Robotics to the rescue
Unsavory deburring jobs handled through automation
The products vary-aluminum wheels, cylinder blocks and heads, jet engine turbine blades, steel valves, silver spoons and plastic child safety seats. The problem is common to all those production lines-deburring.
Manufacturers must contend with problematical burrs, residual to most casting, extruding and machining operations. Burrs, some minute and some major, must be removed for operational, safety and aesthetic reasons.
Alert production managers know that manual deburring operations using hand-held tools may lead to health and safety problems. Carpal Tunnel Syndrome and “white fingers” (permanent numbness) are common complaints when workers are subjected to constant vibrations emanating from hand-held tools. Also, tedious, manual deburring tasks often result in inconsistent quality of the finished part.
Many manufacturers are replacing, or re-evaluating, their unpleasant and undesirable manual deburring processes with a sufficiently accurate automated alternative: robotic deburring. For example:
* At one of the Big Three automotive manufacturers, a switch from manual deburring of aluminum cylinder blocks and heads to robotic deburring produces significant cost savings by eliminating health and safety problems, while at the same time, increasing quality and reducing deburring cycle time.
* A Kentucky machining specialist realizes similar savings in better quality and faster throughput by adopting robotic deburring of aluminum wheel rims. Removal of the relatively small burrs, left over from casting and post– machining processes, improves the aesthetic appearance of the rims.
In an interesting switch in the deburring technique, a Tier One automotive supplier in North Carolina uses a 6-axis robot to deliver steel slip joints to a fixed-in-place deburring tool. The arrangement helps meet high-volume production requirements.
* A Midwest supplier of child safety seats finds that robotic deburring of fiberglass reinforced plastic components eliminates rigid burr-cutter problems resulting from heat induced size variations.
* Other interesting applications in the automotive industry include deburring of steering knuckles and synchronous gears for off-highway vehicles. In the aircraft industry, applications vary from finishing turbine engine blades, to channel vents for commercial airplane bodies. Even shipbuilders apply robotic deburring for finishing channels in steel plates and in stainless steel valve bodies for valves that handle ultra-high
No easy task
Robotic deburring and chamfering are extremely difficult to perform. Workpiece tolerances and robotic inaccuracies make it difficult for the deburring tool to maintain the constant force needed to cut an even chamfer across a workpiece. Also, the robot and its end-effector may vibrate, causing chattering, which may contribute to producing an uneven chamfer.
“Fixes” tried in the past to help maintain a constant force on the workpiece include either adding compliance (springs) to the robot deburring tool, or using force feedback devices on either the robot or robotic end-effectors. The pneumatically controlled robotic end– effector solution was developed specifically for fast edge deburring. No feedback, to or from the robot, is needed. The compliance built into the tool handles workpiece tolerances and robot inaccuracies.
One example of robotic deburring tools proven in many applications is Speedeburr from ATI Industrial Automation, Garner, NC. The tool is a robust, high-speed, floating head pneumatic tool for deburring and chamfering aluminum, plastic, steel, etc. While spinning at high speeds, the light weight, air driven rotary file (tungsten carbide) rides on a cushion of air that provides +/-0.16 of compliance is both lateral and axial.
A patented force control system provides very high stiffness in the path direction, and low stiffness in the contact force direction. This feature avoids chattering, a common problem with robotic deburring. The extremely low inertia of the floating rotary file allows quick deburr of parts to greatly reduce cycle time. Deburring can be as fast as 1 to 3 ips on hard materials; 3 to 12 ips on soft materials. The deburring tool spins at 18,000 to 25,000 rpm when in operation.
The floating head has a Free Flying Piston (FFP), with a tungsten carbide file attached. A spine connection transmits torque from a pneumatically driven rotor to the FFP, where upper and lower bearings allow rotation to occur.
While rotating, the FFP is free to move 0.32- (8mm) axially inside a brass cylinder that also performs as a bearing. Air pressure is applied above the FFP to urge the FFP down at a constant force onto the edge being deburred.
