PrecBuilder

Building complete precedence constraints graphs that can really be trusted.

Business answer to enable line balancing :
PrecBuilder, the precedence builder tool Business answer to enable line balancing :

Despite how difficult and extremely complex it is to build, validate and manage precedence graphs in large and complex environment like in the automotive industry, Optimal Design brings a practical and effective answer to address this, by the combination of a unique solution, a rigorous methodology and a deployment approach.

1. The PrecBuilder tool

Relying on its profound understanding of the mathematical concepts supporting graph theory, and as a true innovator in algorithms to solve complex and large scale industrial processes, Optimal Design has designed, developed and initiated patenting procedures for algorithms to solve and mathematically guarantee the completeness of precedence graphs. The PrecBuilder tool designed by Optimal Design is a powerful tool that runs these algorithms and helps the end-users to attain the following goals:

• input one or several, complete or partial precedence graphs of constraints,
• input actual available assembly line information,
• thanks to the built-in mathematical concepts, have the permanent guarantee of the feasibility and reliability of the graph being manipulated,
• immediately identify conflicts between precedences or between precedences and other supplied information,
• run the algorithms (power analysis) on the graph to identify the most relevant relationships to establish,
• enrich the graph with answers to any of the undetermined relationships, hence moving towards graph completeness,
• obtain and drill down the technical justification for each relationship (i.e. what other information they were derived from),
• enjoy a full traceability of each change made to the graph, or input applied,
• automatically import and export precedence from/to the dedicated, versioned database that comes with PrecBuilder, with OptiLine, or with any standard data exchange interface,

For registered users, the comprehensive and detailed list of PrecBuilder's features is available on PrecBuilder's Technical Features page.

Indeed, besides being a stand-alone tool, PrecBuilder is also completely integrated with OptiLine, the only automated line balancing tool available, which will identify the optimal sequence of operations that best balances the workload while complying with the validated graph of precedences issued from PrecBuilder and the other constraints expressed in OptiLine.

2. A rigorous methodology

The methodology focuses on several iterative and well documented steps, allowing for a fully controlled graph enrichment until it is fully validated. The key steps of this methodology are described here (while the full description is available to registered users from PrecBuilder's Technical Features page.

• Graph initialisation : proceed with an initial load of most suitable precedence graph (either starting from product design, or straight from product manufacturing, or the one that is the richest, or the one believed to be the most reliable, etc...)
• Graph enrichment : it with all other available precedence graphs from other sources and related to that product, and available operation information that have proven to be actually working
• Solve sequence conflicts (a recently added sequence conflicts with the precedence graph)
• double-check that the added sequence is absolutely correct and if not, re-submit the corrected sequence
• as the sequence is correct, the precedence graph it conflicts with is over-constrained or contains erroneous constrains
• use the justification sub-graph of the conflicting precedence to validate each involve precedence (PrecBuilder will point at the subsets of precedences whose rejection or inversion would solve the conflict, significantly reducing the troubleshooting effort )
• once all relevant subsets will have been checked, modify the precedences (may be more than one) that ought o be changed and resubmit the valid sequence of operations, which should now lead to a richer precedence graph, closer to the operational reality and at the same time more flexible (as excessive constraints were removed)
• Solve a precedence conflict (a recently added set of precedences conflicts with the precedence graph)
• ...
• Power-analyse the precedence graph based on unresolved relationships : precedences (strongest resolution strength), sequences (less strong resolution strength) or both at the same time. PrecBuilder will produce the list of questions to answer about the relationship between pairs of operations, by default decreasingly sorted by their strength of resolution
• Resolve power-analysis questions
• group and filter the questions by the required criteria (typically: within a workstation, a group of workstations or a zone, optionally including or excluding the immediately connecting workstations)
• try to have the top questions answered first, given their resolution strength (speed first and narrow approach, recommended when the information is very reliable)
• optionally allow to also answer redundant questions, to consolidate the overall knowledge (security first and broad approach, recommended when the information requires multiple validations)
• feed-back the collected information and add it with PrecBuilder to the precedence graph
• if any additional conflicts are identified, solve them one by one [need for good conflict analyser] as previously described
• Power-solve the precedence graph if OptiLine is available
• Select the most advantageous power-solving scenario
  • ...
• As PrecBuilder immediately checks for and guarantees the consistency of the graph as it is enriched

3. A specific deployment and implementation approach

Having the adequate tool and mastering the methodology to use it effectively are essential, yet efficiently reaping their benefits requires a tailored deployment and implementation approach. Indeed, as the environments where the graph building process is started is typically extremely complex and of very large scale, inefficient approaches would lead to humongous amounts of time and effort to collect the expert information, feed it back, while preventing from or resolving the many conflicts that are likely to arise during this process. In the approach developed by Optimal Design, the following steps are undertaken :

• careful selection and priorisation of available precedence information graphs and sub-graphs
• selection of most relevant sub-groupings of the overall assembly line or process, depending on the point of view of the involved actors, e.g. all constraints related to a set of operations, with or without their predecessors of successors, set of workstations, etc...
• select the required degree of cross-validation during the collection process, based on the quality of the data, degree of proficiency in using PrecBuilder and maturity of the deployment across the organisation
• distribute the analysis and constraints collection tasks to the involved actors thanks to the collaboration features of the PrecBuilder, through the selected operating platforms available
• based on the chosen degree of interactivity, provide feed-back on-line or near on-line or off-line to the central PrecBuilder repository, which will on a continuous basis identify any conflict and accurately point at the identified issue to ease its resolution
• use mechanisms to identify possible over-constrained precedences, and spots to increase precedence graph flexibility
• various progress reporting, graph completion status, and other management reports are made available or can be easily developed upon demand thanks to the extended traceability of all applied inputs and changes

For a practical deployment plan and implementation approach that would fit your specific environment, please check our Implementation Services or contact our Commercial representative.

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