Meeting Minutes, NIST, Gaithersburg, MD, June 16-18 2010
The Boxy part was machined in steel by NIST and Boeing and they were able to show predicted tool wear for the pocketing operations.
The following were agreed to be the successes of this round.
- We were able to use the setup placements defined by STEP-NC to allow the operator to use the same coordinates for each setup by normalizing the coordinates of each setup to match the fixturing.
- We were able to use the workplan/workingstep structure of a STEP-NC program to rapidly and intelligently optimize the feeds and speeds of a program to meet the requirements of the tool and the machining schedule.
Magnus Lundgren of KTH gave a demonstration and discussion of how the Boxy data was built using Mastercam. Martin Hardwick gave a demonstration of how a STEP-NC data set was prepared for machining using the STEP-NC Explorer. Fred Proctor discussed lessons learned during this round on fixturing and organizing the data for multiple setups.
- Introduction to STEP-NC and Boxy [925k, pdf]
- Building Boxy Tutorial [4M, pdf]
- STEP-NC Machining [1.8M, pdf]
- NIST - How We Machined Boxy [1M, pdf]
There was considerable discussion of how to make STEP-NC data more portable and interoperable. There was general agreement that helping the operator to understand the "real" tool requirements was a key issue. The STEP-NC program contains a precise description of the tool that "worked" for the operator that designed the program, but does not contain any data to indicate which attributes of the tool are required for successful machining and which attributes can be varied without consequences. Fred Proctor of NIST agreed to develop an information model for documenting the requirements so that they can be used to control tool selection in future applications. We agreed that the requirements should match ISO 13399 properties so that the tool selection can be performed automatically, and that the simple display of the advice was equally important so that an operator can be given help when deciding what tools to order before machining a new part.
- Tool Requirements Schema [5k, txt]
- Integrated Process Planning and Flow Simulation [11.2M, pdf]
- Physical Cutting Tools Made Simple [470k, pdf]
- Endmill examples [76k, pdf]
- Milling Tool Parameters Documentation [146k, doc]
- Back Counterbore Example [255k, pdf]
We further discussed developing a schema to return tool advice from the tool vendor when a tool has been selected. This advice should include the attributes required to determine chip load and expected tool wear so that the enterprise can plan how to use the tool and optimize the STEP-NC program appropriately.
We discussed Mil Standard 31000. This standard is used to determine the technical data that a contractor must deliver to the DoD when building a system and is in the process of being updated. Consideration is being given to requiring the contractors to deliver information about the manufacturing processes used to create the system. STEP-NC AP-238 is standard that can be used to describe such information and the Army is interested in evaluating its suitability for Mil Standard 31000.
We discussed traceability and process monitoring. A STEP-NC program can add value to process results by describing the operation, feature and cutting tool being used to machine a part when an event happens during machining. We agreed that there are three kinds of information that we would like to correlate against a STEP-NC program. Discrete events such as an operator change or a fire alarm. Continuous events that correspond to the progress of the STEP-NC program and continuous events that do not correspond. The former follow the same encoding as the STEP-NC data so that if measurement values have been captured at the start and end of a tool path, then a value can be computed for the middle of the path. The latter are not correlated because they vary at random during the machining and include properties such as sound and machine vibrations but an analyst would still like to know what was happening to the sensor during the machining of that path.
Several users would like to be able to capture process results in the context of STEP-NC programs using OPC calls or MT Connect. We developed a schema that will allow these results to be added to a STEP-NC data set so that web applications can use the Modular Foundry Language API and STEP Resource Locatiors (STRL's) to extract information about the process and correlate it with information about the product and process being machined.
- Traceability Schema Extensions [2k, txt]
We discussed the requirements for closed loop machining. After much discussion, a schema was outlined that will allow points and axes in the STEP-NC program to be modified using the difference between the as-designed and as built geometry of a part or assembly. Martin Hardwick and Fiona Zhao will refine this scheme and propose a revised information model at a future meeting.
- STEP Closed Loop Machining and Measurement [240k, pdf]
- Dimensional Measurement Feature Harmonization [99k, doc]
We discussed tolerance tracking. The Boxy part contains many workpieces showing the state of the part before and after each machining step. Many of these parts are toleranced and users and applications would like to be able to track the evolution of the tolerances at each stage of the machining. Two solutions were discussed. The first solution allows a tolerance to be modeled on multiple workpieces. This solution will require changes to the STEP resources and it will be challenging to implement. A second solution modifies the ARM of AP-238 to allow for the tracking of tolerances, datums and surface finish requirements between workpieces. This solution can be implemented by a combination of intelligent software on or off the CNC control and user interfaces.
We discussed operator notes. STEP-NC AP-238 allows designers to mark up a part using the presentation information enabled by AP-203 e2 and AP-214 e3, and it allows a list of operator instructions to be defined for each setup. However, it does not let an operator create messages with useful information for other operators such as note to be sure to clean of the chips at the end of this operation. These messages need to be placed in context where other operators can see them and they need to be associated with an operation so that they are not all displayed at once.
- Other New Models [1k, txt]
We reviewed the AP-214 Machine Tool Model.
- Manufacturing Resource Modelling [2.7M, pdf]
We reviewed the Technical Corrigendum for AP-238 edition 1 and discussed the options for creating an Edition 2.
- Summary of Second Edition Enhancements [317k, pdf]
We discussed the date, location and content of the next demonstration. Ideas included machining Boxy, or a new part, at an Army location in late October or early November, and machining a new mill turn part in Sweden in March or June. The users would like to show CAM to CAM data exchange, process monitoring, tolerance tracking, automated tool selection and closed loop machining.
- Fred Proctor to develop Tool Requirements Model
- US Army to determine if Rock Island, Picatinny or Watervliet Arsenal can be the location of the next machining demonstration
- Martin Hardwick and Fiona Zhao to develop a next iteration of the closed loop machining model
- John Michaloski and STEP Tools to develop process monitoring model and interfaces
- KTH and Sandvik to consider requirements for a Mill Turn demonstration.
- Boeing, STEP Tools and Sandvik to consider requirements for an automated tool selection demonstration.