J-CAD Inc. is a global leader in mold design and plastic injection molding. We help clients from every corner of the globe in the 3D design of their product and in the manufacture of the mold required to make it. We have state-of-the-art technology to not only create the prototype but also to manufacture the refined product on a large mass production scale.

Contact us today to have your project quoted by one of our experts.

Plastic injection molding process

Plastic injection molding is the process of melting plastic granules until they are very soft then injecting the melted plastic, under high pressure, into a mold. This results in the plastic taking the exact shape of the mold. After sufficient cooling, the mold is opened releasing the solidified and hardened plastic part. The process is then repeated over and over again until the order quantity is complete.

This process is suitable for the production of a large number of parts. It is a very rapid manufacturing process. The steps followed in plastic molding include;


This is the tightening of the mold to ensure that the plastic melt does not escape when pumped into the mold under pressure.


The melted plastic is pushed from the barrel under pressure into the mold.


This is the application of pressure into the mold to ensure that all the cavities inside it are filled.


The formed plastic part is allowed to cool on its own inside the mold.

Opening of mold

The movable platen is moved away from the fixed platen to open the mold and release the molded product.


The molded product is removed from the mold with the use of air blast, a rod or a plate. J-CAD has state-of-the-art machines and highly skilled mold operators with years of experience to ensure that your products are of very high quality and are outstandingly accurate.

Our presses range from 3 to 30 ton. Our equipment is custom designed for micro-molding. This ensures maximization of parts per second hence minimizing losses and greatly controlling shot size. All of our machines are also highly mechanized to ensure that in-line inspections, insertion and removals of over molding and part removal are very cost- effective. That explains why our services are very affordable.


Plastic Materials for Injection Molding

At J-CAD Inc. we use the following materials for plastic injection molding;

In choosing a material it is necessary to anticipate the product’s environmental conditions.

Will it be outside in the sun all day? Will it be under water most of the time?

There are many factors when it comes to choosing the correct material for your product. J – CAD Inc. will help you with selecting the correct material through our expertise in the materials available for manufacturing your products.

SAN (Styrene Acrylonitrile) – comes in clear and colored but will be transparent. Cannot be finished as a solid color. The material is very brittle and typically used in kitchen appliances as it is food grade safe. Its cost is very low. (About Styrene Acrylonitrile)

PS (Polystyrene) – very similar to SAN (Styrene Acrylonitrile). Very low cost. (About Polystyrene)

ABS (Acrylonitrile Butadiene Styrene) – very popular material found in many household items and products. It is not flexible. It can come in any color or be translucent. It can be metal plated for visual effect. Its cost is average. (About ABS)

PC (Poly-carbonate) – very strong and comes in any color with a solid or transparent finish. Higher cost, about double the price of ABS(About Poly-carbonate)

TPE (Thermo-Plastic Elastomers) – can come in any color. This is a very flexible, rubber material. Usually used as grip on a hard plastic handle. Similar in price to PC (Polycarbonate). (About Thermo-Plastic Elastomers)

TPR (Thermo-Plastic Rubber) – can come in any color. It is a very flexible, rubber material. Usually used as gripping material on a hard plastic handle. Similar in price to PC (Polycarbonate) but less expensive than TPE(About Thermo-Plastic Rubber).

TPU (Thermo-Plastic Urethane) – can come in any color. It is a very flexible, rubber material. Also usually used for gripping applications on a hard plastic handle. Similar in price to PC (polycarbonate) but less expensive than TPE(About Thermo-Plastic Urethane).

