Frequently Asked Questions

Questions about Conformance Classes

What are conformance classes?
A large Application Protocol like AP-238 is divided into conformance classes to make it easier for vendors and users to decide what types of functionality they want to support in their systems. AP-238 has four conformance classes.

What is Conformance Class 1?
CC1 is the easiest conformance class to implement. This conformance class defines a CNC program as a series of working steps that are each defined by a CNC independent tool path expressed as Tool Cut Point data. There is no requirement to include any geometry, GD&T or feature data in the file. A "quick and dirty" CC1 translator for a CAM system can be implemented by translating APT CL data to the AP-238 format. The STEP-NC Write Library is a simple, open-source library for doing this.

What is Conformance Class 2?
CC2 is also easy to implement because it is a combination of CC1 and AP-203 edition 1. This conformance class enables intelligent set-up by including models of the as-is and to-be products, safe areas for the fixtures, as well as the tool holder and cutting data in the exchange file. With this information and its own internal data a CNC can do complete checking of the tool path data.

What is Conformance Class 3?
CC3 is the first conformance class to enable generation and modification of the part program. In this conformance class the definition of the removal volumes defined in the CAM system is included in the data. Therefore, a smart CNC can use this same data to re-generate the paths if some condition changes or another CAM system can read the data and make the changes. Implementing CC3 of AP-238 is harder than CC1 and CC2 but all of the necessary data is already in most CAM systems so it does not require any process changes by the end user.

What is Conformance Class 4?
Conformance class 4 is the ultimate goal. The data in this class enables full generative path planning on the control using intelligent software. It includes everything in the AP and requires the upstream systems to supply at least the GD&T information for the part and better still the part feature (AP-224) information.