Case Study - HPB4³ - Machine Specification
Several machine configurations were considered but in this instance there was no need for a long concept review. A very conventional axis arrangement has been chosen to accommodate components weighing as much as four tonnes enclosed in the workzone of four cubic metres. A full machine specification has been developed around a range of components from the largest LT3 workheads and wheelheads down to small bores on prismatic parts for other machine assemblies.
The final machine performance is predicted to improve on the component specification limited only by the individual parts of the error budget. Values input into the error budget are taken from historical data measured on machines recently made at Cranfield Precision. The magnification of the basic geometrical errors relates to the machine configuration, the Abbe offsets and the temperature control regime.
| Capacity | Metres |
| X Stroke About B Axis Centre Line | ± 1.0 |
| Y Stroke | 1.1 |
| Z Stroke | 1.25 |
| Workzone Volume | 4M³ |
| Workpiece Maximum Weight | 4 tonnes |
| Drift in any 24 Hours | Microns |
| X axis drift | 12 |
| Y axis drift | 12 |
| Z axis drift | 12 |
| Displacement - All Axes | Microns |
| Full travel | 5 |
| Within any 100mm | 2 |
| Within any 2mm | 1 |
| Horizontal and Vertical Straightness - All Axes | Microns |
| Full travel | 10 |
| Within any 100mm | 5 |
| Within any 2mm | 2 |
| Pitch, Yaw and Roll - Full Travel Including Reversal | Arc Seconds |
| X axis | 5 |
| Y axis | 3 |
| Z axis | 4 |
| Squareness | Arc Seconds |
| Z to X, X to Y and Y to Z | 5 |
| Parallelism C to Z | Arc Seconds |
| Vertical and Horizontal | 5 |
| B Axis Rotary Table | |
| Angular Displacement Accuracy | ± 1 arc sec |
| Command Resolution | 0,0001 deg |
| Average Radial Error Motion | 5 µm |
| Average Axial Error Motion | 5 µm |
| B-axis Squareness to X-Z plane | < 0.5 arc sec |
| B table Top run out to X-Z plane swash | < 1.0 arc sec |
| C Axis Spindle | |
| Angular displacement | 2 arc sec |
| Average radial motion at nose | 0.5 µm |
| Average radial motion at 250mm | 2 µm |
| Average axial | 0.5 µm |
| Spindle growth after 30 min warm-up at 1000 rpm | 5 µm |
| Fluid Systems Temperature Control | |
| High Pressure Hydrostatic Oil | 20°C ± 0.5°C |
| Low Pressure Coolant | 20°C ± 0.5°C |
Cranfield Precision operates to ISO9001 quality standard and is accredited by Lloyds Quality Register.
A Division of Cinetic Landis Ltd.
Registered in England
Registration Number 05577045
Registered Office: Cross Hills, Keighley, West Yorkshire, BD20 7SD