PA6 or PA66 (Nylon 6) – is a nylon material mixed with fiberglass which makes it very strong. It comes in any color. It can be mixed with fiberglass at a mixture of 5-50% glass. The final product gets stronger with more glass but also gets more brittle. (About Nylon 6)

PP (Polypropylene) – can be finished in any color or can be translucent. Cannot be fully clear. It is more flexible than ABS and less costly. (About Polypropylene)

PE (Polyethylene) – very similar to Polypropylene. (About Polyethylene)

POM (Polyoxymethylene) – very wear resistant and strong. Used for plastic gears and other parts in friction as it has good friction resistance. Higher cost. (About Polyoxymethylene)

PEI (Polyetherimide) – used for aerospace parts and high precision and strength. It is very expensive and can withstand high temperatures up to 180° C / 350° F. (About Polyetherimide)

Injection mold design basics and guidelines

Designing a plastic injection mold is a complex process. It’s important to take into account every little feature you will require from your part, giving it the strength and geometry to fulfill its functionality, additional cavities, the tonnage it will support, if it has to fit other components, etc.

While designing it’s also important to pay attention to the fabrication process. The stages of entrance, filling and cooling of the part into the line play an important role when it comes to its design, there are basic injection molding rules that should be followed in order to receive stronger parts for lower costs.
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And there are a few things to take into account, like:Stress: Your design should try to reduce stresses as much as possible, try to ensure smooth transitions along the features of your part by adding rounds and fillets in critical areas where there is going to be high stress.

Gate: The design model needs an entrance that allows the plastic to be injected into the mold. The gate should be placed in a cross section to avoid voids and sinks in your part, and away from cores and pins to reduce the chance of obstructions.

Wall thickness: Consider having a uniform wall thickness in your model, if there isn’t uniformity, the portions of your part with thinner walls will cool faster than the thicker ones, and it can cause internal stresses in the product.

Parting lines: This is the line that forms when the two halves of the mold meet, and can also be caused by other tooling. They cannot be avoided without adding a surface finishing process, meaning that you should keep them in mind while designing.

Plastic injection molding tonnage calculator

The tonnage can be defined as the machine’s clamp force required to achieve a proper injection into the molds. You should ensure a proper tonnage to get the desired quality, as having undesired pressures can cause excess material to appear on the parts’ edges.

Pressure is usually stated in tons and has ranges around 5 to 4000+ tons. Selecting the machine that you require will depend mostly on the size of your mold and the viscosity of the material (also known as MFI), as thicker materials will require more injection pressure than others to be fabricated.

In order to calculate the tonnage required there are lots of factors to consider, but you can get close by using the main ones; size (surface area), viscosity (MFI) and a safety factor.
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MFI (Melt Flow Index) is how we measure the viscosity of the plastics. If a plastic has a high MFI, it requires a higher clamp pressure.You can try to get an approach of the required pressure (in tons), by doing 2.5 times the surface of your part (in square inches) multiplied by a standard safety factor of 10%. That’s a rough estimate and you should only use it for average MFI plastics.

Also, it may be cost-efficient to outsource to a company that can both design and produce your molds (like us!), since it’ll be easier for them to optimize the mold according to their manufacturing process, saving you time and money.

If you want to get a closer estimate for your tonnage requirements, just ask us, at J – CAD Inc. we may have just the press you need!

Tolerances for plastic injection molding

In plastic injection molding, tolerance is an expensive thing to attain. Medium to high tolerance parts can double or even triple the costs of a normal tolerance part.

This happens because maintaining high tolerance requires advanced operation of expensive tooling equipment and a good deal of maintenance and assurance checks.

Tighter tolerances may also increase part scrap rates, which will decrease your efficiency and increase your production costs.
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Part complexity, wall thickness, part size, and injection process can all have an impact on the expected tolerance. But a good design and proper manufacturing can ensure a tight tolerance repeatability. This way you may expect an average tolerance in plastic parts made through injection molding of +/- 0.002 inches.Part tolerance will depend on the tolerance-group assigned to it depending on the material and its in-mold shrinkage (while cooling), and it’s recommended to use both geometry and location tolerances.

We advise you to avoid designing for excessive tolerance, you should aim to stay around the recommended tolerances for your parts’ material. Check the table below for suitable tolerances for plastic products according to ISO-2768.

Injection molding wall thickness

It’s important to pay special attention to your design’s wall thickness, since it can have a huge effect on your production’s cost, speed and quality.

