On-Machine Probing effects on OEEAMTS 2008

Moise CummingsTechSolve, Inc.

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Benét Laboratories

“Research was sponsored by the U.S. Army Benet Laboratories and was accomplished under Cooperative Agreement Number W15QKN-06-2-0100. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of U.S. Army Benet Laboratories or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation heron.”

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Smart Machine Technology Thrust Areas

On-MachineOn-MachineProbingProbing

Intelligent Intelligent MachiningMachiningNetworkNetwork

Health & Health & MaintenanceMaintenance

Machine Tool Machine Tool MetrologyMetrology

Intelligent Intelligent PlanningPlanning

Tool Condition Tool Condition MonitoringMonitoring

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Definition of On-Machine Probing

American Machinist magazine 2008 survey of benchmark companies

Perceptions of On-Machine Probing

What is OEE (Overall Equipment Effectiveness)?– Definition of OEE– Calculating OEE– Six big losses in a plant– Obstacles to OEE

OEE and On-Machine Probing– Test performed at TechSolve– Success Stories

Conclusions

Outline

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On-Machine ProbingAn inspection process within a machine tool that requires minimal use of peripheral inspection equipment or additional operators

– Data is used to make process adjustments to minimize non-conforming parts

Benefits to Industry Work offset verification Detects maladjusted fixtures Collects SPC data

Reduced material handling On-machine rework In-process correction

On-Machine Probing

U-TOL

L-TOL

UCL

LCL

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2008 Machine Shop Benchmark Survey Analysis

From the July 2008 issue of American Machinist– “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

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Industrial Perceptions

Probing diverts time from machining and increases cycle time– Instead of focusing on cycle time, we should evaluate overall

equipment effectiveness (OEE)

Probing routines are difficult to write and use– State-of-the-art software makes writing routines easier and more user-

friendly– Once written, routines can be used on repeat parts

The probe is only as accurate as the machine itself

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What is OEE?

Best practice way to monitor and improve the effectiveness of a manufacturing process

Organizes any productivity losses into three components to provide a gage for process improvement

– Availability, Performance, and Quality

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How is OEE calculated?

OEE = Availability X Performance X Quality

Availability = Operating Time / Planned Production Time

Performance = Ideal Cycle Time / (Operating time / Total Pieces)

Quality = Good Piece / Total Pieces

World-class performance OEE = 85%

The OEE percentage by itself may not provide the right answer– You must scrutinize its components

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Six Big Losses

OEE takes into account issues like:– Machine breakdowns– Setup time– Line restraint– Reduced speeds– Start-up rejects– Production rejects

On-machine probing addresses three of the six big losses in OEE

– Is the sum of those losses worth a probing cycle?

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Obstacles to OEE

Availability – Any event that effects planned production– Changeover, setup, break downs, material shortages

Performance – Any event that causes the process to run at less than optimal speed

– Machine wear, operator inefficiency, mis-feeds

Quality – Parts that are not produced to specification and require rework

– Start-up scrap, production scrap

Q: What are the roadblocks to world class OEE?A: Scrutinize the individual components.

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Current State of Manufacturing

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.

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Benefits of On-Machine Probing

Precise Setup: With on-machine probing, setups can be locatedexactly 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.

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For the sake of discussion, all of the comparisons will be done in reference to the SMPI demonstration part

SMPI Demo Part

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Process StepsPre-Technology

Time in minutesTasks 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

106.5 minutes 43.5 minutes

Probing steps in blue

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Setup Time Reduction and Quality

To minimize linear inaccuracy, on-machine probing can establish a local WCS on localized datum

– This is more significant on longer parts with features that may be clustered in different sections of the workpiece

Setting a local work coordinate system showed a 50% average improvement in the true position

Time Savings: Conventional Method = 8.5 min OMP = 1.0 min = 7.5 minutes

True position improvement of 50% and more than 7 minutes saved

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Setup Time Reduction and Quality

A reduction in time at the CMM and an improved part quality means that there is and increase in the overall equipment effectiveness (OEE) of the plant.

Unknown Distance

G55 G56

Success Stories

Successes from actual customers of TechSolve that have adopted the use of spindle probes

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Effect on Availability

One component of OEE is the lost of efficiency due to machine availability

The availability is defined as:– Availability = Operating Time / Planned Production Time

Availability: Less trips to the CMM and less setups means that the customer is utilizing their machine tool to make more parts

– To achieve this the uncertainty of the process has to be addressed

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Effect on Availability

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

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Effect on Quality & Availability

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.

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Effect on Quality and Availability

Quality: The customer realized a 60% increase in the part quality from the use of the spindle probe

Availability: Less trips to the CMM and less setups meant that the customer is utilizing their machine tool to make more parts

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Effect on Quality

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.

Cell #1 Cell #2 Cell #3

Inspection

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Effect on Quality

Solution: The biggest concerns from the quality department was being able to

– Produce parts that were statistically within control for sampling– Have a method in place to make sure that the machine tool was qualified

1. The machine tool was first qualified and tuned to reduce metrology errors

2. Repeatability studies were performed per the ASME B5.54 standards to ensure the quality of the probe itself

3. The CNC machine was “foot-printed” using a diamond-circle-square test and the part was collaborated using a traceable CMM

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Effect on Quality

Result: With a machine that is qualified, repeatable, and traceable the customer can now inspect parts on the machine within a relative certainty

This will result in an a single daily inspection on the CMM and ongoing inspection key features on the machine

This increase in part quality and throughput will have a direct impact on the plant’s OEE because of the reduction in the three of the six big losses:

– Start-up scrap– Production scrap– Waiting for the CMM’s approval throughout the day

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Conclusion

Spindle probes are meant to increase the productivity and the effectiveness of a process

Probing offsets the time and cost of scrap and downtime that is currently in the machining process

Reduction in scrap and reduced time spent performing offline inspections will increase the overall equipment effectiveness (OEE) of the process

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Questions?

For more information see TechSolve at booth # 1022

Moise Cummings(513) 948-2048

cummings@techsolve.org

www.techsolve.org