How CNC trimming ensures quality parts

Applied automation improves thermoforming quality and throughput 

Most thermoforming companies today use CNC trimming to remove the formed part from the plastic sheet after cooling. Why is it so important?

Consistent quality is important for any successful industrial components. Things need to fit properly. Not just part-to-part, plastic products need consistency run-to-run. For years.

Thermoforming is cost-effective for parts produced in low to mid-volumes over years. However, small volume parts aren’t produced continually. Tooling pulled from storage to form the same product once every year requires still meeting the same high tolerances.

CNC trimming offers a key value. Let’s look at how it improves your large OEM parts.

What CNC trimming is

CNC (Computer Numerical Control) trimming is a precise, automated process that uses rotary tools for cutting, drilling, or milling materials. The tool is mounted on a gantry that provides movement in multiple axes.

This type of equipment is used across many industries to work on variety of materials, including metal and wood as well as plastic. CNC machines perform tasks with high accuracy and repeatability.

How thermoformers use CNC

The development of CNC trimming technology offered a new level of production performance for thermoformed plastic parts. After a plastic sheet is formed into the desired shape, the CNC machine trims or cuts away the excess material around the part.

The part is placed in a hold-down fixture, then the tool moves around it. The automated trimming reveals the final shape of the part with detailed features. It also creates vents, holes, slots, and other design features.

CNC trimming is functionally one step in the manufacturing process. It eliminates multiple procedures with hand-held tools. At the same time, it drastically improves quality, part-to-part consistency, overall throughput, and operator safety.

Automated trimming also supports advanced design features like undercuts, or slots and tabs for easy part interlocking. These minimize OEM assembly time and enhance product serviceability in the field.

1979 changed everything

The first CNC trimmer in the thermoforming industry was installed in 1979 at Profile Plastics in Illinois. Before that, quality and consistency depended on the skill of individual operators. It could differ between parts and even more widely between shifts. A single error could turn added value into costly waste.

Profile’s original CNC router was built by Thermwood Corporation for use in the woodworking industry. Programming that first machine was crude and temperamental compared to today’s systems, but it revolutionized plastics post-processing. Over the following 15 years, CNC trimming became a de facto industry standard.

Benefits

Using CNC trimming increases the throughput capabilities of heavy-gauge thermoforming, helping make it a viable production method. Specific benefits include:

• Precision: Highly repeatable and accurate
• Consistent: Critical for quality control
• Efficient: Reduces labor time
• Flexible: Easy to update via software
• Safe: Reduces risk of worker injury

From tools to robotics

There are several different types of CNC machines used for trimming thermoplastic parts.

• 3-axis routers: Trim simple shapes from flat or moderately contoured parts.
• 5-axis routers: Capable of handling complex 3D shapes, they can trim from multiple angles and handle deep draws or undercuts.
• 6-axis robots: Offer extreme flexibility and versatility, adapting to any angle with extended reach.

5-axis CNC routers are most common in the thermoforming industry for trimming automation. Moving the tool in X, Y, and Z axes, these machines offer highly repeatable positional accuracy. They program quickly using standard CAD/CAM software.

New robotic trimmers mount tools at the end of a mechanical arm, ideal for awkward shaped parts. Along with rotary tools, robots can also handle ultrasonic tools for welding. However, they offer slightly less accuracy than 5-axis machines and are slower to program.

Generally, the tighter the tolerance, the higher your manufacturing cost will be. However, efficient trimming equipment helps control production costs. 5-axis CNC trimming delivers high production volume optimized for the tightest tolerances.

Looking forward

Minimizing secondary processes through CNC machining makes large part thermoforming easier while improving quality and maintaining value of each part. These automated machines deliver critical precision and efficiency for plastics manufacturing.

Profile Plastics has unique experience and expertise in employing CNC tools and robots to deliver superior OEM parts. We introduced it to the thermoforming industry over 45 years ago in our continuing drive to upgrade quality and volume.

Today we operate 24 advanced 5-axis trimmers as an integral part of our state-of-the-art high-volume operations. These machines directly contribute to our throughput, ready to deliver high quality parts for years to come.