For efficiency purposes you’ll want the thinnest walls, while maintaining a strong and stable part, furthermore reducing your material usage and, because thinner parts cool faster, quicker cycle times.

Anyway, wall thickness will be influenced by the part’s geometry, structural requirements, and material, but you can generally expect minimum thicknesses to range around 0.080 in – 0.160 in (2-4mm). Although some conventional plastic injection machines can produce parts with walls as thin as 0.010 in.
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When designing, remember to aim for a uniform thickness, since thinner sections cool faster than thicker ones, which take longer to solidify. This can cause cracking, twisting or warping between the two sections.If uniformity isn’t achievable, just try to make the thickness change as gradually as possible, stay around the 10-30% variation in transition. At J – CAD Inc. our professional team could also suggest alternatives like adding design features like ribs or coring if you’re not sure what the best approach for uniformity of design is.

Remember that keeping your part’s thickness within a standard range for your material and manufacturing process can ensure a higher part yield, avoiding unnecessary costs and delays.

Plastic injection molding tooling cost

Your parts’ mold will represent one of the most expensive elements when facing upfront costs of production. When trying to calculate the costs of plastic injection molding, there are some things to take into account, mainly things like part size, complexity, material, and production quantities.

The average cost of mold tooling in the USA can be around $10,000, but it may be higher or lower than that depending on your project specifications.

You can establish a budget for your mold and, according to it, you should get together with your designer and/or manufacturer to plan and optimize every consideration that may affect the mold and tooling costs.
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One example of this is the number of cavities in the mold. Cavities are like the negatives of your part’s shape, which will be filled with plastic during the injection. Allowing for more cavities will make the mold more expensive, but will also increase the number of parts per cycle of production, thus decreasing the cost per part overall, making your production much more cost efficient at scale.Part size is also important, bigger parts will require bigger molds, hence bigger machines and longer production cycles.

Taking these factors into consideration means that you can design based on your production plan and achieve the most cost-efficient outcome.

We recommend again that you find a company who can both design your molds and also manufacture them like we do here at JCAD since this will allow us to design the perfect mold, according to our production facilities and capabilities.

How to know if you should use plastic injection molding or some other injection molding substance

It probably goes without saying, but if you need to manufacture a plastic part, plastic injection molding is the best way to do so.

There’s no way you can get a material that is so manageable, durable, economic, and easy to manufacture as plastic, and the easiest way to manufacture plastic parts is injection molding.

Most of the plastic parts you see every day were (or you can bet they should’ve been) made with plastic injection.
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And if you don’t believe us, here’s a list of benefits that’ll make you know you have to use plastic injection molding over other plastic manufacturing methods.It’s Strong: There are lots of materials and techniques to choose from, like adding fillers to your part during processing to increase the density of the plastic, also increasing its strength and durability.
It’s Precise: It can fabricate almost any type of part. As a result of high pressure injecting, the molds are pressed hard against the plastic, allowing for a high level of detail, and the design of complex shapes.
It’s Efficient: this is the reason why plastic injection molding is one of the most common manufacturing technologies used. It takes an average of 15 to 30 seconds between cycle times, making it stand on its own level of speed and production efficiency for mass manufacturers.
It’s Low Cost: You can get a high level of automation on a plastic injection molding line with a sole operator to control and manage it. This means that with the right setup you can substantially reduce the labor force and overheads required to produce a lot of product. And although upfront costs can be high, in the long run the production costs are significantly cheaper in comparison to other methods.
It’s versatile: There’s a huge array of different materials and colors that can be used with the same molds, these variations allow for huge versatility in production. This process also has the ability of using different types of plastic simultaneously.
Provides a surface finish: Your parts will hardly require any work after production. If you have a good mold they’ll come out of the line with a smooth finished appearance after being ejected from the molds.
It’s Environmentally friendly: it only uses the plastic it’s going to spend in fabricating the parts, since most of the raw material wastage can be recycled. This means that the process generates very little waste.

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