Fully Automated Polishing of Plasticizing Screws at ENGEL

Surface Technology Fully Automated Polishing of Plasticizing Screws

2026-01-20 From Stefan Lenz 4 min Reading Time

Engel Austria relies on a fully automated vibratory finishing concept for the surface treatment of plasticizing screws. Two trough vibrators, an intelligent setup system, and a closed-loop water circulation system sustainably enhance efficiency, quality, and process reliability.

The fully automated polishing cell consists of two trough vibrators, a cleaning system, the loading station, and a fully automated Z 1000 centrifuge. Parts are transported via a gantry system.(Bild: Rösler Surface Technology) — The fully automated polishing cell consists of two trough vibrators, a cleaning system, the loading station, and a fully automated Z 1000 centrifuge. Parts are transported via a gantry system.
(Bild: Rösler Surface Technology)

Plasticizing screws are among the key components of every injection molding machine. Their surface quality has a direct impact on plasticizing performance, energy efficiency, process stability, and ultimately on the quality of the plastic parts produced. For this reason, Engel Austria manufactures its plasticizing screws entirely at its St. Valentin facility—including the complex surface finishing process.

To meet the growing demands for productivity, reproducibility, and cost-effectiveness, Engel has comprehensively automated the polishing processes for plasticizing screws. At the heart of the new solution are two fully automated trough vibrators that are integrated into an intelligent system design.

How Plasticizing Screws Are Polished Fully Automatically

Before the changeover, the plasticizing screws—which were up to three meters long—were polished in a single-stage vibratory finishing process. In particular, the manual loading and unloading of the heavy components was time-consuming and represented a bottleneck in the production process. The goal of the new concept was therefore to significantly reduce the amount of manual handling required while simultaneously shortening turnaround times.

eileaufnahme wird automatisch in den Trogvibrator abgesenkt — The workpiece holder is automatically lowered into the trough vibrator and placed in loops on the left and right. This allows it to move freely among the abrasive media and be easily and automatically removed again.
(Source: Rösler Surface Technology)

Today, the snails are loaded into the trough vibrators fully automatically via a gantry system and removed again after polishing. The gantry system is already integrated into upstream processing steps, ensuring a consistent level of automation across multiple process stages.

Innovative setup concept reduces downtime

A key component of the new solution is a specially developed setup concept. The plasticizing screws are no longer clamped in the traditional manner, but are simply inserted into floating workpiece holders. These securely hold the components while still allowing for the necessary freedom of movement during the honing process.

The advantage: Setup time is reduced to about 15 minutes, which results in a significant increase in productivity, especially when dealing with frequently changing screw types and batch sizes. At the same time, process reliability is improved, as sources of error associated with manual clamping are eliminated.

Why the Surface Quality of Plasticizing Screws Is Critical

Instead of a single-stage polishing process, Engel now uses a two-stage Keramo-Finish process. The first step involves rough grinding, followed by fine grinding in a second trough vibrator. This separation allows for precise process control and further improves surface quality.

The new setup concept further reduces processing time. Previously, the worms had to be clamped on both sides; now they are simply placed into the part holder.(Bild: Rösler Surface Technology) — The new setup concept further reduces processing time. Previously, the worms had to be clamped on both sides; now they are simply placed into the part holder.
(Bild: Rösler Surface Technology)

The resulting surface roughness is less than Ra 0.1 µm. At the same time, the machining time per screw has been significantly reduced. This is also made possible by the optimized initial quality of the components, which already emerge from the preceding grinding process with very uniform surfaces.

High-Performance Drive Technology for Reproducible Results

The trough vibrators used are equipped with powerful direct-drive motors that are specifically designed for use in industrial surface finishing. The unbalanced motors ensure a uniform relative motion between the workpiece and the abrasive media, thereby delivering consistent polishing results along the entire length of the auger.

Thanks to precise process control, even long and complex geometries can be machined uniformly—a crucial factor in the quality of modern plasticizing screws.

Sustainable surface treatment using a closed-loop water system

In addition to the two trough vibrators, the new polishing cell includes a loading station, a specially designed cleaning system, and a fully automatic centrifuge. The centrifuge treats the process water so that it can be reused in a closed-loop system.

This concept not only reduces water consumption but also lowers operating costs and supports Engel's sustainability goals. At the same time, the integrated cleaning system ensures that the screws are clean and ready for the next process immediately after polishing.

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Parallel processing increases plant availability

Another advantage of the new system layout is parallel processing. While one screw is being polished, the next component can already be loaded or unloaded. This reduces downtime to a minimum and significantly increases system availability.

Die beiden Trogvibratoren R 800/3200 TSD-15 sind durch den Direktantrieb mit Spezial-Unwucht-Motoren an den Stirnseiten besonders leistungsstark und flexibel. — The two R 800/3200 TSD-15 trough vibrators are particularly powerful and versatile thanks to their direct drive system, which features special unbalanced motors mounted on the ends.
(Source: Rösler Surface Technology)

Automated vibratory finishing technology reduces setup times and costs

For a long time, the automated loading and unloading of trough vibrators was considered technically challenging and economically unfeasible. The concept implemented at Engel demonstrates that vibratory finishing systems can indeed be integrated into highly automated manufacturing environments today.

The system is not limited to plasticizing screws; in principle, it can also be applied to other industries and applications—such as mechanical engineering, aerospace, or medical technology.