Dual-axis load/unload robots, such as illustrated in FIGS. 1A and 1B, are the traditional and most widely used automation for press to press transfer. This type of automation has a minimum of two axis of motion and a third linear slide used to move the entire unit out from between the presses for die changeover or maintenance. A first axis gives the arm its vertical motion to lift or lower the part. A second axis gives the arm its horizontal motion in and out of the press. The axis motion can be programmable, but in most cases the axes are non-programmable.
The non-programmable models use hard stops for the different positions and the stops must be repositioned for each different part set up. A robot mounting frame 11 attaches to a linear slide which mounts onto the front or back of each press. This type of robot must have a part transfer station including a part transfer unit having a shuttle or a conveyor between the presses to transfer the part from the unload robot to the load robot.
With such dual-axis load/unload robots, a part/blank P is presented to a load robot 10 by a destacker unit (not shown), as illustrated in FIGS. 1A and 1B. After a press, generally indicated at 12, completes its cycle (with its dies 14 in an up position), an unload robot 16 moves to a position 18 and picks up part P. At the same time, the robot 10 has picked up another part/blank at the destacker and has moved to a position 20. As the robot 16 retracts out of the press 12 to a position 24, the robot 10 extends in and releases the part/blank at the position 18. The robot 10 retracts clear and the press 12 cycles. The robot 16 drops the part P onto a nest 26 of a part transfer unit, generally indicated at 28, at the position 24 and the part P is then shuttled to the next press, generally indicated at 30, at a position 32. A robot 34 picks up the part P at the position 32 and is ready to load the press 30. A robot 36 picks up the part P in the press 30 at a position 38 and retracts. Then, the part P is loaded into the press 30 in the same manner as described with respect to the press 12.
When a different part is to be run on the press line all the dies such as dies 14 and 22 of the press 12 and 40 and 42 of the press 30 must be removed and different dies set in the presses 12 and 30. This process must be performed as quickly as possible, so that the press line can be put back into production. To accommodate this process, the robots 10, 16, 34 and 36 and the part transfer unit 28 are typically mounted to slide units or tracks such as slide units 44 and 46 and track 48. This allows for quicker removal and replacement of the equipment from a die change area 33. Once the new dies are set, the robot positions, tooling, and part transfer nest 26 must be manually adjusted before production can begin.
Such systems have the following features:
Each robot has minimum two axis of motion;
Robots mount to the front or back of the press;
Three mechanisms are required to transfer parts between two presses: loader robot, unloader robot and part transfer station;
.cndot. Parts are transferred between the presses by a shuttle or conveyor; PA1 .cndot. Non-programmable or programmable axis motion available; and PA1 .cndot. Slides or tracks are used to move (3) mechanisms out of the die change area. PA1 .cndot. Relatively expensive; PA1 .cndot. Multiple units required between each press; PA1 .cndot. Mechanisms must be moved out from between the presses for die changeover; PA1 .cndot. Removal, replacement, and calibrating these mechanisms after a change significantly increases the part/die changeover time; therefore, the press line productivity is reduced; PA1 .cndot. Limited flexibility to adapt to changes in the part and die shapes or locations; PA1 .cndot. Any changes in part orientation is done on the part transfer unit; and PA1 .cndot. Part quality is reduced because of the number of times the part is handled. PA1 .cndot. Seven axis of motion; PA1 .cndot. Standard six axis robot mounted to a swing arm axis; PA1 .cndot. One robot required to transfer part between two presses; PA1 .cndot. Robot mounts to the floor between two presses; PA1 .cndot. Programmable axis motion with high flexibility; and PA1 .cndot. Slides or tracks are used to move the robot out of the die change area. PA1 .cndot. Relatively expensive; PA1 .cndot. The swing arm axis motor or motors require high torque to enable it to move the heavy robot at high speed, press to press; PA1 .cndot. Swing arm robots must be moved out from between the presses for die changeover; PA1 .cndot. Removing and replacing these robots significantly increases the part/die changeover time; therefore, the press line productivity is reduced; PA1 .cndot. The swing arm axis is redundant and requires special controls to accommodate; PA1 .cndot. A minimum of six axes are required to transport the part, press to press; PA1 .cndot. Seven axes are required for full flexibility; and PA1 .cndot. Reliability is reduced due to the effects of high inertia on the standard robot's wrist axis.
Such systems having the following shortcomings:
Swing arm robots, such as illustrated in FIGS. 2A and 2B are also used in press-to-press applications that require more flexibility and where only one mechanism between the presses is desired. This type of automation consists of a standard six axis robot 50 mounted to an auxiliary swing arm 52. The addition of the swing arm 52 allows the standard robot 50 to reach the large center-to-center distances of most press lines. The robot 50 is typically a standard six axis articulated arm robot. The robot 50 mounts to the swing arm 52 which transports it back and forth between two presses, generally indicated at 54 and 56. The robot 50 is programmable and has a high degree of flexibility to accommodate the variation in parts or die positions. The swing arm 52 is typically mounted to a slide or track 58 which allows the robot 50 and the swing arm 52 to be manually moved out from between the presses 54 and 56 during die changeover.
With such a swing arm robot 50, a part/blank P' is presented to a robot 60 by a destacker unit (not shown) as illustrated in FIGS. 2A and 2B. After the press 54 completes its cycle (with its die 62 in an up position), the robot 50 moves to a position 64 and picks up the part P'. At the same time, the robot 60 has picked up a part/blank at the destacker unit and has moved to a position 66. As the robot 50 retracts out of the press 54 to a position 68, the robot 60 extends in and releases the part/blank P' at the position 64. The robot 60 retracts clear and the press 54 cycles. The swing arm 52 rotates clockwise as the base of the robot 50 rotates counterclockwise (as shown in FIG. 2A) transporting the robot 50 and the part P' to a position 70. A robot 72 moves into the press 56 (at a position 74), picks up another part and retracts out of the press 56. The robot 50 proceeds to load the part P' into the press 56, in the same manner as described with respect to press 54. When the robot 50 finishes loading the press 56, the robot 50 moves back to the press 54 and repeats the sequence.
When a different part is to be run on the press line all the dies, such as dies 62 and 63 of the press 54 and the dies 76 and 78 of the press 56 must be removed and different dies set in the presses 54 and 56. This process must be performed as quickly as possible, so the press line can be put back into production. To accommodate this process, the swing arm 52 is typically mounted on the slide or track 58. This allows for quicker removal and replacement of the robot 50 from a die change area 71. Once the new dies are set, the robot 50 is repositioned between the presses 54 and 56 and their pickup and dropoff positions are reprogrammed before production can begin.
Such systems have the following features::
Such systems have the following shortcomings:
The U.S. Pat. No. 4,695,027 to Lindholm et al. discloses a robot installation for use in a production line including at least one pendulum-type robot, including a primary arm and a secondary arm. A counterweight is displaceably arranged on the primary arm so that a center of gravity of the arm system lies on or is immediately proximate to the pivot axis independently of the position of the secondary arm on the primary arm.