Your newsletter for tips on selecting manufacturing technology.
- Tom Grasson - question of the month
- Tips on selecting - the right fixture: workholding devices
- Hot products
- Manufacturing education and training - center part of nationwide manufacturing partnership
- Reader's gallery of shop photos - shop began in this 1957 garage location
Please e-mail Tom your questions, suggestions, or comments.
- For part turning, shops can opt for three or four-jaw chucks, which grip parts for safe machining, while establishing workpiece location and orientation with specified repeatability. The shape of the workpiece determines the number of jaws needed. There are also sealed chucks, which keep out dirt, chips, and fluid.
- Shops can also use diaphragm chucks, which provide repeatability and clamping force consistency. These chucks have no sliding parts. Most diaphragm chucks use a pneumatic cylinder, which opens to release the workpiece.
- Another option is collet chucks, which secure practially any shape fitting within the collet envelope. Collets resist rotational forces and multidirectional cutting loads; amplify actuation force, converting it to gripping force; rapidly release the workpiece; operate at high repetition levels without loss of accuracy or material failure; operate over a range of rotational speeds with minimal loss of gripping force; and perform with a minimum of rotational inertia.
- Expanding mandrels clamp parts on interior surfaces. Mandrels offer concentricity and rigidity. Their actuation is either manual (turning a bolt) or hydraulics and a drawbar.
Vises and clamping systems
- Vice size and configurations are best determined by the workpiece shape, the machine tool used, and cycle time (if the cycle time is short, power-operated vises save clamping time).
- Shops should look for strong, rigid vises providing vibration-damping qualities. For process flexibility, they may consider modular vises with multiple clamping stations or tombstone setups. Attaching vises to table-mounted plates or indexing units generally makes the most of the workholding envelope.
- Customized vises may be the best for setups designed around specific parts where complex processes, high throughput, and high quality are required.
- For clamping systems, shops should turn to fixture/system designers that can help them select clamping, supporting, and positioning elements for hydraulic workholding systems. For example, an expert can help pick seals in each clamping element that are compatible with the machining center's hydraulic fluid.
- If clamping elements must withstand high-pressure or flood coolant, or be subject to short clamp/unclamp times, as in robotic load/unloading, then consider double-acting clamping components.
- By palletizing workholding systems, shops are providing a common interface to its machines and robots, regardless of workpiece configuration and size. Also, the systems lets operators fixture parts off machines and speed transfers between machine tools.
- The pallet system should have common components holding the blank and common fixtures to secure it to the machine tool. In addition, the system design should guarantee consistent placement of the workpiece, and the chuck/receiver should accommodate a selection of pallet configurations.
Manufacturing Education and Training
Center part of nationwide manufacturing partnership
The Manufacturing Extension Partnership (MEP), a program of the National Institute of Standards and Technology (NIST), comprises more than 70 facilities nationwide that give manufacturers technological resources helping them be efficient, productive, and competitive.
Part of MEP is the Alabama Technology Network (ATN), which, in turn, has 10 technology centers, each tailored to meet local industry needs, linking academia and a state economic-development program. Started in 1988, the Bevill Manufacturing Technology Center, Gadsden, Ala., is the oldest and largest.
Paul Wilhite, CNC engineering manager at the center, explains, "When Bevill began, its main purpose was to demonstrate advanced technologies to companies, showing them what is out there and what they could do. Therefore, we selected our equipment to have a good sampling of what's in the manufacturing environment."
Equipment at the center includes four Hurco VMCs - three VM1s and a VM2 - each of which features conversational programming. One has a probing system for in-process monitoring. Bevill also has other machine tools and EDMs, a load-unload robot, a CMM, an optical comparator, and a lot of small gaging tools.
"And we have a good sampling of software and can do reverse-engineering for companies, " continues Wilhite.
Bevill helps companies get their ISO certifications, provides robotic training, and occasionally runs jobs for shops. The center also performs SPC and lean-manufacturing training. And the Anaston Army Depot, a military facility that reworks equipment such as tanks, has a large machine shop at the center. Many of the center's students, employed with local tool and die companies, are in apprenticeships to get machinist Journeyman's certificates.
Wilhite continues, "We recently adopted a National Institute of Metalworking Standards (NIMS) program that accredits machinists called The National Competency Based Apprenticeship System. NIMS has created national standards, setting up exams and parts for students to make so that someone passing the NIMS level in milling in Alabama, for example, could go to Michigan and there would be a common reference."
Reader's Gallery of Shop Photos
In prior e-newsletters, AMERICAN MACHINIST requested photos from your shop to put on its new website. Pictures could include images of an old shop, your clever machining solution, or even an interesting home project. Thank your for your phenomenal response.
A photo submitted from Boston Centerless, Woburn, Mass. was taken in 1957 in a garage location in Arlington, Mass. On the left, is Len Tamasi, founder of the company. He started with one machine in this garage. Today, the company's state-of-the-art facility is 45,000 sq. ft.
Coming in April's issue: AMERICAN MACHINIST V.I.P Edition focuses on EDM.