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Latest trends in calender lines.

Latest trends in calender lines

The demand for production lines at high output capacities with optimum product quality and short tooling times calls for ultra-modern calender lines for the manufacture of semifinished products.

Recently, we delivered and comissioned calender lines in full compliance with the following demands:

* One, four-roll calender line for the manufacture of textile conveyor belt carcasses up to a production width of 2,300 mm.

* One, four-roll calender line for the manufacture of textile conveyor belt carcasses up to a production width of 2,300 mm.

* One, four-roll calender line for the double-sided coating of tire cord.

* One, roller head line with a three-roll calender for the manufacture of covering sheets for conveyor belts made of steel ropes and for the manufacture of textile conveyor belt carcasses up to a finished width of 1,800 mm.

Four-roll calender lines for conveyor belt carcasses

Technical data and description of function

Double let-off device - The production starts with the let-off device. The latter consists of two mobile let-off stands for each batch of fabric or carcasses. The maximum batch diameter is 2,800 mm. The tension is 1,000-3,000 N and can be adjusted in accordance with the type of fabric to be let off.

If a liner is required, each let-off stand is provided with an appropriate wind-up stand. An expander roll and an edge control unit ensure a foldless and straight edge winding of the liner.

Sewing machine - A special sewing machine connects in an overcast manner the front end of the material sheet to be let off with the rear end of either the thread in fabric or material batch. A belt conveyor, transporting the front end of the fabric or carcass, is arranged between the let-off device and the sewing machine. A let-off accumulator with a capacity of 40 m is located in front of the calender so as to have sufficient material available for the continous operation of the calender when the batches are changed. The dancer carriage of the accumulator is hydraulically actuated. The maximum material tension is 3,000 N.

Feed roll stand - The feed roll stand takes the fabric from the let-off devices and conveys it into the accumulator. The working speed for the filling of the accumulator is 50% higher than the rated line speed. Drive is effected by a four quadrant D.C. motor controlled by the lifting motion of the accumulator dancer carriage via a potentiometer.

Holdback stand - A holdback stand in front of the calender ensures a uniform fabric tension during the calendering process. The holdback stand is driven by a four quadrant D.C. motor and controlled by a load measuring bearing incorporated in the dancer roll system.

The center control unit in front of the calender is used to center the fabric or the carcass before the latter runs into the calender roll gap. Photoelectric cells scan the material edges and give setting pulses to the guide rolls. The photoelectric cells adjust themselves automatically according to new material widths.

Calender - The four-roll calender is the most important and decisive component of the whole line. The rolls are arranged ranged in an S-configuration. Rolls 2 and 3 are arranged vertically one above the other, roll 1 at an angle of 45 [degrees] in front of roll 2, and roll 4 at an angle of 30 [degrees] in front of roll 3. The roll diameter is 750 mm, the roll face length of 2,500 mm. The operating speed of 2-40 m/min. is infinitely variable.

Roll 2 is the fixed roll and rolls 1, 3 and 4 are adjustable. Rolls 3 and 4 are arranged on one sliding block bearing. In this way, rolls 3 and 4 can be adjusted in common at mean and quick speed without any change of the gap between rolls 3 and 4.

Sliding block bearing - This design of the sliding block bearing is a Berstorff patent. The adjusting speed at quick speed is 1.5 mm/sec. and at mean speed 4 or 1 mm/sec. All other rolls can be adjusted by 4 mm, 1 mm and 0.4 mm/sec. The adjusting speed of 0.4 mm/sec. is provided for the connection of an automatic roll gap control.

Axis crossing device - Rolls 1 and 4 are additionally equipped with an axis crossing device. The latter serves for the compensation of the roll deflection up to a maximum 0.3 mm. Thus, a uniform thickness of the rubber sheet over the whole working width can be ensured.

Roll bearings - Ultramodern cylindrical roller bearings in connection with preloading devices ensure an absolute concentricity and a backlash free bearing arrangement of the rolls. (Maximum tolerance 0.005 at operating temperature.) An oil circulation lubrication system supplies lubricant to the bearings of the rolls and preloading devices.

Bearing lubrication - Safety devices prevent the bearings from running dry. In case of any disturbances of the lubrication system, the calender line is stopped automatically.

Preloading device/bending device - The rolls 1, 2 and 3 are equipped with hydraulic preloading devices and additionally, roll 3 with a bending device.

