Reducing Your Injection Molding Cost In Plastic Prototyping

low volume injection mold parts

We live in a world of mass production where there is simply no escaping injection molds. Almost all the items we use in our day-to-day lives contain plastic parts made using injection molding. Given the all-pervasiveness of such objects, gaining insights into injection molding costs becomes vital.

Now, multiple factors determine injection molding cost. There is no one single factor at play here. Accordingly, the objective of this article is to inform and educate readers like you about injection molding costs. That way, anytime you need to get such molds created for your own unique purposes, you can do so while incurring optimal mold expenses.

5 Factors That Affect Cost of Injection Molds

While evaluating the cost of injection molding, you will find that there are 5 major factors at play over the entire production cycle. Below we look at each of these factors to help you gauge the overall impact on injection mold costs.

In every instance, we have shared appropriate injection molding cost examples. They will help you comprehend the difference made by these below-mentioned factors.

Part Size

Plastic parts come in a plethora of varying sizes. Depending on the purpose at hand, there could be a complex assortment of parts to be manufactured. Automobiles are a classic example. In a solitary vehicle, you would have multiple such parts being incorporated. When you think of additional variants of such vehicles, the requirement for parts increases further.

With so many different parts, all of several sizes to be manufactured, the overall injection mold cost is bound to rise. This is especially true since each part would require its own unique mold size.

Part Complexity

complex plastic prototypes

There are some parts that are relatively basic in nature. 3-D prints taken at home on a low volume basis are an apt instance of this, with the degree of complexity involved being especially rudimentary. A single cavity mold would also be considered fairly basic.

On the other hand, you have larger molds, often made of steel with more cavities inside them. A suitable example would be airplane interior parts made of plastic. They are required in large volumes, often in the tens of thousands, with unfailing accuracy. Often, they require company logos embossed on them, further adding to their complexity. As this complexity increases, the plastic injection molding cost is bound to rise.

Part Cavities

In the above instance, we cited steel molds with multiple cavities in them. Such molds can be especially complex. Within these, there is an absolute surfeit of plastic injection molds. Depending on the final output, the cavities required could vary considerably.

As the need for such injection molded part cavities increases, there is a concurrent rise in plastic injection molding costs.

Part Finishing

plastic optical parts

The aptest example to cite here would be customized injection molded parts. The degree of finishing required on a given part will have a direct bearing on the manufacturing costs incurred.

A high-gloss smooth finish, for instance, would require more work hours and effort as compared to a textured finish. The former would need to go through a series of polishing steps before it can attain the desired look. All these added steps will add to the total cost.

When that is the case, the entire injection molding process becomes particularly intricate. Of course, when this happens, the overall plastic injection molds cost rises substantially.

Part Quantities

While determining injection molding tooling cost, part quantities play a quintessential role. As logic will tell you, the greater the number of parts to be manufactured using the same mold, the cost per part would come down.

At the same time, bear in mind that there is a machine cycle to every molding project. This has a dual implication of the time required to create a finished output each time, as well as the overall duration for which one mold can create production parts. Beyond that threshold, quality ends up being compromised. In fact, a typical injection mold simply cannot produce any output once the predetermined quantity of units has been created. Therefore, also consider the need for fresh plastic injection mold in this context.

What Determines Injection Molding Cost?

Yet again, we would emphasize that multiple factors contribute to the cost of a typical plastic injection mold. Do keep them in mind while calculating injection molding costs to create molds.

1. Machine Cost

Suitable injection molding understanding requires that you also realize and appreciate the cost of machines involved in the process. Today, there are mold machines with gargantuan size tonnage, producing injection molds of widely disparate kinds. These larger mold machines, coupled with more complex operations required to run them, all contribute to driving up costs.

Alongside, there are relatively simpler – and also more durable & versatile injection molding machines that are particularly cost-effective. Therefore, always take injection molding machine costs into consideration in this context.

2. Tooling Cost (Mold Cost)

This is nothing but the cost of a typical mold. Herein too, you will find yourself privy to a number of factors impacting tooling costs. They include the complexity of the part(s) being manufactured, the volume of production, the process followed to make the mold, as well as the material of the mold, say an aluminum mold or a steel one, etc.

The following three methods are most commonly used to make injection molding molds:

CNC Machining

This is the most commonly used method for making injection molds. It involves the use of computer numerically controlled (CNC) machines to create molds from a block of material, typically aluminum or steel.

CNC machining is a subtractive manufacturing process, where excess material is removed from a block of raw material using high-speed rotary cutting tools.

Steel or aluminum molds are typically made with this process. A major advantage is the superior level of accuracy that is achieved in this case. It is also relatively quick and cost-effective.

3D Printing (Additive Manufacturing)

Often, 3D printing proves to be one of the lowest cost approaches to injection molding. This is a relatively newer method used to make molds. It involves building up the mold in layers. However, it is not suitable for creating molds with complex geometries.

On the whole, advances in 3D printing technology have vastly increased the overall possibilities at hand, while still keeping costs at optimal levels.

EDM (Electrical Discharge Machining)

Some of the most complex mold designs are brought to fruition using this method. Yes, the costs involved may be high, but the results achieved in this instance are superior to most. Moreover, given the (largely) industrial application of this method, costs are often less of a concern than an exceptional quality of output.

3. Labor Cost

No matter how mechanized your manufacturing processes are, labor costs will always be involved. For instance, you will certainly require a machine operator to run your injection molding process. At the same time, depending on the geography in question as well as its labor supply market and currency dynamics, this may or may not prove to be a compelling factor.

