Frequently Asked Questions

Questions about producing parts using STEP-NC

How do I use AP-238?
AP-238 is a replacement for RS274D. In large enterprises it also replaces APT and BCL.

What is the current method for making parts on CNC Controls?
Today, a customer details a drawing describing the part. The drawing describes the geometry, the material, the dimensions and the tolerances of the part. The drawing is sent to the job shop as IGES and PDF files or on paper. The job shop uses a CAM to define a manufacturing process that makes the part from the stock by removing material. The CAM operator refers to the drawing to understand how to implement the process. In some cases the IGES file contains geometric entities such as surfaces that help the operator define the process. When the process is built, the CAM system then translates it into G-codes that tell a machine tool where to move a cutting tool. The G-codes are sent to a CNC as a file in a vendor specific flavor of the RS274D format.

At large enterprises the process is made simpler by requiring everyone to use an integrated CAD/CAM system. This allows richer information to be passed into the CAM. At these enterprises a Post is used to convert the output of the CAD/CAM system into the RS274D codes that can be used by a particular control.

And the new method on STEP-NC Controls?
In the new method, a customer makes an AP-203 file describing the part geometry using a CAD system. The design requirements are then added as GD&T data. The result is exported to a CAM system as an AP-203 edition 2 file or as an AP-224 file if the detailing also includes the definition of part features. The CAM system is then used to determine a manufacturing plan and this is exported to the CNC as an AP-238 file. The manufacturing plan can be exported as CNC independent tool path data, or as manufacturing removal volume feature data or both.

How to make the AP-238 file?
There are two methods for making the AP-238 file. The first method allows a detailer at either the customer or the job shop to define the manufacturing features and tool paths. In the second method, the enterprise creates a complete manufacturing data set using an integrated CAD/CAM system and exports this data to the job shop as an AP-238 file. In either case if all the parameters are not quite right the job shop can read the file into its CAM system and adjust them because, unlike the RS274D interface, the AP-238 interface is bi-directional.

How will an operator use a STEP-NC control?
Like an automobile, putting more under the hood of a CNC controller makes the controller easier and safer to use ... not harder. Specifically, the many buttons and dials of a traditional control can be reduced to three on a STEP-NC Controller: "Run" to make the part; "Verify" to check for collisions without making the part; and "Document" to generate documentation describing how the part has been made or would be made on this machine tool at this time.

What about shops that do not have a STEP-NC Control?
Until the new controls become widely available, job shops can read AP-238 files into their CAM systems and use them to generate RS274D codes for their machines.