Glass machine
A glass machine forms a workpiece from a liquid glass drop (batch). Glass machines are used in the field of hollow, pressed and sheet glass production.
Process for hollow glass production
All processes for automatic glass production have in common that the three basic steps take place as in manual production:
- Preforming: The formation of the parison
- Reheating: compensation of temperature differences
- Finished molds: final shape
The shape of the parison determines the later distribution of the glass in the finished article and thus has a decisive influence on the thickness of the wall and floor. Therefore, the design of the preform requires a lot of experience.
Blow-blow process
- The liquid glass flows from the melting tank into the feeder . The feeder machine forms an elongated glass gob at the head of the feeder.
- The glass gob is fed into the preform of a production station via a channel through the hinged funnel mechanism. The later opening (mouth) points downwards. ( Figure 1 )
- The bottom of the preform rests on the funnel and closes the mold. Compressed air is blown in from above so that the glass mass completely fills the opening shape at the bottom ( blowing tight, Figure 2 ). The so-called level protrudes into the mouth shape.
- The preform base and then the funnel mechanism pivot back and the preform is closed with the preform base on top. The level moves downwards, and the influx of compressed air blows the glass container into the container into the opening that is created ( Figure 3 ).
- The preform opens and the pre-blown workpiece (parison) is swiveled by 180 ° into the open finished form by the transfer mechanism ( Figure 4 ). The parison is held in the mouth shape. Before the finished form closes, the parcel remains in this position for a short time ( reheating, Figure 5 ). The muzzle is now on top.
- The mouth shape opens. The transfer arm swivels back into the starting position in order to pick up the next drop in the preform. Meanwhile, the finished mold is closed from above by the blow head in order to blow the parison in the finished mold to its final shape with compressed air ( Figure 6 ).
- The blow head swivels back, the finished mold opens and a gripper conveys the finished workpiece onto an air-cooled depositing plate ( Figure 7 ).
- A stripper (pusher) pushes the finished workpiece onto the machine belt , which transports the article into the cooling track .
Press-blow process
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In the press-and-blow process, the parison is not blown, but rather pressed by a punch, the level , introduced through the mouth shape. It was first used in wide-necked containers (e.g. canning jars).
However, the press-blowing of narrow-necked bottles has decisive advantages: The parison cools down more during pressing, which results in higher production figures. Since the glass distribution in the parison can be better influenced by pressing, thinner-walled glass containers such as lightweight bottles can also be manufactured. This is why press-blow molding is increasingly finding its way into bottle production and is referred to here as narrow-neck pressing . The narrow-neck press-blow process is considered the most modern stage of glass processing.
In contrast to the blow-and-blow process, the mouth is formed last in the press-blow process. Therefore, the required gob weight must be adhered to very precisely so that there are no unfinished mouths. The machine operator is often supported by automatic measuring systems, e.g. B. Level control or automatic control of the drop weight.
The blow-blow and press-blow processes are the most widespread in hollow glass production, and most production machines can master both processes through conversion.
Suction blow process
The suction and blow molding process was the first automated process for glass production (see history ), it is no longer used today. This process made it possible for the first time to precisely set the critical drop size.
It differs from the blow-and-blow process in that the glass gob is not formed by the feeder machine and falls into the machine. Instead, the lower edge of the preform dips into the glass mass, and the liquid glass is sucked into the preform by means of negative pressure. The preform is then lifted out of the glass mass and a knife cuts off the excess glass.
Paste-mold process
The paste mold or rotary molding process is used when there is a need for high surface quality, for example for wine glasses.
The pre-formed parison is first held in place by a retaining ring and then elongated a little with gravity using a few blows. This closes the (usually three-part) mold, which is provided with a water-soaked coating ( pasted ) on the inside . The coating must be renewed several times a day.
The paste mold and the glass workpiece rotate against each other during the final blow molding. The water-soaked coating creates a cushion of water vapor between the mold and the workpiece. Due to this steam cushion and the rotation, no molded seam can be seen after opening the mold. The blow cap , which was connected to the blow head and the retaining ring, must then be separated.