4. Injected Material Cost 

The cost of the raw materials being injected into the mold will play a large role in the overall cost of the injection molded parts. There are many types of plastics that can be used for injection molding, including ABS, PS, PE, PC, PP or TPU. The more expensive the material, the more expensive the parts will be. In some cases, exotic materials may need to be used which can drive up the cost even further.

5. Others

  • Polymer resin – The quantity, as well as the quality (which has to be good, to ensure superior output) of polymer resin required, can dramatically lower cost. Keep this in mind while making your engineering resin selection.
  • Mold base – This is where all mold cavities find themselves, including a similar but not identical family mold (if present). If your mold is reasonably large-sized, it would dramatically increase the costs of the base. Of course, adopting a core cavity approach here involving wall cavities would help keep mold costs in check.
  • Cooling lines – Also referred to as cooling channels, they are vital to the speed and efficiency with which molds cool, allowing injected materials to solidify. Yes, ensuring their provision does add to variable costs.

How to Reduce Injection Molding Costs?

injection molding parts

Saving on production costs is paramount when it comes to manufacturing since it minimizes the final cost of the product. As we all know, the simplest trick to reduce the price per piece is by increasing the parts quantity since the upfront costs while machining and designing the mold can be used over more parts. In addition to that, you can also try the following several ways to reduce injection molding costs.

1. Evaluate your design for manufacturability(DFM)

One of the best ways to reduce injection molding costs is to design your part in such a way that it is easy to manufacture. This includes considering factors such as undercuts, wall thickness, and complex finishing. By simplifying your design, you can often reduce the number of mold cavities required, which will in turn lower your tooling costs. Here are a few directions to consider for optimization.

1) Eliminate or reduce the undercuts

Generally, the undercut features complicate and in some instances prevent parts injection. Eliminate them if possible. If you find it hard to get rid of them, try sliding shutoffs, pass-through cores or change the parting line and draft angles to simplify the mold build. If the technique is applied appropriately, it reduces the tooling costs.

2) Avoid wall thickness mold

One way to reduce the cost of injection molding is to use a thinner walled mold. Thinner walls require less material and therefore cost less to produce. In addition, thinner walls result in shorter cooling times, which can lead to reduced cycle times and increased productivity.

However, it is important to note that thinner walled molds may not be suitable for all applications. In some cases, thinner walls can result in parts that are weaker and more prone to breakage. As such, it is important to carefully consider the benefits and drawbacks of using a thinner walled mold before making a decision.

3) Minimize the complex finishing and appearances

Removing unnecessary features that do not add significant value to your final output is an idyllic way to reduce plastic injection molding costs. Textured surfaces, for instance, may simply not be needed. This holds true for cosmetic add-ons like bead blasting or high mold polish too. Remember that excess features might also require more mold cavities that further drive costs north.

4) Try to design self-mating parts

If you are undertaking a project with two interlocking segments, or a snap-together case, it’s recommendable to redesign the snaps to interlock instead of repeating the process for every snap.

2. Universal molds instead of Custom molds

If you do not require a custom mold, consider using the universal mold. These molds are often less expensive than custom molds and can still produce high-quality parts.

Also, If you need a custom mold, always consider having a CAD model in place prior to commencing the manufacturing process. It will help optimize designs and identify potential problems such as steep draft angles, unnecessary wall thicknesses, complex shapes, etc.

This will save you a lot of money (and a headache!) in the long run. Making mold instead of purchasing a new mold altogether when the need arises, is another nifty way to save some precious bucks. Self-mating parts in place of multiple modes also help on this front.

3. Minimize the number of cavities in your mold

The more cavities there are in a mold, the higher the cost will be. Therefore, it is important to minimize the number of cavities in your mold whenever possible.

One way to reduce the number of cavities is to use a moldflow analysis to optimize the design of your part. Moldflow analysis can help you to identify areas where cavities can be eliminated without compromising the function or aesthetics of the part.

4. Use lower-cost materials whenever possible

The cost of the material you use for your parts can have a significant impact on the overall cost of production. Where possible, use lower-cost materials such as ABS or polypropylene.

FAQ

Is injection molding expensive?

There is no simple and straightforward answer to this. But broadly, one can say that, while injection molding can be expensive, it need not always be the case. Factors such as production volumes as well as the complexity of the parts being manufactured play a key role in finally determining injection molding costs. When similar items with tight tolerances are made in large volumes, injection molding proves to be an inexpensive process.

How Much Does Injection Molding Cost?

It can range dramatically from a few hundred to hundreds of thousands of dollars. Think about the vast application of injection molding. There is a virtually limitless array of products made with them. In such a scenario, it is tough to specify an exact figure as far as the cost of injection molding goes.

Is Injection molding environmentally friendly?

Yes, not only can injection molding prove to be a cost-effective solution for manufacturing a plethora of plastic products, but it can be environmentally friendly too, just like 3D printing. Firstly, consider the optimal usage of plastic here with minimal to no wastage or seepage. Further, given that we deal with molten plastic here, several organic elements can be added to the mix to ultimately come up with eco-friendly plastic injection molding output.

Start with Rapid injection Molding

As we have repeatedly asserted throughout this article, there can be significant disparities in injection molding costs for plastic prototyping. Factors such as production volumes as well as utterly complex molds play a critical role in determining end costs.

Companies often choose rapid injection molding for their plastic prototyping needs because it is a cost-effective way to create prototypes quickly. Let get started with rapid injecton molding at WayKen.

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