Industrial Technology
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Quantity Calculations
This unit of work addresses aspects of the following syllabus outcomes:
A student:
H3.2 selects and applies appropriate research and problem-solving skills
H5.1 selects and uses communication and information processing skills.
H5.2 selects and applies appropriate documentation techniques to project management.
Extract from Industrial Technology Stage 6 Syllabus © Board of Studies NSW 1999.
Introduction
Industrial Technology is made up of a number different focus areas and you will be following only one of these focus areas – say Timber and Furniture Industries or Multimedia Industries, but not both of these.
This unit of work provides some general comments about the syllabus section on calculations and provides some specific information on calculations relating to Timber and Furniture Industries, Multimedia industries and Electronics Industries.
Correct measurements, estimates, calculations, sizing and costing are critical to ensuring that your major project is completed to your plans, on-time and on-budget. Errors in calculations, measurement and ordering of components for your major project can result in long time delays, reconstruction of components, and large wastage of materials which can increase the cost of your project.
A common situation that is easily avoided by planning and ordering properly
(Using timber as an example, but this could easily be a problem from any focus area of Industrial Technology)
Imagine if you ordered 3.0 m of timber to cut four legs that had to be 750 mm long. The mathematics seems to be correct, that is 4 x 750 mm = 3000 mm. But, what have you forgotten?
What about things such as dints or checking on the ends of the 3.0 m board that result in the usable timber being 2.9 m worth? (Yes, you can crawl over the board at the timberyard to look for defects, but this may not always be possible.)
What about the width of the saw blade (approx 3.2 mm)? Three cuts wastes 9.6 mm.
What about the allowance you’ll need to clean up the saw cut if it is not properly square?
What about the fact that the timber sold as 3.0 m, may only be 2.98 m long?
What if the timberyard cuts the piece a few millimetres short?
All of a sudden, you realise that your initial calculation on how much timber you need is wrong, so you’ve got to go back (or explain to your parents why they’ve got to take you back) to the timber yard to buy an extra piece of timber, when you could have avoided it by buying 3.3 m in the first place. Let us say that the piece of timber is $8 per metre. You first purchase 3 m ($24) from which you find that you can only cut three legs each 750 mm. You have to buy a second piece, say a minimum 1 m ($8) for the fourth leg. You have spent $32, when an initial purchase of 3.3 m would have cost you $26.40. The job has now cost you $5.60 more than you planned, and you also have a piece of waste timber which will probably be thrown away.
Either you buy extra timber, or you build a table that does not meet your original statement of intent or is uncomfortable to use.
Imagine that you put a phone book on the chair you’re sitting on now, lowering the effective height of the table by, say 30-40 mm. If you make the table lower, you’ve got problems with ergonomics (defined as the study of the interaction between the human body and the objects that the body uses,) as the table is now at an uncomfortable height. Because you have not considered all the factors you have now spent more money than planned, wasted time, produced some unusable waste, and end up with a product that does not look or function very well.
So, now on to a few more details on how to properly calculate how much material you’ll need and how to order it. Use the following links to information on calculations relating to the focus area you are studying:
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