Automated cell for bearing machining, parts sorting
Gaging as part of the automated cell
Wardell and Buck went on to install a cell consisting of the twin-spindle lathe, gage, an engraving machine, and a 6-axis robot. In practice, the lathe’s two part carousels are loaded with raw workpieces, approximately 300 parts. The lathe’s dual gantry loaders feed the spindles and place finished parts on a chute leading to a conveyor for pickup by the robot. The robot places the part on the Equator for measurement and, if acceptable, transfers it to the engraving machine, and finally boxes and palletizes the finished parts.
“We developed our own tool compensation software” to run on the lathe control software, Wardell added. The software uses measuring results from the gage, transmitted in a CSV file, to offset the tools when the part deviates from tolerance. Machining removes about 0.015 in. (0.38 mm) from each side of the part, with the tightest tolerance at ±0.001 in. (0.025 mm) and an 8 microinch (0.5 micron) surface finish. Parts range in size from about 3 to six 6 in. O.D. The gage is “easily able to measure within our tolerances with a high margin,” said Wardell.
“Our OD/ID stays spot on, with perhaps a couple of tenths variation on radius. We batch-process parts by size, so changeovers of chuck jaws and other tooling are minimized.” Gage speed allows it to “easily keep pace with the process. We re-master only once a day, because our shop is climate controlled to 72 degrees F” [22.2 C].
Inspection, automated flexibility
The measuring methodology for the parts is simple. “We made an aluminum block with a hole in the center,” which is placed in the center of the gage fixture plate, Wardell explained. “We use this to determine our center and set our coordinate system. Each part is placed in the center of that block. We touch to get a center on the part, then surface scan for everything else. We planned the measurement process to work without a part fixture or stylus changing. The robot chooses, through the gage software, which measuring program to run for each type of part. We know the critical features we must measure to ensure the part is within tolerance.”
Measuring, sorting used parts
The hard turning cell currently produces about 600-700 finished parts per day, and it led to a follow-up project involving a parts sorting cell for a customer. Based on a concept sketched out by Touchette, Wardell and Buck are developing a measurement and sorting cell for used mud-motor thrust bearing races.
In oil field service shops, used motors are disassembled, refurbished, and put back into service. “The customer was visually inspecting used races to determine if the parts were reusable, and they knew they were throwing away some good parts—and money,” said Wardell. “We wanted to give them a plug-and-play measurement and sorting system that takes human judgment out of the process, so more good races can be salvaged.”
Still in development when this article was written, the cell Buck and Wardell are assembling consists of two gages, a 6-axis robot, multiple lanes of low-profile conveyor, a vision system, and a quick toolchanger for the robot’s end-effectors. The vision system tells the gage what part number is being presented and what measurement program to run. Good parts are subsequently placed on the appropriate conveyor, and bad parts are placed on a scrap conveyor.
“We designed this system to be trucked in for delivery as a unit, and user friendly for the motor shop people—just turn on the power and load parts onto the conveyor,” Buck says.
“For our machining cell, there was no other cost-effective, shop-floor measuring tool comparable to the Equator,” Wardell added. “And we hope that our venture into cell integration for a customer opens a new business avenue in this area for our entire company.”
- Dave Emmett is Renishaw Inc. business manager/CMM and Equator products. Edited by Mark T. Hoske, content manager CFE Media, Control Engineering, firstname.lastname@example.org.
- Conroe Machine hard-turning work cell uses robotic part handling and part inspection.
- Programmable gages measure and sort mud-motor bearings.
- Process-controlled hard turning cell paid for itself in 18 days.
- Vision system helps sort and separate good parts from bad.
How much more productive could you be with a fully automated CNC workcell?