix: Using a can and a compressor from the refrigerator, we degas (get rid of gases, that is): And...... we don’t have time to do anything. The mixture has hardened.
But now I have a beautiful piece of plastic, minus one-fifth: This, by the way, is a very important point: you need to know exactly and be sure of what exactly you are going to do. If the entire process is performed manually, including mixing, degassing, pouring back and forth, it must be understood that the pot life of the mixture must be sufficient to complete all these procedures. Well, there are a lot of small moments that are difficult to foresee without sad experience or advice from experienced people. For example, a degassing chamber. I assembled it on my knee from a refrigerator compressor and a glass jar with a lid. It seemed like nothing complicated, but a lot of bugs immediately appeared. First, it is impossible to get your hand out of the jar if you are holding a glass at this time.
This is what I looked like when I tried to do it for the first time: Secondly, the hose from the compressor enters exactly into the center of the jar lid, respectively, when the pressure normalizes, the air hits with force exactly into the center of the mixture. As a result, minus the second fifth of the plastic and the white, opaque walls of the can. Third, the hose is short and hard, and tends to overturn a small and light jar with its contents. Minus the third fifth plastic. Of course, after that I began to think through all my actions in advance, with various options for the development of events. As a result, I was able to achieve something: I must say that in this case I decided to do without using a compressor. Next, you need to “undress” the matrix: Clean off the plasticine and admire the result: Put the master model in place And assemble the new formwork: Here we will pour the mixture that will form the punch, this is the counterpart of the matrix. Of course, to prevent the studs from being filled with plastic, tubes are mounted on them. If desired, they can then be pulled out of the punch. The inside must be lubricated with a release agent; for this I use a wax solution in the form of a spray.
The result after removing the formwork: A little processing and this is the result: A few words about plastic. During the polymerization process, plastic can get quite hot, and heating speeds up the reaction. Accordingly, the larger the volume we mix, the more heat is released and the faster the mixture hardens. This must be taken into account. The intermediate stage - the gel - lasts literally a minute, at this stage it is still possible to correct minor flaws. After complete polymerization, a product is obtained that resembles ivory in texture. It is lighter than ABS and less durable, but seems to hold temperature better. It can be easily processed mechanically, glued, painted (it is better to use dye when mixing components), sinks in water, and burns. When heated strongly, it first transforms into a less solid phase, then becomes very plastic. But not fluid! That is, you cannot crush it, otherwise it will simply crack. During destructive overheating, the plastic begins to crumble, suddenly turns into a fluid mass, becomes transparent and changes its color to the color of burnt sugar. Of course there is stench and all that. Can it be used as a replacement for thermoplastics? It depends on what for, but in general cases yes, and given the fact that this is not the most durable option existing on the market, it is definitely possible.
Well, now what this whole business was started for is the production of silicone copies. Since I only had white silicone...
In person:...and the buttons needed black, I had to improvise with toner from a laser printer: I already mentioned the difficulties with selecting the silicone/catalyst ratio, here an insulin syringe came to the rescue. I stirred the whole thing and first spread the resulting cocoa onto the punch, and then poured the remainder into the matrix, where the “bulge” that I made from plasticine came in handy. 10 minutes later: Result after trimming: conclusions
The technology is working, there is nothing complicated, the materials are accessible. An excellent option for home or small series. For large products it is suitable in the same way as thermoplastics. A very serious minus is that it is dirty. Maybe I'm such a pig, but the fact that I completely crap my workplace is very upsetting.
Sealants are widely used for sealing seams and joints. Their main advantages are: resistance to vibration, solar radiation, deformation, temperature changes, and so on. Silicone sealants are highly elastic and have excellent waterproofing and adhesive properties. It is thanks to the high consumer potential that silicone sealants have found wide application. Depending on the type, silicone sealants are used for industrial applications, repairs and construction.
There are three types of silicone sealants, which differ primarily in composition. So, for the production of sealants of grade “A” (acidic), it is customary to add acetic acid to their composition. The cheapest and most widely used type, incompatible with non-ferrous metals, marble, cement. The type of neutral sealants contains alcohol or ketoxin and has an unlimited range of uses. The amine-based type of alkaline sealants has a very special purpose.
