Features of Determination of an Error of Installation as a Component of Machining Allowance

Abstract

One of the important tasks of designing manufacturing processes for manufacturing parts is to designate optimal allowances for machining, since an unjustified increase in allowances leads to significant metal losses, increases the complexity of machining, and the appointment of unjustifiably small allowances may not ensure the removal of defective metal layers and achieve the required performance quality details. An effective means of determining the optimal allowances is the calculation-but-analytical method proposed by V. M. Kovan. In accordance with this method, the components of the minimum allowance are the height of the surface roughness and the depth of the defective layer formed during the manufacture of the initial billet or at the previous technological transition of machining, spatial deviations of the machined surface, and also the error in the installation of the billet in the machine tool adaptation to ongoing technological transition. Finding the first two components of the minimum pass is usually carried out using normative tables. The determination of the spatial deviations of the processed surface is discussed in detail in the scientific and technical literature. At the same time, recommendations for determining the installation error require some clarification. Thus, the aim of the work is to clarify approaches and recommendations for determining the installation error as a component of the minimum pass.

It is shown that finding the installation error as a component of the total processing error and finding the installation error as a component of the minimum allowance are significantly different. In the first case, this error is defined as the size dispersion field between the top of the tool adjusted to the size and the measuring base of this size, and in the second, it is found as the dispersion field of the positions of the machined surfaces of the batch blanks. Using this approach, the determination of basing and installation errors as components of the minimum allowance is considered using the example of boring holes in a workpiece of the Lever type.