RU103771U1 - WORM TYPE TOOL FOR CLEAN PROCESSING OF GEARS - Google Patents

Abstract

 A worm-type tool for finishing machining gears, made with continuous helical cutting edges, characterized in that its helical surface has a rectangular profile, while the height of the rectangular profile of the helical surface is greater than the height of the tooth of the machined wheel.

Description

Worm-type tool for finishing gears

The utility model relates to mechanical engineering, namely to tool production, and can be used for finishing machining involute gears.

A known tool for finishing gears with a profile formed by three sections of involute helical surfaces and containing active and inactive sections, the active section being made in such a way that when the tool contacts the surface of the product, the contact points are always within this section, and two other sections made in the form of bevels (patent No. 20738, IPC ⁷ B23F 5/06, B23F 19/00, publ. 27.11.01).

Known worm milling cutter used for finishing machining involute tooth profiles of gears. The worm tool is made with a solid helical cutting edge, has one-sided reinforcement of the side surface of the helical profile and structurally executed front and rear angles (AS USSR No. 1378187, IPC ⁷ B23F 19/00, publ. 07.03.93).

Also known is the worm type tool with continuous helical cutting edges, selected as the closest analogue, used to implement the method of finishing machining the teeth of involute gears. The tool has two cutting edges, a screw profile reinforced on both sides and a structurally executed rear corner (RF patent No. 2005013, IPC ⁷ B23F 19/00, B23F 5/22, publ. 30.12.93).

Due to the complex lateral profile of the helical surface, existing structures are difficult to manufacture and have a small number of permissible regrindings.

The technical problem, which the utility model is aimed at, is to simplify the design of the tool, as well as extend its service life by increasing the number of permissible regrindings.

This problem is solved in that in a worm-type tool made with continuous helical cutting edges, its helical surface has a rectangular profile, while the height of the rectangular profile of the helical surface is greater than the height of the tooth of the machined wheel and is limited only by the technological capabilities of manufacturing.

The implementation of a helical surface with a rectangular profile without reinforcement greatly simplifies the manufacture of the tool. This solution is based on the analysis of the kinematics of cutting and the analysis of emerging stresses by the finite element method, which showed that the lateral component of the cutting force is negligible, therefore, reinforcement of the base of the turn is not required.

The execution of the helical surface of a rectangular profile without a constructive rear angle greatly simplifies the regrinding of the tool, because after regrinding the tool along the outer cylinder, the key parameters of the tool - the shape of the profile and the pitch of the screw surface do not change.

Performing a profile of a helical surface with a height greater than the tooth height of the machined wheel allows you to perform a larger number of possible regrindings, since their number is determined only by the gap between the top of the tooth and the bottom of the cavity.

The applicant does not know the worm type tools for finishing gears with the specified set of essential features and the claimed set of essential features does not follow explicitly from the current level of technology, which confirms the conformity of the claimed technical solution to the condition of "novelty".

The claimed technical solution is illustrated by drawings, where:

figure 1 - a worm type tool for finishing gears, General view;

figure 2 is a kinematic diagram of shaving care;

figure 3 - profile of the helical surface in normal section.

The worm-type tool 1 for finishing the gear 2 is made with continuous helical cutting edges 3. The helical surface has a rectangular profile A in the normal section with a height h without a constructive corner. The height h of the rectangular profile of the helical surface is greater than the height of the tooth 2 of the machined wheel and is limited only by the technological capabilities of manufacturing.

The decision to make a helical surface of a rectangular profile without a constructive rear angle was made based on the definition of involute. The back corner during processing will always be inv a, i.e. at a profile angle of 20 ° it will be 0 ° 51 ', which is quite enough for cutting.

The tool will be re-sharpened only on the front surface - the outer cylinder, which greatly simplifies the tool re-grinding. After each regrinding, it will be necessary to recalculate the angle of inclination of the helix.

The number of permissible regrinds determines the height h of the rectangular profile A of the helical surface. The minimum value of h is determined by the minimum gap between the top of the tooth and the cavity of the profile, the maximum - only by the technological capabilities of manufacturing.

The following is the calculation procedure for a worm type tool:

1. The calculation begins with the definition of the source data of the processed gear (table 1)

Table 1. Gear input Parameter Designation module m number of teeth z profile angle of the initial tooth contour α Source contour offset x

2. Determine additional necessary values (table 2):

Table 2. Gear design Parameter Designation Formula tooth radius r _a m * (z + 2 + 2 * x) / 2 radius of the main circle r _b m z z cos (α) / 2 circumferential pitch of teeth on the main circle p _n π m cos (α)

3. The remaining parameters of the tool are determined based on the following conditions:

- the number of teeth of the machined wheel should preferably not be divided entirely by the number of visits (to compensate for the division error in the manufacture of a multi-start worm);

- the number of visits of the screw cut - 1..11. A lower value is adopted to ensure high accuracy and ease of manufacture. Larger values are adopted to ensure high gear productivity;

- the minimum gap between the top of the tooth and the cavity of the profile serves to compensate for the possible runout of the workpiece and the permissible technological risks at the bottom of the cavity, i.e. ≈2 mm;

- the amount of regrinding should be slightly larger than the allowance for processing, i.e. ≈0.5 mm.

- the number of permissible regrind is taken based on the application. Smaller values reduce the material consumption of the tool and simplify the technology of its manufacture, large values increase the efficiency of use. The optimal value is ≈10;

- the working length of the worm should be more than 2 times the calculated length. A smaller value is taken to provide two-sided machining in one setup, a larger one is to enable the tool to be used for machining wheels with a large number of teeth.

Calculate the necessary values (table 3).

Table 3. The calculated parameters of the shaving worm Parameter Designation Formula worm working length * C outside diameter D _a ≈20m number of screw cuts i - normal pitch p _n p _n helix angle β _{arcsin (p n · i / π} / d a) helical axial stroke P _{x p n · i / cos (β} ) screw width S p _n / 3 minimum clearance between the top of the tooth and the cavity of the profile t _min ≈2 minimum screw thread depth h _min r _a -r _b + t _min number of regrinds n ≈10 regrinding depth δ ≈0.5 screw cutting depth h h _min + n * excluding the angle of the relative position of the wheel and the worm.

The essence of shaping by a worm-type tool (shaving worm) is that if the normal step of cutting the worm is equal to the circumferential step of the gear teeth on its main circumference, then when they are rotated together, the screw edge of the worm will cut out the ideal involute on the tooth’s side surface (in accordance with its definition).

The kinematic diagram of the shaving process is similar to the classic worm gearing. However, unlike a worm cutter, shaping is not done with teeth, but with the side edge of the screw profile (figure 2). Both raw and hardened spur gears can be machined with this tool.

The problem was solved with a simple design of the tool to achieve an increase in its service life.

A worm-type tool for finishing gears can be manufactured on existing CNC equipment using known materials and tools, which meets the criterion of “industrial applicability”.

Claims (1)

A worm-type tool for finishing machining gears, made with continuous helical cutting edges, characterized in that its helical surface has a rectangular profile, while the height of the rectangular profile of the helical surface is greater than the height of the tooth of the machined wheel.