Principles of form grinding

The principle of form grinding is to decompose the outline of complex parts into several line segments and circular arcs, and then grind them segment by segment according to a certain process sequence to make the joints smooth and meet the design requirements of the product. Form grinding has the advantages of high precision and high efficiency, the grinding precision can reach IT5~IT6, the surface roughness is Ra0.4, and the lowest can reach Ra0.1. Form grinding often uses a form grinder or a surface grinder.

Method of Form Grinding

There are many methods of form grinding, commonly used are form grinding wheel grinding method and form fixture grinding method. The forming grinding wheel grinding method is to use tools to trim the grinding wheel into the opposite profile that is completely consistent with the workpiece to be ground, and perform grinding to obtain the required forming surface; the forming fixture grinding method refers to placing the workpiece in the forming fixture On the other hand, the position of the workpiece is adjusted by using the fixture, so that the workpiece can be moved or rotated quantitatively during the grinding process, thereby obtaining the processing method of the desired shape. Commonly used fixtures include sinusoidal precision vise, sinusoidal magnetic table, sinusoidal centering fixture and universal fixture. The sinusoidal precision vise and the sinusoidal magnetic force table are mainly used for grinding planes or inclined surfaces. When the two are used together, they can grind complex-shaped forming surfaces composed of planes and arcs; the sinusoidal centering fixture is mainly used for grinding punches, cores, etc. Different arc surfaces, planes and equal grooves on the same axis; the universal fixture is a more perfect forming fixture developed from the sinusoidal centering fixture, which is used to grind arcs and inclined surfaces of multiple centers.

In production, there are two main methods for forming and grinding parts using a surface grinder. One is grinding with a shaped grinding wheel after dressing, and the other is grinding with a special fixture.

The contour accuracy of form grinding mainly depends on the contour accuracy of the dressed grinding wheel. The primary task of the form grinding wheel grinding method is to use the grinding wheel dressing tool to obtain the required profile. The commonly used grinding wheel dressing method uses a diamond pen mounted on the dressing fixture. Dressing, the used fixtures are grinding wheel angle dressing fixtures and grinding wheel arc dressing fixtures. Grinding wheel angle dressing fixture, when grinding the inclined surface of the workpiece, use the angle grinding wheel, the angle grinding wheel is a conical part trimmed by the flat grinding wheel, when dressing, the grinding wheel is driven by the grinding head, and the diamond pen on the angle dresser is relative to the axis of the grinding wheel Tilt at a certain angle and move back and forth to dress the grinding wheel until the required conical surface is repaired.

Grinding wheel angle dressing fixture

Although there are many structures of tools for trimming arc grinding wheels, their principles are the same. As shown in Figure 4, the grinding wheel arc trimming fixture is shown. The distance from the diamond tip to the center of rotation of the main shaft is the radius of the arc to be trimmed. This value is It is adjusted by placing a gauge block between the diamond tip and the reference surface. When dressing the grinding wheel, the value of the gauge block should be calculated according to the condition of the grinding wheel (convex or concave) and the radius, and adjusted by the gauge block. When the grinding wheel is rotating at a high speed, rotate the hand wheel to make the diamond pen swing back and forth around the center of the main shaft to trim the arc grinding wheel.

Grinding wheel angle dressing fixture

1. Although there are many structures of tools for trimming arc grinding wheels, their principles are the same. Grinding wheel arc trimming fixture is shown. The distance from the diamond tip to the center of rotation of the main shaft is the radius of the arc to be trimmed. This value is It is adjusted by placing a gauge block between the diamond tip and the reference surface. When dressing the grinding wheel, the value of the gauge block should be calculated according to the condition of the grinding wheel (convex or concave) and the radius, and adjusted by the gauge block. When the grinding wheel is rotating at a high speed, rotate the hand wheel to make the diamond pen swing back and forth around the center of the main shaft to trim the arc grinding wheel.

2. Use the forming grinding wheel to grind the punch, that is, trim the grinding wheel into a reverse surface that completely matches the workpiece surface, and then use the grinding wheel to grind the workpiece to obtain the desired shape. There are many ways to dress the grinding wheel, the main ones are as follows:

(1) When dressing the grinding wheel with diamond, most of the geometric shapes of the forming surface are trimmed in sections, but some of the grinding wheels are trimmed into shape. This method of dressing the grinding wheel is mainly done through various grinding wheel tools; Grinding wheel repairing tools in production mainly include angle repairing, arc grinding wheel repairing tools, universal grinding wheel repairing tools, profiling grinding wheel repairing tools, etc. Horizontal grinding wheel angle tool. It is mainly used to grind the forming grinding wheel with various angles between 0º and 90º, and then use this grinding wheel to grind the bevel of the workpiece. When dressing the grinding wheel, the position of the diamond tip is adjusted by calculating the pad value according to the convex or concave shape and radius of the grinding wheel to be repaired. The horizontal arc dressing grinding wheel fixture can dress various concave and convex arcs with different radii, or profiles connected by arcs and arcs. When trimming a non-arc surface, if the shape of the workpiece to be ground is complex or the contour is non-arc, special profiling tools can be used to trim the grinding wheel. The tool is a dedicated; profiling tool for profiling wheels that love to dress convex surfaces. The mold tool for trimming the concave forming grinding wheel is basically the same as the profiling tool for the convex forming grinding wheel, but the contact of the profiling template used should be pointed. When using the grinding wheel repairing tools introduced above, attention should be paid to the diamond tool holders used must be clamped and must not be loosened.

When grinding the workpiece by using fixture grinding, the workpiece can be clamped on the special fixture according to certain conditions. During the processing process, the position is fixed or continuously changed for grinding to obtain the required shape. Commonly used grinding fixtures include: precision vise, sinusoidal magnetic force table, sinusoidal indexing fixture, universal fixture, rotating magnetic force table and center hole splint, etc. This grinding method is generally carried out on a surface grinder. In production, in order to ensure the quality and efficiency of grinding, the method of comprehensive use of shaped grinding wheels and fixtures is generally used, which can greatly reduce the manufacturing cost of parts.

Conversion of form grinding process dimensions During form grinding, the operator needs to convert the design dimensions of the pattern into the process dimensions of form grinding. The reason is that the size of process equipment parts is generally marked according to the design basis, but the construction basis used in form grinding is often inconsistent with the design basis. However, due to the different processing methods of individual parts, there are also different requirements for the size conversion of the forming grinding process.

---EDITOR: Doris Hu

---POST: Doris Hu