What is Small Batch Injection Molding?
Small batch injection molding process
Small batch Injection molding is the process to produce molded objects through the injection of plastic materials that are heated to melt into molds, later cooling them and forming them.
The technique can be used for the mass production of products that have complex shapes. It is also able to take much of the plastic processing industry.
The process of Small batch injection molding can be broken down into six main steps , as illustrated below.
1. Clamping
2. Injection
3. Living
4. Cooling
5. Opening for mold
6. Removal of the products
The procedure is carried out according to the above procedure and products are produced through repeating the cycle.
Injection Molding Machine
Injection molding machine is split into two units i.e. the clamping unit and the injection unit.
The main functions of the clamping device is closing and opening a mold as well as the ejection of materials. There are two kinds of clamping techniques, including the toggle type as shown in the picture below and the straight-hydraulic one where a mold is immediately closed and opened using the help of a hydraulic piston.
The primary functions of an injection device is to melt the plastic with heat , and then inject the molten material into molds.
The screw is turned to melt the plastic that is introduced from the hopper . It also helps build up molten plastic at the front of the screw ( known as the metering ) . After the quantity of plastic melted has been collected, the injection process is started.
As molten plastic is flowing into a mold machine controls the rate of the screw or the speed of injection. In addition it regulates the tension of the dweller after the molten material is able to fill out the mold.
The change in position between speed control and pressure control is set to the point when either screw position or pressure exceeds a predetermined amount.
Mold
Molds are hollow block of steel inside which the molten plastic is instilled from a predetermined shape. While they're not shown in the image below, there are many holes into the block to allow temperature control using hot heating oil, hot water, or even heaters.
Molten plastic is pumped into molds through a sprue, and then fills the cavities with gates and runners. The mold is opened following the cooling, and the rod that ejects the injection molding machine is pushed against the ejector plates of the mold to release molds.
Molding
A mold is made up of a sprue for introducing an molten resin and an runner that leads it into cavities, and finally products. Since getting only one item in one go is extremely inefficient, molds are typically designed with multiple cavities, which are linked by runners so that a variety of products can be created in only one shot.
When the length from the runner each cavity differs in this situation it is possible that the cavities cannot be filled in the same way, which means the dimensions, appearances or characteristics of the moldings can vary from one cavity to the next cavity. So, the runner is generally made to have the same length as the sprue and to each cavity.
Reprocessed Materials Can Be Used for
The runners and striations in moldings aren't objects. Sometimes, these parts are disposed of and in some cases they are ground finely and used as materials to make molds. They are referred to as recycled materials.
Reprocessed materials aren't just utilized as molding materials but are usually blended with pellets made from virgin materials, as there is the possibility of deterioration in the various properties of plastics due to the molding process used in the beginning. The maximum permissible amount of reprocessed material is around 30 percent, since a large a proportion of reprocessed material could alter the characteristics of the plastics that are that are used.
For the properties to be considered when reprocessed materials are utilized you should look up "reprocessing capabilities" within the plastic database.
Condition of the Mold
Molding condition means cylinder temperature, injection speed, mold temperature etc. In a mold machine, the conditions are set to produce the required molds, and the range of combinations of these conditions can be endless. Based on the condition chosen, the appearances, dimensions as well as the mechanical characteristics of molds can be altered dramatically.
So, experienced and tested technology as well as knowledge are needed to determine the best mold conditions.
The most common mold conditions for our products are listed below. Click on the mouse to see the following names for plastics.
What Are Plastic Small Batch Injection Moulding Advantages and Disadvantages
The advantages of plastic injection moulding revolve on high precision and reproducibility, paired along with speed. It also has a lower cost per component and an extensive selection of plastics available.
The disadvantages are a higher initial cost and lead time compared to other methods.
The Advantages of Plastic Moulding
1. Precision
The plastic injection molding technique is ideal for extremely intricate parts. When compared to other techniques that moulding can allow you to add many features with very tiny tolerances. Take a look at the picture to the right. It's possible to put this mold in your palm hand. It's got bosses, ribs, inserts as well as side cores and holes created using the ability to shut off the slide within the tool. It's a amount of features in tiny parts! It's not practical to create using plastic fabrication and difficult to fabricate with the vacuum forming method.
2. High reliability
Once the mould tool is created, similar products can be produced repeatedly. Then repeatedly. A well-constructed mould tool can have a long life span for a mould tool, provided it is treated properly by the setters of the moulding machine !