Machine types in the production of hollow glass
IS machines
An Individual Section machine , in English machine with individual sections or IS machine for short, is a series of individual production units that produce containers independently of one another. Above the machine at the feeder head there is a feeder machine that uses cooled knives to cut off individual glass gobs, which are then fed to the production sections via the gob distributor and a channel system. In this way, a feeder downstream of the melting furnace feeds several production units cyclically with glass gobs.
In the stations, the items are processed into finished containers in three stages using the blow-and-blow or press-and-blow process and transported to the cooling track via a conveyor belt . The machines are driven pneumatically or, in the case of newer types, fully automatically via electric servo drives .
The IS machine is the most widely used machine in hollow glass production . Manufacturers of IS machines include Emhart Glass (for Bucher Industries , Switzerland), GPS ( Essen , Germany), Heye International (Obernkirchen, Germany - for the Ardagh Group ), Owens-Illinois (USA), Bottero and BDF (both Italy ), Sklostroj ( Turnov , Czech Republic).
Rotary blow molding machines
This type of machine is also called rotary or carousel machine and, in the field of hollow glass production, consists of 7 to 10 production sections that are mounted on a carousel. A feeder machine located above the machine forms a gob of glass that falls directly into the machine station passing below - a gob distributor is not necessary.
To load the various stations, the molds are rotated one station at a time. The individual production steps are carried out in the course of a 360 ° rotation. The rotary movement can be continuous (the turntable revolves at a constant speed, customary when blowing) or intermittent (the turntable stops for each process step, customary when pressing).
Rotary machines are not only limited to the blow-blow and press-blow processes, but are also used in pressing and centrifuging (see below). Since a large mechanical mass is kept in motion in rotary machines, the speed of the process is limited.
Rotary machines are mainly used in the production of wine glasses and other high-quality drinking vessels using the paste-mold process and in general in the production of vessels that are not mass-produced (beverage bottles, canning glasses , perfume bottles). The GDR relied heavily on rotary technology for hollow glass production using the blow-and-blow process, as this was state of the art after the Second World War. The manufacturer of the machines was VEB Glasmaschinenbau Freital . Because of the disadvantages mentioned, most production lines were converted to IS machines after the fall of the Wall.
German manufacturers of rotary machines for blowing, pressing and centrifuging are the companies GLAMACO (formerly Glasmaschinenbau Coswig ), Füller Glastechnologie from Spiegelau , Waltec in Steinberg, County of Kronach and Forma-Kutzscher in Zwiesel . The Italian manufacturer Olivotto is of international importance .
Tape machines
Ribbon or chain machines are mainly used in the production of light bulbs . These machines have a large number of pasted, two-part molds attached to an articulated metal belt. The belt rotates in the machine at high speed while the individual production steps take place.
Further procedures
Press
When pressing glass articles, the glass gob is connected to the metal mold on all sides. The mold usually consists of three parts: the (hollow) mold, the press ram and the cover ring, which prevents glass from escaping from the gap between the ram and the mold during pressing.
For pressing, the glass gob is first fed into the mold, then the press ram is lowered hydraulically or pneumatically into the mold. After solidification, the stamp is pulled out again. The press machine is usually a rotary machine with 4–20 shapes.
Typical articles made by pressing are television picture tube screens, vehicle headlights, mugs, and fireproof housewares.
fling
When spinning, one makes use of the effect that a surface is formed in a rotating liquid that corresponds to a spinning parabola ( rotational paraboloid ), i.e. forms a cavity.
During use, a thin gob of glass is fed into the mold. The mold is then set in a rotation, causing the glass to spread. If the speed is high enough, a very steep spin parabola is created so that cylindrical articles can also be produced.
Many household glasses, but also technical system parts made of glass, are produced by spinning. The process is not limited to rotationally symmetrical bodies: the funnels of television picture tubes can also be shaped in this way.
