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PGM-V - the Development of a Wireless, Portable, Gob Monitor

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Saturday 26 September 2009

Monitoring with the PGM-V at the Blank LoadOver the past 20 years, in tandem with significant advancement in forehearth control, glass throughputs have increased putting ever more burden on the feeder system.  Hence the old adage “you can’t make a good bottle from a bad gob” is as true today as it ever was. If the feeder delivers good gobs, and the delivery system is maintained to achieve optimum loading, then high productivity levels can be maintained.  Monitoring gob length, speed and diameter is a convenient way to keep control of these variables.  The new wireless PGM.V, from GTS, is a new, highly refined design eminently suitable for this task. 

The instrument has evolved significantly over the past 30 years with successive generations helping production operatives around the world to maximise productivity and profitability.  Before reviewing this latest development, it is worth explaining why monitoring gob length is so useful in container manufacture. 

Variation in gob length and speed is a common cause of defects (such as washboards, loading marks and brush marks) hence monitoring length helps operators keep control.  Major changes in length can arise from misalignment of delivery system components; wear on delivery equipment coatings, and incorrect delivery equipment size for gob shape at shear.  Adjustments to the delivery system are commonly made by eye and watching glass quality for changes.  With the PGM.V the effect of a change can be measured immediately. 

While monitoring during job changes is extremely useful to hasten the change over, on-going monitoring is equally important to reduce gradually occurring changes over a period of time; particularly an issue for long running jobs. 

The work that GTS has done on gob length over many years has exposed a number of surprising facts that even those working closely with IS machines may not be fully aware of; for instance: all gobs lengthen between shear and blank; they stretch when travelling through the scoop/ distributor and deflector, but stay fairly constant in the trough, or may even shorten.  Typically gobs are up to 40% longer at blank than they were at shear and as a result are usually longer than the blank they enter. 


Development of the PGM - clockwise from left: GobLI2, GobLI3 and S700-PGMReturning to the evolution of the PGM.V; this can be traced back to the 1970’s.  The organisation that is now GTS was, at that time, known as the British Glass Industry Research Association (BIGIRA).  The Forming Section was very active in improving the control of IS machines and length monitoring was one area of activity [1] .  The fundamental technology that was developed, that is still the basis of the PGM.V, has been found to be extremely robust through 30 years of widespread industrial use. 

In the early 1980’s a fixed-position commercial unit was developed and fitted into several factory sites [2] .  This was however not widely adopted due to the size of the rack mounted electronics, which were not convenient in factory use. A handheld device was developed called the GobLI2: Gob Length Indicator.  This proved extremely popular, and a number of these units are still in regular use today, nearly 30 years later. 

The initial GobLI2 was basically a box with a handle behind it that was held up to the deflector with live readings displayed at the back.  This was a good design for single gob machines, but became less convenient as double and triple gob machines became more commonplace and access became more difficult.  A separate hand held “wand” was therefore developed with a compact head able to fit into small spaces, and wired to electronics in a separate portable box.  At the same time advances in computing made it possible to save volumes of data/ readings more readily.  The result was the GobLI 3, launched in the early 90’s which, while having better functionality, was never as popular as the original device because of the size and weight of the large batteries and electronics. 

Development in electronics and computing in the 90’s allowed this design to be greatly improved, and a smaller, more portable unit was developed and launched as the S700-PGM (System 700-Portable Gob Monitor) in 1999.  This device again proved very popular, and was adopted by many glass plants Worldwide. 

With further advances in electronics and computing power over the past decade, and the widespread growth of wireless technologies, it was decided that the system needed bringing up to date. 

New PGM-V Launch

The latest PGM-V with separate base unit, or handheld console, and wireless wandThe new PGM.V launched in 2009, boasts the latest wireless communications technology, completely eliminating the need for cables.   Standard cell batteries are now situated in the handle of the wand which greatly improves the balance of the unit reducing operator fatigue during use.  The new light weight head design can now also fit into the smallest of spaces in triple and even quad gob machines. 

The new head design is also more robust than the head on the S700-PGM, while maintaining the rotation that allows it to fit different machine configurations.  The internal rechargeable batteries have been replaced by standard AA and D cells which are easily changed and allow the user the option to use standard rechargeable cells if desired. 

Ease of use has also been a critical part of the design process.  The handheld, or belt mounted, base unit features three “soft keys”, plus selection buttons and large LCD screen , which allows set up while on the shop floor.  This also allows the review of data without the need for a PC.  Both of these functions can also be done on the PC.  The compact size of modern electronics means that this unit fits comfortably into the hand, while the wireless connection means that it can be left at the end of the machine while measurements are being taken.  The exceptional speed of the electronics also allows monitoring to be effectively carried out at shear even on fast machines. 

A single easy to operate button on the wand allows measurements to be carried out single handed once they have been set up on the base unit.  The same button can be used immediately the unit is turned on to put the unit into GobLI mode for quick measurements that are not stored and a storage mode to record routine checks.  Finally the wireless link allows stored data to be downloaded directly into Excel for reporting and further analysis. 

In summary, monitoring gob length and speed is an invaluable aid to the machine operator to optimise production and assist in problem solving.  GTS has built on 30 years of experience to develop the new wireless PGM.V as an exceptional tool for the job. 

For further information please send us an enquiry or contact us. Support, guidance and software is also available for the PGM-V.


Reproduction of this published material is provided courtesy of Glass Worldwide. Published in Glass Worldwide, Issue 25, September 2009 - pages 88-89.


  1. [1] P. Grayhurst and C. Lucas, Glass Technology Vol 21 no 5 October 1980, pg 244-248
  2. [2] F. Shaw, Measurement and Control, Vol 17, November 1984, pg 380-382

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