presented by dan lange, manager - services · see what you’re missing u2u conference abstract...

SEE WHAT YOU’RE MISSING U2U Conference SEE WHAT YOU’RE MISSING U2U Conference

“HOW TO REVIEW A CETOL 6σ ANALYSIS” Presented by Dan Lange, Manager - Services

SEE WHAT YOU’RE MISSING U2U Conference

Abstract

Reviewing a CETOL 6σ analysis requires a comprehensive understanding of the assembly being studied and the capabilities of the software. In this presentation we will review a methodical approach used by Sigmetrix engineers to review analyses submitted by newly trained students during post-training support. The approach covers modeling, validation, and results interpretation and can be applied to your own analyses or analyses created by your peer.


KEY SUBJECT MATTER

Advisor Window

Part order

Joint order, type, location, orientation, considerations

CETOL 6 Analyzer CETOL 6 Modeler Assembly Modeling

Create joints Set joint properties

Define Objectives

Create measurements Set measure properties

Part Modeling

Constrain features (dimensions, GD&T, etc.)

Specify tolerances

Validate Model

Check Advisor messages “Show Part Locations” Visualize sensitivities

Review Results

Inspect measurement variation plots Inspect sensitivities and contributions

Generate Report

Improve Quality/Reduce Cost

Adjust tolerance values Incorporate mfg. data Etc.

Run Analysis

Measurements

Model behavior

Results


Advisor Window

Clear all messages

Why? – Impact can range from no

impact to incorrect answer or no answer at all.

Action – See Advisor Message Table

– Note: Selecting message in Advisor window will jumps to the item in the CETOL Tree, if applicable

CETOL 6σ Advisor Window

Unconstrained Part DOF


Advisor Messages ADVISOR MESSAGE ACTION

"Feature is unconstrained by ##" Add dimensional constraint

"All constrained variables are redundant" Determine which constraint to keep; delete other

"The constraint controls no variables" Delete constraint if not needed

"Measure appears to be discontinuous" Define measurement direction

"Endpoints invalid for measure type"

"Direction feature invalid for this measure" Chose valid direction feature or delete

"One or more derivatives failed" Review Analyzer Sensitivity List; KB Article - SSC.

"The 2nd order Taylor Series used for the SWC solution has an internal critical point"

The measurement has a minimum or maximum that is not at tolerance limit for one or more of the variables. Use visualize sensitivities for the largest contributors to see if any of those variables have internal critical points. Use a scale factor of 1.0 and look for curves in which the maximum or minimum value is not at one of the endpoints of the curve.

"The 2nd order Taylor Series used for the SWC solution has a saddle point"

KB Article - SSC.



"Component is under-constrained" Select part, highlight under-constraint. Add joint

"Joint is over-constraining" Review joint order. Remove DOF Tip: rotational)

"Object is Invalid" Yellow triangle; reselect a reference.

"The GDT callout type is not supported for this feature type“ Workaround or redefine dimension scheme

"The DRF is not valid for this GDT callout" Redefine DRF

"The orientation tolerance is larger than allowed by the related location tolerance”

Adjust orientation or location tolerance.

"The feature is not valid as a datum feature" Redefine datum feature

"The feature is not valid as a multiple datum feature" Redefine datum feature

"No orientation feature for joint with tangent bias" Define orientation. Review DOFs. Tx-Ty may switch

"The tolerance limits are far from the design nominal" Review tolerance settings for constraint

"The distribution mean lies outside the tolerance limits" Review distribution.

"No orientation feature for joint with ambiguous orientation"

Define orientation. Review DOFs. Tx-Ty may switch


Advisor Messages ADVISOR MESSAGED ACTION

"Datum feature has no size dimension and is not RFS" This indicates that there is an (M) or (L) modifier applied to a datum feature that does not have a size dimension (e.g., the feature references a Creo datum plane or a datum axis). You do one of the following: 1. Edit the feature and add the related geometry. For example, if the feature references a Creo datum axis, add the hole or shaft geometry to the CETOL feature 2. Remove the the material condition modifying symbol (i.e., change it to RFS)

"The linked CAD GDT has unsupported attributes" There are some attributes [(P) (F) and (T) or <ST>} that are not supported and their affects are ignored.

"The CETOL DRF does not match DRF of the linked CAD GDT" This happens if you edit the DRF in the CAD system after establishing the link to the CETOL object.

"The CAD object linked to this CETOL object is missing" You should do one of the following: 1. Delete the object 2. Unlink the object

"The dimension nominal does not match the linked CAD dimension's nominal"

This happens if you link a CETOL dimension to a CAD dimension that may not be directly associated with the geometry that the feature references and that dimension is changed in the CAD model.



"The tolerance type of the linked CAD dimension is unsupported"

The dimension has an unsupported tolerance type (e.g., MIN or MAX). I think this is only applicable to SolidWorks models.

"The model has unsupported units" You get this if you try to synch with a CAD model with unsupported units (e.g., angles in deg/min/sec) Supported linear units: Supported angular units:

micrometers radians millimeters degrees centimeters milli-radians meters gradians mils (1/1000th inch) inches feet angstroms nanometers kilometers micro-inches yards miles


Part Order

Order parts to represent actual assembly sequence as best as possible

Why?

