How to Use and Apply Iterative Logic in Your Tolerance Analysis Model

Understanding and Using the Iteration Move in 3DCS Software

This article compiles information about the Iteration Move in 3DCS to help you use it and apply it in your tolerance analysis modeling. For more about Iteration Move, visit the DCS Community at:

https://community.3dcs.com/help_manual/iterationmove.htm?zoom_highlightsub=iteration+move

https://community.3dcs.com/help_manual/dcu_loopmv_dll.htm?zoom_highlightsub=iteration+move

What is the Iteration Move?

Welcome to 2019 - Let's Get Started

Let's Talk About 2018 and What's In Store for 2019

2018 has been a good year. DCS is happy to welcome new clients, and work further with existing clients as Quality 4.0 and Tolerance Analysis continue to develop. 

Is Cloud Computing Really Better for Business? Survey says... 

Iterative and Conditional Logic, Iteration Move and Mechanical 

Understanding how to create, use and apply iterative and conditional logic in statistical tolerance analysis. 

DCS is hosting a webinar on the use and application of Iteration Move, Iterative and Conditional Logic and Mechanical Moves tomorrow, Thursday December 13th at 11 am EST. As part of the Digital GD&T Series, all current registrants will have access to the webinar and recording. 

3 Tools to Support Tough Tolerance Negotiations 

DCS Solutions offer a number of tools to support your tolerance discussions with customers. 

Tolerance Negotiations are never easy. Customers will try to hold their suppliers to difficult or over-engineered tolerances, or simply don't know that certain tolerances can be opened without affecting the assembly quality, or need to be opened (increased) in order to keep costs reasonable. 

DCS provides 3 tools to support tolerance negotiation by using data to back up tolerance change requests: 

1. Tolerance Negotiator -- QDM Analyst Tool

2. 3DCS Variation Analyst Simulation Results

3. QDM Management Reports 

1. Tolerance Negotiator - QDM Analyst Tool 

How do I get it?

Tolerance Negotiator is built into the base QDM Analyst software, without the need for add-ons or additional purchases. If you have QDM Analyst, the standalone QDM template maker software, you have Tolerance Negotiator. 

Using Tolerance Negotiator

Tolerance Negotiator is under the Tools tab of QDM Analyst. 

After clicking Tolerance Negotiator, a table with all of the imported data measurements is generated.

Two types of data are usually used in Tolerance Negotiator.

Plant and Measured Data can be imported from any inspection device and used to demonstrate production tolerances and metrics. Suppliers use the first 30 parts in a production line, or prototype measurements to demonstrate measured values and whether they are meeting or failing to meet statistical objectives (Pp or Cp). 

Simulation data from an analysis tool can also be used before production. As a DCS Software, QDM is already configured to utilize 3DCS data. Importing 3DCS simulation results can show the risk of failure for given objectives. 

Tolerance Negotiator gives two sets of values:

1. Tolerance changes required to meet given Cp / Pp objectives

2. How Tolerance changes affect Cp and Pp 

This lets the user change tolerances, values and objectives and instantly see the results. For example, if your customer gave a required Pp of 1.33, you can show which tolerances in the provided design can actually meet that objective. With 3DCS, you can demonstrate how 3D stack ups affect those tolerances and further determine the final Pp or Cp values, and may affect the final range of variation. 

Tolerance Negotiator Demonstration

The video below demonstrates how the use of Tolerance Negotiator:

2. 3DCS Variation Analyst Simulation Results

3DCS Variation Analyst simulates assembly builds across a normal distribution (default) using Monte Carlo Simulation. Incorporating part tolerances and assembly processes, 3DCS provides outputs of simulated measurements that include the 3 dimensional variation stack of all parts and processes in the model. 

The results are the measured results of hundreds or thousands of virtual product builds compiled and analyzed statistically. Beneath the simulation results are the sensitivity results, which include the largest contributing tolerances to the given measure. 

In the simulation results window, upper and lower specification limits can be dragged to adjust and see the statistical outputs, Cp and Pp, change accordingly. It also demonstrates the expected failure rate for each given measurement with its given specification limits. This information can be valuable in showing the risk of build failure for each feature based on current design specifications, and how changes can affect either the Cp/Pp or the risk of failure. Adjusting a tolerance and re-running the analysis can show the change to the simulation results and whether an adjustment will positively or negatively affect the model outputs. 

Here is a video example of one method of how 3DCS simulation results can be used for tolerance negotiation: 

3. QDM Management Reports

QDM Management Reports are an effective way to present results to managers and business leaders. They summarize and display simulation or production results, giving visual context and information to make it easy to understand the content. 

Within the reports, as part of tolerance negotiation, a user can set specification limits or pass/fail criteria and color coding to show whether given measurements passed or failed inspection. 

This is a good way to show simulation results from 3DCS or production data in QDM and whether those simulation results will meet quality expectations. It can be helpful for pointing out trouble areas and leading into a tolerance negotiation on resolutions for those given measurements and tolerances. 

Learn more about Tolerance Negotiation and Supplier Quality with Supplier Quality for Suppliers Webinar - FREE On-Demand 

Click to View the Webinar

 How to Better Treat Thickness Tolerances in Sheet-Like Materials

We encounter many situations where there is a form tolerance on a primary surface and then the other side of the part has a thickness allowance. Often implicitly it is assumed to have the same form or a very local refinement. (i.e. stamped sheet metal, composite lay-ups)There are many situations in both aerospace and automotive I would think where sheet of material is stamped and parts are indexed to both sides and sheet metal is accepted using a spec tolerance. 

One method used in the past has been to use ghost parts but it seems like there should be an easier way. What am i missing?

Mechanical Modeler Add-on Expands 3DCS to Support Kinematic Joints and Constraints

Extracting Joints and Constraints from CAD can make model creation easy. With embedded GD&T (PMI, FTA) tolerancing your model and Joints and Constraints brought in as 3DCS Moves, a user only has to create Measurements to complete their Tolerance Analysis Model. 

Mechanical Modeler is an inexpensive add-on for all versions of 3DCS Variation Analyst Software

This tutorial will cover  Fixed Constraints and  Fix Together Constraints to illustrate common constraints you can expect to use. The Fixed Constraint holds all of the parts in the Move Parts list in their current location and orientation. Any moves that list one of the parts as the "object" will force the "target" part to move instead. The Fix Together Constraint holds all of the parts in the Move Parts list perfectly rigid relative to one another. If one of the parts is moved then the other parts will move with it. Additional constraints include Coincidence, Contact, Offset, and Angle.

This tutorial will cover Revolute Joints and Cylindrical Joints to illustrate common joints you can expect to use. The Revolute Joint move locates two axes to one another controlling four DoFs (degrees of freedom) and uses a pair of plane constraints to control a fifth, translation, DoF. The Cylindrical Joint move locates two axes to one another controlling four DoFs. Additional joints include Prismatic, Spherical, and Planar.

Setting Up Supplier Quality Assurance for Tier 1 Suppliers

Many Tier 1 Suppliers support different customers with different expectations and needs. A well implemented quality assurance system can make it easy to meet these different expectations, with monitoring, communication and problem solving built in to the system. 

• When: November 29th, 2018 -- 11 am EST
• Where: Gotowebinar
• Register FREE: https://register.gotowebinar.com/register/4757837893591746561

In today's demanding automotive marketplace, OEMs rely on large Tier One suppliers for major systems across vehicle platforms.  This in turn has put the onus of validating parts on the Tier One.  OEMs demand high quality systems - Tier Ones have to demand high quality parts from their supply base to put into those systems.