Regularities of changing the dimensions of the main bore of the cylinder of TMZ-450D diesel engine during the technological process

The article deals with the problems arising during the mechanical and thermal treatment of the TMZ-450D diesel engine cylinder, which is the base part of the engines of small-sized generators and compressors, which are widely used for mobile units in the oil and gas and mining industries. It was found that the metal in the casting has a non-uniform structure, the density of which ranges from 6.75 to 7.25 g/cm3. Redistribution of dislocations and residual stresses in the casting leads to significant changes in the size and shape of the main bore. In addition to the successive changes in size specified by the technology due to the removal of the designated allowance, the dimensions and shape change arbitrarily, uncontrollably in the course of the technological process. It is shown that artificial aging by a thermal method does not provide the desired dimensional stability; therefore, it is proposed to supplement it with natural aging after rough boring for six months. It was revealed that the use of morally and physically outdated equipment makes it necessary to increase the number of finishing operations of honing and, accordingly, to increase the labor intensity of cylinder manufacturing. The use of a two-position boring machine is substantiated, on which the transitions of semi-finishing and fine boring are combined. This completely eliminates the copying of errors that arose when changing the base on previous operations. The use of a two-position modular boring machine ARS-4/Ts of increased accuracy and rigidity significantly increases the accuracy of the bore hole, which makes it possible to reduce the number of honing operations. A variant of the technological process of mechanical and heat treatment is proposed, including natural aging, the use of double boring on a modular boring machine, which will reduce the number of honing operations to one, including rough and finish transitions.

Machinability of Thermo-Plastic Carbon Fiber Reinforced Plastic in Inclined Planetary Motion Milling

The study deals with an improved method of milling thermo-plastic CFRP with a radius end mill. The authors use inclined planetary milling to carry out a fine CFRP boring technique. The inclined planetary motion milling consists of the two independent spindle motions of tool rotation and revolution. The eccentricity of the tool rotation axis is realized by a few degrees of inclination from the revolution axis. The movement of eccentric mechanism can be reduced by comparing it with that of orbital drilling. The inclined planetary motion milling reduces inertial vibration and decreases cutting force. Owing to the geometrical cutting principle, material delamination and burrs can be decreased. Thermo-plastic CFRP has recently been under development as an alternative structural material for the next generation of automobiles and in response to demands for bored fastening holes. The shape of the cutting edge of the ball end mill is suitable for the inclined planetary milling, as revealed by results of past experiments done on thermo-set CFRP. However, the ball end mill has left burrs and melted matrix on the exit side in the case of thermo-plastic CFRP. The radius end mill has the advantage over the ball end mill in terms of finishing fine boring. Based on the consideration of the schematic model and experiments using the Taguchi method, the improved milling conditions are examined.