The Cabiran Coordinate Dimensioning Method
The larger the distance, the greater the tolerance range. The shortest distance to any given feature on the cast is from the theoretical center point of the casting. (See Tolerance Tables.) The Cabiran dimension method:
- results in decreased tolerance requirements,
- eliminates certain machining operations,
- facilitates “machining start” (datum planes),
- establishes inspection correlation, and
- obtains symmetry between casting and machining patterns.
Tooling Points & Datum Planes
Tooling points are specific locations on accessible areas of the casting that serve as contact points for inspections and machining operations. Six tooling points define three datum planes. These are reference planes from which the casting features are dimensioned. These same planes are used to establish the three machining starts. If the casting does not have centerline features on which to locate the tooling points, Cabiran adds tooling lugs or other features that often remain a part of the finished casting.
Functional Dimensions |
Notes |
| Size Limitations |
Cabiran generally casts parts up to 800 mm/31.5” (diameter) x 800 mm/31.5” (length).
Larger and custom sizes are available upon request.
|
| Wall Thicknesses & Tolerances |
For selected areas of the cast, it is possible to obtain thin walls (1 mm thickness).
Areas up to 200mm x 200mm a tolerance of ±0.25 mm is allowed.
Areas larger than 200 mm x 200 mm min. tolerance± 0.35 mm is allowed.
Areas larger than 300 mm x 300 mm min tolerance = ± 0.50 mm is allowed.
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| Angles |
Achievable angular tolerances ± 0.5º |
| Roundness |
Out of roundness tolerance = approximately 50% of linear variation |
| Surface Texture |
125 RMS maximum |
| Fillet Radii |
Internal corners fillet radii: no less than 0.5 mm;
as a rule: fillet radii = ½ the general wall thickness.
Outside fillet radii: may be expensive to incorporate into dies; specified only where functionally required.
|
Tolerances & Tolerance Tables
The total tolerance range of a given casting feature represents the sum of the linear and geometric variations.
- Linear tolerances are variations of feature locations (point to point) and size.
- Geometric tolerances are variations resulting from perpendicularity, parallelism, flatness, straightness and other control-related characteristics.
The form attitude and location of the total part are defined by the general envelope tolerance. The tables present guidelines used for functional dimensions. Appreciable savings may be realized by using greater tolerances on non-functional dimensions. In consultation with Cabiran, closer tolerances can be used for selected dimensions.
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