Technische Berichte


Headline A Future Trend in Hollow Glass Manufacturing
Author(s) Dipl.-Ing. Klaus Pöting


Outlook of the hollow glass production in Germany Economic development of the production of tableware during the last years in Germany To give an indication for the future we have to face the present now. The economic situation of tableware and container industry in Germany is summarized in Table 1.

Tableware Industry

    1995 1996 1997 difference %
Factories No. 47 44 42 -10,6
Employees No. 8600 7950 7500 -12,8
Production Mio. DM 1048 965 960 -8,4
  1000 t 112 107 105 -6,3
Turn over Mio. DM 1250 1200 1175 -6,0

Container Industry

    1995 1996 1997 difference %
Factories No. 36 35 33 -8,3
Employees No. 14700 14450 13200 -10,2
Production Mio. DM 3430 3340 3152 -8,1
  1000 t 4578 4505 4290 -6,3
Turn over Mio. DM 4060 3915 3650 -10,1

Table 1 German production of tableware and glass containers

We can take Germany as an example for Western Europe, because the situation there is not much different. We see that both annual turnover and earnings were bad during the last few years and the preview for 1998 is not that much better. In tableware particularly we have to face another problem which is related to this kind of industry. We are able to manufacture big series - 20.000, 30.000, 50.000 pcs a day - but the problem today is not manufacturing this big amount of items, but to sell them. To find a market which takes the annual production of billions of pieces is difficult and in this particular market every supplier is trying to put his foot in the door. So the prices are weak. Tableware in mass production is already today manufactured in low labour-cost countries like Turkey or Indonesia.   Let us have a look at the typical tableware ex-works production costs as a function of the lot size (Fig. 1)

We can see that the lot size in an area bigger than 1.000.000 pcs can be manufactured economically at a price lower than DM 1 for stemware, a second segment which is located between 1.000 and 5.000 pcs. This is the manual or semi-automatic production with a lot of labour. Especially in Eastern Europe and in Far East local manufacturers are able to produce tableware and stemware of this segment starting from DM 2 per piece up to DM 30. Finally we have artistic production of unic items or high quality image for some hundreds DM per piece. Obviously there is a big gap in the area between 1.000 and some 10 thousands of pieces. The market however is more and more asking for lot sizes especially in this domain. Each airline, each hotel chain etc. wants to have its own typical shape. We all, as customers, do not want to have mass production, we want to have a very typical - probably also fashionable - article at a very reasonable price.

All this represents a big market potential for glassware. The younger generation is not willing to accept a glass series as a gift on wedding and have this type of glass for the whole life. We as consumers are asking for decorative, fashionable, reasonable quality glassware at an affordable price, but we may have it for different occasions - for summer, for winter, for lunch, for dinner - but it should be a well-fitting accessory to the appearance of the whole table. In the porcelain market and the cutlery we have to face the same development. The consumer fairs in Frankfurt, Milano, Paris and New York are guiding in this direction.

The 2nd point is that one series of drinking glasses for instance is made of up to 16 different types of glasses. It starts with champagne flute, sparkling wine bowl, red wine, white wine, burgundy wine, beer glass, water, sherry and schnaps, totally different types of glasses as an average. However, the amount in selling of each of these glasses is totally different. (Fig.2 and Fig.3)

We have 2 to 4 bestsellers - mostly wine, red wine and water - but the supplier has to manufacture all of them and it is not possible to get a price related to the production costs. The price must be a combination which fits to the whole series. In fact the bestsellers have to support the badsellers - in other words - a big number of items is only creating losses when it is produced, but it must be kept in the production range, because it is necessary to sell the bestsellers.


Seeing the economic situation and the actual kind of production, two tasks are urgently needed Cost reductionand Flexibility

Technical equipment of the today's glass factories

The container industry is nearly 100 % working with IS machines with minimum 8 sections. The maximum which is achieved today is 18 sections tandem machines and these machines can run double-gob, triple-gob or, in a few applications, quadruple-gob. The maximum speed is 720 pcs/min. More and more lines are installed at one furnace. The daily capacity per furnace may achieve up to 300 t, 400 t, 500 t and the output is millions of bottles per day. Today we have an overcapacity in the container industry and several lines have to be shut down. The market is divided between 5 or 6 big companies, global players, who are owning glass factories all over the world. The main goal for the production is to have more and more pieces with less and less people and less and less glass weight with the same technical features and demands. The articles are standardized in dimensions, appearance and physical resistance. So the point of flexibility is not that interesting in this industry.

