Include Inspection in Automation Plans
Expand your thinking for process and quality improvement.
Improving automation efficiencies remains a very hot topic, but because inspection often requires measuring components offline, this can be overlooked. Typical solutions highlight robotic loading and unloading or built-in dual-pallet systems on your coordinate measuring machine (CMM), but to maximize value, automating inspection has to be integral to the production process. Says product specialist Brian Johnson of ZEISS Industrial Quality Solutions (zeiss.com/metrology), “Automation equals productivity. It’s as simple as that.”
Yet inspection has its own issues that must be accommodated. Traditionally, inspection is at the end of the production process, so moving inspection onto the shop floor can reduce throughput time, and the same dedicated tools and fixtures that improve efficiencies in the inspection lab can be used on a CMM in the production line, he says.
The current state of inspection entails a dedicated off-line inspection room or lab with inspection equipment set up and ready; calibrated and certified inspection gages; and standardized and detailed work instructions. Improving inspection efficiencies, whether in the lab or on the factory floor, must start in part design, Johnson says. What are the component’s dimensions, production volume, inspection frequency needs? Knowing design parameters up front opens the opportunity for acquiring, pre-building, and staging modular fixturing and tooling kits to maximize CMM throughput by reducing setup time between inspections. While reduced setup time and improved efficiency are benefits, modular fixtures and tooling do require increased investment up front and staging and storage space, which can be budgeted against projected efficiency gains.
First, the Equipment
Upgrading CMMs to take advantage of higher performance dynamics should also be a regular consideration. PC and software updates should happen regularly to accommodate faster processing and report delivery as well as staying on top of corporate security measures or industry standards compliance.
Moving lab-based inspection to the shop floor is not to be feared. Depending on how many hand gages can be eliminated while inspecting on the production line, this could actually turn out to be a money-saver, Johnson explains. While the selected CMM models could offer shorter optimized routines and be flexible for many part configurations and sizes, the shop floor environment and its attendant temperature and humidity variations, dust, and vibration all must be considered.
“Select a shop-hardened CMM when possible,” Johnson advises. Bearings are designed for large temperature swings, machine guarding and covers are in place to protect critical components, machine scales are thermally stable, and temperature compensation is available for both machine and workpiece.
Having a plant utility package for shop-floor CMMs is valuable for filtering and treating both air and incoming electric power beyond the requirements of typical shop equipment. Modern CMMs feature pressure regulators, booster and accumulation tanks to maintain minimum air pressure, multi-stage coalescing air filters for oil removal, and a high-efficiency and volume membrane air dryer.
Shop-floor electrical capacity may have noise and spikes. In addition to a sine-wave-generating uninterruptable power supply to treat and filter electric power supply to the CMM, a multitap step-down isolating transformer with proper fused disconnects or breaker panel is strongly advised.
And there are industry-specific advantages as well. Automobile manufacturing requires measurements of countless bores in addition to edges, sections or transitions. Checking boreholes can be extremely time-consuming work, particularly for serial inspection. Optical scanning probes like the ZEISS Eagle
Such results are based in part on an articulating probe holder. To obtain the required measuring results quickly and easily, the sensor has to be optimally integrated into the overall system. The ZEISS RDS-CAA stepping, articulating probe holder works well because only a few single positions have to be calibrated, but all angular settings are available for the application. This enables a considerable reduction in measuring times. Through the utilization of an additional manual rotary axis, the ZEISS Eagle
Take advantage of supplier process engineering teams to see if manual, semi-automatic, or fully automatic part-handling systems best optimize your current and projected production flow. From roller tables and transport carts to robots and shuttle depots, including those with integrated temperature sensors, there is a wide availability of components to automate your inspection function.
Pay attention to inspection machine components as well. “Harder stylus material such as silicon nitride and diamond minimize buildup, which can reduce calibration frequency,” Johnson says.
Controls and communication protocols need to be addressed as well. “We run the gamut from hardwired discrete I/O to Profibus and ProfiNet favored by Siemens users and single Ethernet/IP cables and interfaces,” he adds. “In such cases, setting up an in-line CMM can be like treating the CMM like CNC equipment.”
Driving Out Fear
There are very important human factors to address when engineering an automation solution. Automating inspection can have very straightforward goals. Reducing lead time from production to inspection together with reduced setups between inspections can increase the availability of production equipment and increase inspection efficiencies.
“It’s important to identify that making more efficient routines makes for more efficient metrologists,” Johnson adds. “Automation is widely seen as a job killer when in fact it is a job creator and identifies value-added opportunities in the time savings.”
Improved maintenance routines, for example, add value and can increase machine performance. Visual checks, daily cleaning of stylus tips and spheres, running stylus qualifications, cleaning and replacing filters, and keeping granite and guideways free of debris all go a long way to increasing machine life in line with improved efficiencies. In such cases, automation can equal more than productivity.
By James Gaffney, Product Engineer, Precision Grinding and Patrick D. Redington, Manager, Precision Grinding Business Unit, Norton Company (Worcester, MA)
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