Glass Inspection and Measurement Systems: The Buying Guide

What a glass inspection system does and where it sits on the line

Inspection is not one station. It is a decision about where to put a camera, and there are five useful places.

Before cutting. The sheet is checked as it moves from the loading machine to the cutting table, so defects can be pushed into waste areas the layout already plans. Deltamax OPT does this on unwashed sheets, so no washer is needed first.

On the flat line after washing. This is the general purpose position, where glass, coating, print and edge faults are all visible. Deltamax EVO and the Gudetech Glass Quality Inspection System sit here, and Cugher Glass Vision Systems and Quality Control puts its glass quality control station immediately after washing.

On the insulating glass line, the last moment before the panes are sealed. Deltamax GlassInspector and Deltamax Q+ are built for this position, because a defect trapped inside a sealed unit cannot be corrected.

On the finished unit. Deltamax IGU Scanner inspects the completed insulating glass unit to certify the line before shipment.

Off the line, in a test room. Fragmentation testing is a laboratory task. Deltamax FROG and Deltamax TemperCheck live here.

Measurement is a separate job. Deltamax PROFILER detects the dimensions and shape of the sheet, compares them against a DXF file or similar reference, and sends the result back to the line.

Types and configurations

Four splits decide which system you buy.

The first is what you are looking for. Defect detection finds bubbles, inclusions, scratches, stains and coating faults. Dimensional inspection measures the sheet against the drawing. Print inspection checks silkscreen or logos. Fragmentation testing certifies tempered glass. Some systems do more than one: Deltamax EVO detects glass, coating, silkscreen and edge defects, and adds dimensional and silkscreen control as options.

The second is horizontal against vertical. The two need different frames and lighting. The Gudetech Glass Quality Inspection System is offered with vertical and horizontal scanners, and Deltamax EVO adapts to all production lines, horizontal and vertical.

The third is washed against unwashed glass. Water and dirt look like defects to a camera, so most systems sit after the washer. Deltamax OPT and Deltamax PROFILER are the exceptions: both work on unwashed sheets, which is what lets them sit upstream.

The fourth is single channel against dual channel. Deltamax Q+ integrates two inspection technologies in one solution, sharing a single camera array, which is how it reaches defects a single channel misses.

• Pre-cutting defect isolation: Deltamax OPT, integrated with the cutting table software.
• General flat line inspection: Deltamax EVO, the Gudetech Glass Quality Inspection System, and the ITECH Glass Quality Control Scanner.
• Insulating glass line inspection: Deltamax GlassInspector and Deltamax Q+.
• Finished unit inspection: Deltamax IGU Scanner, for single, double or triple chamber units.
• Shape and dimension: Deltamax PROFILER, against a DXF file.
• Print line vision: Cugher Glass Vision Systems and Quality Control, covering glass and print quality, frame adjustment and frame breakage.
• Tempered glass certification: Deltamax FROG, and Deltamax TemperCheck where the standard requires fragment weights.

How it works, step by step

Step one is lighting. Different faults need different light. Bright field shows what blocks light, such as an inclusion. Dark field shows what scatters light, such as a scratch. Backlight shows the outline. The Gudetech Glass Quality Inspection System uses all three. The illuminator is also the part that ages: on GlassInspector it is the system's only component subject to wear.

Step two is scanning. A linear-array camera reads one line of pixels at a time while the glass moves past, and the software builds a full image of the sheet. Resolution is quoted in millimetres per pixel: 0.1 mm per pixel on the Gudetech Glass Quality Inspection System, 0.2 mm per pixel on Deltamax GlassInspector and Deltamax OPT.

Step three is detection. The software compares the image against thresholds and marks anything outside them. Deltamax GlassInspector states a minimum detectable defect size of 0.4 mm per pixel, and Deltamax OPT states 0.4 mm.

Step four is classification. Not every mark is a reject. A defect is sorted by type, size and position, then judged against the quality level for that order. GlassInspector uses recipes for different quality levels, Deltamax Q+ allows customizable parameters for each defect class, and the ITECH Glass Quality Control Scanner lets the customer adjust both identification and classification parameters.

