Development of manufacturing process of YaMZ-238NB engine piston pin

Contents

Table of Contents.

Chapter 1. Analysis of YaMZ-238NV engine piston pin

1.1 Purpose, structure description, parts

1.2 Part processability analysis

Chapter 2. Workpiece Design

2.1 Selection of procurement method

2.2 Calculation of procurement parameters

Chapter 3. Procurement Process Design

Chapter 4. Calculation of cutting mode

4.1. Selecting a Turning Cutter

4.2. To Assign a Cutting Depth

4.3. Assign Feed Value

4.4. Determination of cutting speed

Chapter 5 Rationing of Operations

List of literature

Application

Chapter 1. Analysis of YaMZ-238NV engine piston pin

During operation, the piston pins of the four and two-stroke engines are subjected to alternating loads including shock loads from the combustion process, which poses high requirements for the accuracy of their processing and the parts associated with them (piston bosses and the upper head of the connecting rod) as well as for the quality of the materials used. Due to the high temperatures in the piston bosses, the finger operates under conditions of semi-liquid friction, which in turn increases the temperature more, worsens the lubricant, causes increased wear and tear of friction pairs. The fingers are made of low carbon alloy steel (usually with a chromium and nickel additive), followed by cementation of the surface layer to a depth of 0.5-1.5 mm or high carbon steel, followed by surface quenching with high frequency currents.

1.1 Purpose, structure description, parts

The operating conditions define the following requirements for the design of the piston pin: it must have a small mass, minimum deformation during operation, sufficient strength and wear resistance, taking into account variable and impact loads.

The piston pin YaMZ236 - hollow, floating type, is installed in the hole in the piston. Axial movement of the pin is limited by locking rings installed in special grooves in the piston bosses.

During engine operation, pin is heated to operating temperature and rotates freely in bosses. Due to change of value and direction of pressure, piston pin adjoins alternately to one or the other sides of holes in bosses of piston and bushing of upper head of connecting rod. Under such conditions, the oil layer does not have sufficient thickness and the joints of the parts operate predominantly in the frictional boundary phase at high specific pressures and loads when abrasive is present, resulting in increased finger wear.

As wear increases, the gap between the parts increases. With alternating loading, increasing the gap leads to the appearance and gradual increase in impact loads, which causes extrusion of the lubricant and a progressive increase in wear.

The gap at which a metal knock appears in the conjugate should be considered extremely permissible, it is equal to 0.02 mm.

Piston pin is made of low-carbon chrome-nickel steel (GOST 454371) with hardened cement layer of outer cylindrical surface.

Under action of sign-alternating forces the piston pin bends, and bushing of upper head of connecting rod and bosses of piston are deformed.

1.2 Part processability analysis

Piston pins for the YAMZ238NV engine are made of low-carbon chromium-nickel steel 20XN, a steel rod is used in the form of a blank. Nominal dimensions of the piston pin: long 1020.23, inner diameter 29, outer diameter 50,+,0,016.

The following requirements are applied to machining of piston pin blanks:

1) on the surfaces of fingers cracks, hairs, scale, nicks are not allowed, and on treated surfaces, in addition, blackings, dents and hairlines;

2) sharp edges on the ends of fingers should be rounded, and burrs should be cleaned;

3) the hardness of the external surface of the finger after chemical-thermal treatment for cemented steels should not be lower than 56 HRC;

4) depth of cemented layer of external cylindrical surface of fingers with wall thickness of 10.5 mm shall be 1.1... 1.7 mm

5) limit deviations of dimensions of external cylindrical surface of fingers shall be according to the 6th quota;

6) the tolerances of the shape of the outer cylindrical surface shall not exceed 0,005... 0,015 mm;

7) limit values of finger difference at diameter of 50mm shall not exceed 0.5 mm

8) roughness of machined finger surfaces for external surface Ra = 0.10 mcm, and for other surfaces Ra = 0.32 mcm.

9) accuracy of control of all dimensions up to 0.0001 mm.

Chapter 3. Procurement Process Design

step 05 - trimming and aligning the ends and cutting the outer surface - is performed on the lathe. The finger is installed in the centers. Allowance is left for finishing: in the middle part

(subject to cementation) - 6.4 mm in diameter, in end parts in length - 4.8 mm;

step 10 - Material quality check - flaw detection. It is performed using technical means (magnetoscopy), as well as by immersing the finger in a saturated soda solution, which, after drying the finger, occurs in the cracks;

step 15 - cementation;

operation 20 - drilling of the central hole - is performed on a vertical drilling machine;

step 25 - turning the ends of the fingers with an allowance for grinding;

Operation 30 - Finger Locating (peeling burrs, holes, etc.)

step 35 - quenching;

step 40 - grinding and polishing;

step 45 - polishing.