– Reporting of assembly under-constraints

– Animations are affected

– Example DOFs: (6) DOV part versus (4) DOV part

– Affects solving for closure

Action

– Review order using component highlight


Part Order Matters

Constrains (4) DOF (6) DOV PART

(4) DOV PART

• BASE is ground part. • (4) DOF applied to (4) DOV

BUSHING results in Over: 0 Under 0

• BUSHING is ground part. • (4) DOF applied to (6) DOV BASE

results in Over: 0 Under 2


Joints – Order, Location, Type

For most conditions*, the first joint controls the orientation of the part. Joints 2, 3, … control location. Represent actual assembly process order as best as possible. Check location, orientation & type of joint

*Not always … shaft held at ends or 3-legged stool

Why? – Reporting of over-constraints is based on order

– Animations & results are affected

Action: – RMB in CETOL Tree Tree Level \ Joints & Measures

– Show Part Loc

– TIP: Empty config to show DOF progression


Joints - Considerations Watch for and review the following:

– “Joint balls” blurry or have distance between?

• Do you want the joint to close the gap or should it be redefined?

– Custom joints • Why was a custom joint used? Does it simplify the

analysis? Will it affect answer?

– Closure, the ability to put the model in the position defined by the joints. Can result in Solved Nominal = CAD nominal. More later …

Not coincident investigate Reduce symbol size


Measurements

Verify measurement accurately defines assembly requirement

Why? – Could lead user to make unnecessary

changes, especially nominal design changes – Got to ask the right question to get the

answer you need

Action: – Activate a configuration – Set assembly in SHOW PART LOC mode – Review direction & attachment locations – Review nominal values.

• “Plus” or “minus” ? • Solved nominal = CAD nominal? Should it? Joints

used that close gaps?

– Review Target Limits • Fit analysis (1-sided failure limits) or

performance analysis

Example shows solved nominal different from CAD nominal. CAD constraints centered teeth. Tangent gear teeth altered position of GEAR2.


Configuration Joints

Verify assembly position Why?

– Need to ensure position matches use-case for analysis

Action – Use SHOW PART LOC – Make sure “new” position of parts

does not create interference ANYWHERE in the model. (ProE: Global I/F or Pairs Clearance) • Eg. Does it really touch at location 1

first, or does it touch at location 2 first? • Focus on parts that move

(Continuation from previous example.)

JOINT LOCATION

SMALL CLOSURE CLOSED

EDGES OF GEARS INTERFERE

EDGES MADE TANGENT

“BLURRY”


Configuration Joints, continued

– Example: Does it really touch at location 1 first, or does it touch at location 2 first?

– Theory was that the connector “head” orientation was controlled by the contact channel (first image).

contact channel

head

interference

Actual contact locations


Model Validation

Verify proper “movement” of model

Why? – Animations should look natural. If not, sensitivities and

results will be incorrect.

– Joint definition may be incorrect.

– Dimension scheme may be incorrect • E.g. center of width feature versus side

Action – Run Worst Case Animation

– Run Sensitivity Animation for top variables, sensitivities and contributions

– Visualize response to understand how features respond


Model Validation

Review Contribution Data Why?

– Identify tolerance value errors – Identify derived variation values

• Envelop rule • Characteristic length

– Joint scheme may be too simplistic • Rotation arbitrarily constrained, eg.

planar versus 3 pts

Action – Access Plots tab and look for outliers – Validate any outlier – Answer: Are the highest contributors

the variables you expected?

TOLERANCE TYPO


Model Validation

Review Sensitivity Data

Why? – Gain confidence that measurement,

joint and dimension modeling was done properly

Action – Compare values in sensitivity plot.

• Do expected variables have sensitivity?

• Do variables with sensitivity = 0.0 make sense?

– Size automatic included.

• Any variables with value order of magnitude different?

• Don’t forget angular variables

SMOOTH. NO OUTLIERS

TRANSLATION

UNDERSTAND “ZEROS”

DON’T FORGET ANGLES


Model Validation

Review Sensitivity Data, cont.

Action

– Review Sensitivity Graphs

• Linear when Scale Factor = 1.0?

• No? consider 2nd Order

NON-LINEAR

LINEAR


Model Validation

Tip & Guideline – Combined Approach – Review sensitivity &

contribution at same time in Analyzer

Action – Add New Layout tab in

Analyzer – Assign Filter


Model Validation

Watch measurements during animation Why?

– Ensure measurement direction & attachment updates consistent with measurement intent, i.e. should measurement location move or stay locked?

Action – Run worst-case and sensitivity animations

• Measurement should not jump around other than arrow change • If jump occurs during WC animation, at what value? Compare value to statistical result.

16:1 leverage


Model Validation

Worst-Case is Conservative

– Use to id unusual areas of assembly.

• May be joint DOF not appropriate

• May be excessive variation limits from characteristic length. Eg. position specification on shallow hole

Excessive angle limits? WC


Model Validation

Review Variables Why?

– Ensure inputs have proper distribution and limits

Action – RMB in CETOL Tree and select

Tree Level>Variables – Select first variable in list – Select Distribution tab – Select each variable and see

that distribution is as expected


Thank You !!

Check Sigmetrix Support Center for

– Advisor Message List

– Model Review Checklist

presented by dan lange, manager - services · see what you’re missing u2u conference abstract...

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