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#045 Scraping Work

Category : Technical Information
June11, 2010

Scraping work is that of scraping off very fine depressions on the polished surface using a tool called a "scraper". Such scraping operation is done on the sliding surface of the bed of a machine or on the surfaces of moving machine parts.

The purposes of scraping operations are the following.
(1)To make the lubricating oil stay evenly on the surface.
(2)To reduce the friction resistance by making the contact area small.
(3)To reduce the generation of friction heat by making the contact area small thereby reducing the friction resistance.
(4)To suppress thermal expansion by reducing the generation of friction heat.
(5)To suppress the increase in friction resistance due to thermal expansion.

There are the following types of scraping work,
(1)Flat scraping
(2)Hook scraping
(3)Cant scraping

When carrying out scraping work, it is very important to maintain a clean environment in the work place. It is essential to remove all the time any dust, cutting shreds, sand, etc., using a vacuum cleaner, etc. In addition, when carrying out scraping work, an appropriate cutting oil should be selected, and the work should be carried out while applying it in suitable quantities.

Red lead is used for carrying out scraping work. This is a technique for carrying out scraping work uniformly while checking the scraped surface.

As explained above, scraping work is a precision finishing operation that is to be made mandatorily on the sliding surface, etc., of a precision metal working machine. The reason why Japanese metal working machines are of high precision and with very little deviation is the presence of scraping work.

Although there are very limited examples of carrying out scraping work in forming the parts of molds for plastic molding, depending on the usage this some times has very useful functions. This is the ideal method for preventing the biting of slide cores or moving parts.

The history of the design and preparation of molds for plastic molding is still quite shallow being only about 50 years. It is possible to obtain useful effects by observing well and applying the know how used in other precision machine technologies.

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