Videocon International: CRT Glass - Process Equipment

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Process Equipment

Batch House
The company has a modern, well-equipped batch plant with updated computerized controls for the accurate weighing and mixing of batches for color television panels and funnels to the exacting standards desired.

Furnace
The company has 3 furnaces for melting panel and funnel glass separately on totally independent lines. The furnaces capable of melting approximately 100 MT per day are fired with natural gas and are cross-port regenerative furnaces. The glass flows from the melter through a throat in to refiners and there on to forehearth for delivery to the forming press.

The furnace activity involves maintaining of the furnace temperature profiles as per set values to assure proper melting and fining of molten glass. The furnace department is also responsible for maintaining the refiner and glass consistency till it reaches the forming presses.

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Panel Forming
The panel forming section as the name indicates is where the forming of the panel takes place. The molten glass, as a gob at around 1010°C, is delivered from the forehearth to the mold of Forming press in which the panel is pressed under very high pressure into the desired shape and contour.

The Company has ELP presses capable of pressing the panels into shape utilizing a fully automatic handling system integrated with computerized measuring and controlling system for critical parameters such as weight, temperature of the glass gob and also of the mold settings.

An automatic transfer system conveys the hot panel to the Stud Insertion Machine (SIM) where the studs of appropriate size are inserted into the sidewall or band of the panel. Thereafter another automatic loader loads the hot, studded panels into the Annealing lehr (tunnel) for conditioned cooling.

After exiting from the lehr the panels are sufficiently cool to permit inspection. 100% dimensional check is done by automatic contour and periphery gages after visual inspection.

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Funnel Forming
The funnel forming section as the name indicates is where the forming of the funnel takes place. The molten glass as gob at around 1020°C is delivered from the forehearth to the mold of the Forming Press in which funnel is pressed under very high pressure into the desired shape and contour.

The Company has ELP press capable of pressing the funnels into the shape utilizing the fully automatic handling system integrated with the computerized measuring and controlling system for critical parameters such as pressing pressure, mold temperature, timing variables and forehearth temperature.

After the funnel is formed, it is automatically transferred via a "takeout and turnover" mechanism onto a conveyor belt that takes the funnel to a gas button machine (GBM) where the anode buttons are inserted into the body of the funnel.

From the GBM, the buttoned funnels are transferred to annealing lehr for controlled cooling to bring it to room temperature for inspection. 100% dimensional check is done for periphery of funnels after visual inspection.

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Panel Finishing
The raw panels after visual and dimensional inspection go through the next stage of operations that is Finishing. This essentially consists of the following steps:

  1. Single Head Grinding
    The panel face is rough ground on a single-head rotating machine so that a thin layer of surface glass is ground off taking away the surface defects. The panel then becomes ready for the final grinding and polishing actions that give the panel face a polished appearance. 80 grit Pumice is used as grinding medium.

  2. Pumicer
    After the single head grinding the panel is rinsed and then loaded into a 14 head Pumicer machine that mainly takes off the roughness of the single head grinding process. On a rough estimate, the layer removal of the Pumicer would be 1/10 of the single grinding machine. 100 grit Pumice is the grinding medium.

  3. Polisher
    From the Pumicer, the panel is loaded into a nine head Polisher. The glass removal is negligible at this stage. The main function is to give a high polish to the panel face with Cerium Oxide as polishing Medium using a felt sleeve to deliver the high gloss.

  4. Abrasive Rinse - Washer -- Dryer
    The panel is then thoroughly washed and rinsed (with DM water and corn-cob that delivers a scrubbing action without scratching the glass) and dried to bone dry condition by "air knife drier" before exiting the machine for inspection and packing subsequent to release for dispatch to the customer. At this stage, 100% gauging is done for monitoring the Center Face Thickness (CFT).

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Funnel Finishing
The raw funnels after visual and dimensional inspection go through the next stage of operation that is Finishing. This essentially consists of the following steps.

  1. Funnel Edge Grinding
    The funnels are gripped with the help of vacuum suction pads from the nubbin (the short glass rod at the yoke end of the funnel caused during forming operations) end and pressed firmly with rotation against rotating diamond wheels in presence of water. The purpose is to grind off the funnel edge to make it perfectly flat to facilitate matching with the flat seal edge of the panel at the customers’ end. There are 2 diamond-grinding mills in operation.

    The high capacity Diamond Grinding Machines from The Netherlands were installed to replace conventional machines which use garnet as grinding medium. Apart from the higher quality and increased output the diamond machines use only water, which results in substantial savings on garnet.

  2. Mechanical Seal Edge Polisher
    After the seal edge is ground, there is an optional facility to polish off the ground edges depending on customer preference. The funnels pressed - seal edge down - against polishing pads in the presence of water. A smooth finish is given to the seal edges.

  3. Washer - Drier
    The funnels after MSEP pass through a washer where they are thoroughly rinsed with hot water and cold water to remove garnet stains and then dried by air.

  4. Crack off
    The ground, polished, washed and dried funnels then move on to the Nubbin Crack off machines where the nubbin is "cut off" by point heating by oxy-gas flame at a precise height on the nubbin of a rotating funnel followed by the cold touch of a cut off wheel. There are six crack off machines used for this purpose.

  5. Automatic Vertical Neck Sealing (AVNS) machine
    After the nubbin has been cut off the funnel moves to the last stage of operations that is sealing of a neck on to the yoke end. The funnel is placed seal edge down on to the machine and the neck gets perfectly sealed to the yoke at the crack-off point. Pot annealing to relieve stresses followed by normal cooling over an open conveyor completes the operations.

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The funnels are inspected for visual defects and dimensional tolerance by NTRO (neck tilt - run out) gage before packing and release for dispatch.

Laboratory
A modern fully equipped state-of-the-art laboratory, with Atomic Absorption Spectrophotometer, UV-VIS, Coulter Multisizer, TV interfaced Petrographic microscope etc has been set up for glass and raw material analysis.

Mold Shop
The company has a fully equipped mold shop capable of producing and repairing mold equipment such as plungers, shell rings and mold bottoms for the panel and funnel forming sections. Considering the accuracy desired the shop is equipped with:

  1. CNC lathes for computerized cutting and contouring.
  2. CMM for automatic dimension measuring at programmed points.
  3. State of the art benches for hand benching requirements.
  4. Robot aided computerized plasma spray equipment.
  5. In addition, there exist the normal facilities such as general-purpose machines, annealers, welding, electroplating, stripping and cleaning facilities.

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  Batch House
  Furnace
  Panel Forming
  Funnel Forming
  Panel Finishing
  Funnel Finishing
  Laboratory
  Mold Shop