The standardized roll unit type P-600 can be used both horizontally and vertically without special equipment or modifications. Thus a single unit can replace any other in a group of roll stands.
Unique axial rigidity
Large load zones
Long bearing life
Low unit weight
Simplified roll changing and maintenance
Short stops for changing of grooves, guides and stands
Designed for automatic process control and high productivity
In working position, the roll unit (A) is held in position by a supporting post (B), the latter being designed differently for various arrangements. The supporting post shown is designed for horizontal movable arrangement.
Radial rolling forces
Radial rolling forces are absorbed by the four optimum dimensioned mill screws (a), which are under straight tension under rolling. The mill screws are placed close to the roller bearings in order to eliminate deformations in the chocks. The upper and lower chocks are joined together by means of right- and lefthand threaded nuts (b) respectively.
With the Morgårdshammar design of the load-carrying elements, the rolling forces are kept within a short length and large area, and the roll unit becomes highly rigid.
Counterbalancing of the upper roll unit is accomplished mechanically.
The roll gap
The roll gap is adjusted by means of worm gearing (c) on top of the mill screws.
Rolling force gauges
Rolling force gauges can be mounted in the roll unit (d).
The height of the pass line
The height of the pass line is always fixed, regardless of the roll gap and roll diameter. When the distance between the rolls is changed, the upper and lower roll move symmetrically around the fixed pass line.
Entry guides and exit guides
Entry guides and exit guides are mounted on separate rest bars or pedestals applied on the roll unit supporting post or ist foundation. As a result, the guide centre-line is always at the same height as the roll groove centre-line. By this means, the guides require no extra adjustment in connection with repositioning and replacement. Ordinary rest bars mounted directly on the roll housings is another alternative which is available.
At stand-changing, the roll unit is taken out of the train and replaced with a preadjusted roll unit.
Prior to delivery from Morgårdshammar
Prior to delivery from Morgårdshammar, each side of the roll unit is completely assembled and adjusted. The side units are to be handled as completed components, not requiring any final adjustments in the rolling mill.
For automatic process control
For automatic process control, the roll units are well prepared thanks to the application of load cells and the generous poportioning of the mill screw gears and drives.
The four-row cylindrical roller bearings
The four-row cylindrical roller bearings (e) have high load capacity and low deflection. As the cross-sectional height of the bearings is small, the roll neck diameter is large in relation to the roll diameter.
Axial rolling forces in both
Axial rolling forces in both directions are absorbed by the thrust cover on the chock (g). Each cover is provided with two adjusting screws (h) located to the centre of the roll. By means of this arrangement, the following advantages are obtained:
Uniform absorption of rolling forces on each side of the chock.
Uniform distribution of axial forces on all elements of the
bearings prolongs bearing life and minimizes spring.
The two axial bearings
The two axial bearings on each roll (f) are mounted to a separate unit placed on the thrust side. The unit, adjusted to practically zero-gap, does not have to be removed or adjusted at roll changing.
Roll couplings, alternatively spline sleeves, are mounted on the cylindrical roll necks using tapered adapter sleeves by the SKF pressurized oil method.
After changing of stand, the roll unit is brought to the roll-changing shop to be cleaned and placed in a jig.
Using equipment specially designed for this purpose, the spline sleeves on the drive side and the covers on the thrust side are easily dismantled. Each side unit, consisting of the upper and lower chock with mill screw and mill screw gear, is withdrawn from the worn rolls and mounted on the necks of reconditioned rolls.
By this system, it takes only about ten minuted for two men to carry out the roll-changing operation including routine control.
After changing of rolls, the roll unit is placed in a supporting post equipped with guide-ways and locating surfaces similar to the ordinary arrangement in the mill train.
Here all adjustments and pre-settings for the next rolling programme can be made under favourable conditions. This means:
Control of the parallel position of the rolls and
adjustment when required
Zero-setting of the indicator drums
Axial adjustment of the rolls
Pre-setting of the roll gap
The complete roll-changing shop – layout and equipment – is normally built up in close co-operation between Morgårdshammar and each customer.