FIELD OF THE INVENTION
The present invention relates generally to the field of metal casting. More particularly the present invention relates to the cutoff of excess material on metal castings after it has been removed from the mold. In even greater particularity the present invention relates to the removal of riser or gate remnants after a cast part has been removed from the mold and to a process for perfecting the cutoff operation by conjunctively using a robot and a compliant cutoff saw.
BACKGROUND OF THE INVENTION
In the casting arts, molten metal is poured into a mold through an opening in the top of the mold with a certain excess metal filling the channel to the mold cavity. When multiple parts are cast in the same casting vessel, the mold will include channels in the form of a sprue to each cavity for each part, which will create undesired dross on the outer surface of the casting once the molten metal has hardened into the casting. The excess metal, such as those referred to as risers or gates, is frequently required to be removed by a cutoff or grinding operation in order for the casting to perform the purpose intended.
There are several common practices used by foundries to remove the risers or gates from the castings. These practices include, but are not limited to, removal of the riser by means of a gas torch, a grinder, a conventional cutting blade or saw, or some similar machine for forcefully removing the dross. Moreover, after the gates or risers have been removed from the casting through any of these methods, the operator commonly has to further grind or finish the casting due to an uneven cut caused by the respective trimming method.
The most common practice of cutoff operation is conventionally done either by an operator controlling a machine having a cutoff blade or automatically by means of a robotic device having a cutting blade. In the first example, the operator controls the machine that applies a cutting force that may come from an external force, such as a hydraulic cylinder, or it may be generated manually by the operator physically controlling the cutting force with his own strength and weight. In the second embodiment, the robot may be used to hold the casting to engage a fixed cutoff saw, or to the contrary the robot may hold the cutoff saw while the casting is in a fixed position.
Robots have been used for years to control the movement of a casting through a cutoff blade. In addition, hydraulic, pneumatic or electric cutoff saws have also been used in the common foundry to push the blade (or casting) through the casting (or blade). However, these solutions incorporating the use of the robot experience inherent problems. For example, one inherent problem with the use of the robot to control the cutoff operation is that the cutting wheel will have a short abrasive life. In addition, this solution requires a long robot cycle time to cut the riser. Moreover, significant heat is generated in the casting in such a method due to incorrect cutting force or pressure. Cutting forces that are lower than that prescribed by the blade manufacturer can cause excessive heat in the blade and the material being cut. These high temperatures in the material can degrade the properties of the material, resulting in scrap or wasted castings. Finally, there is frequently an inconsistent cut in the casting due to deflection and vibration in the robot, which could lead to possible damage to both the robot and the cutoff saw due to inconsistent gates or risers.
What is desired, then, and not found in the prior art, is a compliant cutoff saw assembly having a design that will accurately and efficiently cut a casting supported by a constant force or pressure as chosen for the particular casting to maintain the integrity of the casting and the functionality of the assembly.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an assembly for removing excess material from a casting.
A further object of the present invention is to provide an assembly incorporating a compliant cutoff saw in conjunction with a robot to eliminate risers on castings.
Another object of the present invention is to provide an assembly for cutting through a casting that provides a cooler temperature in the casting when being cut.
Yet a further object of the present invention is to provide an assembly for cutting through a casting that provides a consistent cut.
A further object of the present invention is to provide an assembly for cutting through a casting that has a long abrasive wheel life for the cutting element.
Another object of the present invention is to provide an assembly for cutting through a casting that will reduce deflection and vibration in the robot by maintaining a constant cutting force.
In particular, the compliant cutoff saw assembly includes a robot assembly that is used with a cutting apparatus to remove various undesired metal extensions from a casting. The compliant cutoff saw assembly has the ability to cooperatively and conjunctively control both the position of the casting as well as the force exerted by the cutting apparatus on the casting. The combination of controls allows the compliant cutoff saw assembly to provide a clean and even incision on the casting, which eliminates or at least reduces the amount of work required to finish the casting after the undesired metal extensions have been removed.
The robot assembly of the present invention includes a multi-positional robot arm that is connected to a system controller. A tooling clamp is connected to the free end of the robot arm, with the tooling clamp being used to engage and securely hold the casting to be cut. The robot arm is able to move in three dimensions, and can therefore position the casting in any dimension as desired by the operator. Consequently, the cutting apparatus saw will be able to cut most any side, surface or portion of the casting as desired by the operator of the system.
The cutting apparatus of the present invention includes a frame having a mounting assembly to which a support beam is pivotally affixed. A drive motor is preferably attached to the lower end of the support beam, with a cutoff blade being rotatably attached to the upper end. The drive motor is mechanically connected to the cutoff blade to drive and control the rotation of the cutoff blade as desired by the operator pursuant to the casting being cut.
In addition, the cutting apparatus includes a compliance control system that includes a compliance actuator that is connected to a compliance regulator. The compliance actuator is connected between the upper end of the support beam and the frame, such that the compliance actuator will be able to actively vary the force of the cutting blade with respect to the casting. The compliance regulator, which is connected to the system controller, will measure and regulate the pressure in the compliance actuator. Consequently, the system controller has the ability to adjust the setpoint of the compliance regulator and precisely control the movement of the robot arm so that the casting will be cut as desired by the operator.
These and other objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiment of the invention.
The second component of the present invention is the cutting apparatus 20 which preferably includes a frame 22 that is sturdily positioned on a ground or floor surface. The frame 22 comprises a mounting assembly 24 that preferably includes a shaft and a pair of bearings, with a support beam 26 being pivotally affixed to the mounting assembly 24. The support beam 26 includes a lower end 28 a and an upper end 28 b, with a drive motor 30 being attached to the lower end 28 a and a cutoff blade 32, such as an abrasive blade, carbide blade, diamond-tipped blade or other cutting device, being rotatably attached to the upper end 28 b in the preferred embodiment. The drive motor 30 is mechanically connected to the cutoff blade 32 to drive and control the rotation of the cutoff blade 32 as desired by the operator pursuant to the requirements of the casting 16 being cut. Moreover, the drive motor 30 is connected to a drive system 40, which preferably includes a vector drive, such that the drive system 40 can control and vary the operation of the drive motor 30 and thus the speed of rotation of the cutoff blade 16. The drive system 40 is further connected to said system controller 18 via drive cable 42, such that the drive system 40 can receive communications from the system controller 18 directing operation of the drive motor 30.