Flexible CNC belt grinding machine

Abstract

A belt grinding machine is disclosed that includes an automatic pressure and position control systems for robotic grinding and polishing applications. The machine will be combined with off-line programming package, capable of carrying out complicated operations that cannot be performed on traditional types of machines. The multiple contact wheels of the machine give the flexibility to accommodate complicated geometry of workpieces with a large material removal rate (MRR) and great surface finishes. The basic components of this belt grinding machine consists of the followings: a power source, a drive wheel or active wheel driven by a motor, multiple contact wheels; an idler for tensioning and tracking the belt, an active force control device to keep the constant pressure on the workpiece, a proper coated abrasive belt, and a dust collection system.

Description

BACKGROUND OF THE INVENTION

The invention relates to a belt grinding machine with a compliant frame which has a plurality of contact wheels arranged around a common axis of rotation. The compliance can be set or controlled according to the need from the robotic grinding process. The compliance is provided an active pneumatic device and con also be provided by other actuators and sensor combinations. Existing designs of compliant belt grinders uses a linear guide way to guide the contact wheel frame.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a belt grinding machine of a kind in which the compliant system of the grinder is possible with a simple device that allows the motion of the frame which supports multiple contact wheels.

According to the invention, this object is achieved with a rectangular, parallel four-bar linkage connected to an actuator or a passive spring for delivering compliant motion that allows the contact wheels with a belt to yield or compensate automatically based on the change of grinding force between the workpiece and the belt.

The belt grinding machine according to the invention makes is possible not only to deflect in a simple way, but also to deflect without having any mechanical interference between the belt grinding machine frame and the robot with even a large workpiece. By means of the parallel compliant frame of the four-bar linkage, the grinding force applied to a workpiece can be well controlled, and wheels of various diameters can be controlled and used in an optimized way.

The grinder in this invention is designed for any part in robotic grinding and polishing applications. The travel compliance and excellent media access allows a robot to easily manipulate workpiece of any shape over the abrasive belts. As shown in FIG. 1, the following features make the grinder in this invention unique:

• • Active and continues force control (passive option available);
  • Direct contact wheel and grinding head displacement measurement using LVDT or laser
  • Laser detect belt centering and auto-adjustment
  • Changeable multi-geometry contact wheel in grinding process
  • Active pneumatic contact wheel with adjustable contact stiffness
  • Shaped pneumatic contact wheels
  • Modular design make the different combination easy for different geometry workpieces
  • Accurate and continuous belt speed control (0 to 8000 SFPM)
  • Direct gear drive
  • Different belt width in one machine;
  • Active adjustable pneumatic belt tensioning
  • Both linear and rotational travel floating belt heads
  • Stationary belt guards

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a belt grinder is shown. The abrasive belt (not shown in the drawing) runs around driven wheel 1 which also serve as tracking wheel, tension wheel 3 and contact wheels 4. The abrasive belt is guided round at least three contact wheels 4. The contact wheels can be changed during grinding by contact wheel turntable 5 to adapt the shape of workpiece. Driven wheel 1 is actuated by motor 2. To carry out the desired surface grinding, the workpiece (not shown in the drawing) runs on the abrasive belt on different size and shape contact wheels. The abrasive belt is designed as an endless belt. The driven wheel, tension wheel and contact wheel are aligned parallel to each other, so that the abrasive belt extends parallel to the contact wheels (grinding zone). The abrasive belt is pressed against the workpiece by means of a pressure formed from pneumatic cylinder 6 through parallel bar mechanism 7. The pressing force is adjusted by means of a pressure valve to accomplish different grinding task. The parallel mechanism and cylinder stand 8 are mounted on base 9. The length of slide 10 in the bar of parallel mechanism is adjustable to adapt the different length of abrasive belt.

Claims

1. A belt grinding machine comprising a compliant frame of a parallel four-bar linkage which carries multiple contact wheels of various diameter and width, and hardness. Active force sensing, compliance control and automatic wheel size control allows belt grinding to be performed on various workpieces with an enhanced productivity.

2. A belt grinding machine as claimed in claim 1, wherein the compliance of the four-bar linkage is provided by a pneumatic actuator or a device.

3. A belt grinding machine as claimed in claim 1, wherein the compliant linkage oscillates according to the change of grinding process force.

4. A belt grinding machine as claimed in claim 1, wherein the frame carries a group of contact wheels of various properties with the grinding belt wrapping around the wheel system.

5. A belt grinding machine as claimed in claim 4, wherein the wheels are arranged around a common axis of rotation with an active motor to position the wheels so that the right contact wheel that fits the shape and size of the workpiece to be machined will be aligned automatically in a position that grinding can be performed efficiently with the compliance system working properly.

6. A belt grinding machine as claimed in claim 5, wherein the rotation of the contact wheel group is CNC-based.

7. A belt grinding machine as claimed in claim 4, wherein the frame carries a tensioning wheel.

8. A belt grinding machine as claimed in claim 4, wherein the frame carries a tracking wheel.

9. A belt grinding machine as claimed in claim 1, wherein the grinding force sensing means includes a detection means for detecting grinding force variations in the signal output from the force sensor to the signal-processing unit means and determines the deflection of the contact wheel based on the process requirements.