Concerned about the reliability of a 20 year old lathe, Aero Race Wheels, a supplier of premier steel racing wheels for NASCAR events, turned to a machine re-builder for help
Founded in 1995, Aero Race Wheels of Iowa has grown to become the largest manufacturer of steel racing car wheels in the US, with the company supplying its wheels for NASCAR events. Drivers participating in IMCA and WISSOTA events use Aero Race Wheels’ products, and more Cup, Nationwide and Camping World Series races have been won on the company’s 59 Series NASCAR wheels than all other brands combined, it claims.
Spin forming techniques are used by the company to produce its high performance racing wheels, a process which involves rotating a cylindrical steel work piece and a forming tool at high speed while exerting localised pressure using a roller, causing the metal to flow over the tool. The technique is suitable for manufacturing axially symmetric parts such as wheel rims as it creates a very strong, seamless component from a single piece of material.
The shape forming operations are performed on a 20-year-old Autospin metal spinning lathe. This features two sets of pressure rollers – one at the front of the work piece, the other at its rear – which enable both sides of the wheel rims to be formed without manual intervention. Each set of rollers has two motion control axes, X and Z, driven by four hydraulic cylinders, plus the motor-driven lathe spindle.
However, the machine is vital to operations, and Aero was becoming concerned about its reliability. Not only was obtaining replacement parts for the original motion control system nearly impossible, but the control had limited functionality and could only be programmed using a point-by-point data entry table that made it difficult to visualise and modify machine motion, demanding extensive operator training. Furthermore, the system could only store programs for a few types of wheel, so production changeover could take over four hours.
Re-building the machine
To overcome these issues, the company turned to a machine re-builder which performed a comprehensive mechanical and electrical rebuild of the lathe. For the critical CNC element, it chose to retrofit a high-end solution from NUM. The software is a tailored version of the NUMspinform control package for spin forming applications. The retrofit also includes a NUM FS151 operator’s panel, a custom HMI programming interface and a customised machine panel.
Prior to the Aero Race Wheels application, the NUMSpinform interface employed a teaching method of programming where the operator begins by copying the shape of the forming tool, or mandrel, and specifying the desired wall thickness of the part. The
CNC system then calculates a two-dimensional safety zone to prevent any roller-tool collision. Next, the operator spin forms the new part by controlling the X and Z axes of the roller manually via a joystick, while the CNC system records the motion paths. Before it is saved as the final production program, the recorded spinning cycle can easily be optimised by modifying the roller path in the X or Z axis – on the fly – using a calibrated hand-wheel.
In the case of Aero Race Wheels’ four-axis Autospin lathe, the preferred programming approach was to teach the mandrel safety zone, but to then draw the spinning cycle as a series of spline curves using an on-screen drafting tool. This drawing approach is now also part of the NUMSpinform solution. It has many benefits for a spinner, including a reduction in direct exposure to the machine elements and a simplified learning curve for operators.
NUMSpinform also accommodates offline program generation. Users can choose to create their own tooling files with the software’s graphical drawing facilities, or import them from a design automation source such as AutoCAD, and then program a spin cycle using simple mouse-driven point-and-click techniques. As soon as the design is ready, all defined geometry can be converted into a production program with a single click of a button and exported to the lathe’s CNC system to produce a trial part.
The NUMSpinform package accommodates either a simple two axis spinning lathe or a four axis machine as in the case of Aero Race Wheels. Aero’s machine slides can be programmed and operated as independent paths or in a method where the operator programs one X1/Z1 slide and the other X2/Z2 slide simply follows in a mirrored mode.
Marv Dailey, design/process engineer of Aero Race Wheels, commented: “Product changeover typically now takes less than 20 minutes, and the semi-automated method of generating and optimising spin cycle programs has significantly reduced development and operator training times. Offline programming also frees up time on this critical production machine, further boosting productivity.”
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