Gear unit/driving motors - Each roll is individually driven by a D.C. motor. Driving power is 4 x 110 kW. For the operation of "double-sided coating," the gear unit is additionally equipped with a synchronizing step to be engaged by hand and arranged between rolls 2 and 3. Maintenance free, universal joint shafts transmit the torque onto the rolls.

Control desk - The central control desk enables a quick recognition of the actual operating function due to the well arranged, high-precision indicating instruments on the vertical desk panel. The switches and potentiometers for control and regulation tasks are arranged on the horizontal desk panel.

Roll gap control - The contactless measuring of the thickness of the material sheet from roll gap 1 and 3 is effected over the whole width according to the backscatter measuring procedure with strontium sources. Deviations from the rated value are corrected automatically by the adjusting devices of rolls 1 and 4. The same measuring system controls the axis crossing devices of the rolls 1 and 4 as well. overhead surfaces in either thin layers (minimum of 1/4 inch) or with relatively high rates of build-up. In addition, it cures rapidly to very high compressive strengths.

Because it is designed for gun application, hand labor is greatly reduced. In addition, it is a simple system - water addition to the mixing equipment is all that is required. No mixing of various ingredients. It has low rebound (a characteristic needed for the shotcrete application) and it allows passage of water vapor in the same way as normal concrete.

The shotcrete technique applies a layer of concrete to a surface by pneumatically "hosing" a layer of material onto the appropriate surface. Mixing of the concrete with water occurs at the nozzle as the material is applied, resulting in a continuous rather than a batch process. Mixing with water is done at a predetermined ratio at the mixing head. This allows for use of only the amount of material needed for the job as well as rapid application.

There are several important factors in successful shotcrete application:

* Distance of nozzle from surface (2-6 ft.).

* Angle of nozzle to the surface (90 [degrees] optimal).

* Consistency of the mortar (should be somewhat plastic).

This method reduces the high labor factor required with normal mortar. Because of the high impingement velocities, it is also able to fill cracks and voids to a much greater degree. Finally, the process also allows (and somewhat requires) use of a fast curing material.

Prior to application of this type of material, the surface to which the new material will be applied should be thoroughly cleaned. This can be done using a high pressure water blast (6,000 psi) or sandblasting. With this material, no additional primer or surface preparation was needed.

The Sikachem 103 is reported to behave very much the same as normal concrete except it is stronger and cures faster. Table 1 shows typical values for strength of the cured material. Reports indicate that there is no problem bonding to other cured concrete or to itself, whether cured or not.

Table : Table 1 Comprehensive strength (ASTM C-109)
 2 days 6,000 PSI
 7 days 8,100 PSI
28 days 9,000 PSI

Flexural strength
 7 days 1,000 PSI
28 days 1,400 PSI

Tensile strength
 7 days 600 PSI
28 days 750 PSI

How did the material work? With the Sika material, it was possible to apply up to a 1-1/2 inch layer of material in one pass with no sag problems. Application was done using 300-400 psi air.

All work was done in a closely confined space, requiring low dust material. With the shotcrete method, the material was applied and was able to be tooled right away on all surfaces. According to the applicator, the material had the consistency of a firm jelly when applied. As the data in table 1 indicates, compressive strength develops to over 6,000 psi within two days. (Normal concrete has a compressive strength of 4,000 psi when fully cured). From the beginning, the work proceeded smoothly. In approximately one week, the work crew had cleaned and prepared a 20 foot by 12 foot by 12 foot chamber by cleaning to bare aggregate. Two inch by two inch wire mesh was applied to floor, walls and ceilings. Then 1-1/2 inches of Sikachem 103 was applied, tooled and cured.

After almost a year of use, the surface is reported to be in good shape. Good enough that Bridgestone/Firestone is planning on using the same material and methods to repair hot wells in other plants.

Any potential problems? Virtually none. Minimum temperature for application is 45 [Degrees]F. Surfaces should be clean and free from deteriorated material. The surface to which the material is applied should be "saturated surface dry."

As with normal concrete, pH extremes (particularly acid) should be avoided. No problems would be expected with use in the range of pH 5-9.

Application is typically done by commercial applicators who are trained and approved by Sika. Shotcreting is done per standards established by ACI 506-R85.

