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.

The Stages of Blow Moulding

today virtually all cast plastic parts are manufactured using blow molding technology.

Blow molding is a process used to cast plastic parts that are hollow. Since 1942 when the first polyethylene bottle was produced using blow molding technology, blow molding has become the standard manufacturing process for making cast plastic parts. Blow molding involves the fabrication of a tube made of molten plastic called parison. The next stage of the process is to shape the tube into the desired form using one of several blow molding processes.

Heating The Resin

The first step in any blow molding process is to heat the resin. Thermoplastic resin is heated to about 400 degrees. Once the resin reaches its molten state, it is extruded over a die head. The die head forces the thermoplastic resin to flow around it, thus creating a hollow center in the resin. The resin has now formed a tube called parison.

Molding

The parison is then placed inside a pre-determined mold. The interior shape of the mold cavity is what will ultimately determine the shape of the finished casting. The mold is then closed around the parison. At this point in the process, the parison is still very warm. The mold however, is cooled with water.

Inflation

Compressed air is then blown into the mold. The air fills the center of the parison tube and forces the sides to expand, thus conforming to the shape of the mold interior. The parison is still very warm at this point to allow it to expand without breaking. As the warm parison expands to meet the cold walls of the mold, it freezes off and becomes rigid.

Cooling

Once the warm parison has cooled off, it solidifies inside the mold. Once properly cooled, the parison will maintain the form in which it was cast. The mold can now be opened and the finished plastic component removed.

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Steps of Injection Molding

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Many popular plastic items are produced by injection molding.

Injection molding has continued to grow since the late 19th century. Capable of producing small items such as combs, it is also used to create parts for airplanes and medical supplies. It is hard to imagine the world without the products it produces. The process was patented by John Wesley Hyatt and his brother Isaiah in 1872. Today, injection molding is used to produce about 30 percent of all plastic products. The process is relatively simple, but expensive. Thus it is usually only used to mass produce items.

Instructions

1

Clamp the mold shut. This will hold the mold in place while the mold is filled with melted plastic. It will also keep the mold still while the plastic cools.

2

Inject the melted plastic into the mold. The plastic starts out as polymer resin pellets which are poured into a large open-bottomed hopper. A motor turns the auger, feeding the pellets into the cylinder where they are melted and turned into molten plastic, then pushed into the mold. The auger injects the melted plastic into the mold at a pressure between 10,000-30,000 pounds per square inch. The auger then holds the plastic, forcing more plastic in to fill the mold completely. This guarantees that the final product will not contain any gaps. A gate closes keeping the plastic inside the mold while it cools. Molds are usually either water ic belting. 35+ years' experience.

3

Drill small holes into the mold, if it is cooled by water or another liquid. The cooling period accounts for about 85 percent of the molding process. The temperature of the water is usually between 33 and 60 degrees Fahrenheit. Water below freezing can be used. However, glycol, or a similar additive, needs to be used to keep the water from freezing. The major disadvantage to using water to cool the mold is the buildup of condensation.

4

Loosen the clamp and open the mold. Remove the plastic part that was just created. Then clean the part, removing any excess plastic.

How to Clean Injection Molds

Injection molding is an industrial plastic-making process.

Injection molding is a production process in which plastics are heated until liquid and sprayed into a mold where they cool and are given the final shape of the manufactured product. As the project cools, it shrinks away from the mold walls, allowing it to be ejected. To keep this process working efficiently, molds need to be systematically and regularly cleaned. Although most molds are cleaned haphazardly and by hand, there are also a number of technological solutions available.

 

Instructions

1.                            Cleaning Molds by Hand

1

Disassemble the mold using a screwdriver to disconnect the parts. Separate the parts that are most susceptible to corrosion and contaminate build-up. These include the front and rear clamp plates, bubbler plates, bushings, water lines and wear plate grease grooves.

2

Spray the pieces of the mold with a cleaning spray, or place them in a solvent bath. More abrasive cleaning chemicals may work more quickly, but they will also cause wear and tear on the mold that can shorten its life.

3

Scrub the mold with a stiff brush to remove the contaminants, then wipe dry.

2.                            Cleaning With Dry Ice Pellets

4

Connect a dry-ice pellet blasting system to an air line near your mold. A double-line system introduces the pellets at the spray nozzle, while single-line systems introduce them at the hopper and offer a more powerful spray.

5

Disassemble the mold and strongly secure the parts to be cleaned. The force of the dry-ice pellet impacts can easily knock over unsecured parts, possibly damaging them.

6

Ensure the area is clear. These guns spray dry ice at 900 feet per second, which can cause severe injury.

7

Put on safety gear. This includes a face mask, gloves and an apron as well as ear protection that can block the 102-decibel noise produced by the sprayer.

8

Turn on the air line and squeeze the trigger to spray the parts. The dry ice will dissolve on impact, taking residue with it. This method, however, may not be very effective at rust removal.

3.                            Cleaning Molds Ultrasonically

9

Disassemble the mold and immerse the parts in a detergent solution. The exact type of detergent depends on what kind of contamination is to be removed. Heavily alkaline solutions like sodium hydroxide are very effective with most contaminants, but are dangerously caustic. Mildly acidic solutions are better for rust, but will turn steel gray.

10

Connect an ultrasonic generator to a shop power line. This generator transforms regular current into the very high frequencies necessary for ultrasonic cleaning.

