SPC 160 Twin Screw Replacement and Troubleshooting Guide

Site Observation Summary

During replacement of the SPC 160 parallel twin-screw assembly, the client company observed apparent differences between the new and old screw/barrel components and raised concerns about whether the replacement design could affect extrusion performance. The following analysis compares the component designs, reviews the current-instability issue observed after replacement, records the on-site findings, and summarizes the corrective actions that restored normal production.

New and Old Screw Design

 New and Old Barrel Design

Review of the engineering drawings shows that the new and old screw geometries are essentially consistent. The main structural difference is in the barrel: the original barrel uses a three-section configuration, while the upgraded barrel uses a two-section configuration.

The original extruder used a traditional three-section barrel. During long-term production, material could remain in the final barrel section, creating a potential accumulation area.

When PVC/SPC material remains in a high-temperature zone for an extended period, the retained material can degrade and form burnt residue, which may contribute to black spots and unstable product quality.

This observation is consistent with the earlier SPC production analysis, where accumulated and degraded material was identified as an important source of intermittent defects.

To reduce material retention, the upgraded barrel was changed to a two-section design to improve material flow and reduce the possibility of accumulation. Based on the drawings reviewed for this replacement, no significant change was identified in the screw geometry itself.

 Evidence of Burnt / Degraded Material

July 22, 2026 – Current Instability After Screw Replacement

The client company started the extruder after installing the new screws and observed unstable motor current, uneven material discharge, and incomplete plasticization.The client company initially suspected that the new screw geometry might be different. After StarsPlas discussed the condition with the on-site operator and the screw manufacturer, the preliminary technical assessment was that the screw structure was unlikely to be the primary cause. StarsPlas considered improper installation or alignment to be more probable, and the issue was not considered to be related to the formulation.

Comparison of the Two Screw Types and Current Changes Before and After Replacement

July 24, 2026 – Preliminary Root Cause Assessment and Support Plan

StarsPlas advised the client company that the most probable cause was incomplete or incorrect installation of the replacement screw assembly. Because this type of SPC 160 parallel twin-screw replacement requires precise axial positioning, barrel-to-gearbox alignment, and correct relative positioning of the two screws, an on-site inspection was recommended.

To ensure correct installation and commissioning, StarsPlas proposed sending a screw engineer to the client company site in Brazil for inspection, reassembly, commissioning, and operator guidance.

StarsPlas would cover the engineer’s international airfare. The client company would cover local accommodation, transportation, meals, and the agreed daily service charge.

July 28, 2026 – On-Site Engineering Support Confirmed

StarsPlas confirmed that a screw engineer would travel to the

client company plant in Brazil to install and commission the screw assembly and provide practical installation training to the local team.

August 4, 2026 – On-Site Inspection Findings

The StarsPlas screw engineer arrived on site and found an excessive approximately 11 mm clearance between the screw and barrel assembly. During disassembly, the secondary-shaft sleeve was found jammed and required a three-jaw puller for removal. The inspection also found a height/alignment mismatch between the screw axis and the distribution gearbox shaft. The machine base screws were adjusted to bring the screw axis and gearbox shaft to the same level.

A trial run was then performed. Motor current remained unstable and plasticization was still incomplete, confirming that further mechanical inspection was required.

After the assembly was opened again, the rear connection between the screw and the machine was found not to be fully seated, and the installation-clearance error remained excessive.

Rear screw/shaft connection, barrel-side inspection, and motor-current data during troubleshooting.

August 5, 2026 – Corrective Action and Validation

A 5 mm shim was installed at the rear of the screw assembly. This prevented the sleeve from binding, reduced the excessive screw/barrel clearance, and corrected the rear seating condition. The engineer also instructed the team that the two screws must enter the spline sleeves in the correct relative tooth position and remain symmetrical; misalignment between the two screws is not acceptable. After reassembly and restart, the motor current became stable, plasticization returned to normal, material discharge was uniform, and production resumed normally.

Extrusion and board production after installation correction and restart.

Reference Information

Recommended replacement interval for the screw and barrel: 3-6 months.

Reference replacement video (conical twin screw):

https://youtu.be/QRNYET74LK8?si=mG4oevbgu_xmHpev

Commercial reference – SPC 160 Twin Screw only: FOB Shanghai USD 18,000.

Commercial reference – SPC 160 Twin Screw + SPC 160 Twin Barrel set: FOB Shanghai USD 40,000. Production lead time: approximately 2 weeks; estimated sea transit time: approximately 45 days.

Assembly Prohibited Practices

1. Do not move only one screw independently in a single axial direction. This can cause the screw to scrape against the inner wall of the barrel.
2. Protect the screw-flight working surfaces from impact or collision. Surface damage can lead to material accumulation, scorching, poor plasticization, and accelerated wear.
3. Do not start the machine if a sealing gasket is damaged, missing, or incorrectly installed, as this may cause material leakage during production.

160 Parallel Twin Screw Change SOP