A New Color Spectrometer for Plastics Quality Control

A White Paper on a New Multi-Channel, In-line Spectrometer that is Dramatically Improving Color Quality Assurance in Plastics Manufacturing, sponsored by Liad

Plastics and injection molding is a relatively simple process. Resins, additives and masterbatch are blended together, pumped into a mold (in the case of injection molding) and a new piece of plastic is created. This process can theoretically continue uninterrupted indefinitely.

The challenge for plastics manufacturers, including extrusion and blow film producers, oftentimes begins after the new plastic is produced, when it will be checked by quality control to determine that the new plastic object has the correct color shade. Depending on the use, shape and size of the new plastic piece, engineers performing color quality control may check every new piece, or a sample of several pieces at different intervals.

The process of plastics color quality control requires considerable expertise, as the seemingly simple task of checking plastics color can in fact quite complicated. For instance, the costs associated with color spectrophotometer instruments are high, as are the costs of product rejects and lost opportunity costs. In addition, choice of QA instrumentation will have a direct correlation with the location of color quality control. While color verification should ideally be performed at the processing line and check every piece of plastic, in many instances, the quality control process for color is performed at an external location or factory laboratory due to the shortcomings of existing handheld and in-line spectrometers.

This white paper examines the technology of a new portable spectrometer that integrates seamlessly within the production line, and opens up the possibility for new levels of quality control, fewer product rejects and enhanced raw material savings for plastics manufacturers.

The demands placed on quality control in today’s highly competitive and cost-sensitive plastics-manufacturing market have never been greater. It’s easy to understand why. Even the slightest deviation in pigment concentration, base-material optical properties, additive quantity, batch consistency, or quality of the injection-molding and extrusion machines can substantially alter color shading. Unwanted variations in shading — resulting in product rejects or excessive dosing of masterbatch additives — negatively impact the factory’s bottom line.

Today more than ever, quality control equipment, and color spectrometers in particular, play a paramount role in providing plastics manufacturers a competitive edge by helping to keep production costs low, quality levels high and the amount of product rejects to a minimum.

Spectrophotometers for Color Quality Control

Spectral technology has been used by quality control engineers for assuring plastics coloring for many years. But despite the tremendous technological improvements in color spectrometers, existing bench-top and handheld spectrometers are hindered by design limitations that impede product-line integration and keep system costs high. To date, spectrometer manufacturers have not succeeded in designing a cost-effective spectrometer that enables in-line and real-time applications for color quality control.

Furthermore, as color spectrophotometer systems are highly sensitive, plastics and injection molding quality control frequently takes place in laboratories away from the processing lines under the supervision of highly trained personnel, oftentimes requiring frequent recalibration, specific lighting and even physical contact with the measured part. And even in plastics factories where quality control is performed on the production line, existing color spectrometers are expensive, cumbersome, limited in their applications and do not perform in-line adjustments to the production process.

Optical Probes Used for Color Spectrophotometers

One of the primary detractors and limitations of the popular spectrometers available today are the optical probes used. Essentially, each probe is in effect its own spectrometer. A single spectrometer is associated with a single probe or test application, and multiple spectrometers are thereby required to test multiple parameters. As effective color quality control testing involves much more than just color, but also must consider haze, transparency and opacity, existing spectrometers have become a costly financial burden on the factories looking for a well-rounded solution for performing effective color quality assurance on plastics.

A New Color Spectrophotometer

To address the challenges of improving plastics color quality control and minimizing product rejects, while at the same time maintaining production efficiency (and minimizing the drain on masterbatch inventory), an Israel based company has developed a versatile color spectrometer that integrates within the production line and opens up the possibility of real-time analysis for all new plastic products.

The company’s patented in-line spectrometer can be placed at the molding machine or extruder for all types of plastics and films, and makes possible a range of high-demand and real-time QA applications including digital setting of the pass/fail criteria and in-line testing of product color.

The new color spectrometer’s versatility can best be expressed by its novel optical probes. For the first time, transmitted color, opacity, reflected color shade or haze can be measured simultaneously or separately according to quality control requirements, by allowing multiple probes to be simultaneously used, and enabling easy switching between probes within the spectrometer.

The company’s versatile spectrometer can also be operated in either differential, absolute, or detailed absolute modes, enabling measurement of new-product color differences with either a reference part or coordinated L*a*b*.

Finally, the new color spectrometer offers plastics manufacturers added value by enabling real-time analysis and in-line correction of masterbatch and color additive dosing quantities for 100% of machine cycles by communicating with the additive feeder or other plastics auxiliary equipment.

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