What to look for when specifying a vision system?

Its all about delivering a quality solution within budget and on time. This can be summarized by looking at cost, capability, reliability and support. Most vision systems are now completely solid state, unless there are moving parts such as linear slides or conveyors to move your product. Modern systems use LED lighting , solid state cameras and often high performance processors with no mechanical disk drives.

The specification of a vision system for web and sheet operations, is key to a project's success. This article will focus you on the key issues that will help reduce cost of purchase while optimizing performance. The key sections are:

• 3 key figures that will decide the cost of your inspection system.
• 5 steps to categorizing defects.
• The whole is greater than the sum of its parts.
• 4 results gained from specifying your system correctly.

If you are part of a team that uses, purchases or plans capital expenditure for inspection systems, read more as this framework will add value.

System Overview

The goal of this document is to review the inspection system technically and to identify future support issues. The diagram above shows the 4 key areas that are then surveyed in detail below.

1.  Camera system
2. LED Lighting system
3. Image processing system
4. Software

Rollers are used to guide the web material along a predetermined path through a process
line. Let's take a printing press as an example. The path will vary on most presses as different
print jobs have varying print requirements (number of colors, cold seal, side of printing,
drying time, etc.). The web path will also vary depending on the drying times and drying
temperatures of the inks. Under the inspection head, rollers are used to present the web to
the cameras in as stable a condition as possible. There are a couple of configurations often
used for both surface inspection and print inspection.

When purchasing an inspection solution you must think about the end user. Often it is a project engineer that specifies a vision system for their surface inspection requirements, but does not consider how it works for all the key users who operate it daily.  Let’s look at the key stakeholders in a factory that interact with vision systems:

• The operator - this includes the personnel at the process line and converting lines.
• The engineer - this normally is the process engineer that is responsible for the
  operation and upkeep of the process lines.
• The quality supervisor - this is the individual tasked with using the data to guarantee quality of goods and the interface between customer service and production.

100% inspection system work flows

When manufacturing discrete items like boxes of biscuits, pharmaceutical products, cans and bottles there has always been the capability to inspect and reject. This has been taken for granted. When operating in a roll to roll environment the challenges are quite different. It is not always possible to stop the line so when a defect is detected it will continue to the rewind and become part of the product to be shipped.

The effects of choosing proprietary vision solutions become evident within years of a purchase. Imagine investing hundreds of thousands of dollars, even millions in a network and finding out 5 years later that the complete system is out of date and cannot be modernized. Yes, you would seek out the purchaser and possibly hang them from the nearest tree. However it never fails to amuse me that the same thought process making sure office infrastructures are open systems, are not employed when purchasing an IT solution for the factory floor.

Benefits of inspection on plastics

The modern extrusion and converting/laminating lines now use surface inspection systems as standard. Your customers demand 100% quality control.  All plastic film include some level of contaminates, arising from the production process or due to the nature of Polymers. Therefore gels are only a question of resolution. Extrusion and converting lines classify many defect types such as gels, black specs, fish eyes, holes, oil stains, insects, scratches, coating voids, air bubbles etc. These all originate from different issues but most all can have an impact on the further processing.

Automotive molded parts inspected automatically using    VisionFlow 

Seattle based molded part supplier to the automotive industry requested a system to take a wide variety of large parts, some 24" wide and inspect each part as it is placed on a conveyor by a robot and then removed. OneBoxVision developed the complete unit, including the transport and pre-configured to to be used for all SKUs.   The system was built using off the shelf components and OneBoxVision used  VisionFlow, a complete suite of vision tools for part inspection. This includes tools for measurement, defect detection and the part verification . The software supports machine parent control interfaces for conveyors, linear slides or direct PLC communications. 

Plastic film extruder required multiple systems to inspect and track defects

A US plastic film client with multiple US locations  approached OneBoxVision with a challenge. The company was producing bags for powered milk. The goal was to inspect the film while being extruded on a blown film line and alert the operators in real time to carbon specks so that it can be corrected at source. The extruded plastic would then be shipped to a second site where the film would be used on an automated line producing bags. The client wanted us to check again and also allow the second plant to access the inspection data for the first process.