Feature Machine building/frameworks & safety
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’
Getting the
ounded 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 perfor- mance 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
20
wheels in motion F
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 pro- grammed using a point-by- point data entry table that made it difficult to visualise and modify machine motion, demanding exten- sive 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 mechani- cal 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 applica- tions. 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 appli- cation, the NUMSpinform interface employed a teaching method of pro- gramming where the operator begins by copying the shape of the forming tool, or mandrel, and specifying the desired
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
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 draft- ing tool. This drawing approach is now also part of the NUMSpinform solution. It has many benefits for a spinner, including a reduction in direct expo- sure 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 produc- tion 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 inde- pendent paths or in a method where the operator programs one X1/Z1 slide and the other X2/Z2 slide simply follows
The machine retrofit includes a NUM FS151 operator’s panel, which clearly
displays the profile of the wheel that is being formed
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.”
NUM (UK) T: 0871 750 4020
www.num.com
Enter 214 OCTOBER 2012 Design Solutions
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