Technical profile: new rollermill
November 01, 1995
by Teresa Acklin
Contributed by suppliers, technical profiles feature new technology, products, specific applications or proprietary concepts. This material was prepared by Sangati S.p.A., Padova, Italy.
At first glance, the Sangati AUTORO/E rollermill appears to be a simple evolution of its predecessor. On closer inspection, it is apparent that the AUTORO/E is a completely new machine with innovative manufacturing and operating concepts that differ completely from previous models.
Three primary reasons prompted the company to research and develop the new rollermill:
the need to simplify the manufacturing process and therefore minimize maintenance requirements;
the need to automate the rollermill to reduce operator intervention while simultaneously simplifying machine operation by enabling the machine's connection to a personal computer-programmable logic controller; and
the need to comply with new international standards for safety and sanitation.
A number of features make the AUTORO/E different from other roller-mills, including simplified construction and elimination of the oil-bath gearbox for the feedrolls. The AUTORO/E's design allows simple dismantling of the feed chamber to facilitate cleaning and rapid changing of rolls, either singly or in pairs. Another standard feature permits direct pneumatic pick-ups.
The AUTORO/E has a new patented system for rapid engagement/disengagement of rolls as well as the micrometric adjustment of the roll gap by means of a single electric device. The rollermill also features the “Integrated Milling Control,” or I.M.C., a microprocessor control unit for the operating management of the machine. Another feature is an analogic indicator for the manual setting of the feed gate aperture.
The new rollermill has been designed on a CAD system. Its steel plates are cut with a laser cutter, while machining of components is done on numeric control centers. This manufacturing method guarantees precise and uniform production of each component and machine.
The AUTORO/E is available in two models. One has four grinding rolls in 250 or 300 millimeter diameters and 800, 1,000 or 1,250 mm length; and the other has eight rolls of the same diameters in 1,000 or 1,250 mm length.
The feeding chamber has a base area of 700 by 500 mm, which allows an even spread of the product over the feedrolls, resulting in a uniform flow to the grinding rolls. The chamber is made in two parts from antistatic polycarbonate, which facilitates access for cleaning and can accommodate an aspiration point if desired.
Because of recent safety regulations prohibiting access to machine moving parts, adjustment of the AUTORO/E is done via a handwheel with analogic indicator located externally on the rollermill, making it no longer necessary to open the upper plexiglass inspection door to set the feedgate. Automatic adjustment with a microprocessor is available as an option.
In the past, the opening and closing of rolls, as well as their adjustment, was performed by separate pneumatic or mechanical systems. These systems acting on separate rotating shafts and levers required a duplication of parts, which resulted in increased maintenance and spare parts.
The AUTORO/E patented system uses a single control and actuating device on a rotating shaft, enabling rapid opening and closing of rolls and roll adjustment. The device is capable of fine adjustment tolerance and has a position sensor that transmits the roll position to the microprocessor for data processing. In addition, the upper side of the support is connected using a flexible mounting, which is designed to absorb shocks from grinding or from foreign material passing through the rolls.
Power transmission between the two grinding rolls is achieved by a toothed belt with a MULTI-V back. This method, used successfully in Sangati rollermills for many years, facilitates a constant transmission of power and makes the machine both silent and vibration free. The noise level has been reduced further by lining the grinding chamber with sound absorbing material.
Removal of grinding rolls is simple and quick. The side covers slide easily off their mountings, and the front cover is mounted with quick-release clips. The toothed belt simply slides off the take-up pulley. The front roll is removed complete with its bearings and supports, and the rear roll is removed complete with its bearings after the front support is removed.
An optional system permits removing the entire roll block, including rolls, bearings, supports and lower bar in a single operation. This option dramatically reduces the time required to change grinding rolls to 30 minutes per pair, compared with 60 minutes per pair with the standard system.
Rollermill automation has been accomplished through the I.M.C., a small computer installed in the AUTORO/E. The terminal, including an alpha-numeric display and keyboard, is located on the right side of the rollermill.
The I.M.C. coordinates a number of operations, including setting feedroll speeds and maximum speed, setting minimum and maximum parameters of feedroll revolution to maintain a constant grind, setting roll gaps and setting or correcting the roll parallelism. The I.M.C. also displays the alarm status and sets the minimum/maximum probe level.
The I.M.C. also calibrates the ammeter transformer, as well as zero and maximum roll gaps, which is useful when removing rolls. The I.M.C. can be connected to a central P.L.C. or P.C. using a serial card.