Production Machining

JUL 2018

Production Machining - Your access to the precision machining industrial buyer.

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the company promotes, fit the needs of the customers, many of whom have ISO medical accreditation and/or FDA accredita- tion. ey require the ability to show an established process that is transferrable and repeatable across multiple machines, which is obtained with consistent preci- sion, from setup to change-over, on a single platform. e machine also features measuring capabilities in the toolchanger. Incorporating Renishaw technology, the OMP400 infrared probe measures the part, and the TS27R contact tool setting probe checks for tool breakage in length and diameter. It's a compact machine, yet provides good rigidity at 10,000 pounds. Standard spindle speed is 30,000 rpm, with a 40,000-rpm option, and the linear drives offer 1.2-G acceleration. Using a wedding cake style, three-tier carousel, the toolchanger can accommodate 90 tools (30 per platen). Palletized Loading In the Bumotec showroom, the s191 is set up with a palletizer rather than a bar feeder for the production of the femoral head. Ten pallets are loaded at a time, each with 20 to 30 workpieces (depending on the part sizes). The B axis is used for both machining and part manipulation. Using an HSK 40 toolholder, the B axis performs turning and milling operations during the machining process. But once the part is complete, it swaps out the current tool for a Schunk two-jaw gripper. The pallet comes back into the workzone, and the B axis grips the ball and loads it back onto the pallet. The focus is to get the people out of the machine and allow the process to take care of itself. finished product, including turning, milling, grinding and superfinishing. e femoral head part family includes three different sizes, produced from chromium cobalt bar. Different barstock diameters and collets are used to accommodate the varying part sizes, but the program and tooling remains the same. Grinding wheels can also be adjusted, from 28 mm to 35 mm. During production of the part, station one, the main spindle, handles the ID, the face and the initial stages of the OD. e subspindle then receives the part with an Ottet collet, a brand of collet designed primarily for thin-walled workpieces that allows clamping on either the ID or the OD. For the femoral head's cutoff operation, it clamps by expanding on the ID. At this stage, the sphere of the part is cut, beginning in the horizontal position (for better chip clearance), then rotated to vertical. ree different grinding wheel grits are applied, and then polishing and superfinish work complete the part on the machine. e finish on the part is 4 microns, and it takes about 12 minutes to complete. e real value of the machine comes in its autonomous nature in producing parts such as the femoral head. e program is already written. Once the bars are loaded, the machine takes very little supervision. As long as material is available and fresh tooling is maintained in the toolchanger, the machine can continue to produce indefi- nitely. e toolchanger is located outside of the workzone, so tools can be changed out at any stage of the process. With the machine working unattended, the operator can be repurposed for doing something else during the day. He or she may be running three or four of the machines at the same time or may be involved in other projects. e turnkey machine can deliver a robust, repeatable process that needs little monitoring. When it hits the floor, it's making parts right away, and the well-defined process can be easily trans- ferred to other locations for process repeatability. Starrag USA Inc. / 859-534-5201 / starrag.com :: The femoral head, made from chromium cobalt bar, requires turning, milling, grinding and superfinishing. Here's another article on this topic: Accuracy Helps Swiss Watches Keep Perfect Time Production engineering solutions required by many Swiss watchmakers are already installed in their CNC machines when they buy them. LINK :: short.productionmachining.com/swisswatch The Part While the s191 is used for a range of complex parts for various industries, one application does well to demonstrate its full capabilities. During hip replacement surgery (performed to relieve arthritic pain or sometimes as treatment for hip fractures) the femoral head—the ball at the upper end of the femur (thigh bone)—is replaced with a prosthesis. Bumotec specializes in machine adaptations for processes such as the production of the femoral head and has found a nice market niche for medical suppliers requiring these parts. According to the company, the turnkey process it has developed for these parts is different than how it had been produced in the past. It takes advantage of the retaking unit to manipulate the part in the workzone, taking it from bar to 40 PRODUCTION MACHINING :: JULY 2018 MEDICAL

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