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How to buy a screw - Part I

Modified on Saturday, 31 January 2015 03:32 PM by mpieler Categorized as Consultants Corner
How to buy a screw - Part I
Vol. 21 #2, October 1994

We are going to write a continuing article on how to purchase an extruder screw. I will write this article, but it will be a compilation of edited comments from consultants, end users, designers, and manufacturers. Following are some questions that should be raised in your mind about your extruder screw:

Do you know if the screw is worn, chipped, gouged, or bent? Measure the flight OD and channel depth of each flight when the screw is new, and then, at convenient intervals there after. (Alternatively, get the original dimensions from the manufacturer.)

Has your output decreased? Only fifty pounds per hour loss in output could cost $100,000 in labor and overhead. As sales are now increasing in most companies, sales can sell more then the plant can produce. Upgrading the screw technology may be a very low cost alternative to increased product sales.

"Push your pencil" - make these type calculations and you will probably be convinced that a new screw is an extremely attractive investment.

Topics to be discussed in future articles:

- How to generate meaningful quotations from suppliers. What you should provide. What should their quotation specify?
- How to select a supplier. (How to separate facts and experience from sales hype.)
- Is output, stock temperature, stability, and/ or mixing quality of most importance to you?

- Russ Gould

See also:
  • How to buy a screw, Part II
  • How to buy a screw - part III
  • Naming screws for materials, compression ratios …

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