The pneumatically driven tool has one air line to spin the cutting file, and a second air line to apply force, axially on the cutting file. The second air line combined with the axial motion of the cutting file provides a floating head feature. Regulated air pressure on the floating head provides the constant force needed to produce a good quality chamfer. The tool is extremely light allowing it to hug the workpiece edge at a constant force even as the robot moves across the part as fast as 12 ips.
Automated Cells and Equipment Inc. (ACE), Painted Post, NY, designs, builds and installs factory automation projects. They focus on cells involving robots as a main component. Cell projects perform machine loading, material handling, dispensing and material removal.
ACE President Jim Morris says that a cell devoted to the deburring process is a logical extension to his company’s cell product line.
“It’s tough for a manufacturer to justify the purchase of a robot that will deburr only, and do nothing else. Price– performance ratio is crucial to purchase rationale. However, justification becomes more real on complex, high-volume, high-quality parts where there is 100 percent confidence that deburring will be successful-without the need to touch up.”
ACE is marketing its BurrACEr as a solution for small parts deburring, deflashing, beveling and surface finishing. Its main component is a 6-axis Fanuc LRMate 200i robot that has a load capacity of 6.6 pounds, and a reach of 27.6-. Powerful software features include 3D palletizing.
Morris lists some of the available options for the ACE deburring cell. These include, an ATI tool changer, passive force control devices, and custom end-of-arm tooling. A key tool is the high-speed turbine Speedeburr. Other options include a sanding belt, workholding fixtures, and a parts-feeding conveyor with an escapement feature. Deburring media choices are a variety of brushes, wheels and discs. Morris concludes:
“The BurrACEr design allows either the movement of parts to the media or media to the part. The robot as the heart of the machine allows advanced flexibility in the automated factory.”
J.H. Benedict Co., East Peoria, IL, designs, fabricates and manufactures precision tooling including stamping dies, jigs, molds and fixtures. You will see its type of products in operation in most metal parts manufacturing plants across a wide spectrum of industry.
Supplementing the primary business
is the design and building of a number of robotic systems that weld, handle material (machine load/unload, pick and place) and remove material by grinding, polishing and deburring. Robert E. Everts, director of engineering, explains:
“Most molding and stamping operations leave burrs and unfinished edges. It’s the nature of the process. Manufacturers using our type of products inevitably need to perform some type of material removal to improve the surface finish.
“Usually we are asked to take the undesirable manual surface finishing, grinding and polishing out of the hands of laborers. When we automate any operation by applying a robot, we not only improve the product by eliminating inconsistency, but we also reduce excessive cycle time.
“Our robotic material removal systems are predicated on a customized Fanuc robot with, specific for the job, metal-removal tools. Applications range from precise grinding of turbine engine blades and aluminum wheels to polishing to smooth out a plasma sprayed coating.
“Deburring is process-intensive. Today, we manually teach robots using part surface data. Handling surface inconsistency is one of our challenges. Advances in robotic deburring are incremental today. But it is likely that giant leaps forward will occur when adaptive robotic systems become more mature.”
Ron Osowski, a manager for Ellison Machine Tools and Robotics, Warrenville, IL, is convinced that deburring cells are a major emerging technology that promises a 35 to 40 percent gain in productivity of the deburring process. “Machine tools and CNC machines make a lot of buffs,” he says. “Users of gear cutters, vertical machines, wheel stampers, all have to contend with an end of the manufacturing cycle chore of burr removal. Complicating the problem is the fact that manufacturers are having difficulty finding people to take the jobs loading and unloading and performing the deburring or grinding task.”
Ellison Machine Tools and Robotics is a National Robotics Systems Integrator exclusive with Fanuc Robotics. They engineer, build, integrate, service and support customer needs focused on turnkey integrated systems for a wide variety of industries. Ellison has been successful in supplying deburring cells that use the Speedeburr tool. Osowski continues:
“Selling deburring cells is an extremely competitive business. We must exhibit the ability to handle both large and small buffs. The compliant Speedeburr has proven successful on several challenging jobs. The larger manufacturing companies probably have a number of deburring needs to help justify the robotic cell. The key to success is to assure that the automated deburring operation can perform 100 percent of the deburring task.” ATI Industrial Automation, Garner, NC, http://www.OneRS.net/106tp-401 or circle 401.
Copyright Adams Business Media Jun 2001
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