CNC Machining · Fan-Drive Pulley Case Study
Background
This project covers a family of custom fan-drive pulley components developed for a Scania DC13 engine installation used in agricultural equipment. The system includes larger multi-rib drive pulleys and smaller idler / tension pulley positions, together with bearing assemblies and retaining hardware.
The parts were produced in relatively small recurring quantities. Instead of investing in dedicated mass-production tooling, we used flexible CNC turning and secondary machining routes so different pulley variants could be machined directly from solid stock while maintaining the rotational features required by the belt system.
The end-equipment OEM, part numbers and proprietary drawing details are intentionally omitted from this public case study.
Fan-Drive System Context
The simplified schematic below shows the functional relationship between the larger drive / fan pulleys, the smaller idler / tension pulleys and the belt path.
The Challenge
The individual pulleys are straightforward turned parts, but a multi-rib fan-drive system is sensitive to runout, groove geometry and bearing fit. The belt-running diameters, bores and bearing seats need to remain concentric so the assembled system tracks and rotates predictably.
The component family also uses different material and finishing routes. Steel pulley variants are CNC-machined from 45# carbon steel and receive a black oxide finish; aluminum variants are machined from 6001 aluminum and left in their natural metallic finish. Smaller idler / tension components are completed with SKF bearings where specified. Keeping these variants consistent in small batches requires a flexible but controlled production route.
Our Approach
We planned the pulley family around common CNC turning datums and then separated the downstream operations by material and component function. The same low-volume strategy supports both larger fan-drive pulleys and smaller bearing-equipped rollers without forcing the customer into mass-production quantities.
From Solid Stock to Finished Fan-Drive Pulleys
CNC turn from solid stock
Large pulley bodies are produced directly from solid stock using CNC turning. This keeps the route practical for low recurring quantities and avoids dedicated casting or forging tooling.
Machine multi-rib pulley features
The belt grooves, bores and mounting features are machined from controlled rotational datums so the working surfaces remain concentric and repeatable.
Apply the material-specific finish
45# steel pulley variants receive black oxide after machining, while 6001 aluminum variants remain in their natural metallic finish.
Fit SKF bearings & inspect
Smaller idler / tension pulley variants are assembled with SKF bearings where specified, followed by checks of the bearing interface and critical rotating features.
CNC Turning in Practice
Direct machining keeps customized pulley production practical.
For small recurring quantities, CNC machining directly from stock provides a flexible route for producing several related pulley styles without the cost and lead time of dedicated blank tooling.
- 45# steel and 6001 aluminum variants can follow different downstream finishing routes.
- Multi-rib grooves, bores and bearing features stay referenced to controlled turning datums.
- Small batch sizes remain practical for customized fan-drive and replacement applications.
Flexible CNC machining makes small recurring pulley programs practical.
Not every industrial requirement is a high-volume program. Customized fan-drive, accessory-drive and replacement pulley components may be needed in recurring quantities that are too small to justify dedicated mass-production tooling.
By machining directly from solid stock, applying material-specific finishes and assembling SKF bearings only where required, we can support multiple related pulley variants while maintaining the dimensional control needed for belt and bearing interfaces.
