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How Urschel machines are made.

How Urschel Machines are Made

Urschel machinery is made with meticulous care. Many of the processes used in making their machinery are not used by other manufacturers but these processes are economically helpful to customers who use it. Urschel Laboratories Inc have manufactured food cutting machinery for over seventy-three years. During these years a number of customers have made suggestions and have set standards as to how the machinery should be made. This has caused continuous improvement in manufacturing methods, changes in material used and changes in design of machines and parts. The following gives an outline of what goes into the making of their machinery.

From the earliest days of the company, a continuing search for better metals and various other materials has been made. Testing programmes have used to determine which metals have the best wear characteristics. Corrosion tests have been made on many different kinds of metal, both in the laboratory and in food plants. Samples from every shipment of metal coming into the plant are tested in the metallurgical laboratory. Some samples are mounted, polished, etched and examined under the microscope. Other samples are heat treated and tested for hardness and strength. Spectrographic analysis is made of most samples to insure that the metal is of the correct alloy. Some of the research has resulted in the selection of a bronze alloy being used in most of their machines; this has good corrosion resistance and a yield strength greater than stainless steel. Castings made from this alloy will stand more abuse than castings made from stainless steel. Changes are often made to improve the strength or corrosion resistance of a part even though this will reduce the sale of this particular part.

For many years, the company would not use stainless castings because no stainless steel foundry could be found that produced castings of the required quality. They did produce stainless steel parts by fabricating them from stainless steel plate and other shapes obtained from steel mills. The company installed a stainless steel foundry about ten years ago where quality castings are now made by the lost wax process. Castings made from any metal will warp and twist out of shape over a period of years. To reduce this problem to a minimum, castings from both the stainless steel foundry and the bronze foundry are reheated and cooled in such a way as to relieve most of the stress caused by the casting process. The metallurgical laboratory constantly checks and controls the analysis of metal used by both foundries.

They have a heat treatment department where many stainless steel parts are hardened and tempered. These parts are heated electrically in an atmosphere of hydrogen gas which produces bright and oxide-free finish. Certain alloys are given a cold treatment at one hundred degrees below zero Fahrenheit between two tempering operations. This insures they will not change size or hardness during use. Many knives are hardened by high frequency electrical induction on the knife edges only. This insures maximum hardness to the edges of the knives and maximum toughness to the body of the knives.

At one time, the company purchased special stainless steel bolts and nuts from companies who specialize in this kind of work. Some were purchased from companies making bolts and nuts for the aircraft industries. At time the quality of these items became so poor that the rejection rate became unbearable. Today, almost all stainless steel nuts and bolts used in the various knife assemblies are manufactured by the company. By so doing, the company is able to control the alloys used, all dimensions and heat treatment. Some hardened bolts are made of an alloy that will not become brittle during use.

It is common manufacturing practice to size holes in gears, pulleys and other parts with a reamer. This often results in holes that are not round but bell shaped. It is for this reason that all holes on Urschel parts are honed to size with a special machine tool for this purpose. Centreless ground stainless steel shafting as purchased from the mill usually is not round and is difficult to purchase to close size tolerance, For this reason, shafting is purchased oversize and centreless ground to close dimensions in the company shop. This ensures that when gears, pulleys and other parts are replaced by the customer, they will slide easily on to the shaft but the holes will not be so large that parts will vibrate loose on the shaft during use. All circular knives are machined to an extremely close size tolerance on thickness so that when assembled on a spindle with spacers, there will be no serious cumulative error in the distance between the first and last knife on the spindle. This ensures there will be no danger of metal to metal contact between the knives and other machine parts.

The way knives are made for the Model OV Slicer illustrates the care required in making many of the parts for their machines. When in use, these knives are stretched under approximately one thousand pounds tension between holes in the ends of the knives. These knives are held under tension with hardened and ground stainless steel bolts. Holes that are punched always have tapered sides and therefore would not be suitable in this application. The holes are first punched then honed to a smooth straight-sided hole. Although the knives at one time were made from a high grade hardenable stainless steel, considerable breakage often resulted during use. It was discovered that the acid in certain foods caused these knives to become brittle even though they showed no signs of corrosion. The knives are now made from a precipitation hardening' stainless steel that remains hard and tough under all operating conditions.

The following will explain how required accuracy is maintained with Urschel parts: When machining any part to size, the finished size will be in error from the size listed on a drawing. It is always desirable to keep this error within a certain small measurement, although it cannot be smaller than the ability of the machinist to measure it. In many factories, it is considered sufficient to measure within one thousandth of an inch and keep the size of parts within some multiple of this. For many of the parts operating at high speed in Urschel machinery, an error of this kind cannot be permitted. For some parts, it is necessary to maintain tolerances within one ten-thousandth of an inch or a multiple of this. The engineers in the Urschel machine shop use measuring instruments capable of this accuracy. All such instruments are constantly checked against gauge blocks that are accurate to within eight millionths of an inch. All of this ensures that a customer can buy a part for an Urschel machine that is twenty-five years old and know it will fit the machine in the same way as did the original.

At various times over the years, other manufacturers and job shops have performed certain operations for making parts for Urschel machines. Today, with the exception of electrical equipment and rubber belts, almost everything going into an Urschel machine is made in their own workshops. The company has invested in a considerable amount of automation so as to increase efficiency and reduce costs. Many numerically controlled machines are used. Urschel have built many special machine tools to increase the speed of making parts. Many of these are controlled with the company-built electronic units.

The company maintains a very large inventory of finished parts to meet customer's requirements. A mainframe computer, purchased twenty years ago, has been replaced three times with improved equipment. This computer updates the complete inventory four times each week. The computer contemplates future customer usage of parts from past history and issues orders to the machine shop when indicated. It is rate that a repair part for a customer's machine cannot be shipped the same day the order is received. An effort is made to keep repair parts for obsolete models of machines as long as it is known that someone continues to use the equipment.

The care with which their machinery is manufactured is made possible by the quality of the employees who work in the shop. There is almost no turnover of in the workforce, with most employees spending their lifetime in the employ of Urschel Laboratories.

Only a few of the company's special manufacturing procedures have been listed here. We know this special effort increases the cost of Urschel machines and repair parts but we feel that the customer is more than compensated by long periods of uninterrupted operation and minimum usage of maintenance personnel.

In the UK the company is represented by Urschel International Ltd of 6 Groby Trading Estate, Groby, Leicester, tel:0533 876251.
COPYRIGHT 1991 Food Trade Press Ltd.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Urschel Laboratories Inc. makers of food cutting machines
Publication:Food Trade Review
Date:Sep 1, 1991
Words:1464
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