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In most shops, labor is the biggest expense over which management has much control. Costs of raw material, rent, utilities and equipment can’t be changed in the short term or for any one particular job. And, to compete with countries with labor rates only 10 percent of ours or less, shops must always be looking for ways to do the job better, faster and with fewer labor hours for each part produced.
Shops have widely embraced a few effective techniques for reducing operator pacing of machining. A great many have adopted mill-turn centers in recent years. Extending the unattended machining run time by combining operations with multitasking, mill-turn lathes can cut in half the number of times the lathe sits idle waiting for the operator to change the workpiece. Many shops have also embraced short magazine bar feeds, which can even more dramatically reduce labor costs. Since the operator does not need to load each workpiece, the lathe never waits, and it runs unattended through breaks, lunch and into the night.
But, what options does a shop have when parts don’t fit through the spindle, and thus cannot be bar fed? Some solutions are available. Fully automated, multi-axis robot cells can be used to eliminate manual workpiece loading. But according to ATS Systems (Rancho Santa Margarita, Calif.), fewer than 5 percent of shops in North America use multi-axis robot technology. Shops commonly avoid using these systems because they feel they are too complicated, too expensive, and/or they require too much change-over time for the typical 25- to 100-piece batches.
H-Bot Gantry Loader
To address these concerns, ATS offers the H-Bot lathe gantry loader, which allows job-to-job setup change-over in less than 10 minutes. With its standard gripper it is designed for round slugs, castings and forgings ranging from 2 inches to 6 inches in diameter, with mass up to 50 lbs and machining cycle times of 1 minute or longer. Options are available for parts that fall slightly outside of these ranges.
The unit will fit on most common 6-inch, 8-inch and 10-inch chuck lathes, whether single or sub-spindle configuration. The robot commands the door open, unloads the completed workpiece, fires an air blast to clean the chuck jaws, and inserts the blank workpiece. The approximate time required from door open to door close command is 25 seconds, which will vary slightly by lathe and part characteristics.
After the workpiece exchange, the robot transports the finished workpiece out of the cell via a chute. An optional conveyor is available for parts that cannot be dinged. The robot then fetches the next workpiece blank and waits. Approximate time to retrieve the next blank and return to the ready position above the lathe is about 30 seconds.
While the robot waits, its material magazine stages the next blank for pickup. Pneumatic cylinders gently guide the next blank down a chute to set it in the proper pickup location.
Setup change-over is quick and easy. The standard gripper is a three-jaw chuck with very long jaw stroke. The standard jaws have three steps, which allow gripping any diameter from 2 inches to 6 inches with no adjustment at all, for a gripper setup time of zero. If required, special jaws can be changed in minutes. To program the gantry moves using the intuitive Setup Wizard and 7-inch color touchscreen, the operator simply jogs the system to the pickup and drop-off points and presses the teach button. Finally, the incoming material magazine is adjusted for the new workpiece length. The complete gantry setup typically takes less than 10 minutes and is easy to learn.
ATS uses a few key technologies in its design to provide an affordable, rigid and robust system. The two servomotors are paired for all linear axis moves, doubling the available power while keeping cost down. The wrist axis is servo-driven by a torque tube through the mast, keeping the servomotor out of the machine in a clean environment. The wrist size is compact, and gravity drives the material magazine. The overhead design keeps the work zone clear for access by the operator.
ATS provides both an automation experienced project team and locally based service technicians. The project team reviews applications, provides custom proposals and builds the systems. The local technicians provide installation, training and other lifetime support.
The H-Bot system is designed to address the common concerns of robots being too complicated, too expensive or requiring too much change-over time and can be retrofit to existing lathes or new lathes being brought onto the shopfloor.