When a material is processed by a plurality of steps successively as in the case of production of parts of a machine, an oil agent such as a lubricating oil agent, a cutting oil agent or a grinding oil agent used for lubrication or cooling at the time of mechanical processing such as plasticizing, cutting or grinding is deposited and remains on a workpiece obtained by mechanically processing a metal material in a pre-step. The amount and kind of the remaining oil agent may be unsuitable for a mechanical processing step or an assembling step after that.
Moreover, an oil agent such as a lubricant or a releasant used for lubrication or mold-releasing at the time of plasticizing such as stretching, molding or compressing is deposited and remains on a workpiece obtained by plasticizing a synthetic resin material in a pre-step. The amount and kind of the remaining oil agent may be unsuitable for a plasticizing step or an assembling step after that.
When the amount of the oil agent remaining on a workpiece of a metal material, a synthetic resin material, etc. is too large or too small for the step after that, the amount of the deposited oil agent is needed to be increased/decreased to a suitable amount for the post-step in such a manner that a part of the remaining oil agent is washed off or the same oil agent is added to the remaining oil agent. High-grade skill and much experience are required for adjusting the amount of the deposited oil agent to a desired amount suitable for the post-step in the work of increasing/decreasing the amount of the deposited oil agent.