7 essential questions for choosing a molding supplier

You’ve got your product. You’ve got customers lined up. You’re ready to make your product a smashing success.

How do you choose the right partner to make your product?

The truth is that there is no single company that is the right fit for all products. Each has its strengths, and you’ll want a supplier that fits what you need in your business. Here’s 7 questions you can use to interview potential suppliers.

1. What types of materials do you work with?

Some molders specialize in exotic materials that are used in small quantities, have very particular performance profiles, and have high costs. If that’s what you need, seek out a molder that specializes in these parts. If you need regular polypropylene or HDPE parts, these exotic material molders will likely be much more expensive than what you need.

Likewise, if you would like to use recycled material in your products, ask what portion of the molder’s production uses recycled material. Recycled material can be much more challenging to run because of material contamination from things like paper or metal, and variances in material properties. A molder that runs long jobs of virgin material will often not have the suppliers or processes in place to handle jobs that use partly or entirely recycled feedstock.

2. What run quantities do you typically do?

Some molding operations specialize in very short runs, which require fast setups to be economical. At the same time, a molder specializing in short runs will likely be more expensive than a molder that is accustomed to long runs that last weeks or more.

3. How does mold maintenance work? What tooling equipment do you have? Am I responsible for mold maintenance costs?

Okay, that’s three questions. Sorry. But they’re all important ones.

Some molding shops do not have internal tooling operations with CNC automated mills, because it requires specialized skills. This will make it more difficult to conduct some types of tooling maintenance.

All tools wear, and breakdowns can happen in the middle of an important run you have for your customer. Having to rely on a third party introduces a dependency on a shop that may be backed up - possibly for weeks.

A molder with an integrated tool maintenance operation with the right equipment will often be able to fix the mold and get it back in the press.

Ask where the financial responsibility for tool maintenance is. Do you have to pay for regular maintenance? Or is it included in the per-piece rate?

4. What is the range in injection capacities you have? Shot sizes?

Some molders specialize in very small microparts. Others will make a part that could weigh fifty pounds. There are none that do both. Consider the properties of your part: is it big, or small? How much does it weigh? If you need 1mm plastic parts made on a 40 ton press, you don’t want to select a supplier whose smallest press is 300 tons and typically makes bigger parts. And vice-versa.

For a rough idea of how much tonnage your part will need, look at the projected area (that is, squish your part into 2-dimensional space), calculate the square inches of that projection, and multiply by about 2-3X.

5. Can you manage mold builds?

Many molders do not get involved in mold builds and will expect customers to be able to project manage mold builds. If you have time and experience in getting a mold built — or you already have a mold — that might be fine. But if you’d like project management help, ask if the molder can manage the mold build process for you.

6. Do you offer prototyping?

There are a variety of services that offer prototyping, but it can be helpful if your molder can offer the service, because they will catch part design issues that will become a problem during scaled production. Ask if the molder will handle 3D prototyping for you, using 3D printers.

7. What do your quality control procedures look like?

Is there a single person on each shift responsible for signing off on quality control? How often are parts checked? (Usually, parts are produced too quickly to check every part manually, which would be very expensive. But see what sort of sampling is done.) What kind of quality checks can be done - for example, cold temperature, brittleness, color, dimensions? How does the supplier store quality control specifications so it’s recalled correctly at each run?