Choosing Low Volume Injection Molding or Thermoforming for Short Runs?

Not every order for custom plastics is going to require 100,000 identical components. In fact, smaller orders for just a few thousand pieces are common, especially if you want to try a new product or test out a component to see how it holds up or works for your business. How can you make a smaller order both time-efficient and cost-effective while getting what you need? Our injection molding company in North Carolina is looking at whether you should choose low volume injection molding or if thermoforming may be the right fit for your company.

What Is Low Volume Injection Molding?

Also called “short-run manufacturing,” low volume injection molding generally refers to an order that is fewer than 10,000 pieces. Think of it as the bridge between the prototype and high-volume production that allows for a limited investment in materials while getting the product in use quickly.

Traditional injection molding is ideal for high-volume manufacture because the upfront costs tend to be higher due to the cost of tooling. Molds are generally made from steel or a copper alloy that can withstand the highly pressurized injector and not bend from the force of the melted plastic. Their intricate designs and heavyweight tend to require more time and money to fabricate.

Low volume injection molding is generally completed using aluminum molds, as opposed to steel or copper alloy, and the injection tool is set at a lower pressure to prevent damage to the mold. This reduces the cost of tooling from 5 to 25 percent and aluminum is faster to shape into a tool, reducing the lead time.

Advantages and Disadvantages of Low Volume Injection Molding

So, what makes low volume injection molding the right choice? Advantages include:

• Small components and parts that can have varying thickness and high levels of detail;
• Offer the opportunity to affordably “test run” a plastic component – perfect for pilot programs;
• Reduce up-front investment – while per-unit prices may be higher than they would be in bulk, the overhead is lower.

But what are the disadvantages of low volume injection molding? When is it not ideal for your project?

• While it may be faster and less expensive than traditional injection molding due to the lower tooling cost, the fabrication process is still more than thermoforming, typically
• Larger components and pieces may not be cost-effective or time-efficient to manufacture, such as vehicle dashboards or luggage casing.
• Part design restrictions to ensure the lower pressure of material injection will still achieve accurate results (ie: improved draft angles, minimal undercuts, and less severe angles)

What Is Thermoforming?

Thermoforming involves heating large sheets of plastic until pliable, then fitting them around a custom fabricated aluminum tool. For a precise shape, we either use vacuum forming – suctioning out the air between the tool and the plastic to ensure a tight fit, or pressure forming– blasting the plastic sheet with highly pressurized air while a vacuum suctions the air between the sheet and the tool, to get the tightest possible fit against the mold. Vacuum forming is ideal for larger pieces that don’t require as much detail or as sharp of angles, pressure forming is a bit more intensive but can be an excellent alternative to injection molding due to the amount of detail it can get.

Advantages and Disadvantages of Thermoforming

Typically, low to mid-volume manufacturing does tend to favor thermoforming due to the following advantages:

• The mold is single-sided and made from lightweight aluminum, minimizing lead times and lowering costs;
• Larger pieces are easier to fabricate through thermoforming and size has minimal impact on lead time and cost;

While lower costs and faster lead time are definitely perks to thermoforming, there are disadvantages:

• High levels of detail, such as variable thickness and sharp corners, especially in smaller parts and components, are difficult to achieve;
• If the part goes into a continued manufacturing cycle or a second, much larger, run is needed, it may be better to shift to injection molding.  /li>

Schedule a Free Quote for Custom Plastics

Whether you need 1,000 or 100,000 custom plastic components, we will work with you to determine the best method of manufacturing to provide you with the durable, high-quality plastics you need at a low per-unit price with as quick a lead time as possible. We proudly serve the Mid-Atlantic and Southeast, including North Carolina, South Carolina,  Pennsylvania,Maryland, Tennessee, Georgia, and Virginia.