CF Collection of features
Collection of features · Anotaciones de plano · ISO 1101
Example in plan
How to interpret it
On the drawing, “Note: collection of surfaces A1-A3 with common ⏥ 0.05” states a collection of features requirement.
What controls
A callout that groups several geometrically separate features so that a single requirement applies to the set rather than to each one on its own. The practical difference is significant: if the requirement is individual, each feature is evaluated against its own zone; if it applies to the set, all the zones are fixed relative to one another and the part is only acceptable if all the features fit within that arrangement at the same time. It is used when several surfaces or features work together, such as the mounting pads of a machine base or the faces that form an interrupted seat.
How to verify
Coordinate measurement with a single alignment for the whole group: the datum reference frame is built once and all features are evaluated against their zones in that same reference, without realigning between one and the next. The result is reported as conformance of the set. Realigning the part for each feature is precisely what cancels the requirement and makes a bad part look good.
Common mistakes when interpreting it
- Evaluating each feature in the group separately, realigning between measurements.
- Confusing it with a regular pattern of repeated features.
- Machining the group in different setups without a common reference, which is what breaks the set requirement.
How to get it in the workshop / if it comes out of tolerance
A group like this should be machined in the same setup whenever possible: if it is machined in two different positions, each setup change introduces error between features and the common requirement is the first thing to fail. When inspecting, it is not enough for each feature to pass separately. And do not confuse it with a repeated pattern: here the features can differ from one another and need not follow any regular repetition.
If the group fails but the features pass individually, the problem lies in the relationship between them: look at the number of setups, the order of operations and the repeatability of the workholding. If the part is machined in several machine positions, consider a fixture that allows the whole group to be done at once. And if a setup change is unavoidable, use a common reference machined in the first setup.
Alternative symbol:n elementos
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