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Products : MetaCut Finish : White Paper


MetaCut Finish & Pro

White Paper


Northwood Designs, Inc. has been involved with improving the quality of machining toolpaths through the use of arc fitting and other optimization methods since 1991. The algorithms used by Northwood Designs, Inc. were developed in house and have been proven throughout the world by companies both large and small. Through continual improvements and the addition of unique and beneficial features, Northwood Designs, Inc. has gathered a rapidly growing and satisfied international customer base with concentrations of users in Japan, Germany, and of course, the U.S. With the release of MetaCut Finish , virtually any type of point file, from any CAM system, may be imported, manipulated, and then exported as machine code or geometry. MetaCut Finish  represents the fourth generation of the toolpath optimization technology developed by Northwood Designs, Inc.

"The software (MetaCut Finish) from Northwood Designs has been a big time saver...

...allowing us to produce our parts in as little as 30% to 40% of the time that it took before."

Tom McDonald
(CNC Programmer)
Milton-Bradley Co., Massachusetts, USA
Used for: Molds
2 Copies




The primary purpose of MetaCut Finish  is to reduce machining and polishing times on complex molds without sacrificing accuracy. This is accomplished through the intelligent approximation of lines and arcs or NURBS curves relative to the original point to point data. Additional features control machine feedrates and exact stop/continuous switching. As a byproduct, toolpaths are often 60 to 90% smaller than the original.


Arc and line approximations

MetaCut Finish will automatically produce a highly accurate approximation to an ordered set of points (and lines) such as commonly found in toolpaths. Separate tolerances are provided for lines and arcs. These tolerances may be viewed as the maximum deviation from the original points in the file. In addition to maintaining a tolerance to the original points, a maximum deviation from the original lines is also maintained.

Arcs may be fit in one of three methods: 1) relative to the standard orthogonal planes (XY,XZ,YZ). 2) relative to any rotation of the standard orthogonal plane. 3) to completely arbitrary planes (3D arcs). Almost all controls will machine arcs using the first method, some controls will allow method number 2, and a few controls are able to machined true 3D arcs. (*note- a 3D arc is not a helix).

MetaCut Finish  will always fit the most appropriate entity. If any set of data falls within tolerance for both a line and an arc, MetaCut Finish  will only produce the entity with the closest fit. MetaCut Finish  also has user defined limits for largest and smallest arc radius as well as the smallest distance between arc endpoints and smallest arc length. All settings may be saved to a named parameter set which may be loaded at any time while in MetaCut Finish.

NURBS approximations

The NURBS curve fitting available as an option for MetaCut Finish produces both small and accurate files for use with controls which support true NURBS machining. The benefits of this technology include very smooth finishes similar to the arc fitting, but with absolutely no dependence on planes as there is on most controls with arcs. In addition the control will prevent overtravel of the machine tool when using NURBS machining. The NURBS machining also produces good results with true 3D toolpaths such as "flowline" type toolpaths.

NURBS machining is the next step forward in complex mold machining.

Automatic feedrate modification

MetaCut Finish is able to continuously vary the feedrates while your part is machining. This feedrate adjustment is easily adjusted by the user for optimal feeds on different machine tools. Feedrate adjustments are used to prevent following error while simultaneously decreasing your machining times. By changing the feedrates of individual arcs MetaCut Finish will machine large arcs at high feedrates while slowing down for small radius arcs.

Exact stop / Continuous switching

With the greatly increased feedrates available when machining using MetaCut Finish, sudden changes in tool direction can produce overtravel. MetaCut Finish will set your machine to exact stop mode (come to a stop at the endpoint) whenever the change in direction exceeds a user defined angle. When the toolpath becomes smooth again your machine will be set back to continuous mode (keep moving through the endpoints). This feature combined with the "automatic feedrate modification" feature will help to maintain accuracy while still allowing your machine to travel at the highest possible feedrates for any given situation.

Import / Export and the TOOL language

Northwood Designs, Inc. has developed a complete language similar in syntax to the C language but with specialized abilities which are particularly useful for the manipulations of the types of files commonly found in the CAD/CAM industry. This language is available to the end user and may also be used to make custom programs.

Import and export of files is handled in two ways within MetaCut Finish. Many common formats are "hard coded" to allow for quick I/O. With the first release, MetaCut Finish will support ASCII, DXF, G&M codes, and Mastercam NCI as hard coded formats. These will not be complete import/export filters but will instead support the types of entities which will be commonly used in MetaCut Finish. These include lines, arcs, and NURBS curves. We expect support for additional entity types to be added as necessary. The second type of import/export is the "custom" engine. These filters use the TOOL language and are completely customizable. This gives the product the ability to import file formats that are not included with the base package. You can also modify existing filters.

Batch Language

There is a full featured batch language which allows the user to run the product from a batch file over a network. The batch language allows for the loading of multiple files which may be optimized using different parameters, then exported with different export filters. All unattended. This is useful for running multiple conversions of large files overnight or for running across a network.

General Features

  • Unlimited undo (limited only by your disk space).

  • You may save an unlimited number of default settings for different machine tools or uses.

  • The primary toolset is greatly simplified and combined into a dragable toolbox, the most commonly used features are always close at hand.

Things to keep in mind when considering MetaCut Finish

  • MetaCut Finish was not designed to fit arcs to your old toolpaths. The best results are obtained with new files made with the process in mind. You can use MetaCut Finish with old files but the results may not be as optimal.

  • Best results are obtained with higher precision files, this usually means 6+ numbers after the decimal point in the original file. MetaCut Finish can format and truncate all data on export.

  • Your original file should be run to small chordal deviations for best results. MetaCut Finish will actually return a smaller file from a highly defined large original file than it will from a coarsely defined small original original file.

Technical Support

Northwood Designs, Inc. stands behind each of their products. Most problems are quickly identified and solutions offered at the time of the call.

Software problems

We have a policy of fixing any problems which reduce the functionality of the product immediately. Customer satisfaction with our products is paramount.