Screw Rebuilding and Repair

At R. Dray Mfg., our goal is to provide the most economical way to get the most out of your extrusion or injection molding operation. The feed screw is the prime mover in the extrusion and injection molding process. Although careful consideration should be given to the proper screw design for your operation, wear is a key factor that impacts performance. As pioneers in the plastics industry we have developed many of the standard screw building and rebuilding processes that are used today. With the same rigorous quality standards as our custom screw solutions, we can rebuild your worn screws to save you time and money.

 
 

Screw Wear

The performance of a given plasticating unit is defined by the feed screw’s ability to melt and convey the desired rate and quality of polymer to the die or mold. As the screw flights, channel geometry, and surface treatment wear, performance and quality degrades while energy consumption soars. The overall screw design and material(s) processed has a major impact on the wear-life of the plasticating unit, so it is vital to monitor screw wear and performance, regardless of application. Minor wear will have little effect on the overall performance - as machine parameters can be adjusted to maintain productivity. As the radial clearance gap between the screw and barrel increases, energy costs and cycle times rise while rate and quality plummet. To avoid costly downtime it is important for every company to have a robust maintenance program in place. When screw wear isn't monitored, the overall wear on the screw can become so severe it is no longer economical to rebuild - leaving you with crippling downtime that can ultimately cost more than the components you attempted to salvage. 

Let R. Dray Mfg. work with you and your team to develop a screw rebuilding/replacement program that will increase your productivity and profitability!

 

Screw Rebuilding / Repair Experts

When we receive your screw for potential rebuilding, our team performs a thorough inspection of the overall condition of your screw as well as the current design. When it is cost effective we can refurbish your screw to like new condition, re-chrome, nitride, hardface, and even re-cut the existing design to improve performance and wear-life. When a feed screw is rebuilt properly, without narrowing of flight widths, the screw can be rebuilt time and time again - pushing massive savings to your company. With almost 50 years of screw design, manufacturing, and rebuilding experience, we have developed many of the standard feed screw building and rebuilding processes used in the industry today. Trust the experts in screw design, manufacturing, and rebuilding with your production. 

 

Things to consider:

  • How worn are the screw flights and root
  • What are the wear characteristics
  • Can the current screw design be greatly improved
  • Can the surface treatment be improved
  • Cost of Repair vs. Replace
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Worn screw Flights

When we receive your damaged screws for rebuilding services, our expert team performs a thorough inspection. Once the extent of the wear, wear patterns, and overall screw design is quantified, our team will make recommendations for the most cost effective way to get your production up and running. We can manufacture and rebuild screws up to 20" in diameter and sections up to 40 feet in length!

 

high quality hardfacing

With almost 50 years of screw manufacturing experience, we have developed many of the standard manufacturing and rebuilding processes in the industry today. When rebuilding your worn screws, our team applies the highest quality hardface welds in the industry. We offer a full range of hardfacing options to accommodate any molding challenge you may face.  

 

Re-establishing OEM Tolerances

We re-establish OEM tolerances to all crucial screw dimensions. Once the final OD, channel geometry, drive end, etc. are repaired within spec, our team polishes the screw to like-new condition. We offer a full range of secondary screw treatments (re-chroming, nitriding, encapsulation, etc.) to improve wear life. 

 
 
 

Excessive Screw Wear

It is important to monitor overall screw and barrel wear before performance and efficiency plummets. Wear can become so severe that the screw is too costly to repair and you are faced with excessive downtime. Proper screw and component design partnered with a robust maintenance program will ensure that your company is profitable and competitive in the marketplace. 

 
 
 

Stay Ahead of the Wear!

Every company should have a robust preventative maintenance program in place to eliminate costly downtime. When we build or rebuild screws and components we work closely with the customer to develop a plan that works. Scheduled annual, biennial or triennial wear evaluation can ensure that you stay ahead of the wear! Rebuilding or replacing screws, barrels, and components before performance plummets and energy costs soar is crucial for overall productivity. Ask us about a tailored screw and barrel rebuilding/replacement program designed with your company's goals and schedule in mind!

 

How Much Money are You Losing?

Excessive screw and barrel wear comes with rate and quality loss and rising energy consumption. When the radial clearance between the screw flights and barrel wall increase, leakage flow is inevitable. In extrusion applications the operator will typically see a reduction in rate, forcing higher rpms to achieve the desired output. As the material leaks over the screw flights, the material experiences excessive shear. This raises melt temperature, and is only compounded with higher rpm.

In an injection molding environment, screw, barrel, and valve wear can cause a host of issues. Worn components can cause erratic cushion variation, and even the inability to hold a cushion at all. Worn, and/or damaged components will cause a reduction in plasticizing efficiency, increasing normal recovery time and melt temperatures, naturally increasing overall cycle times. Scrap rates will soar due to potential streaking, burns, and non-uniform parts due to poor melt quality and degradation. Instability in the molding process and increased melt temperature caused from excessive wear will increase cycle times, energy consumption, and waste. Injection screw assembly and barrel wear all leads to wasted time and money!

To help you and your team better understand and plan for screw and barrel wear, our team at R. Dray Mfg. has developed a simple calculator that helps estimate the potential reduction in productivity and profitability from your screw and barrel wear in extrusion applications (a comparable calculator for injection applications coming soon!).