In the tableware industry, however, flexibility is one of the main goals. Cheap glassware is already manufactured in Turkey or Indonesia and imported from there. The small, manual, semi-automatic factories in Germany - or in Europe generally - are closing step by step. Only the big companies will survive and the market will be dominated by only a handful of international operating companies. Tableware is today manufactured on rotary-type pressing as well as blowing machines. A standard number of sections is 12, double-gob for the pressing is a common process and sometimes triple-gob is in use. The maximum output for pressware is about 150 pcs/min.

Having a look at the cost distribution depending on the lot size, we see that the part of the mould costs is dramatically increasing and becoming a really important factor with lot sizes lower than 100.000 pices. Fig 4.To give an indication: One full set of moulds for a 12 section rotary-type machine costs in the area of DM 120.000 - DM 140.000. It is easy to calculate how much the selling prices for a simple piece must be, if the lot size is that small. Actual prices/pc for simple stemware ex factory are DM 0,50 to DM 1,- and for high quality stemware are about DM 2,-. With such high mould costs it is impossible to manufacture normal items at that price if a lot size is smaller than millions of pieces.

Automatisation and flexibility - the only chance to survive in Europe

The only answer - and this development is visible for all suppliers and glassware manufacturers - is increased individuality, customized production, smaller units, fewer moulds, high flexibility with fast and easy job change. If you have a small job, you do it on one section, if you have a bigger job, you select more sections. Mathematic modelling is part of more flexibility. Each item and every kind of machinery can be designed by experienced people, but it has to be developed with a machine in a glass factory in any case. This development needs a few days - depending on the difference of the new and the experienced articles - and in any case some modification of the moulding parts has to be done.

These costs are difficult to calculate and are different from factory to factory, we estimate about 8 % - 14 % of normal production costs are necessary for development and mould adaptation. Two directions can be taken regarding the modelling of the glass forming process. Optimizing the manufacturing method of glass forming. Decrease dramatically development time and effort from article to article finding the optimum.

The technologies used today have been developed by try and error and are related to the experiences of traditional methods. The systems are working, but nobody knows if the optimum of manufacturing this item at that time with that method is the most economic and most reasonable. A lot of theoretical work can be done with the computer in modelling different processes, differents parameters and different methods to find out which method for which article is the most efficient. This kind of development work was hardly done in the glass factories, because the production, once started, was kept running and the basic development work in varying basic parameters was never done. Optimizing each article, the thermal behaviour of plunger, mould, mould ring, grippers, blow moulds and all elements contact the glass is closely related to the selected method.

The same article which is pressed has a totally different thermal life when it is manufactured manually or in a 6-section machine or in a 12-section double-gob machine. This kind of development work has to be done in each glass factory for each different article. As soon as tools are available the glass manufacturer is able to answer the customer´s requirements very fast, because he can model this item on his own computer, calculate the real speed, give the customer a good answer about price and delivery. Manufacturer is on the safe side because the economic result is visible before production and he is sure that the mould design afterwards is nearly done and no big modification and development time are needed.


The today economic situation is forcing glass manufacturers to completely change, thinking in technology. Beside cost reduction the main goal is more flexibilty to answer fast and with very reasonable prices market demands and customer´s requirements. Customized production is needed. Traditional methods hardly allow to fulfill these requirements, so new technolgies have to be developed. Machines and technology are already available or are under development. A general problem however is that enough experience is not available yet which allows the manufacturer to switch over immediately to new technologies and that is why the modelling of processes becomes very important. If we can model the process reliably, if we do not need to do the development work in the glass factory with hot glass, with existing moulds and existing machines while the daily production is running, but on the computer in the office most of the problems are solved.

The delay for answering to customer´s requirements can be shortened dramatically. If we can optimize the relevant processes, the manufacturers have a reliable base for their calculation to quote fast on customer´s demands.

Both steps for the glass industry have to be done. Different technologies, but combined with modelling of the processes are needed and these methods will give the European manufacturers in particular and all glass manufacturers in general the potential to react on the market´s requirements.