Literally 3-4 years ago, the market for the production of sealants experienced a sharp decline in demand. The cause was the consequences of the global economic crisis, and the consequence was the deterioration of the situation in many industries. Now, according to experts, a rise is possible. The reason is a new field of application. Experts suggest that the use of sealants in the renewable energy industry and the expansion of their use in the production of lightweight building structures are helping to increase demand for this type of product.
In the Russian market, the leader in the production of silicone sealant is considered to be the Henkel company, which in 2016 opened its work areas for trade not only in Russia, but also in neighboring countries. It is difficult to compete with giants, but it is quite possible to work exclusively in your region, offering high-quality and cheaper silicone sealants.
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Working areas.
To produce silicone sealant, it is worth renting a production facility with warehouses with a total area of at least 400 square meters. It is best to work in an industrial area or far from residential buildings. An important criterion for choosing a room will be good ventilation (natural and artificial), lighting (natural and artificial), the presence of all communications (heating, drainage, water supply, power line that can withstand 380 V, gas). The premises must be clean, pest-free, spacious, with the possibility of zonal separation.
Depending on the territorial location, you must pay monthly rent with utilities from $1.5 thousand.
Equipment.
To produce silicone sealant, the following production line is required:
1. Vacuum reactor - $10 thousand
2. Receiving funnel - $400;
3. Automatic cabinet for weighing equipment - $2 thousand;
4. System for supplying recipe components to the reactor - $5.5 thousand;
5. Homogenizer - $1.7 thousand;
6. Frequency converter - $2 thousand;
7. Emulsifier with a capacity of at least 300 liters - $4.5 thousand;
8. Vacuum mixer-storage with a capacity of at least 1.5 thousand liters - $7 thousand;
9. Piping for pumping products - $1.2 thousand;
10. Pumps for unloading - $1.6 thousand;
11. Control panel - $300.
The cost is approximate and may differ depending on the selected equipment manufacturer.
The minimum amount for the purchase of a line for the production of silicone sealant will be $40-45 thousand.
Materials.
Silicone sealant differs from other similar types in its natural composition. It is customary to use silicone rubber as a base. Acetic acid, alcohol or ketoxime, and amines can be used as additional components. In this way the base can acquire an environment of use. The most expensive are silicone sealants made from 100% silicone rubber. Additives change the composition and make the product cheaper.
To make silicone sealant, the following additional components are used:
1. Extenders of natural origin to give the base better viscosity;
2. Chalk, glass or quartz dust to ensure adhesion;
3. Fungicides for use in environments with high humidity levels. The components perfectly fight and prevent the formation of mold and mildew;
4. Dyes. After complete drying, silicone sealant cannot be painted in colors, therefore, at the production stage, dyes are added to its base to improve consumer qualities.
You can buy silicone rubber and other components from intermediaries or directly from the manufacturer. Most often, the choice of supplier is determined by the volume of purchase.
The total cost will be about $6 thousand and above.
Staff.
A sealant manufacturing plant must have three units. Management personnel: directors, foremen, chief specialists. We also need specialists with chemical and technological education: line operators, laboratory assistants, technologists. And support workers: laborers, managers, accountants. The staff will be 16-20 people.
At least $6-7 thousand is allocated to pay for their labor.
A business needs to be advertised targeting an audience of potential buyers. It is most profitable to invest in creating a website, advertising it on the Internet and constant promotion. It can also invest in external advertising located geographically in an industrial zone. It is beneficial to participate in exhibitions, conduct seminars, and take part in them. It is also worth focusing on specialized literature. It is no less profitable to approach construction companies with proposals.
Basic expenses.
The silicone sealant manufacturing business involves the following types of investments:
1. Rent of premises - $1.5 thousand;
2. Equipment - $40-45 thousand;
3. Materials - $6 thousand;
4. Staff - 6-7 thousand $;
5. Advertising - $400-600.
A business in the chosen industry will require capital of $60 thousand.
Profit calculation and payback.