11

Attach transducers to the bottom and sides of the tank. These transducers will vibrate at the high frequencies coming in from the generator, which produces tiny bubbles in the water that impact the mold pieces with force enough to strip away contaminants, while leaving the metal mold undamaged.

12

Set the timer on the generator, and walk away. The cleaning process will proceed on its own.

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Two Different Types of Injection Molding

Injection molding is a manufacturing process for producing high volumes of finished parts at a low cost per part. Various plastic or rubber parts are produced in a wide range of colors. The injection molding machine injects heated molding material to the part mold through input channels. The two principal types of injection molding machines use either a cold runner channel or a hot runner channel.

Cold Runner Machines

Cold channel injection molding machines cool the entry channel, or runner, after each part is molded and ejected. During each molding cycle a part is produced with material in the runner channel. After the part is ejected, the runner is waste material and must be separated from the molded part. Runner waste is reground and reused or thrown away. Disposed material affects part cost. Reground and reprocessed material may affect part quality. Changing part colors in a cold runner machine is fairly easy since each ejected parts carries the material with it. Cold runner machines offer the advantages of cheaper mold designs, lower maintenance costs and lower operator skills.

Hot Runner Machines

Hot runner injection machines keep the runner portion of the mold hot. This reduces or eliminates runner scrap material, which may reduce part costs. Hot runnermachines are more expensive than cold runner machines. Hot machines require more skilled operators and require costly maintenance. Changing colors in hot runner machines is difficult because material is hard to remove from the runners. Hot runner machines eliminate wasteful runner scrap and the need to separate them from molded parts.

Changing Injection Molding Technology

Until recently, all injection molding machines were hydraulic devices. Newer machines are operated by an all-electric process or a hybrid combination of both technologies. Each injection molding process has an advantage. Hydraulic injectors offer high injection rates. Electric injection machines produce precision parts accurately and consistently. Hybrid machines are best suited to part positioning accuracy and repetitive parts. In a paper presented in May of 2008 to the Energy Technology Conference at New Orleans, Amit Kanungo and Eric Swan, senior engineers for RLW Analytics stated, "though it is a challenge to choose a right machine for molder's processing needs, by most accounts in the near future, all-electric machines will dominate the injection molding industry in the U.S."

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What’s hot runner mold?

  It use an assembly of heated components in plastic injection molds that inject plastic into the cavities of the mold. There are two general types of runnerless molds  - the insulated system and the hot runner system. Hot runners mold retain the advantages of the insulated 
  runner system over conventional cold runner system and eliminate a number of the disadvantages. Hot runner system is one of the more important enhancements you can incorporate into a mold to improve molded part quality, reduce production times and remain price competitive

  Injection Mold with Hot runner Solution will use reliable hot runner system and mold design tools. Our engineering department work harder and quicker than any other supplier to offer you new design ideas and mold concepts using any kind of hot runner system.with long history of experience and reliability for plastic injection molding and hot runner mold manufacturing,  we can deliver the best solutions. 
  Although there are many hot runner manufactures , a few major components is same:
  1. Hot runner plate (MANIFOLD)
  2. Nozzle

3. Temperature Controller
  4. Auxiliary parts

  Advantage of hot-runner mold in injection molding industry  

 Why some many customer select hot runner to make injection mold .This is mainly due to such injection mold has following salient feature:

  Less plastic raw materials: in the age of expensive oil and raw materials . hot runner technology is the effective way to reduce the materials cost.

  Quickly cycle time for injection molding, Due to no cooling time constrains runner system.

  Plastic can be more uniform state injection into each cavity, the result is consistent quality
  parts. Such injection molding components of good quality and low residual stress after ejection part distortion. reduce product costs, improve product quality

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what's color mold? double shot molding two shot mold double injection

Color mold : two on the same plastic injection molding machine , a two- molding, but the product just only in one mold die . In general, this is also called double injection molding process. it is usually done by a mold , and need specialized color injection molding machine . Color mold growing popularity on the market today , it can make the appearance of the product is more beautiful from the process, easy to change colors and no no painting, also expensive and high technically demanding .

1 two female molds are different , each forming one kind of products, and the two male molds are the same.

2 before the mold, the mold in the center of the rotation after 180o, must match. This inspection must be done during mold design , this points have high demand for the mold base positioning  process.

3 The total thickness of the front plate plus A plate must be not less than 170mm. Please carefully review the reference data of the injection molding machines. for example, the maximum and minimum thickness of the mold, KO -hole distance etc.

4 the gate of three plates mold preferably designed to automatically release action. Particularly pay attention to the gate release of soft part..

5 when design the second injection of the female die , in order to avoid secondary mold insert ( or rub ) the first part with good product molding, can make some clearance . However, the intensity must be carefully considered . During injection ,if there will be a big injection pressure , it will cause deformation , resulting in flash problem in the second injection ?

6 during the injection , the first injection molded product may be slightly larger size , so that it can be formed in the second well tightly, in order to achieve the effect of sealing compound .

7 pls note that in the second injection , the plastic flow will impulse the first product and cause part deformation ? If there is the possibility, must find ways to improve .

8 Before A, B plate clamping , pay attention to the mold slider or lifter ,if they will be reset and the crushed product ? So , we must find ways to make the A, B plates first clamping , then make the slide or lifters reset second.

9 the water of two female molds and the male mold transport as fully and balance as possible

10 99% of the injection molded hard plastic case is the first part of the product , and then injection molded soft part . Because soft part have deformation problem .