Many factors of a part, whether it's the roughness, material, cycle time, or more, greatly affect its price. Here are our top tips to reduce the price of your parts without sacrificing the components you need to succeed.
1. Material Selection
You can keep costs low by understanding what the best material for your part is. The first factor for deciding which material to use is where your part will live. Will it be outdoors, indoors, next to an oven? The temperature, durability, and stability needs of your part will help inform your material needs. We often recommend Matweb and Nexeo Solutions to our customers as two great resources for material property recommendations. Pro Tip: A quick way to determine your material is to look at the materials of existing products that perform in a similar environment of your product - no need to reinvent the wheel.
The second factor to consider is price per pound. Materials can vary greatly in price depending on their features and advantages. For example, HDPE (High Density Polyethylene) can cost around $1.50 a pound, whereas a material like Polysulfone can range $12-15 a pound. Nexeo Solutions is a great resource to view the approximate cost of a material. When you are able to use a cheaper material without sacrificing a requirement for your part, you can save money by opting for the most cost-effective choice.
2. Cycle Time
The quicker the cycle time, the less overhead cost there is per part. Cycle time is how long it takes for a part to be formed during the molding process. Cycle times are dependent on your mold build, water circuits, and its ability to cool the plastic to a solid state.
The cooling time for your part will greatly depend on the material you select. For example, HDPE cools very quickly, while a material like Polysulfone will need its mold to be heated which will then require it to be cooled (adding time to the cycle). Pro Tip: if your mold will need to be heated/cooled, ensure that your mold has water circuits in it, as these will change the cycle time and appearance of your part.
The mold build can also dictate cycle times depending on the materials you select. For example, aluminum has a faster thermal transfer rate and therefore will lead to faster cycle times, but aluminum can also be damaged easily, especially with complex mold geometry or type of plastic material ran through it. Steel will take longer to machine because it has a slower thermal transfer rate, but it is more durable.
3. Surface Finish
Understanding the surface finish your part needs can save a lot in unnecessary costs. We’ve seen customers quote a part for an A class finish (mirror polish), but upon further conversation discovered a D-1 finish works just as well (matte) for the use of their part. Selecting a finish based on what you need can save a lot of money. We recommend referring to an SPI Finish Chart to compare the industry standards for roughness and determine what is best for your parts.
Overall, the higher the luster you require for your part, the higher the price of the tool will be. This is because more labor hours are required to make a part shiny, which significantly adds to the time and upfront cost.
4. Post-Molding Operations
The more post-molding operations required, the more your price will go up because of the additional labor involved.
Only consider machining slots, holes, tapping, etc. when necessary, because these can greatly increase its cost. Design these features into your part design and have these molded in.
Elaborate cooling fixtures can increase costs, but you can eliminate the need for a cooling fixture depending on the material you choose and part design coring.
The level of packaging your part requires will also save extra money - if your part is not fragile it will not require extra packaging. For example if an egg crate is not necessary, a Gaylord box can be sufficient to protect your delivery. The same applies for special handling requirements for your delivery.
It’s also important to decide how much special inspection and testing you’d like to request for your parts. If you’re making many parts, do you need each one to be inspected? Or just one out of every dozen or hundred? And do you require your parts tested by us before delivery, or are you able to test them upon receiving them? Knowing what you can do without will help you save big.
The best way to reduce costs for your parts is understanding exactly what your part will be used for, which will help inform you of what it does and does not need. Whether it’s the surface finish, material, or post-molding operation of the part, you can save money by figuring out where the breakevens are in your options.
Xometry is here to help. Get started with Xometry’s Injection Molding service through our request for quote page, and receive a quote within one business day!