Troubleshooting and optimization for drilling process

Troubleshooting and optimization for drilling process based on deflection and breakage of HSCO twist drills in use with multi spindle, Jigs and fixture on special drilling Machine

Amir Alinaghizadeh , Soheil Nazarpour , Behnam Davatgar

1-Faculty member of mechanical engineering department, Energy and Sustainable Development Research Center, Semnan Branch, Islamic Azad University, Semnan, Iran

1,2,3-Research and Development office, Technical and Engineering Department, Tabesh Abzar Pars Company, Tehran, Iran

Abstract

Drilling is a cutting process which uses a twist drill bit to cut or enlarge a hole of circular cross-section in solid materials such as metals, polymers, etc. In this study, optimization of the cutting parameters on drill deflection and fractions was performed. The optimization of the cutting parameters was evaluated based on imperfection in Drilling tools and substantial tool life decreasing. The control parameters were considered as machine properties, cutting speed, feed rate, drill ratio lengths to diameters, workpiece material and other relevant parameters in order to detect malfunctional root causes.

All of the parameters were studied deeply in order to detect the root cause. All parameters as tool originality, tool material, machine properties, tool lengths, and all the possible parameters step by step and at the end root cause of problem had been detected in machine tool clutch system. All the parameters and study methods are explained in detail and step by step accordingly.

Introduction

Drilling is one of the popular machining methods and is used in most assembly processes. Various aspects of drilling have been investigated, such as process modelling, tool material, cutting force, and surface roughness. The Aim of this case study is to Troubleshooting and optimization for drill machining based on deflection and fraction in HSCO drills in use with multi spindle, Jigs and fixture equipped special Machines in which tool life has been saliently decreased. All the technical explanations about this malfunction, studies and results will be explained accordingly in the next steps.

Problem Explanation, Innovations & Aims of Paper

As illustrated in Figure 1 there are six holes to be machined on each workpiece. Multi-spindle machine had been used in order to machine six holes in three steps (drilling, stepping drilling, and reaming operations)

Cutting tool specification and cutting conditions were used to drill 4 holes (10.00mm) and 2 holes (8.7 mm) in three stations (Figure 1) based on information in Table 1:

Troubleshooting and optimization for drilling process

Troubleshooting and optimization for drilling process

All the necessary parameters to discuss are categorized as below:

Troubleshooting and optimization for drilling process

Figure 1: Workpiece and holes machining points.

As already mentioned, normal tool life for drilling is 200 Pcs per each twist drill tool and the number had been decreased to 3 Pcs per tool after malfunction appears (Figure 2)

Troubleshooting and optimization for drilling process

Figure 2: Drilling tools deflection after three holes machining

In parallel another malfunction appeared in product line was drilling tool breakage inside workpiece which causes production line stoppage in order to rework the parts and detach fracted tool from workpiece. (Figure 3)

Troubleshooting and optimization for drilling process

Figure 3: Broken twist drill piece inside workpiece hole

Another important parameter which must be considered were exhaustion of production timeworn drill machine with following explanation:

Multi-spindle drilling machine with three rotational workstations and three-station fixtures and a jig plate with three jig bushes for operations such as drilling, step-drilling and reaming (Figure 4)

Troubleshooting and optimization for drilling process

Figure 4: Drilling machine in use

Research Method and Assumptions

Research method was considered based on TAP Tools company method and all the studies were based on mentioned method in accordance of machine’s structure and its operation conditions in production line. A summary of study will come in resumption:

Tools identity: First study was about originality of the tools and to check all the parameters in case if damaged tools have different origin.

Specifications checked as shown in Table 2:

Table 2: Tool identification information

Troubleshooting and optimization for drilling process

Tool material: material test on twist drills was performed by “Razi Applied Science Foundation” in order to check if there is any material difference between old and new tools in use and the result replied as below:

Chemical Analysis by Atomic Emission Spectrometry (OES)

Standard Test Method: ASTM A751 (2014a)/ ASTM E415(2017)

Standard Practice for Reporting: ASTM E1950 (2017)/ ASTM E29 (2013)

Instrument: HITACHI PRO.2

Preparation sample: Grinding

Material type: Ferrous

Result of chemical analysis test has been shown in Table 3. According to the result, chemical composition of the sample conforms to the designated requirement of DIN HS 6-5-2-5 (1.3243) as illustrated at Table 4.