Simple Solutions That Work! Issue 11

35 pleted mold back onto the mold conveyor. This system is designed to accept flask sizes in the range 20” x 16” up to 36” x 24,” with production rates of between 300 to 400 mold per hour. The CROSS-LOOP arrangement has two moulding lines, one to produce the drag and the oth- er to produce the cope, as they span the mold conveyor loop. This arrangement is normally used for flask sizes above 36” x 24,” and/or where heavy cores are placed in the drag, as in a cyl- inder block, for example. Produc- tion rates on the CROSS-LOOP are slower than the IN-LINE, nor- mally between 260/300 molds per hour. The benefits which these two systems offer are the in-finite flexibility in use, high productiv- ity and adaptation to all types of castings, especially those requiring cores where the tight flask system is found to be more efficient and economical. This is because more castings can be produced within the same given mold area when com-pared to flaskless molds. Core placing does not slow pro- duction, since the coring zone is designed to give maximum flex- ibility, whether two or ten cores need to be placed. Mold pouring can be automat- ic, but a pouring zone is always designed into the system to retain flexibility and allow for manual pouring as necessary. The extra cost of labor required for manual coring and pouring is insignif-icant, because the system is kept running at its maximum output, 300 to 400 moulds per hour, which assists the profitabili- ty of the entire foundry. To further improve the flexibility of these systems, the molding machines can be equipped with a pattern shuttle change unit, so that pattern changes can be made with-in the automatic cycle without loss of production. Two patterns can be run at the same time or varied to suit conditions and even out core demand, and/ or metal availability. The IN-LINE and CROSS-LOOP systems offer the foundry the most productive and flexible approach to mechanized mold- ing for castings requiring cores at a high production rate of +250 mph. The cost per mould is less than with any other system, calculating initial capital cost, against productivity and running costs. For lower or more versatile pro- duction requirements of today’s jobbing foundry, many of these continuous mold line conveyor loops have been replaced with index pallet systems. Pallet index systems offer the flexibility of parking lines for extended cool- ing times and can also take up less floor space due to closer line proximity and the elimination of the mold conveyor radius. The molding machines used in any of the IN-LINE, CROSS-LOOP or even more common today the Pallet Index systems are typical- ly of the high pressure squeeze type. Investigation using a wide range of squeeze pressures has shown that a casting produced in a mold which has been compacted to a squeeze pressure of 100/110 pounds per square inch, is as accurate as one produced us- ing a squeeze pressure of 200 to 220 pounds per square inch. Therefore today it is generally accepted that the degree of mold compaction increase is very small above a pressure of 140 pounds per square inch in relation to the extra pressure applied. Therefore, molds can be produced which will make castings of consistent accuracy and soundness to meet the technical and dimensional re-quirements of today’s cast- ing users, by using much lower squeeze forces than was previ- ously thought necessary. The only advantage to be had by increasing the squeeze force above this pressure is to de- crease the time taken to make a mold, since the higher the initial squeeze force the less time this force has to be applied to the mold in order to achieve opti- mum compaction. That is, the greater the squeeze force above 100 pounds per square inch, the higher the production rate, until a maximum is achieved around 2OO/22O pounds per square inch. Above this figure, there is no gain in mould production, or cast- ing quality. Using this information, some machine manufacturers have de- veloped various means of com- pacting the mold inside the flask. That is Blow Squeeze, IMPACT molding with squeeze, vacuum molding, or even squeeze (top and bottom in some cases) with compensating peen feet, all in order to reduce the operating noise of the machine by eliminat- ing the proven jolt and rap mold- ing meth-odology. In practice however, all of these machines have limitations, as to what type of castings they can produce and they are extremely susceptible to varying sand conditions. In- consistent mold hardness is also common. In addition, improved hardness distribution is also achieved by jolting or rapping for some sec- onds to uniformly compact the Continued on next page MAKING YOUR INSTALLATION ASUCCESS