The estimated profit on 1 ton of sealant will be $1.8 thousand. From 4 tons of sealant can be produced per month, depending on the capacity of the equipment. On average, about 1.5 thousand tons of sealants for industrial and construction purposes are used in our country per year. Leaders in this industry will take over 80% of the market. In this case, you should count on the remaining 10-15%.
The monthly profit of the enterprise under favorable working conditions will be about 9-12 thousand $. It will be possible to recoup the business in just 1 year of operation.
Business development and clients.
Clients: construction and industrial facilities. You can develop by deciding to produce several types of silicone sealant. You can also purchase equipment for packaging and produce silicone sealant for household use.
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Almost everyone is familiar with such a material as silicone. Men use sealants made from this material. Women often use molds made from it for baking. Many different items are made from it. I wonder if it is possible to make soft silicone on your own at home, as well as forms from it? Yes, you can! Read below to learn how to do it yourself. Production will not take much time, and the simple composition will make it easy to make at home.
What is needed to make silicone
The following materials are required:
Before you start making a rubber-like material, you need to ensure safe conditions. The work must be carried out with rubber gloves, because this material itself is very toxic.
It is also necessary to choose the right place to carry out the work. The room should be good ventilate. The ideal conditions for working on creating silicone products are outdoors. But if this is not possible, then you can do the work on the balcony.
It is also worth knowing the peculiarity of the material - fast hardening. Therefore, it is recommended to produce molding material in small quantities or to carry out all actions quickly.
Other materials can be used to make silicone:
Place sealant in a plastic cup. Add glycerin and paint to it. To do this, it is convenient to use a pipette or straw. Add white spirit. Now you need to mix the mixture thoroughly so that the mass is homogeneous. Silicone is ready! It will remain in a liquid state for about 4–5 hours, and then the pouring silicone will harden, and then it will be difficult to melt it.
First of all, to make the material you need to mix ethyl alcohol with liquid glass in equal proportions. This can be done in any plastic container. During mixing, you need to add dye to the mass according to your own preferences.
Both a wooden stick and a regular spoon are suitable for kneading. After kneading, you will get a mass reminiscent of casting, plasticine or rubber. It can be used in several ways in the future. For example, knead with your hands. You can also put the mixture into a regular cooking bag, a gun for construction silicone or a syringe with the necessary attachments and squeeze out the amount that is needed. You can use regular cookie cutters or take some. Or another option is to cast the required shape.
Important! Repeating the shape of an object will only be possible if you apply silicone mass to the outside of the object. To put it another way, apply the mass not into the mold, but from the outside.
Another important point: before applying the rubber mass, the surface should be lubricated with vegetable oil or soapy water.
How to make a silicone mold
For this you will need special material - compound, which consists of:
- catalyst (hardening agent)
- silicone pastes.
Thanks to these components, any shape can be cast. True, this is not exactly injection-molded silicone (it is more reminiscent of rubber in its properties), nevertheless.
To make an analogue in the form of a silicone mold, you need to do a number of steps:
The required silicone mold is ready!
How to make a mold on a plate
To do this you will need liquid/cast silicone.
The stages of work are as follows:
- A plaster or foam plate must be treated with soapy water.
- Take a brush and apply silicone to the surface.
- Now we need to work out the details. Particular attention must be paid to the top layer.
- Wait until the silicone dries.
Now all that remains is to remove the silicone and the required shape on the plate is ready!
How to make a mold from silicone sealant
There are no difficulties here either. You will need any silicone sealant.
Stages of work:
You can also do this. Roll the silicone dough into a ball and press the dough into it. Align the edges. After a few hours, check whether the silicone has hardened or not. If yes, then the workpiece can be removed. The resulting homemade form is ready!
Work very interesting with the material, especially creative people. You can do whatever you want with this material, make various castings for makeup, make an unusual toy or figurine, make a silicone mask, and also use it as glue for crafts. The technology for making complex products, of course, requires certain skills, but simple figures are not difficult to make even for a child. However, if you want to use such a silicone mold for baking, then you should refuse such a desire; it is not suitable for food use. It is better to purchase an industrial silicone mold.
On the Internet you can find many videos that detail how to make silicone and molds with your own hands, as well as how you can replace some components.
