Mass Finishing in a Less Frenetic Fashion
While most finishing processes use a large vibratory tumbler, parts with complex or delicate features need a softer touch.
The vast majority of mass finishing processes I’ve encountered in shops use a large vibratory tumbler inside of which a mishmash of workpieces and finishing media swirl around in contact with one another, serving to smooth, deburr, radius or polish the workpieces.
While this might be perfectly fine for some applications, what about for parts that have complex shapes or delicate features that could become damaged if they were to bump into each other during such a frenetic finishing process? For these parts, an alternate method of introducing them to finishing media might be required to prevent potential damage from occurring.
In fact, Rösler Metal Finishing (Battle Creek, Michigan) suggests three automated options to completely finish workpieces such as these or to perform targeted finishing of specific surfaces in a high-production environment, leveraging the advantages of robotic handling.
One is called Surf Finisher, which uses one or two robots with custom grippers to pick workpieces from a conveyor, immerse them in a rotating work bowl filled with the appropriate grinding or polishing media, and then return them to an outbound conveyor. The work bowl is available in different sizes to enable the finishing of a single, large part or the simultaneous finishing of multiple smaller parts. The robot can guide the workpieces through the processing media in pre-programmed movements including defined treatment angles, different immersion depths and rotary motion to enable the targeted finishing of specific surface areas.
The work bowl with processing media rotates as fast as 80 rpm (actual speed is determined by the types of workpieces and finish requirements). The robotic movement, combined with the work bowl rotation, creates a “surfing” effect with very high pressure between workpiece and media. This concurrent, intensive pressure is said to create a surface smoothing effect in a relatively short amount of time, achieving surface finishes to 0.04 micron Ra.
Another option also uses one or more robots that perform two functions: material handling and programmed movement of workpieces through the processing media. For this system, which is called High-Frequency-Finisher (HFF), the media for wet or dry processing within the work bowl spins as high as 3,000 rpm and also is agitated by vibration. The robot with custom gripper immerses the workpieces into the agitated media, and the dual movement of the robot gripping the part and media results in a high-pressure, highly intensive treatment of the parts completed in fast cycle times.
A third is a new version of Rösler’s Drag Finishing system that includes automatic workpiece loading/unloading. In fact, this automated system was developed for Walter AG, the multinational cutting tool manufacturer, to enable the company to automatically deburr a variety of different-sized tool bodies instead of having its employees do that manually.
This system uses two interlinked drag finishing machines, each having six working spindles, served by a robot that automatically installs and removes tool bodies in and out of the spindles. The finishing process for these tools requires a safety load system that combines workpiece surface modeling and load pattern simulation. To ensure that handling errors do not occur, electronic sensors continuously monitor the pneumatic coupling system to ensure tool bodies remain safely fixtured in the spindles.
Once loaded, the tool bodies are then “dragged” through the stationary wet or dry processing media. Process parameters such as carousel and spindle speeds, immersion depth, and treatment times are stored in preset programs in the system’s programmable logic controller (PLC). After completion of the finishing cycle, the robot removes the tool bodies, moves them to a rinse and cleaning station, and then places them onto a tray.
The company says this system can also be used to perform effective, repeatable surface finishing for items such as orthopedic implants, geared components, and aerospace and automotive parts.
One of the most common methods of tapping in use today on CNC machines is 'rigid tapping' or 'synchronous feed tapping.' A rigid tapping cycle synchronizes the machine spindle rotation and feed to match a specific thread pitch. Since the feed into the hole is synchronized, in theory a solid holder without any tension-compression can be used.
The more common twist drill point geometries often are not the best for the job at hand. By choosing the best point for the material being drilled, it is possible to achieve better tool life, hole geometry, precision, and productivity.
Reducing cutting fluid use offers the chance for considerable cost savings. Tool life may even improve.