Step five is the decision. The result goes to the operator, to the line, or both. Deltamax EVO can interface with the production line, for example to manage an automatic reject system. On a Cugher Glass Vision Systems and Quality Control line, when print errors come from incorrect frame positioning, the system corrects the position within limits without interrupting production.

Step six is the record. Images and results are stored, and that record turns inspection from a filter into a tool, because it shows which fault repeats and where. The Gudetech Glass Quality Inspection System offers closed-loop quality control with data traceability per sheet. Deltamax EVO stores results and defect images and generates custom reports, and the Production Analyzer software supplied with Q+ does the same for scanner data.

The figures that decide the purchase

Inspection is sold on a short list of numbers, and two are commonly confused. Image resolution is how finely the camera samples the sheet. Minimum detectable defect size is the smallest fault the software will reliably call, and it is the one that matters to your customer.

Choosing by what you produce

Insulating glass units. The defect you must catch is the one about to be sealed inside. Deltamax GlassInspector is built for these lines, adapts automatically to different glass colors and inspects glass of any shape. Deltamax Q+ is the more sensitive option, identifying halos, low-contrast stains and thin scratches. Deltamax IGU Scanner then checks the finished unit, including spacer-bar bowing and muntin position.

Tempered glass. Two separate needs. On the line, Deltamax Q+ identifies roller streaks, a furnace fault worth catching early. Off the line, safety certification needs fragmentation testing: Deltamax FROG reports fragment count, largest-fragment data and size distribution against the standard selected from its database, and Deltamax TemperCheck adds the weight of the 10 largest fragments for stricter standards.

Printed and silkscreened glass. Cugher Glass Vision Systems and Quality Control covers the print line end to end: quality control after washing, printing quality control that shows defects on the video image, automatic frame adjustment by cameras and servo motors under the printing table, and frame breakage detection for ink spots on the underside. Deltamax EVO adds a silkscreen control option covering completeness, position, rotation and legibility.

Coated and Low-E glass. The Gudetech Glass Quality Inspection System detects coating defects across float, clear, ultra, coated, Low-E, printed and laminated glass. GlassInspector covers all transparent glass, including low-E, selective and body-tinted.

Mirrors. Deltamax EVO can be used for mirror control, inspecting a clean sheet for bubbles, inclusions and scratches, or for silvering defects such as missing areas.

Shaped and machined glass. Deltamax PROFILER compares the detected shape and dimensions against a DXF file, and the dimensional control option on EVO checks hole position and diameter, shape and machining.

Cutting yield. If your losses come from bad jumbo stock rather than bad processing, Deltamax OPT is the answer. It isolates structural defects before the cut, so only an area around each defect is scrapped instead of the whole sheet, and it avoids processing sheets below the chosen quality level.

What a quote should include

Inspection systems are quoted as hardware, software and integration, and integration is where budgets fail. Ask for it priced as its own line.

Then ask the manufacturer these questions. What is the minimum detectable defect size on your glass, proven in a trial? What happens on coated, tinted or printed product? Who writes and tests the interface to the line controller and the reject system? Which parameters can your staff change? What is the false reject rate on a normal run? Deltamax states that on GlassInspector later innovations can be applied to already-installed units, including at replacement of the illuminator. Ask for that upgrade path in writing.

• Factory-direct price with the exact system and configuration named.
• Number of scanners, and whether the line is horizontal or vertical.
• Stated image resolution and minimum detectable defect size, and how each was proven.
• Software: defect classes, quality-level recipes and reporting.
• Line interface, including any automatic reject system.
• Crating, freight with the Incoterm stated, insurance and port charges.
• Installation and commissioning, with the acceptance test run on your own glass.
• Training for operators and for whoever sets the quality thresholds.
• Spare parts, with the illuminator and cameras priced.
• Warranty, software support and the later upgrade path.

Lead times, installation and running costs

Lead time on inspection equipment is shorter than on heavy machinery, but commissioning is longer. The hardware is a frame, cameras and lights. The work is tuning, and tuning happens on your glass, against your quality standards. Budget for that, not for the shipping date.

