## Posts Tagged ‘calculations’

### The Methodology Behind Gear Train Torque Conversions

Sunday, June 22nd, 2014
 Last time we learned that gear trains are torque converters, and we developed a torque ratio equation which mathematically ties the two gears in a gear train together.  That equation is: T1 ÷  T2 = D1 ÷ D2       Engineers typically use this equation knowing only the value for T2, the torque required to properly drive a piece of machinery.   That knowledge is acquired through trial testing during the developmental phase of manufacturing.       Once T2 is known, a stock motor is selected from a catalog with a torque value T1 which closely approximates that of the required torque, T2.   Then calculations are performed and lab tests are run to determine the driving and driven gear sizes, D1 and D2 which will enable the gear train to convert T1 into the required value of T2.   This series of operations are often a time consuming and complex process.       To simplify things for the purpose of our example, we’ll say we’ve been provided with all values required for our equation, except one, the value of T2.   In other words, we’ll be doing things in a somewhat reverse order, because our objective is simply to see how a gear train converts a known torque T1 into a higher torque T2.       We’ll begin by considering the gear train illustration above.   For our purposes it’s situated between an electric motor and the lathe it’s powering.   The motor exerts a torque of 200 inch pounds upon the driving gear shaft of the lathe, a torque value that’s typical for a mid sized motor of about 5 horsepower.   As-is, this motor is unable to properly drive the lathe, which is being used to cut steel bars.   We know this because lab testing has shown that the lathe requires at least 275 inch pounds of torque in order to operate properly.       Will the gears on our gear train be able to provide the required torque?   We’ll find out next time when we insert values into our equation and run calculations. _______________________________________

### Food Manufacturing Challenges – HACCP Design Principle No. 7

Sunday, November 27th, 2011
 Ever overdraw on your checking account or max out a credit card?  It’s not hard to do if you’re not keeping track of things.  How can we manage household expenses without some sort of record keeping?       Away from home, in the business sector, record keeping becomes even more important.  In fact, it’s the very thing covered by HACCP Design Principle No. 7.       Principle 7:  Establish record keeping procedures. – This HACCP principle requires that all food manufacturing plants maintain records to show they implemented a HACCP plan, are following all principles, and the plan is working effectively.      Let’s look at an example.  In keeping with the directive of HACCP Design Principle 7, the engineering department of a food manufacturing plant must keep records for each design project.  The design record for a new cookie forming machine would contain things like engineering calculations to determine strength requirements of machine parts and supports, as well as power requirements for the electric motor that drives the machine.  This design record would also contain documentation concerning materials selected to construct the machine, as well as dimensioned mechanical drawings of the machine and its parts.  These dimensioned drawings will show all physical dimensions of the machine and its constituent parts.       The record would also contain test results and analysis of the results.  Lastly, the design record must include a risk analysis of potential hazards that could result.  Other activities include identification of CCPs, establishment of critical limits, and other factors in accordance with HACCP Design Principles 1 through 5.  In other words, the record must be complete, bearing witness to an effective adherence to HACCP Design Principles 1 through 5.       Principle 7 also encompasses guidelines set in place through Design Principle 6, which calls for the establishment of procedures to govern Principles 1 through 5.  A complete record would contain the procedures themselves, along with any revisions.  It would also contain documentation that the procedures were reviewed and approved by management along the way.      Finally, of what use would records be if they were incomplete, disorganized, and outdated?  A document control system not only establishes procedures, but assigns responsibilities to personnel within the department for filing design records to make sure that everything is up to snuff.  This system would encompass everything, from the creation of engineering documents, to their timely entry into the record keeping system.      We have now exhausted our discussion on HACCP Design Principles.  We’ll switch to a new topic next time, examining some basic concepts behind the control of industrial equipment and machinery.  ____________________________________________

### Food Manufacturing Challenges – HACCP Design Principle No. 4

Sunday, November 6th, 2011
 Imagine going on a diet and not having a scale to check your progress, or going to the doctor and not having your temperature taken.  Feedback is important in our daily lives, and industry benefits by it, too.       Generally speaking, feedback, or monitoring, is a tool that provides relevant information on a timely basis as to whether things are working as they were intended to.   It’s an indispensable tool within the food manufacturing industry.  Without it, entire plants could be erected exposing workers to injury and consumers to bacteria-laden products.  It’s just plain common sense to monitor activities all along the way, starting with the design process.  Now let’s see how monitoring is applied in HACCP Design Principle No. 4.      Principle 4:  Establish critical control point monitoring requirements. – Monitoring activities are necessary to ensure that the critical limits established at each critical control point (CCP) established under Principle 3 discussed last week are working as intended.  In other words, if the engineer identifies significant risks in the design of a piece of food processing equipment and establishes critical limits at CCPs to eliminate the risk, then the CCPs must be monitored to see if the risk has actually been eliminated.      Monitoring can and should be performed in food manufacturing plants by a variety of personnel, including design engineers, the manager of the engineering department, production line workers, maintenance workers, and quality control inspectors.  For example, engineering department procedures in a food manufacturing plant should require the engineering manager to monitor CCPs established by the staff during the design of food processing equipment and production lines.  Monitoring would include reviewing the design engineer’s plans, checking things like assumptions made concerning processes, calculations, material selections, and proposed physical dimensions.      In short, monitoring should be a part of nearly every process, starting with the review of design documents, mechanical and electrical drawings, validation test data for machine prototypes, and technical specifications for mechanical and electrical components.  This monitoring would be conducted by the engineering manager during all phases of the design process and before the finished equipment is turned over to the production department to start production.       To illustrate, suppose the engineering manager is reviewing the logic in a programmable controller for a cooker on a production line.  She discovers a problem with the lower critical limits established by her engineer at a CCP in the design of a cooker temperature control loop.  You see, the time and temperature in the logic is sufficient to thoroughly cook smaller cuts of meat in most of the products that will be made on the line, however the larger cuts will be undercooked.  The time and temperature settings within the logic are insufficient to account for the difference.        This situation illustrates the fact that monitoring does no good unless feedback is provided with immediacy.  In our example, the design engineer who first established the CCP and the critical limits was not informed in a timely manner of the difference in cooking times that different size meats would require, resulting in the writing of erroneous software logic.  Fortunately, continued monitoring by the engineering manager caught the error, leading her to provide feedback about it to the design engineer, who can then make the necessary corrections to the software.      Next week we’ll see what design engineers do with the feedback they’ve received, as seen through the eyes of HACCP Principle 5, covering the establishment of corrective actions.  ____________________________________________