Finishing is done by normal methods. The surface can be broomed to a rough texture, wood floated to a granular texture or steel troweled to a smooth finish. Finishing should begin about 5-10 minutes after initial set of the material.

If local conditions are likely to cause premature surface drying, a fine water mist spray, wet burlap or a curing compound should be applied. Conditions likely to cause this include high temperatures, low humidity and strong winds.

The material is a microsilica filled cement. As such, normal safety procedures for handling dry and wet concrete need to be observed: use dust masks, safety goggles and rubber gloves. Skin and eye contact should be avoided.


Many of the maintenance functions and requirements go unnoticed by engineers and technologists who are busy making products. General maintenance is an unsung hero in our industry. Without attention to problems so mundane as hot wells, we wouldn't be able to make very many acceptable products.

The report on this product looks very promising for one aspect of maintenance that certainly deserves attention. It obviously seems to be of benefit to Bridgestone/Firestone.

After coating, the finished product (double-sided coated fabric) is checked by means of a transmission measuring device. The transmission measuring device is moved in transverse direction to the material sheet for the latter to be checked and corrected in an optimum way. The profile of the coated product is always visible on the control stand.

The transmission measuring device also controls the bending device of roll 3 as well.

Heating/cooling of rolls - A separate heating/cooling device is provided for every calender roll. All calender rolls are peripherally drilled.

Heating/cooling is effected by hot water via electric controllers and continuous valves. The maximum roll surface temperature is 150 [Degrees]C. Heating up or cooling down is effected by 1 [Degree]C/min. via a time-lag control.

Hydraulic unit - The hydraulic unit is used for the generation of pressure and the hydraulic control of the cylinders of (a) the preloading device, (b) axis crossing device, and (c) the hydraulic pressure compensation unit (hydraulic cushion) for the automatic relief of the center roll gap when a splice passes through.

Cooling unit - The cooling unit consists of four driven double-walled rolls, diameter 1,000 mm, with multichamber cooling system. A hydraulically actuated dancer roll with integrated load cell controls the drive of the cooling unit so that the preset material tension of maximum 10,000 N is ensured.

Double wind-up device - The material sheet runs to the double wind-up device over a feed belt conveyor ascending by 25 [Degrees]. The wind-up device consists of two laterally movable stands with liner let-off above which a horizontally movable transfer belt conveyor is arranged.

This design enables the automatic, continuous winding of even the most heavy carcasses without any manual operation by the personnel. When the batch in the first winder has reached its set length or the maximum diameter, the coated material sheet and/or the carcass is cut on the feed belt conveyor by the cross cutting device.

The end of the material sheet runs over the feed belt conveyor into the winder. At the same time, the transfer belt conveyor moves forward and takes over the front end of the new material sheet.

The second winder starts automatically to turn and the first meters of the material are found automatically on the winding shaft by means of the previously threaded and wound liner.

The maximum wind-up diameter is 3,000 mm and the maximum tension 3,000 N.

Surface winder - Rubber sheets are wound up according to the surface winding system without any tension. In this case, the belt conveyor serves as drive for the batch to be wound up.

A hydraulic pneumatic system is provided for the automatic weight relief.

Preheating of rubber - One pin barrel extruder GE 250 K8 x 12 D for each calendering roll gap is provided for the preheating of the rubber compounds to be processed. The extruded strip is fed via take-off belt conveyors and feeding devices into the calender roll gap. The extruder output capacity is regulated to controlling the rolling bank height by means of three ultrasonic probes and a microprocessor, thus, a continuous and uniform roll gap feeding is ensured at every calender speed.

Electrical equipment - The line is equipped with a free-programmable control unit and a process master computer. Thus, the complete data of the line and product can be programmed from the control desk.

Variants of production The calender line is rated for a continous operation. For this reason, it is necessary to use a thread-in fabric which runs through the line according to the material flow. Double-sided coating of fabric and one sided frictioning of fabric are shown in figure 1. Covering of conveying belt carcasses A conveyor belt consists of (1) the carcass of e.g. three layers of coated fabric, (2) a rubber sheet on the bottom side as the backing whereas a thicker one on the top side is the carrying side, and (3) the edge protection on the left and right sides.

Figure 2 shows the production step "covering of conveyor belt carcasses." Compared with the conventional procedure, this working method is a considerable rationalization. While formerly, the backing, carrying side and edge protections had to be separately applied to the carcass in several steps, this ultramodern calender line renders it possible to carry out all three operating steps in one single pass.

