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Machine Vision Application Analysis and Implementation - Part 3
by Nello Zuech, Contributing Editor - AIA Posted 12/18/2000
This is the third of a series of articles designed to provide the framework for a successful machine vision system installation. The process described is targeted at companies that are planning the adoption of a machine vision system for the first time or that have a unique application that no one has previously attempted to implement.
As observed in Part 1, today one can find many application-specific machine vision systems for somewhat generic applications in many manufacturing industries. Purchasing these 'off-the-shelf' solutions poses little risk to any first time buyer. In some cases, one can find application-specific software developed by suppliers of general-purpose machine vision systems, imaging board/frame grabber suppliers, software suppliers or merchant system integrators. While these are not turnkey packages, the vision experience is itself less risky. Examples of these packages include: alignment, OCR/OCV, LCD/LED inspection, BGA inspection, etc.
Even less risky are the turnkey machine vision systems that are industry specific; e.g. bareboard or assembled board inspection for the electronic industry, overlay registration/critical dimension inspection for the semiconductor industry, various industry specific web scanners, systems targeted at food sorting, etc. Virtually every manufacturing industry has these systems, many of which can be identified through the resources of the Automated Imaging Association.
Where these 'solutions' are not the answer and a machine vision application has been identified, success requires proceeding systematically and not treating the purchase as if one is purchasing a commodity item. It is not sufficient to send good and bad parts to various vendors and ask them if they can tell the difference.
Table 1 - Application Analysis and Implementation
|Know your company|
|Develop a team|
|Develop a project profile|
|Develop a specification|
|Get information on machine vision|
|Determine project responsibility|
|Write a project plan|
|Issue request for proposal|
|Conduct vendor conference|
|Conduct vendor site visits|
|Issue purchase order|
|Monitor project progress|
|Conduct systematic buy-off|
The above table depicts the process that should be used as one proceeds with the deployment of a machine vision system that is uniquely defined for a company. In Part 2 we covered a process for how to assess an application's requirements with ideas of what should be included in a functional specification. In this article we are going to cover the topics in bold. In future articles we will cover the balance of the topics in the table.
GETTING INFORMATION ON MACHINE VISION
Staff - often companies have corporate staff that are 'gatekeepers' for various new technologies. These individuals might be found in a corporate quality department or manufacturing engineering department or possibly in a research and development department.
Line personnel with experience - In the case of multi-plant organizations, it may be possible that someone at another plant has already deployed a machine vision system. These people should be sought out to review their experience in the light of one's own application.
Data to aid in selection can be secured from vendors. Besides technical advice and assistance, vendor representatives can furnish written materials and brochures. Recommendations generally have to be taken with a grain of salt since they may lack objectivity.
Consultants who do not design and build machine vision systems or act as sales agents for machine vision vendors or system integrators can objectively examine plants to identify technically feasible and cost-effective applications. In addition, they can assist in developing specifications and identifying and evaluating the most appropriate vendors to be solicited.
Technical Society Meetings and Papers
Meetings and proceedings can provide insight into experiences with machine vision as well as provide information concerning new developments. The following organizations offer programs and/or conduct trade shows with content related to machine vision. The first two cited offer programs that are targeted specifically at users of machine vision systems. The latter two offer programs that are targeted more at developers of machine vision systems.
- Automated Imaging Association (AIA), 900 Victors Way, Suite 140, Ann Arbor, MI 48108
- SME/MVA, the Society of Manufacturing Engineers and Machine Vision Association, One SME Drive, P.O. Box 930, Dearborn, Michigan 48121
- IEEE, the Institute of Electrical and Electronics Engineers, 345 East 47th Street, New York, New York 10017
- SPIE, the International Society for Optical Engineering, P.O. Box 10, Bellingham, Washington 98225
The AIA and the SME/MVA both publish directories of machine vision companies, which can be useful in identifying potential sources of machine vision systems.
While every company will have their own web site that includes product details, there are a couple of web sites that are more generically in the field of machine vision. Perhaps the foremost one is machinevisiononline.org, managed by the Automated Imaging Association. It includes a directory of companies with linkages to their web sites. It also includes a method to broadcast application requirements to AIA member companies making identification of companies with relevant experience as well as project interest reasonably easy.
It is also noted that many trade periodicals host a website today. These often include their 'Buyer's Guide,' which can make it relatively easy to identify machine vision systems that are targeted at specific applications within an industry.
Determine Project Responsibility
The best manner to handle a project should be found. For example, if the division or company does not have experienced staff in machine vision or related automated equipment, it may be necessary to look to the outside for assistance. There are a variety of alternatives:
- Rely on the machine vision equipment supplier for overall direction of the project.
- If line automation and/or material-handling equipment is involved that must be integrated with the machine vision system, a system integrator may be the one to take on overall project direction. The system integrator should be one with experience integrating machine vision with line equipment and, ideally, experienced with the machine vision vendor whose equipment is best suited for the application. When using a system integrator it is important to understand that there are three parties that all must be involved for the project to succeed: the company itself is chiefly responsible for bringing process knowledge to the project; the machine vision vendor must be prepared to provide the comprehensive product knowledge that may be required; and the system integrator must have the skills required to perform the application engineering and 'staging' design as well as the controls and integration skills for both line integration and man-machine integration.
- Consider using a consultant in machine vision to act as a project leader and carry the program through to completion. Such consultants can conduct feasibility assessments, assist in the development of the specifications, identify the vendors with the most relevant experience, qualify the vendors, and recommend the most appropriate vendors. In addition, they can manage the project through training, installation, and acceptance testing. They can also provide training on machine vision that is appropriate for all involved in the project.