3. Low cost per piece
Although there is a large investment in the injection moulding machine made of plastic however, once it is used, the cost per component is quite affordable. Other methods of plastic processing may require multiple steps, such as polishing, but injection moulding can handle it all in one go. If you choose to CNC cut the part above, it will cost you hundreds of dollars per piece. If you're planning to move into production, inject moulding could be the best way to proceed.
4. Fast
The cycle time can be as little to 10 secs. Add an injection moulding tool that can be multi-impression and you can make a lot of goods rapidly. The above process will take more time because it's a special material that contains a number of functions to be properly moulded, however, at around 50 seconds you'll still have 70 parts per hour per cavity. CNC machining one-off parts could take a full day, but 3D printing it would take even more time!
5. Material selection
There are a variety of plastic materials that are available for injection moulding. A variety of the more popular materials, but also other things like antistatic thermoplastic rubber, chemical-resistant plastics and infrared. They are biocompostable...and with masterbatch color compounding or colouring there's a wide range of colours. The mold above is boring black, however it's constructed from PPO - poly(phenylene oxide) that is a very rigid and flame-retardant substance.
6. Custom Surface Finishes and Special Finishes Printing, Engraving, Printing
Alongside a variety of colours, the moulding tool is also available with a specific finish that will be visible how the tool is moulded. You can choose any look you prefer including leather-like soft touch or sparked, high shine You know it. You can also get the logo or any other text you want to imprinted on the tool. Additionally, you can get your mouldings printed as various inks are available to print on plastic.
7. Small amounts of plastic waste
Part repeatability is extremely high with injection moulding. Even the runners and sprues (the pieces of plastic that remain that are created by the tunnels in which plastic gets to an actual mold) are reground, and reused. You can look into this in greater depth on our environmental impacts of injection moulding.
Plastic Moulding's Negatives
Doesn't that sound amazing ? Of course there are certain disadvantages:
1. The high initial cost
In most cases, multiple cycles of design and modeling is required before the final approval is granted. After that, the injection moulding equipment needed to create the mouldings requires designing and manufacturing. The tool for making moulds is a complex part that takes workers, material, and many manufacturing hours and is the most expensive cost when it comes to getting injection mouldings. Once everything is done, the cost is low, and repeatability is very large for hundreds of hundreds of thousands of mouldings.
2. Initial lead time
From the initial concept to the final component can take months of designing testing, tool production and testing. However, if you are clear on the specifications you're looking for you can get the mouldings finished in six weeks. (Toolcraft's flowchart of Chinese mould tools illustrates how this could be done). In addition, as we've mentioned under the advantages that the tool has, once it is in place it only takes a short time to make the mouldings particularly when you use the multi-impression mould tool. (Here's the list of moulding tool types).
3. Big Part Size Limits
Large machines are required for the production of the plastic mouldings. Large parts require an enormous moulding tool. They also cost a lot to create and in this case, an approach like Plastic Fabrication could be a better choice according to the type of the product required.
4. Careful design needed
Moldings made of plastic require cautious design to avoid tooling problems like undercuts (which could increase the costs for tooling) Lock-in features, a locked-in feature and inadequate draft (What draft angles are appropriate for plastic Mouldings ?). The temperature and material have to be considered when designing the wall, otherwise the mould might not be filled completely. The positioning of ejectors as well as cooling lines must be taken into consideration to ensure that the aesthetics of the product.
Molding in Smaller Batches Ought to Similarly Choose the Appropriate Material?
Material selection plays a crucial component in nearly every aspect of the process of plastic injection molding It's crucial not to ignore this aspect. We'll explore what's the "why" of choosing the material that affects the product you're making and the manufacturing process and the "what" which is it will help you learn about the most widely utilized plastic injection molding products and what they offer and their purpose.
The simplest solution to the query "why is selecting the right material important in injection molding of plastic?" is what we previously mentioned. It influences almost everything in the design process. For example:
End of Product
The material you choose to use plays an important role in the final effect and the performance of the product If you choose the wrong one, and your product won't perform as expected. A flexible resin will not work in a situation where strength and rigidity are needed. Additionally, non-food grade or medical grade materials could be a real health risk and risk if they are used for medical or food purposes.
Plastic Injection Molding Process
Different resins possess different characteristics that are crucial to the process of manufacturing, such as melting point as well as cooling point and viscosity. Molds with more complex designs may require a product that is more in its ability to cover every area for complete coverage. Various melting and cooling points may assist in avoiding issues like sinks and cavities within your product.
