Low Volume Custom Plastic Injection Molding Cost

How much does low volume plastic injection molding cost? In this blog post, we break down the various factors that affect the cost of plastic injection molding. The costs involved in producing low volume plastic injection parts can be divided into two categories. The first is the one-time tooling cost, and the second is the production cost.

Injection Mold Costs

Part Complexity

The complexity of the part is the most significant factor when it comes to the cost of plastic injection molding. If the corners have sharp edges, then a secondary machining process known as EDM will be used. Likewise, rib features that require machining deeper than 1/2 inch and thinner than 1/16 inch into the mold can also require secondary EDM machining. Undercut features on plastic parts will always increase the cost of plastic injection molds. They can also require bigger molds to accommodate the additional space needed for the moving parts. Sometimes, the overall mold size of a part can also be larger to accommodate the additional space required for the moving parts.

Mold Construction

There are many different methods used for plastic injection mold construction. In this blog post, we break down the various construction methods into two groups: insert mold and free standing mold. Although there are many different types of injection mold construction, we usually try to simplify them into two groups: insert mold and free standing mold. Although there are many different styles and sizes of insert molds, they can be significantly less expensive than free standing ones.

Injection Molding Costs

Molding Part's Structure

Side actions are often used within a molds construction to release plastic parts during the part ejection process. The most common type of side action that's used in our industry is called a hand load. This method involves manually removing loose parts of the mold that get thrown out of the machine. Hand loads are typically not cost-effective tools for dealing with undercut parts. They can increase part cost and produce inconsistent quality. At TEAM MFG, we prefer to use more automatic side actions in our mold constructions to provide a better and faster injection process. Although automatic side actions are usually less expensive than manual ones, they require a higher amount of work to complete.

Number of Part Cavities

The number of cavities within a mold will also affect the price of the injection molding. Parts with low quantity of parts will typically have a single cavity, while those with high quantity of parts will typically have multiple cavities. Although multi-cavity molds are more costly than single cavity ones, their overall cost will still be influenced by the overall project cost.

Part Size

The relationship between the size of the part and the mold cost is also related to the complexity of the part. In order to produce a larger part, a larger mold requires more space and equipment. Sometimes, the cost of a small injection mold can be more than that of a large mold. For instance, a complex part may require a larger injection mold than a simple one.

Material Choice and Part Weight

The material selection that you make for your plastic part is also a huge factor in determining the cost of production. Raw material costs can vary from $1 to $25 per pound. It's important to consider the weight of the part when choosing plastic material. The selection of the right plastic type can help lower the overall costs of your parts while achieving faster cycle times. For small parts, the material's price can affect the unit price.

Cycle Time and Mold Cavities

In addition, the amount of time required to complete one production cycle is also known as the cycle time.

● mold closing time

● injection fill time

● injection pack/hold time

● cooling time

● mold opening time

● part ejection or take out time

● re-cycle time (which would only apply when parts must be ran in a semi-automatic mode with a machine operator)

So how does cycle time relate to part cost? Let’s discuss the primary sources of the non-material related costs for injection molding.

Non-Material Related Costs

The capital investment required to run a high-tech injection machine depends on the size of the machine and its surrounding equipment. A small tonnage machine is commonly used for producing small parts and batches, while a large tonnage machine is used for large parts. Even a small injection machine will cost you around $100,000. A large machine, on the other hand, will require millions of dollars to run. It is also known that the lifespan of machinery is a finite one. As technology advances and the cost of ownership increases, it loses its technological advantage over time. Knowing the cost of running a high-tech injection machine is very easy to understand. It shows that the machine's hourly operational cost is computed based on the machine's effective life cycle.

Aside from the capital equipment costs, another cost that you may not be aware of is the rental charges for manufacturing space. Through simple math, these costs can be easily calculated. The sum of all non-material costs that you'll incur during the course of your production cycle will become known as the machine rate. Finally, here is how the simple non-material related cost of an injection molded part is determined by cycle time:

● The # of units produced per hour = (3600 sec / cycle time sec) x number of mold cavities

● $ Non-Material Part Cost = $ Machine Rate per hour / # of units produced per hour

Since cycle time and the number of cavities in a mold are two of the most critical factors that affect the cost of a plastic molded part, it's important to keep in mind that machine rates are always competitive.

Packaging and Extras

Aside from the machines, there are also other factors that can affect the cost of a molded part such as packaging.

● Layer packing

● Cell packing

● Poly bagging

● Retail packaging

● Plating

● Painting

● Pad printing

● Secondary machining

Contact TEAM MFG

All of these factors combined will make up the injection molding costs involved in your project. Call or email us today to get with one of our sales engineers!