Installation is mostly space and light. The system needs a run of conveyor where the sheet moves steadily, a stable mounting and control of stray light. Deltamax EVO adapts to all production lines with a reduced footprint, and Deltamax PROFILER has its own dedicated transport, which is what allows its precision. A fragmentation unit needs only a bench and a PC.

Running cost is low compared with any processing machine, and it has three parts. Consumables are the first, and in practice that means the illuminator. Software support is the second, because thresholds and defect classes change as your customers change. Operator time is the third, and the one people underestimate: someone has to review borderline calls, or the system is either ignored or over-rejecting.

Set against that is what the system saves. OPT reduces scrapped glass surface by placing defects inside waste areas already planned in the layout. An IGU Scanner catches a fault before a unit ships rather than after. Neither saving appears on the quotation, and both are the reason to buy.

Mistakes buyers make

All five are avoidable at the quotation stage.

• Buying resolution and calling it detection. 0.1 mm per pixel describes the camera. The minimum detectable defect size, 0.4 mm on Deltamax OPT, is what you can promise a customer.
• Putting the scanner in the wrong place. A camera after the last process finds faults you have already paid to add. A camera before cutting, like Deltamax OPT, stops the spend earlier.
• Forgetting what the system cannot see. Deltamax OPT is stated for all transparent glass excluding acid-etched, sandblasted or mirrored. Plan separately for those.
• Ignoring line speed and thickness limits. GlassInspector is stated at 60 m/min and 50 mm maximum thickness. A system that cannot keep up becomes the bottleneck it was bought to remove.
• Nobody owning the thresholds. A system set too tight rejects good glass and gets switched off. Name the person who owns the quality levels before the system arrives, and check your staff can adjust the parameters.

Machines on GlassMachines.net

Eleven systems are listed here, from four manufacturers. The eight below cover the main positions on a line. Cugher Glass Vision Systems and Quality Control, the ITECH Glass Quality Control Scanner and Deltamax TemperCheck are covered in the sections above.

• Gudetech Glass Quality Inspection System: vertical and horizontal scanners with a linear-array camera at 0.1 mm per pixel and bright-field, dark-field and backlight illumination, with data traceability per sheet.
• Deltamax GlassInspector: the insulating glass line scanner, at 0.2 mm per pixel, up to 50 mm thickness and 60 m/min line speed, inspecting glass of any shape.
• Deltamax Q+: a dual inspection channel sharing a single camera array, aimed at the harder faults, halos, low-contrast stains, roller streaks on tempered glass and thin scratches.
• Deltamax EVO: the modular flat glass system, covering glass, coating, silkscreen and edge defects on horizontal or vertical lines, with dimensional and silkscreen control as options.
• Deltamax OPT: pre-cutting inspection on unwashed sheets, integrated with the cutting table software so defects fall inside planned waste areas, at 0.2 mm per pixel.
• Deltamax PROFILER: shape and dimension measurement to plus or minus 0.5 mm on its own dedicated transport, comparing the sheet against a DXF file.
• Deltamax IGU Scanner: finished unit inspection for single, double or triple chamber units, covering transparent-area defects, spacer-bar placement and muntin position.
• Deltamax FROG: bench-top fragmentation analysis over a 5 x 5 cm area, with a pass or fail result against the standard selected from its database.

Specs to compare, in one list

Image resolution

No software recovers detail the camera never captured.

Minimum detectable defect size

This is the figure a customer specification is written against, and it is not the same as resolution.

Maximum line speed

A scanner slower than the line becomes the bottleneck it was bought to remove.

Glass types accepted

Coatings and etched surfaces change how light passes through, so the list is a hard limit.

Illumination fitted

Each type of light reveals a different family of defects.

Line and unit interface

Without a tested link to the reject system, it only produces a screen nobody watches.

Adjustable defect classes and quality levels

Thresholds you cannot change yourself become thresholds nobody maintains.

Questions buyers ask