Budget
Understanding the needs of your particular process (like the design of the mold and its the complexity) and the specifications of the finished product, will aid you in selecting an appropriate material that has the characteristics you require, with the lowest price possible. Do not pay more for materials or features that you do not want or need.
Once you have a few areas where the choice of materials can make a difference The following checklist could serve as a useful reference of things to take into consideration:
- Durometer (or the quality of your hardness and flexible)
- Strength
- Resistance to corrosion
- Resistance to heat
- Viscosity
- Melting point
- Point at which the temperature is cool
- Time to cool
- Thermoset and thermoplastic
- Color/appearance
- The ability to have colorants added, if needed
- Reactivity to other materials
- Medical grade, food grade or other requirements for specifications
Let's look at several of the commonly used resins that are used in plastic molding, along with the advantages they offer and their best applications.
ABS
ABS is a common thermoplastic, which can be utilized to make a variety of final products. It's relatively cheap and offers a strong, rigidity and resistance to shattering or breaking even after impact. It also resists various acids and other corrosives however not all. ABS should not be used for use in food products as it is highly very flammable, and exhibits poor protection against sunlight. In terms of aesthetics,
ABS in its raw appearance is translucent or white however it is able to be colored with additives. ABS can be found in various applications such as electronic casings, automobile components where resistance to shock is essential as well as toys such as Lego.
Acrylic
A lot of times, acrylic is used to imitate the look of glass, acrylic is often used in products like display cases, sunglasses and so on. Acrylic has a very hard rating, which makes it extremely resistant to scratches, and is also very resistant to breaking.
Epoxy
It is a thermoset plastic which, as such, provides an extremely strong strength and resistance to heat as well as many chemical compounds after curing. It is crucial to remember that the characteristics of epoxy vary based upon the curing (or hardening) agent employed in the process, so make sure you know the full extent of the end-product's requirements prior to deciding on epoxy as a plastic molding resin. Because of its excellent electrical insulation capabilities it is often employed in transistors and circuits. The epoxy is also found in transformer and motor components as well as in marine applications like plugs.
Polycarbonate (PC)
Polycarbonate is a translucent thermoplastic that is among the strongestand most shatter-resistant materials for injection-molded plastic products. Polycarbonate is usually transparent in its natural form and very receptive for sterilization, which makes it ideal for use in medical settings (although it shouldn't be utilized for medical devices designed for use in an individual's body). Although its durability and strength makes polycarbonate an ideal option for eyeglass lenses, and certain kinds of shatterproof and bulletproof glass, it's not very scratch-resistant which is why it will require treatment by coating it with a tougher substance after it has been molded by injection. Polycarbonate isn't particularly resistant to repeated vibrations or stress as parts from aerospace or automotive would meet, and shouldn't be utilized for these purposes.
Polyethylene (PE or PET)
Polyethylene is a strong thermoplastic with a high melting point and high viscosity. Applications with thin walls and high strength are the most suitable for polyethylene. It is often found in water bottles made of plastic that are disposable. Polyethylene is characterized by the highest viscosity which allows it to be used in larger molds. However the set-up and cooling times could be more lengthy. In cases where recycling is a consideration Polyethylene is among the best choices you could make.
Polypropylene (PP)
Polypropylene is a popular material utilized in consumer packaged goods such as water bottles as well as in household items such as garbage cans pails, flatware and pails. It is also employed in living hinges as well as laboratory equipment due to its shatter-proof characteristics. Because of its low price and high strength, as well as its flexible properties, polypropylene is perfectly for large-scale production runs and is able to work in molds with complex structures due to its extremely high viscosity. Polypropylene can be found in its raw, clear form, though it is naturally opaque.
Polystyrene (PS)
Polystyrene is a good material for injection molding using plastic when budget is an issue However, there are tradeoffs with the strength and other characteristics. If a product that is break-resistant is needed, it's best to consider alternatives. Polystyrene is the best choice for disposable items and is often utilized in food packaging , as well as in single-use lab equipment such as petri dishes. Be aware that polystyrene doesn't provide a high degree of resistance to heat (only up to 100 degrees/212 degree Celsius).
Conclusion
At present, there are not many companies able to deliver small-batch injection molding. Most of them do not want to deliver small-batch injection molding because they think the profits of orders are not high after machining. But JTC-Machining always delivers small-batch injection machining. Solve the problems of customers.
If you need small batch injection molding service, you can contact us through our official website phone or email, we are to provide you with free quotation service.
