Gear cutting – milling – or planing – Milling – Means to remove scale or raised surface imperfection
Patent
1987-05-12
1988-11-15
Weindenfeld, Gil
Gear cutting, milling, or planing
Milling
Means to remove scale or raised surface imperfection
29 761, 511659, 409138, B23C 312
Patent
active
047845406
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device in a rotating drive means for a tool, e.g. a burr or a milling tool, intended for mounting on the arm of an industrial robot or another automatic device for burring onmachined workpieces or the like, comprising a casing with a motor, especially a pneumatic motor for actuating said tool.
Removal of burr on a workpiece by the aid of an industrial robot is a new and difficult application with special demands ont he dynamic properties of the robot. Such a robot should be able to follow a conour on a workpiece with great speed and accuracy at thesame time as varying forces are transmitted from the burring tool to the robot arm. Widespread use of industrial robots for burring is completely dependent on a reduction of cycle periods and increase of flexibility. The present robots operate with high speed, but with large and heavy tools attached tot he robot arms the properties that may be achieved are reduced below acceptable levels. At the same time as more rigid and more lightweight robot structures as well as improved servo systems are developed it is, thus, necessary to reduce themass which a robot must move--the tool mass.
Using robots there were, at certain times and inconnection with special applications problems with inaccuracy of the workpieces and their fixation in relation to the programed path of the robot. In connection withmilling and burring it is necessary to compensate for such inaccuracies by introducing a flexible movement between robot and workpiece. Wear and tear of the milling tool and subsequent changes of geometry in the same cases of application also resulted in a demand for ocmpensating for such wear and tear.
In principle, three different methods may be used for generating and maintaining a constant or adjustable force between milling tool and workpiece: spring. and the tool is, thus, rigidly fixed to the robot (or to the support if the used robot is carrying the workpiece).
In removing burr, i.e. removing loose material, and bevelling and corresponding applications method (b) mainly proved useful. with this method the entire tool or portions of the tool can be spring-cushioned.
In case of great speed across an uneven surface it is improtant that the mass of spring is as little as possible (cf. cars and wheel suspension on potholed roads).
When external and internal circular arcs or arcuate contours are to be burred it is important too that the tool is constructed to place the centre of gravity of the burring tool as closely to the central axis of the circular arc as possible. This distance is called centre of gravity distance in this context.
The tool previously used for burring was characterized by the fact that the elastic force and, thus, the elastic movement had a direction orthogonal to the axis of rotatio of the burring tool, and that the entire tool for burring was springcushioned. Rubber suspension secured spring action in all directis orthogonal to the axis of rotation. This resulted in problems in connection with vibrations of the burring tool. Consequently, the restriction was adopted that the tool only tilts about one axis that is orthogonal to the axis of rotation. THe force is provided, e.g. by a mechanical spring arranged to have an approximately linear characateristic and, thus, yielding an approximately constant force of contact with the workpiece. The disadvantages of the presenst methods are: orientation of the axis of rotation for burring circular arcs or arcuate contours extending in one and the same plane. This means that the robot must have an additional degree of freedom (servo), just for this orientation. An additional servo outermost on the robot arm has a very negative influence on the dynamic qualities of the robot. invarious orientations in space the tilting axis must be placed through the centre of gravity of the grinding tool. This involves large and heavy means of suspension. rough burrs (large cushioned mass).
The main object of the present invention is to propose a drive means for a tool, e.g. a burr or a milling
REFERENCES:
patent: 3712174 (1973-01-01), Granfield
patent: 4371297 (1983-02-01), Hirose
patent: 4543022 (1985-09-01), Bonner
patent: 4610075 (1986-09-01), Eriksson
Bishop Steven C.
Weindenfeld Gil
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