Peter Fong, Sales Manager at Plastopia

By Peter Fong  Posted on Jun 2nd, 2016

6 Tips on Cheap Injection Molding

Cheap injection molding is essential especially when you have a limited budget for a new project, or just need a low volume of injection molding production. There is another reason why you need low-cost injection molding: your volume is high, but the end users need affordable plastic parts, like dispensable razors, plastic caps for toilet cleaners.

Whether your volume is 100,000 units or 100 units to start, in today’s post, I’ll share 6 practical tips you can use to get your own cheap injection molding.

Tip 1: Make a simple part design

The more complicated you parts are, the more money you would spend. Keep the part design simple is the most important factor for cheap injection molding. Undercuts on the parts add both tooling and molding production cost. Most of the undercuts could be avoidable if you redesign your part.

design guide for undercut-1

Also, keep the less molding processes as less as possible. Co-molding or overmolding seems great for bonding 2 plastic part together, but it is expensive as well. There’s solution like to make 2 separate parts, not via co-molding to save the injection molding cost. For overmolding, you may consider tapping the plastic parts manually by end users. This is often seen like fan shrouds of a battery or electronics housings.

Tip 2: Use a regular part color like black if possible, not white or clear

Black Part color for Cheap injection molding

Black is a popular color, which applies to a wide arrange of  plastic housings. If white or clear colors required, the injection molding manufacturers will have to use many resins to clean their machines first to avoid leftover colors. Also, a cleaner injection condition is required to avoid black spots. So if you want cheap injection molding, sometimes you would have to give up using white or clear colors.

Tip 3: Find a mold manufacturer at smaller size

When a manufacturing facility comes bigger, so does their profit, as they will have to pay off the factory rent, human expenses, and managing cost to maintain their running. However, these will make your injection molding expensive. So if you work with a small injection molding company, everything is based on lower pricing.

China injection molding manufacturer

Tip4: Let the mold maker know the mold life

To some customers, this could be difficult to decide. They would say: “well, I don’t know. It’s a new product, let the market decides” or “just give me the price, you don’t have to worry about the quantities”. Actually, an unsure mold life will surely make the injection molding not cost-effective. Why? The mold maker will have to use a longer mold life in case you need an increasing volume in future. So no mold life equals to longer mold life to injection molding manufacturers.

Injection Mold life

In other cases, the customers brief the molders the mold life clearly, like 1,000 pcs per order. 50,000 pcs for mold life. This will send them a message: the project is for the low volume of injection molding, and it should be as cheaper as possible. In China, mold makers might consider making the mold as below to lower the mold cost:

A) use a Multi-cavity molding solution if you have many parts. This will lower the setup tooling cost much.
B) use a non-prehard mold steel like 738H.
C) use existing mold base they have to save more mold cost.
D) make a simple mold design like manual molding solution, not automatic.

Multi-cavity mold for Plastic toys

Tip5: Compare offshore pricing & lead time with on-shore

With labor advantages, offshore injection molding like China is mostly competitive on pricing. However, you may compare China pricing with onshore’s, especially for a small run of 25 or 50 pieces. In this case, China injection molding may not be cheap, as local companies could use Aluminum molds Also, consideration on international shipping cost and lead time are also necessary.

Tip6: Give up cheap injection molding

The process of injection molding may not cheaper than you thought. For some parts, use other processes like 3D printing, CNC machining, blow molding or plastic extrusion could be more cost-effective. To give you an example, the below part design is much cheaper than injection molding: extrusion mold cost of US$1000, comparing injection mold cost US$3500.

plastic extrusion

Conclusion:

Cheap injection molding is possible if you get it right. Make a simple part design, communicate with your injection molder, and compare advantages of offshore and onshore. You will save your money for your project.

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