Many factors of the part, such as its roughness, material, cycle time and other aspects, can greatly affect its price. Here are our best suggestions for reducing the price of parts without sacrificing the parts needed for successful injection molding.
1. Selection of materials
You can reduce the cost can be reduced by knowing the best material for your parts. The first factor to decide which material to use is the placement of the part. For example, will it be placed indoors or outdoors or next to the oven? Besides, the temperature, durability and stability requirements of the parts can also help you understand the material requirements. We often recommend Matweb and Nexeo Solutions to our customers as two great resources for material performance recommendations. Tip: A quick way to determine materials is to look at the materials of existing products that operate in an environment similar to yours, which needs no reinvention of the wheel.
The second factor to be considered is the price per pound. Based on characteristics and advantages of the materials, their price may vary greatly. For example, HDPE (high-density polyethylene) costs about $1.50 per pound while materials such as polysulfone cost $12-15 per pound. Nexeo Solutions is the best resource for checking the approximate cost of materials. You may use cheaper materials while meeting requirements for your parts and can save money with the most cost-effective option.
2. Cycle period
The faster the cycle, the lower the indirect cost per part will be. Cycle time refers to the time required for a part to form during injection molding. The cycle time depends on the mold structure, the water cycle, and its ability to cool the plastic into a solid state.
The cooling time of the part depends largely on the material you choose. For example, high-density polyethylene cools very quickly while molds for materials such as polysulfone need to be heated before they cool down (cycle time added). Tip: If your mold needs heating/cooling, please make sure that you have a water loop in your mold because this will change the cycle and appearance of the part.
During the construction of the mold, you can determine the cycle time according to the material you choose. For example, aluminum has a faster heat transfer rate, so its cycle time is faster. However, aluminum is also prone to be damaged, especially when complex mold geometry or plastic material types pass through it. Because the heat transfer rate of steel is slower, it needs more time to process the steel, but it is more durable.
3. Finishing
By knowing finishing processes, you can save a lot of unnecessary costs. We once saw customers quote for parts with Class A finish (mirror finish), but upon further conversation, we found that that D-1 finish (matte finish) was just as effective for the use of their parts. Choosing finishes according to your needs can save you a lot of money. We recommend you to refer to the SPI Finish Table and related industry standards for roughness so that you can determine the best parts suitable for your parts.
In general, the higher your requirements for the gloss of the part, the higher the price of the tool. This is because it takes more man-hours to make a part glossy, which will greatly increase time and cost of the early stage.
Xometry offers a wide range of finishing processes for injection molding. We can also provide additional finishing according to specific situations. Instead, you should add your demands to the quote request.
4. Post-forming operation
The more operations required after molding, the more your price will rise as additional labor is involved.
Processing slots, holes and taps should be considered if necessary. This will greatly increase their cost. Please add these features into the part design and mold into it.
Elaborately made cooling units can add the cost, but you can eliminate the demands for cooling units based on the materials selected and part design coring.
The level of packaging required for your part will also save you additional money. If your parts are not fragile products, there will be no need for additional packaging. For example, if an egg holder is not needed, a Gaylord box is sufficient to protect your cargo. This also applies to special handling requirements at the time of delivery.
It is also important to decide how much special inspection and testing you expect to do on your part. If you need to make many parts, do you need to inspect each part? Or do you just want to check one out of every dozen or every hundred? Do you need us to test your parts before delivery? Are you able to test them after you receive them? Knowing what you don’t need will save you a lot of money.
Key points
The best way to reduce the cost of a part is to know exactly what the parts will be used for. This will help you understand what it needs and what it doesn’t need. When it comes to surface treatment, material or post-form operation of a part, you can save money by determining the break-even point that you chose.
About Xometry
This paper is written by various contributors at Xometry. Xometry is a leading resource for CNC machining, sheet metal machining, 3D printing, injection molding, vacuum duplexing and other manufacturing fields.
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