RTCP Function is suitable for 5-axis machining.
August 8, 2002 - RTCP (Rotation Tool Center Point) Function maintains rotary axes at constant angle between tool and surface to be machined. Machine also allows OEMs to set up function based on mechanical properties of users' machines. RTCP function manages all irregularly shaped offsets automatically, and keeps tool in contact with programmed point. It uses contact point as reference point in all calculations, allowing users to directly program machine using part contour and desired tool angle.
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|Original Press release |
Num Corp., Schneider Electric
603 E. Diehl Rd., Suite 115
Naperville, IL, 60563 1452
NUM's RTCP Function Means Never Losing Contact With The Part When Doing Precision Five Axis Machining
Chicago, July 24, 2002
As a pioneer of the RTCP (Rotation Tool Center Point) function, the Naperville, Illinois-based NUM Corporation offers definite advantages in machining jobs for the mold making, automotive bodywork, aerospace, and woodworking industries. In order to accurately keep a constant angle between the tool and the surface to be machined, the company has developed a particularly user-friendly solution, which allows OEMs to set up the function rapidly and easily, based on the mechanical properties of their machines. To do so, they simply define the tool head geometry on graphic views and enter the dimensions of specific mechanical systems.
In machining applications, the rotary axes of the machine keep the angle constant, such as a dual rotary tool-head or a table and cradle holding the part. These axes allow the tool or part to rotate around axes accurately. This type of setup is found on 4- and 5-axis milling machines.
Things are much more complicated when the surface to be followed isn't flat but has an irregular shape. Keeping the tool in contact with the part then requires taking into account all the offsets due to the tool-head mechanics, tool length, and other factors (see sketch). The enormous advantage of the RTCP function is that it not only manages all these offsets automatically but also guarantees that the tool is effectively in contact with the programmed point.
One of the advantages of the RTCP function is that it uses the contact point as the reference point in all calculations. The user therefore directly programs the machine using the part contour and indicating the desired tool angle. The CNC then determines the position of the tool-head and all the axes so as to reach this point. In addition to a significant saving of time and simplification of the CAD/CAM system, the user is also certain of correctly remaining in contact with the surface to be machined.
Conversely, without the RTCP function the reference point is the tool-head position, and the contact point is determined mechanically from this reference point by application of all the mechanical shifts.
This difference between "contact point used as reference point" and "contact point obtained mechanically" is key. For instance, with a pivot length of 600 mm, the length between the tool tip and the center of the rotary head, a positioning error of only one-hundredth of a degree (1/36,000th of a revolution) causes an error of 0.1 mm. Without the RTCP function this error exists on the tool tip, with the result that the part may be either damaged or the tool doesn't touch.
The RTCP function has many other important advantages. The program is independent of the machine and the tools used, since the programmed coordinates are those of the contour, not the machine. Similarly, it is possible to apply a tool offset without changing the part program. In addition, RTCP is part of the CNC post-processor, which makes part programs more portable.
The quality of surface condition is controlled much better since the programmed speed is applied to the contact point, not to the rotary tool-head. This in turn preserves optimal surface conditions. Lastly, with RTCP the part program is smaller and takes up much less memory space.
The NUM Corporation is the U.S. arm of an international company with nearly forty years of experience in CNCs. It is a specialist in the field of automating machine tools and special machinery in a variety of industries, including the processing of metal, wood, plastics, and stone. Today the focus at NUM is on providing complete solutions to meet the needs of its customers, including CNCs and drives, as well as supplying advice and expertise.
A subsidiary of Schneider Electric, NUM is now the group's expert for path control. It has three European production facilities, eight sales subsidiaries, and thirty-five service centers, with over 500 employees worldwide.
For more information, please contact
Mr. Brian Kordzinski
603 East Diehl Road, Suite 115
Naperville, IL 60563-1477
Tel: (630) 505-7722
Fax: (630) 505-7754
FRENCH TECHNOLOGY PRESS OFFICE
One East Wacker Drive, Suite 3740
Chicago, IL 60601
Tel: (312) 222-1235
Fax: (312) 222-1237