“HOW TO REVIEW A CETOL 6σ ANALYSIS ” Presented by Dan Lange, Manager - Services U2U Conference U2U Conference SEE WHAT YOU’RE MISSING SEE WHAT YOU’RE MISSING
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. U2U Conference SEE WHAT YOU’RE MISSING
KEY SUBJECT MATTER Advisor Window Measurements Part order Model behavior Joint order, type, location, Results orientation, considerations CETOL 6 Analyzer CETOL 6 Modeler Assembly Modeling Define Objectives Review Results Create joints Create measurements Inspect measurement variation plots Set joint properties Set measure properties Inspect sensitivities and contributions Part Modeling Improve Quality/Reduce Cost Constrain features Adjust tolerance values (dimensions, GD&T, etc.) Incorporate mfg. data Specify tolerances Etc. Validate Model Generate Check Advisor messages Report Run Analysis “Show Part Locations” Visualize sensitivities U2U Conference SEE WHAT YOU’RE MISSING
Advisor Window Clear all messages Why? – Impact can range from no impact to incorrect answer or no answer at all. Action CETOL 6 σ Advisor Window – See Advisor Message Table – Note: Selecting message in Advisor window will jumps to the item in the CETOL Tree, if applicable Unconstrained Part DOF U2U Conference SEE WHAT YOU’RE MISSING
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 The measurement has a minimum or maximum internal critical point" 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 KB Article - SSC. saddle point" U2U Conference SEE WHAT YOU’RE MISSING
Advisor Messages ADVISOR MESSAGE ACTION "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 Adjust orientation or location tolerance. related 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 Define orientation. Review DOFs. Tx-Ty may switch orientation" U2U Conference SEE WHAT YOU’RE MISSING
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 This happens if you link a CETOL dimension to a CAD dimension's nominal" dimension that may not be directly associated with the geometry that the feature references and that dimension is changed in the CAD model. U2U Conference SEE WHAT YOU’RE MISSING
Advisor Messages ADVISOR MESSAGE ACTION "The tolerance type of the linked CAD dimension is The dimension has an unsupported tolerance type unsupported" (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 U2U Conference SEE WHAT YOU’RE MISSING
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 U2U Conference SEE WHAT YOU’RE MISSING
Part Order Matters (6) DOV PART Constrains (4) DOF • 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 (4) DOV PART U2U Conference SEE WHAT YOU’RE MISSING
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 U2U Conference SEE WHAT YOU’RE MISSING
Joints - Considerations Watch for and review the following: – “Joint balls” blurry or have distance between? Not coincident investigate Reduce symbol size • 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 … U2U Conference SEE WHAT YOU’RE MISSING
Measurements Example shows solved nominal Verify measurement accurately defines different from CAD nominal. assembly requirement CAD constraints centered Why? teeth. Tangent gear teeth altered position of GEAR2. – 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 U2U Conference SEE WHAT YOU’RE MISSING
Configuration Joints (Continuation from previous example.) Verify assembly position Why? – Need to ensure position matches JOINT LOCATION use-case for analysis “BLURRY” Action – Use SHOW PART LOC – Make sure “new” position of parts SMALL CLOSURE CLOSED does not create interference ANYWHERE in the model. (ProE: Global I/F or Pairs Clearance) EDGES OF GEARS INTERFERE • Eg. Does it really touch at location 1 first, or does it touch at location 2 first? • Focus on parts that move EDGES MADE TANGENT U2U Conference SEE WHAT YOU’RE MISSING
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