The carcass is guided below the calender and provided with the backing and edge protection into the lower roll gap. The carrying side is applied to the carcass in the upper roll gap after having been calendered in the center roll gap.

Four-roll cord line for double-sided coating of tire cord Technical data of the machine is shown in table1. Equipment arranged in front of the calender includes:

* Double let-off device, diameter range 200-1,200 mm, let-off tension 500-2,500 N.

* Splice press, electrically heated up to 200 [Degrees]C, heating time 10-120 seconds, specific splice pressure 250 N/cm2

* Feed roll stand cord tension 500-2,500 N, operating speed 3.5-70 m/min plus 50% advance when filling the material accumulator.

* Automatic center control hydraulic optically operated.

* Material accumulator pretensioned hydraulically, tension 500-2,500 N, accumulator capacity 140 m.

* Automatic center control.

* Expander roll.

* Roll liner. Equipment behind the calender (calender train) includes:

* Dancer roll system with integrated load measuring unit for the control of the cooling unit.

* Drum drying unit and/or pull roll stand for a cord tension of 2,000-20,000 N.

* Pricking device.

* Pick breaker.

* Marking device.

* Creel for cotton threads.

* Material accumulator, pretensioned hydraulically, tension 500-2,500 N, accumulator capacity 70 m.

* Automatic center control.

* Pull roll stand, cord tension 500-2,500 N, operating speed 3.5-70 m/min plus 50% advantce when emptying the material accumulator.

* Cross cutter and automatic threading unit for the double wind-up device.

* Double wind-up device with two liner let-off stands, wind-up diameter 200-1,200 mm, wind-up tension 300-2,500 N.

Used for rubber preheating are two extruders (GE 250 KS x 12 D, output 2,300 kg/h each), complete with all additional equipment, namely:

* Extruder for the calender gap formed by rolls 1 and 2.

* Extruder for the gap formed by rolls 3 and 4.

Complete electrical equipment with a free-programmable control unit for the control and regulation part with a process master computer for the whole line including the automatic calender roll gap and rolling bank control. Three modes of operation are possible:

* Manual operation. All rated values preset by personnel.

* Semiautomatic operation. Rated values are partially programmed.

* Automatic operation. All rated values are stored and the line is completely controlled by the process master computer.

Roller head line for conveyor belt carcasses Technical data of the machine Extruder GE 200 KS x 18 D with wide extrusion head, output capacity 2,500-3,500 kg/h pending on the viscosity and permissible stock temperature. Screw speed 33 min-1, driving power 300 kW.

Three-roll type calender 600 x 2,200 mm, with axis crossing device on the center and bottom rolls and preloading device on the top and/or center rolls. The rolls are driven by three D.C. motors via special gear units. The driving power on the top roll is 40 kW and on the center and bottom rolls 48 kW each. The operating speed is 0.5 - 20 m/min.

Equipment behind the calender (calender train) for the production step "sheeting":

* Take-off device

* Roller train

* Thickness gauge

* Three daylight cooling unit for indirect water cooling

* Longitudinal cutting device

* Cross cutting device

* Conveyor belt and double surface winder with hydraulic weight relief

Supplementary equipment for the coating of the fabric or carcasses:

* Let-off device with liner wind-up stand

* Expander roll

* Edge trimming device

* Pull roll stand with three rolls

* Wind-up device with liner let-off stand

* Electric drive for the D.C. and three-phase current section of the whole line

Variants of production: Technical product data

* Thickness of rubber sheet: 1.5-18 mm

* Width of rubber sheet: 1,000-1,800 mm

* Fabric tension: 2,500-7,500 N

* Let-off diameter: 200-1,200 mm

* Wind-up diameter: 20-1,500 mm

Manufacture of rubber sheets for conveyor belts made of steel ropes or of sheets made of fiber loaded compounds for raw-edge v-belts, one-sided coating of fabrics for conveyor belts or v-belts and one-sided covering of conveyor belt carcasses made of several fabric layers are shown in figure 3.
COPYRIGHT 1991 Lippincott & Peto, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
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Title Annotation:design and construction of a production line
Author:Capelle, Greg
Publication:Rubber World
Date:Jul 1, 1991
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