In general, it is not a good idea to have the machine vision vendor serve as the project director if there is any material handling or other specialized equipment needed. The small machine vision companies generally do not have the personnel trained in product handling. They are for the most part computer hardware- and software-trained.
Writing a Project Plan
Having analyzed the application and written the specification, a project plan should be written. A project timetable should be established. The schedule should be realistic, not too fast that projecting dependence on the system can cause delays in overall production start-up and not so extended that it will become difficult to maintain a project commitment.
Three to five prospective vendors should be identified with demonstrated product capabilities consistent with the requirement. In other words, merely identifying prospective bidders is not enough. They must also be evaluated to assure that they have the necessary skills to conduct the project as well as to assure that they have an interest in doing the project. If gaging, they should have systems installed performing gaging. If flaw detection, applications of their techniques should have been installed performing, for example, cosmetic inspection. Furthermore, there should be confidence that the company can apply the required resources in a timely manner so that they can complete the project consistent with the required schedule.
Keeping the number of prospective vendors down reduces the number of proposals that have to be evaluated as well as avoids too many vendors making an investment in a proposal.
During this prospective vendor identification phase a telephone survey should be the mechanism used. After reviewing the project, the vendor's interest and related experience should be ascertained. In addition, the price for similarly installed systems should be determined. The average of these figures can serve as a 'budgetary estimate' for the cost of the project. This figure, in combination with estimates of material handling, training, line modifications, and so on, can be used to perform a rough return-on-investment analysis. If the results are reasonable, a more serious bid cycle should begin.
Request for Proposal
A formal request for proposal (RFP) should be written that includes a description of the project in detail along with a brief discussion of the business of the operation. The description of the system should be as follows:
- Review in detail the specific functions the machine vision system is to perform. Describe part(s) in detail indicating variables in parts, process, suppliers, and so on. Make sure tolerances are realistic from a production point of view and are in fact currently being met. Review all defects anticipated and outline their properties.
- Describe how the machine vision system will be integrated into the line, especially reviewing cycle times.
- Review environmental considerations.
- Benchmark criteria and acceptance test procedures (if not part of the specification already), both for vendor facility buy-off and post installation buy-off, should be spelled out clearly.
- If necessary, because of technical uncertainty, outline a feasibility demonstration requirement at the vendor facility. This should be treated as a separate line item in the cost proposal.
The rationale for the project solicitation should be reviewed as well as the schedule. The functional requirements (what, why, when, where) should be spelled out in detail in the specification. Where possible, separate the 'needs' from the 'wants' - those requirements that are essential (otherwise the system is worthless) from those requirements that are less critical.
In addition, the RFP should define the response wanted with respect to the following:
- Cost. The cost of a system to satisfy the application should be separated from the costs of training, warranty, and installation. In the case of specifications with needs and wants, the costs should be separated, so the incremental costs associated with enhancements can be assessed. Engineering charges should be separated from system charges. If several units are anticipated in the future, the cost for the quantity should be requested at this time. Feasibility studies should be cost out separately.
- Schedule. A project schedule should include important milestones for anything that is not 'off the shelf.' These might include scheduled preliminary and final design reviews and specific benchmarks associated with building and proving out. Potential intermediate approval points during the project could be identified in such a schedule.
- Description Solicited . This should include a review of lighting, optics, fixture or staging designs, and image-processing techniques. The detail should be sufficient to assess whether resolutions and image-processing throughput are adequate for the application. Both operation interface and engineering interface should be reviewed as well as issues such as memory, enclosures, environmental considerations, diagnostics, electrical interfaces, and calibration procedures.
The description requested should do the following:
- Ask to review the specific functions the machine vision system is to perform.
- Ask for a description of how the machine vision system will be integrated into the line, especially reviewing cycle times of the computer and processing as well as mechanical cycle times.
- Ask for a review of the environmental conditions.
- Policies to be reviewed in the RFP should include the following:
- Software upgrades
- Relevant Experience . The proposal should be asked to include a review of both specific and generic installations: number of systems, how long operational, types of installations (beta sites, laboratory, shop floors, etc.).
Along with the RFP photographs of the application site, part prints and representative samples should be forwarded to each of the solicited vendors. If possible, videos of the proposed installation site should be included with the bid package. If setup costs are involved to evaluate samples, a fee should be anticipated to cover those costs. The samples should be representative of all production and should include good and bad samples as well as samples that are marginally good and marginally bad.
A vendor conference should be conducted at the prospective installation site 10-14 days after the RFP is received. Ideally, the vendor's technical personnel will be present as well as the local salesman. The vendor's conference performs a number of functions:
- It is an opportunity to clarify objectives and requirements.
- It demonstrates the vendor's interest.
- It permits a facility review and first-hand appraisal of the operation on the part of the vendor.
- Being a one-time session, it avoids the need to tie up staff for individual visits by each of the vendors.
- It assures the same information is given to all in attendance.
The agenda for the vendor conference should include the following:
- Briefing on company/operation's business
- Review of project
- Why it is under consideration
- How it fits into overall plans
- Management support
- Review of specifications, line by line
- Review of response required
- Review of proposal and vendor evaluation criteria
- Facility tour with emphasis on installation site
- Time for one-on-one question-and-answer period
Participants at the vendor conference should include representatives from each of the departments that will be involved in the installation. A project manager should conduct the session, though individuals from, for example, management and purchasing should be used to provide briefing on the specific issues.
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