Your newsletter for tips on selecting manufacturing technology.
- Tom Grasson - question of the month
- Tips on selecting - the right testing and inspection equipment
- Hot products - guard areas and perimeters without a controller
- Manufacturing education and training - simulation-based training teaches measurement and inspection
- CMMs
- Know the size of parts to be inspected, tolerances, operating environment details, and desired thoughput.
- When considering a supplier, attend a demo of the CMM software. Have the supplier create a part program from a 3D CAD drawing (this feature should be standard).
- Request a gage repeatability and reproducibility (GR&R) test with production parts.
- Have a qualified inspector perform a vibration site survey.
- Ask about warranties, software upgrades, services, maintenance agreements, and telephone support.
- Select a CMM that incorporates materials with the lowest practical coefficients of thermal expansion. Also ensure the CMM is not highly software-compensated to achieve stated accuracies.
- Make sure the included software has been on the market for a while. Software should include Dimensional Measuring Interface Standard (DMIS) compatibility, the ability to use native CAD files, and an intuitive user interface.
- Choose the CMM sensors based on your application -- a limited range of parts and features probably requires only a touch-type probe. Shapes and forms typically require scanning technology. And for delicate profiles, such as on soft workpieces, lasers and video can be the better choice.
Multisensor systems - Consider mainly what type of sensors are included -- for example, combining vision and laser sensors provides plenty of edge and surface-contour data for complete part characterization.
Optical measuring equipment - Consider mainly optics quality, stage size, screen size, magnification requirements, and type of light source -- a horizontal source measures round parts, while a vertical one handles flat surfaces such as gears.
- Ensure the system has edge-detection capability, which lets it automatically detect and measure transition points of a profile image. This feature is becoming an industry standard.
- Look for self-contained systems because they can weather the shop floor.
- Also look for integral edge detection and an internal lens turret -- these features prevent damage and save storage space.
Gaging tools - Consider a highly modular system, which lets shops build special gages from standard components.
- Look at the tradeoffs. Pneumatic gages are inexpensive, but require a continuous supply of clean, dry air. Noncontact/optical solutions are programmable, but require clean, dry parts. Contact-type electromechanical gages offer the advantages of both air and optical gages and they are rugged. But they also require physical contact with the part surface, which may not be suitable where aesthetics are important.
Manufacturing Education and Training
Precision Measurement for Machinists
The Precision Measurement for Machinist (PMM) course from MasterTask Training, Rockford, Ill., which currently comprises video-taped lessons, a CD-ROM with tests, and printed worksheets, will soon be accessible on-line. Course topics include basic print reading, geometric dimensioning and tolerancing, and the metric system of measurement.
In PMM, trainees learn from simulated examples of actual workpieces, prints, and more than 35 measuring devices such as micrometers, roughness gages, rulers, calipers, plug gages, optical comparators, and CMMs. The sections teaching basic skills do so in the context of each job task. For instance, converting fractions to decimals is covered in the lesson on reading a steel rule.
The lessons also eliminate common shop mistakes, such as the 25-thousandths error that often occurs when reading micrometers.
The course tests determine trainees' recall of facts, reading of precision instruments, math ability, and understanding of concepts -- as well as their practical application of knowledge to everyday shop problems.
For example, the test on CMMs has the trainee perform a simulated measurement of perpendicularity. The student must first select the correct measurement sequence, then move the probe to touch off on the workpiece surface -- and must perform all operations correctly to get the question right.
For more information on PMM or other training systems from MasterTask, including Mastering CNC Machining Centers, SPC for Turning, and courses based on specific machines and controllers, call 800-624-6968 or visit mastertask.com
Coming in February's issue: AMERICAN MACHINIST will focus on small businesses.
Find out how small shops can wring out a profit in today's global economy.
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