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“ This year, there was a noticeable increase in the uses of in-process measurement, coordinate measuring machines, barfeeders and prefixturing of workpieces, especially for shops in the benchmark shop categories.”
Increasing the overall equipment effectiveness (OEE) is one of the hallmarks of the machine shops in the benchmark categories
Start-up scrap: One of the biggest losses to a production environment comes from the setup procedure . This may be because the setup process is very dependent on the skill of the operator. There is also a chance that the wrong rough stock can be loaded.
Production scrap: Another major loss to a production environment comes from the production process itself (such as tool wear and features “drifting” out of tolerance).
Time loss: Time is lost in production due to waiting in (off-line) inspection queues and conventional setup procedure.
Precise Setup: With on-machine probing, setups can be located exactly to the rough stock to avoid air cuts or buried cutters in a roughing process.
Process verification: Features can be inspected during the production process and reported back to the operator. This will reduce time at the CMM and allow for more uptime at the CNC.
Time savings: Routines can be written that will allow setup to be performed in a fraction of the time of conventional (manual) setup procedures. Local work coordinate systems can also be used to eliminate positional accuracy of the machine for a high-tolerance, local set of features, such as bolt hole patterns.
For the sake of discussion, all of the comparisons will be done in reference to the SMPI demonstration part
SMPI Demo Part
Process Steps 106.5 minutes 43.5 minutes Pre-Technology Time in minutes Tasks Why & Benefit Post-Technology Time in minutes 20.0 Set G54 Establish work coordinates 2.0 4.0 Validate rough stock Inspect for correct stock 2.0 4.0 Laser inspection face mill Accurate tool length - TCM 1.5 10.0 Face mill surface Optimized tool path - IM 5.0 4.0 Laser inspection end mill Accurate tool length - TCM 1.25 21.0 Roughing two pockets Optimized tool path - IM 10.5 8.0 Finishing two pockets Optimized tool path - IM 5.5 8.5 Set G55 & G56 Set local work coordinates 1.0 4.0 Laser inspection drill Accurate tool length -TCM 0.5 4.0 Drill holes in G55 & G56 Optimized tool path - IM 2.5 19.0 End mill roughing two bores Optimized tool path - IM 9.5 3.0 Laser inspection measure tool Accurate tool wear - TCM 1.25 1.0 Finish 50 mm holes Improved accuracy of holes - IM 1.0 varies Final inspection On-machine probing vs. CMM 3.0 Probing steps in blue
Scenario: A company manufactures complex aircraft components during a three shift (24 hour) operation. The components must be inspected to a traceable standard before they can be signed-off. The queue at the CMM and the inspection process is one hour. The CNC must idle while the inspection is taking place or risk making scrap parts.
Solution: After tuning the machine and performing repeatability studies on the machine, the CNC can inspect the parts with a high level of certainty per ASME B5.54. The shop is able to move from lot inspections to first and last article inspection while sampling CTQ features on the CNC.
The availability of the machine increases by 12%, which adds to the OEE due to the increase operating time.
Availability = Operating Time / Planned Production Time
Problem: A customer has to machine a cast aluminum housing. The housing has two production locating pins that are used as datums that span 24 inches apart. Between those datums are a series of machine features, among those features are four bored holes surrounded by bolt hole patterns that have to maintain true positions of 0.040”.
Solution: The client is able to use a spindle probe to establish a local work coordinate system within the bore diameter. By using that local work coordinate system as the origin of the bolt hole pattern, the process is able to easily hold a true position of 0.001” (previously 0.040”) to the main bore without breaking the setup or making multiple trips to the CMM.
Problem: A manufacturer has an issue with bottlenecks at the inspection area due to the volume of work being produced on the CNC machining area.
Goal: To utilize on-machine probing to go from ongoing inspection to first article inspection, which would reduce the inspection time by 80%. This would lead to an increase in production due to less time spent waiting for inspection .