Flatness Measurement Errors from a Datum - Test Method

C

cslauenwhite

#1
Hi all....

:lmao:

I have been racking my brains for this for quite some time and I have come up with nothing... So time to ask the experts..

We have a part which is approx the size of a piece of paper and approx 3mm thick. On this part in the beginning was a flatness callout of 0.020mm. The 1st problem came from the question that the engineer wanted to see direction of any flatness errors from a datum.. After much discussion this was changed to a profile of a surface...

The issue I am running into is it is now listed as a offset tolerance of +0.005mm/-0.035mm.

To boot this measurement is also listed as a "restrained state" measurement with 17 lock down points.

Right now we are doing this on a touch trigger cmm with a clamping fixture. Cycle time to complete is 6min. takt time needed is approx 6 sec to do the measurement complete with restraining. Also the GRR (TV) of the CMM method is approx 30%

Any ideas would be greatly help full.

:thanx:
 
#2
The 1st problem came from the question that the engineer wanted to see direction of any flatness errors from a datum..
That, I can imagine, as flatness can have no datums: It only concerns how flat a surface is, regardless of any other datum’s or features.

To boot this measurement is also listed as a "restrained state" measurement with 17 lock down points.
Which I assume corresponds to how it is assembled? What is the function of this surface?
 

Ron Rompen

Trusted Information Resource
#3
Cory: Have you considered using an optical flat, rather than a CMM? The GR&R will (probably) not be much worse than the CMM, hopefully better. The throughput time should be significantly faster, which I understand to be one of your significant constraints.
 
N

ncwalker

#4
The flatness question: If this is a primary datum, I don't see how you can control it with a profile because there is nothing to call it back to. So having a non-centered tolerance on the object doesn't make sense. But only if this flat surface is a primary datum. If it is a primary datum, than flatness is your callout and it only has one direction - away from dead flat.

As to your throughput - I don't know the part (other than it's the size of a piece of paper) but 17 restraining points seems excessive. That's a whole lot of opportunity for bolt torque order and amount to warp the thing. And if that is actually mimicking installation points, I'd gather that with that many of them, you could take a part considerably out of specification and draw it up with all the bolts. To increase throughput I would:
a) fight with engineering to get the number of required restraint points reduced
b) fight with your boss/tooling to make you a fixture that would clamp all the points automatically either with air or hydraulics. That's way cheaper than buying more CMMs to keep up with through put. In fact, get two of them. So you can be clamping up the front part while the CMM measures the back one and vice=versa. OR get a specialized machine with clamps and transducers and do the entire measurement one shot at a faster cycle time.
 
Thread starter Similar threads Forum Replies Date
hogheavenfarm GDT Flatness measurement question Inspection, Prints (Drawings), Testing, Sampling and Related Topics 10
E Flatness Measurement of Plastic Molded Parts - Clamping / Holding Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
F Flatness VS parallelism Design and Development of Products and Processes 6
B How to do a control chart - Machining product that requires flatness control Capability, Accuracy and Stability - Processes, Machines, etc. 1
S Difference between Surface Finish (Ra) and Flatness (GD&T) Inspection, Prints (Drawings), Testing, Sampling and Related Topics 6
G From an ISO 17025 auditor perspective must micrometer calibration check anvil flatness? General Measurement Device and Calibration Topics 4
I Flatness - Rectangular part using the three jack method Inspection, Prints (Drawings), Testing, Sampling and Related Topics 10
N Do I need to approach galvanized steel sheet flatness issue with DOE? Problem Solving, Root Cause Fault and Failure Analysis 9
G How to compute or estimate a micrometer or caliper flatness using optical flat General Measurement Device and Calibration Topics 2
W Standard for Micrometer Anvil Flatness Oil and Gas Industry Standards and Regulations 5
G Caliper or Micrometer's Dimensional Flatness General Measurement Device and Calibration Topics 5
P Checking flatness with Go and No Go Jig Manufacturing and Related Processes 2
J Flatness measured to locations of a plane Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
B Result of a Flatness MSA on a CMM Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
C Measuring Flatness of a Pump Cover General Measurement Device and Calibration Topics 14
N The right method to Measure and Evaluate a Flatness Callout Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
F Reason a plane would have a runout applied and not a flatness callout Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
C Micrometer Parallelism and Flatness Calibration Requirements and Specs General Measurement Device and Calibration Topics 10
G Determining flatness and parallelism rapidly Manufacturing and Related Processes 2
Q Micrometers to Measure Coating Thickness - Failed Calibration Flatness & Parallelism General Measurement Device and Calibration Topics 9
optomist1 GD&T Flatness Automatic Indirect Control Rule #1 Inspection, Prints (Drawings), Testing, Sampling and Related Topics 20
B Flatness Call Out confusing me - What they are wanting and how to check it? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 42
C Surface Plate Calibration - How to verify the flatness of a granite surface plate General Measurement Device and Calibration Topics 1
A Ovality and Flatness generated after Heat Treatment of Rolled Rings Manufacturing and Related Processes 3
B Inspection Tools for Flatness and Channel Depth of Bipolar Fuel Cell Plates Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
C Techniques for Measuring Flatness General Measurement Device and Calibration Topics 37
Z Inspection of Flatness of a part using an electronic device Inspection, Prints (Drawings), Testing, Sampling and Related Topics 2
W Warping / Flatness SPC - X bar-R chart - Control is Max 0.15 Statistical Analysis Tools, Techniques and SPC 5
D Flatness tolerances for tempered cold rolled stainless steel coils Manufacturing and Related Processes 3
Proud Liberal Flatness / Straightness / Bow specification Various Other Specifications, Standards, and related Requirements 12
D Optical flats - "FLATNESS INTERPRETATION CHART, Light Wave Band Pattern Guide" General Measurement Device and Calibration Topics 4
D Looking for 100% sort testing equipment for overall length, flatness, and parallelism General Measurement Device and Calibration Topics 1
S What is the best method for checking the flatness of a flexible part? General Measurement Device and Calibration Topics 4
M IATF 16949 SI # 10: Integrated self-calibration of measurement equipment- Needs for explanation IATF 16949 - Automotive Quality Systems Standard 2
I QMS monitoring, measurement, analysis and evaluation requirement - Template ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 9
F Physical Part Measurement General Measurement Device and Calibration Topics 6
M Measurement Uncertainty in Optical Microscopy Measurement Uncertainty (MU) 1
B ISO 6508 and portable hardness measurement instruments General Measurement Device and Calibration Topics 0
C How to Establish the Calibration & Measurement Capability (CMC)? ISO 17025 related Discussions 1
Ron Rompen Measurement of residual magnetism General Measurement Device and Calibration Topics 2
M Surgical angle measurement guide device with an application software Medical Device and FDA Regulations and Standards News 1
M Disabling measurement data during fault conditions IEC 60601 - Medical Electrical Equipment Safety Standards Series 5
J Most versatile measurement device General Measurement Device and Calibration Topics 2
P Surface scratch measurement General Measurement Device and Calibration Topics 1
N Drawing tolerance vs. Measurement device General Measurement Device and Calibration Topics 7
Ron Rompen MSA on automated measurement system - Multiple Step Vision System Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
P Thermo-Hygrometer - Measurement of 10DegC @10%RH ISO 17025 related Discussions 4
K Software Validation for Measurement Tools used in Process Validation ISO 13485:2016 - Medical Device Quality Management Systems 2
K Best Measurement Systems Demos in California? General Measurement Device and Calibration Topics 1
M Measurement Error - How to determine what is acceptable? Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3

Similar threads

Top Bottom