Track Construction Swivel Bearing - The Challenge

In the field of Heavy Machinery, Plasser & Theurer from Linz, Austria develops tamping machines for railroad construction, which employ tamping picks to compact the ballast bed underneath the railroad sleepers for high-speed and mainline railway operation. In order to bring a newly developed tamping unit of the type Unimat 09-2X-4x4/4S to the test station on time, FIT was commissioned with the rapid additive manufacturing of prototypes ready for assembly and testing, because these parts could not be procured in the required time by using conventional manufacturing. However, idle time on the test bench would have entailed immense costs as well as a considerable time delay in the project.

After selecting a suitable material, a high-temperature, low-alloyed chrome-molybdenum steel material, FIT first identified a suitable process parameter combination for the reliable processing of the selected wire material using WAAM. For the near-net-shape production of the prototypes, factors to be taken into account were thermally induced distortion and the shortest possible production time in order to ensure the economic viability of this solution. Significant effort was laid into implementing the buildup strategy and the associated programming of the travel paths used to generate the individual welding beads, a process that requires a lot of manual input due to the lack of algorithms in the CAM software. In the following near-net-shape production of the five prototypes, a total of approx. 500 kg of wire material was welded layer by layer within just three working weeks. Approximately 110 hours were needed for the production of the largest prototype, which is characterized by a length of about 1 meter and a mass of about 165 kg as well as by a large number of thin-walled geometry features. After heat treatment for stress relief, the parts entered a quality assurance step using high-precision optical 3D technology. "We are really thrilled by the quality of the components; all functional surfaces are 100 percent pure." (i.e. defect-free), explains Markus Ratzinger, design engineer at Plasser & Theurer after completion of the machining.

The lead time reduction of up to 70% compared to conventional manufacturing proves that WAAM is an excellent solution for the fast production of large-volume prototypes or spare parts as casting substitutes.

Track Construction Swivel Bearing - The Challenge
Track Construction Swivel Bearing - The FIT Solution

Track Construction Swivel Bearing - The FIT Solution

Rapid Prototyping with ADM-D

Feasibility test
Result: Additive manufacturing of several large-volume and heavy machine components is possible in the required time using WAAM.

Feasibility study
- Validated material: high-temperature, low-alloy chromium-molybdenum steel
- Technology used: WAAM

ADM-D
A prerequisite for the feasibility of the components is the step of material validation which has its own specific requirements for the manufacturing process. A special process and assembly strategy was defined for this project.

Rapid prototyping
Additive manufacturing of components in the field of rail transport (track & railroad construction), especially for track maintenance

Post-processing
The prototypes were delivered near-net-shape with minimal offset, reducing cost and time for the CNC milling on the functional surfaces during post-processing, a task performed at the customer's site.

Quality assurance
- Heat treatment by stress-relief annealing
- GOM scan
- Metallographic examinations to determine the relative density and to evaluate the structures with regard to internal defects such as pores or cracks


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Am Grohberg 1
92331 Lupburg
Germany

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