Tubular glass
→ Main article: Tubular glass
Many products in the medical industry, such as ampoules, syringes and vials, are made from glass tubing. The production of fluorescent tubes also requires large quantities of glass tubes. The production of the glass tube itself and the further processing to the end product are separate, so the manufacturers of drug ampoules buy glass tube by the meter and process it on rotary machines.
In most production processes, an "infinitely long" glass tube is drawn directly from the melt, which is then cut into pieces.
Machine Operator
The glass machine is operated by a machine or machine operator. This monitors the production process, adjusts mechanical movements and control times and changes worn molds. In addition, it constantly lubricates moving parts as well as glass-bearing machine components (e.g. funnel, ejector, machine belt ...) with graphite-containing lubricant.
Usually a machine operator is responsible for each glass machine per shift. In addition, there is usually a shift supervisor or foreman who monitors the melting process and steps in when a machine operator takes a break.
The work of the machine operator is not without danger: the glass machine can practically not be enclosed, since sufficient cooling and accessibility would be impossible with a cover. As a result, the machine operator is permanently exposed to the risk of crushing and burns. If, for example, a mold has to be changed on an IS machine, only that station is stopped. The machine operator works at the stationary station while production continues 30 cm from him. Constant work in a hot, noisy environment is also physically demanding, especially since the machine operator is responsible for a system that costs several million euros on the one hand and for the quality of the goods produced on the other. Therefore, the machine operators are among the best-paid production workers in the glass industry.
Many glassworks train their machine operators to become process mechanics for glass technology (see the web link to the job description at BerufeNet).
history
First attempts to automate the process of glass blowing were made in the middle of the 19th century. As early as 1882, Philip Arbogast demonstrated a machine for the press-and-blow process for wide-necked containers and three years later Howard Ashley for the blow-and-blow process for glass containers with narrow openings. However, these machines were not yet working automatically. The first fully automatic glass production machine was patented by Michael Joseph Owens in 1903 . It worked according to the rotary principle, whereby the liquid glass was initially sucked directly from the melt by means of negative pressure (suction-blow method, see above).
In 1914, KE Peiler of Hartford-Fairmont Co. announced a process for distributing molten glass drops from the drop feeder to several individual production units . But it was the IS machine with fully automatic distribution troughs and four sections developed, patented and commissioned in 1927 by Henry W. Ingle and Charles Goodwin Smith at the Hartford Empire Company that made this technology successful. Redirecting the glass posts and loading the stations posed major problems for the developers, so that initially a maximum of four stations could be linked together. Later, rotary machines were also supplied from gob feeders. Ingle and Smith are also cited as the inventors and even namesake of the IS machine.
literature
- Wilhelm Giegerich, Wolfgang Trier: Glass machines . Springer, 1964.
- H. Hessenkemper, A. Berg, G. Nölle, H. Uhe, R. Weißmann: Forming of glass . Ed .: HVG - Metallurgical Association of the German Glass Industry. 2nd Edition. Verlag der Dt. Glass techn. Society, Frankfurt a. M. 1997, ISBN 3-921089-20-4 .
- Dieter Schumann, Jan Peter Müller, Hermann Schier: Machines of glass technology . Ed .: Central Office for Vocational Training of the Ministry of Glass and Ceramics Industry, Ilmenau. 2nd Edition. German publishing house for basic industry, Leipzig 1980.
Web links
- Video of a producing IS machine (single drop, blow-blow) on YouTube
- Historical recording of a running Owens machine on YouTube
- Process mechanic for glass technology at BerufeNet
- Codd Bottle - Old soda glass container with a glass marble as closure (Glass Industry, 20th Century) on YouTube
- NNPB glass forming process
Individual evidence
- ↑ Individual Section machine . Encyclopædia Britannica. Retrieved November 22, 2013.
- ↑ Container Making . Encyclopædia Britannica. Retrieved November 22, 2013.
- ↑ Method of and apparatus for feeding molten glass, United Kingdom Patent 157160-A . Directory patent. Retrieved November 22, 2013.
- ↑ Hans R. Kricheldorf: People and their materials: From the Stone Age to today . Wiley-VCH, 2013, ISBN 978-3-527-33082-9 .