Food and Pharmaceutical Industries and Materials Handling

Application: Manufacturing, Coating and Repairing Screw Shafts

Screw shafts perform important conveying and dosing tasks in production and conveyor systems – for example in the food and pharmaceutical industries as well as in materials handling and logistics. Their geometry, material and surface properties must be precisely matched to the respective system, the material being conveyed and the operating conditions. Depending on the application, the objective may be to additively manufacture a new screw shaft, protect highly stressed areas against wear by applying a coating or repair a damaged component.

For these applications, OSCAR PLT primarily uses Laser Metal Deposition with Wire. This process enables material to be applied selectively to an existing screw shaft or the screw flights to be built directly onto a tube. The appropriate welding strategy, material selection and any necessary pre- and post-processing steps depend on the component geometry, base material, operating loads and the required machining result.

Targeted processing of screw shafts

Building application-specific screw flights

When a screw shaft is required for a specific system, the diameter, pitch and spacing of the screw flights must be matched to the respective requirements. Variable flight spacing or different diameters within a single component can also be taken into account during digital planning. Selective material deposition allows the screw flights to be built close to the required final contour.

Compared with conventional manufacturing as a welded construction, Laser Metal Deposition offers the advantage of enabling flexible implementation of geometric variations and combining the build-up of the screw shaft with coating in a continuous process chain. This can reduce downstream processing steps and shorten delivery times.

Applying targeted wear protection

The material being conveyed and the operating conditions determine where and to what extent a screw shaft is subjected to stress. Abrasive media can cause material loss, particularly on the screw flights and other contact-loaded surfaces. A deposited layer adapted to the specific load protects these areas without requiring the entire shaft to be manufactured from a wear-resistant material.

OSCAR PLT processes both solid and flux-cored wires for this purpose. The adjustable energy input used in Laser Metal Deposition enables a strong bond between the deposited layer and the base material while subjecting the component to comparatively low thermal stress. This can limit distortion and the need for post-processing while extending the service life of the screw shaft.

Automated restoration of damaged contours

Abrasion, spalling or other local damage does not necessarily mean that the entire screw shaft must be replaced. Depending on the condition of the component, missing material can be selectively added and the required contour rebuilt.

Combining component scanning, digital path planning and automated material deposition makes it possible to establish a reproducible repair process chain. The damaged area is recorded, the required material deposition is planned digitally and then carried out in a controlled manner. This can reduce repair times and enable recurring repair tasks to be automated cost-effectively.

A successfully implemented application

In a previous customer project, OSCAR PLT initially manufactured several application-specific screw shafts for different requirements. Laser Metal Deposition with Wire, also known as wire-based LMD, was carried out using a compact ProFocus system. Both screw shafts were built additively and conventionally manufactured welded constructions were coated with wear protection.

A stainless martensitic chromium steel with the material number 1.4115 was used as a solid wire to build the screw flights. A flux-cored wire was used for the wear-resistant layer – in this case WA Hardface LD with a wire diameter of 1.2 mm. This allowed the geometric build-up and surface protection to be precisely adapted to their respective functions using different materials.

In addition to the screw shafts, the process development resulted in a customer-specific system based on the OSCAR LaserCell. It enables the customer to manufacture and coat screw shafts independently using the coordinated material deposition process or to refurbish them where the initial condition is suitable. The project therefore demonstrates both the capabilities of the process and the expertise of the OSCAR PLT team in process and system development.

Processing multiple materials in a single setup

Building a screw flight and protecting a highly stressed surface place different demands on the filler material. The ProFocus system can process multiple wire materials in a single setup. This makes it possible to build the geometry using a solid wire and then coat a highly stressed surface with a suitable flux-cored wire.

The wire material can be changed within just a few minutes. Unlike powder-based filler materials, this does not require time-consuming cleaning of powder feeders or supply lines. OSCAR PLT can develop the appropriate process parameters and provide them for the respective process via the OSCAR Competence Center, or OCC for short.

During Laser Metal Deposition, the wire is continuously fed into the process zone, melted and applied to the component in a controlled manner. Laser power, wire feed rate, motion control and welding strategy are adapted to the material, geometry and required layer properties. Further information is available on our knowledge page about Laser Metal Deposition with Wire.

Which system solution is right for your application?

OSCAR PLT considers not only the individual component but the entire application. The following information is particularly relevant for an initial technical assessment:

•	Is the screw shaft to be newly built, coated or repaired?
•	Which diameters, pitches, spacing, contours and tolerances are required?
•	Which base and filler materials are to be processed?
•	Which quantities, cycle times and variants are planned?
•	Which motion and positioning systems are required for the component and processing head?
•	Should the system be integrated into an existing installation or implemented as a stand-alone production cell?

Based on these requirements, OSCAR PLT develops a concept for automated manufacturing, coating or repair. Such a system solution can combine the following components, for example:

•	ProFocus processing head and suitable wire feeding system
•	Rotary, linear or robotic systems for the required motion control
•	Sensors and component scanning for the digital acquisition of geometries and damage
•	Path planning, process control and documented welding parameters
•	Integration into existing CNC machines or implementation as a stand-alone LaserCell

If the process, material combination or system configuration has not yet been finalised, a feasibility study provides a reliable technical foundation. The OSCAR PLT team combines material analyses, component scans, digital path planning and welding trials with its experience in process and system development. This provides an early indication of the possibilities the technology offers for the specific application and how these can be developed into an automated, reproducible manufacturing process.

From process development to a production-ready system

Component size, accessibility, geometry, production quantity and the required level of automation determine how a system must be designed. OSCAR PLT therefore develops not only the welding process but also considers the component fixture, motion control, sensors, control system and potential post-processing as an integrated system.

Depending on the application, the modular ProFocus system can be combined with suitable positioning and automation technology. ProFocus Compact is available for compact integration into existing CNC machines, robotic systems or application-specific installations.

Would you like to automate the manufacturing, coating or repair of screw shafts? Talk to us about your application and the right system solution.