Before discussing the subject, let us understand what is schreiner calender? It is a two bowl calender – one is cotton bowl or woollen paper bowl and the other is steel bowl having engraved lines with internal heating arrangement. Metal bowl is the driving bowl. The machine specifications are different compared to other standard calenders.
What are its standard specifications?
BOWLS – One special quality steel bowl of 12 inches dia [305 mm] engraved as per requirement of the user. The other one is – cotton/woollen bowl of 24 inches dia [610mm].
Bearings — ends of steel bowl are supported in split but sturdy and accurately designed suitable for forced lubrication and water cooling. Bearing material is generally phosphors bronze. The bottom bowl bearings are provided with forced lubrication system. For easy changing of steel bowl arrangement is provided with removable steel arms.
The machine generally is subjected to a temperature of 240/250¦C.
Loading – it is hydraulic. Yes, it is a special calender with special features to deliver a different finish on the fabric. This machine used to be in first in row for finishing poplins, printed fabric, umbrella cloth and other material. With the arrival of new technology machines they are not treated as common today.
The trick of the machine in nutshell is – the engraved lines with fixed angles transfer their impression on fabric face and their reflection in light is dazzling/brilliant. This is because all the rays converge at one point, creating extra shine effect.
The lustre it produces is somewhat similar to that of mercerised cotton but without altering the microscopic structure or increasing the tensile strength or affinity to dyed stuff.
What should be the pre-treatment of fabric before passing through schreiner calender?
Yes, pre-treatment is essential for obtaining good Schreiner effect. If one mercerises the cloth before calendering it will be an excellent pre-treatment. If this facility is not there around then it is better to just pass the fabric through an ordinary calender nip so that wrinkles, projecting fibres and other minor flaws vanish. It is important that the cloth has the required moisture content and the temperature is adequate enough to match the moisture content.
Can knitted fabrics be schreinered?
Yes. It is an advantageous proposition because the angle of engraving is not crucial or critical. Because the loop formation of its knitted construction does not allow the material to meet the engraved lines at constant/fixed angles.
What should be the engraving on bowl?
The engraving, precisely to say, the angle of inclination and the number of lines per/inch vary according to the twist of the yarn, the weave of fabric and desired finish. Since the engraving is solely dependent on the construction of cloth it cannot be vaguely recommended. It is important to understand that with one particular type of engraved bowl all fabrics cannot get the expected effect.
Big mills having their own engraving plant can afford to experiment and then engrave the bowl to a particular specification for a particular finish. Hence small units get the sampling done on other machines and decide the type of engraving that fits into their requirement.
For any clarifications, contact:
D V Prabhakar, Calender machine specialist. Mobile: 09594932222/09821265631. Email: chinacalenders@gmail.com, dvp_calender@rediffmail.com