Rotary Percussion Drill Bit Hard Material Insert Bonding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Rotary percussion drills face high internal stresses due to temperature differences between the hard material insert and the shank end during joining and drilling, leading to potential failure in the brazing material, which affects the bond strength and service life, especially when drilling concrete.
Innovation Solution
A rotary percussion drill design featuring a hard material insert with a chamfered base surface and wedge-shaped radial edge for improved solder distribution, along with an X-shaped insert with radial chamfers, reduces stress concentrations and accommodates tolerances in the soldering process, enhancing bond strength and drilling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the hard solder thickness is increased to improve bond strength, then the bond strength increases, but internal stresses in the hard solder and hard material insert increase leading to potential failure
Solution Approach 1:
The patent applies different chamfer angles at different radial positions of the base surface. The outer radial edge has a first chamfer angle while the inner radial edge has a second chamfer angle that is different from the first. This local variation in geometry optimizes the solder distribution and stress state locally, allowing adequate bond strength while reducing internal stresses that lead to failure.
Solution Approach 2:
The patent changes the geometric parameters of the base surface by introducing chamfers with specific angles. The chamfer angles are optimized to control the flow and distribution of hard solder during the brazing process, thereby controlling the final solder thickness and stress state without simply increasing the overall solder amount.
2Strength
If a small thickness of hard solder is used to increase bond strength, then bond strength increases, but high internal stresses remain in the hard solder and hard material insert
Solution Approach 1:
By applying different chamfer angles at different radial positions, the patent creates a non-uniform solder thickness distribution that is optimized locally. The outer radial area with one chamfer angle accommodates solder to reduce edge stresses, while the inner radial area with a different chamfer angle maintains adequate bond strength with controlled solder thickness.
Solution Approach 2:
The chamfered base surface geometry is designed beforehand to accommodate and balance out tolerable amounts of hard solder during mass production. This pre-designed geometry acts as a cushion that absorbs variations in solder thickness and distribution, preventing excessive stress concentrations before they can cause failure.
3Reliability
If radial chamfers are formed on the base surface, then stress concentrations are reduced and solder distribution is improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies chamfers only at specific radial positions (outer radial edge and inner radial edge) rather than uniformly across the entire base surface. This localized approach reduces stress concentrations where they are most critical while minimizing the additional manufacturing complexity compared to a uniform design.
Solution Approach 2:
The patent uses asymmetric chamfer angles where the first chamfer angle at the outer radial edge is different from the second chamfer angle at the inner radial edge. This asymmetric design optimizes stress distribution and solder flow in different radial zones, achieving better reliability with a relatively simple manufacturing process that only requires two different chamfer angles.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design significantly increases the service life of the drill by minimizing extreme stress values and accommodating production tolerances, resulting in improved drilling performance and reduced risk of crack initiation, particularly when drilling reinforced and non-reinforced concrete.
Implementation Method 1
a hard material insert with at least one cutting edge and a base surface opposite the cutting edge, which is cohesively fastened to an axial base surface in the end of the shank with a hard solder
Implementation Method 2
Due to the radial chamfer formed on the base surface at the outer radial edge, the hard solder extends over a wedge-shaped radial edge area during hard soldering. As can be shown with corresponding simulations using the finite element method (FEM), the von Mises equivalent stress and the hydrostatic stress state, which can be regarded as a failure criterion for hard solder, do not show any extreme values at the edge
Data Source
AI summary
Percussion drill comprises a hard material insert (2) with cutting edges (3) and a base surface (4) fixed with a hard solder (5) to an axial base surface (6) which is chamfered an the outer radial edge. Preferred Features: The axial thickness of the hard solder between the base surface and the axial base surface is less than 0.6 mm.