Designing of Tooling Solution for Workpiece Handling in Highly Automated Manufacturing System

: A flexible manufacturing system (FMS) is an integral part of a smart factory of Industry 4.0 in which every machine is interconnected and works autonomously. Robots are in the process of replacing humans in every industrial sector. As the cyber-physical system (CPS) and artificial intelligence (AI) are advancing, the manufacturing industry is getting more dependent on computers than human brains. This modernization has boosted production with high quality and accuracy and shifted from classic production to smart manufacturing systems. However, workpiece handling for such an automated production system is a challenge and needs to be addressed with the best possible solution. Conventional clamping systems are designed for manual work and are not suitable for highly automated production lines. Researchers and engineers are trying to find the most economical solution for loading/unloading and transportation of workpieces from a warehouse to a machine shop for machining operations and back to the warehouse without human involvement. This work aims to propose an advanced multi-shape tooling solution for highly automated manufacturing systems. The currently obtained result shows that it could function well with automated guided vehicles (AGVs) and modern conveyor belts. The proposed solution is following requirements to be automation-friendly, and universal for different part geometry and production operations. We used a bottom-up approach in this work, starting with studying different case scenarios and their limitations and finishing with the general solution


Introduction
The smart factory is a new concept for manufacturing companies as a part of Industry 4.0.It represents the leap forward from traditional automation to a fully connected and flexible system.It works by employing technology such as AI, robots, analytic big data, and the IoT with the ability of self-learning and control.The main characteristics of a smart factory are enlisted in Figure 1  The biggest problem to implement this concept in the production company is the optimization of the FMS and agility of transportation.Conventional tools cannot be used to attain a high level of automation, such as conveyor belts cannot be used for logistics and fundamental fixtures cannot be used without human involvement [2].Therefore, this work aims to design a set of tools that can be attached to different fixtures and clamping systems to make them usable in a highly automated manufacturing system.
Some requirements need to be fulfilled by the tooling solution [3].e.The tool should be strong enough to bear the weight of the clamping system and workpiece with the cutting force applied during a machining operation.

Workpiece classifications
There are 11 basic types of mathematical geometric shapes depending on sides and angles.Mostly, the workpieces are based on these shapes or a combination of them.Based on industrial research, some of the workpieces have been selected to demonstrate the functioning of the tooling system [4,5].Some of them have been enlisted in Figure 2.

Conceptual design of the tooling system
Based on the shortlisted workpieces, some clamping systems were selected.These conventional clamping systems shown in Figure 3, can hold multi-shape bodies for different machining operations which include milling and drilling operations.According to the considered requirements, we designed an adapter that can be transported through AGVs, loaded and unloaded through a robotic gripper, and hold a clamping system during the machining operation.
Figure 5 shows the workflow of the tooling solution.All the fixtures can be attached to the same adapter, and it can be fixed in the base, which is placed in the machining cell.In this way, multi-shape workpieces can be machined under the same platform through an automated process.

Vise clamping system
In-mold clamping system

Chuck clamping system
Adapter / tool

Modular clamping system
Base for tooling system

Material selection
The material of this adapter should be lightweight with high strength to bear maximum fatigue cycles.Therefore, steel is the most suitable material for the adapter.Many tools such as HSK-A63 are made of steel .
Contemporarily, there are different kinds of steels available in the market depending on the heat treatment process and alloying elements, they have been graded.The alloyed stainless graded steel 304 and 430 are good options for manufacturing the tools.A comparison of the mechanical properties of mentioned steel is shown in Table 1.

Analytical calculations of stress and deformation
An adapter is divided into three main sections according to stress distribution areas.The scheme of the adapter is shown in Figure 6.The total cross sections area is described in Equation (1).
where A 1 is cross-sectional area of section-1 in mm 2 , A 2 is cross-sectional area of section-2 in mm 2 , A 3 is cross-sectional area of section-3 in mm 2 .Total deformation: Total deformation is the sum of deformation in each section.The value described by Equation (2).
where δ is deformation in mm, F is the force applied in Newton, L is the thickness of the section in mm, E is Young's modulus of the section.Total stress distribution: Similarly, total stress is calculated by summarizing stress from each section in Equation (3).

Establishing the finite element model
Material considered for FEA: We considered steel as a material for the tool.The mechanical properties of steel are mentioned below in Table 2.

FEA:
There are two kinds of static structural analysis: a. linear structural analysis; b. non-linear structural analysis.
In linear structural analysis, the applied force and displacement have linear relations.We considered linear analysis because the applied force lies in the elastic region [6,7].Static structural analysis has been carried out in ANSYS Workbench 18.2.This software can be used for fluid flow, heat, and mass transfer.Furthermore, stress-life fatigue analysis has been done with the same software. Meshing: Meshing is an important part of FEA.The whole body is divided into a finite number of elements and software solves the problem according to given constraints and boundary conditions for each element [8].After accumulating the result of all elements, we can predict the behavior of the body.It is better to have a greater number of elements to have a more accurate result.Similarly, our tool has been divided into 70,514 nodes and 41,451 elements for the analysis, as shown in Figure 7.

Total deformation:
In ANSYS, we have two types of deformations: a. total deformation; b. directional deformation.Total deformation is an accumulation of all directions (x, y, z-axis).But in directional deformation, the effect of stress on a particular axis can be evaluated [9,10].
In our case, total deformation is considered and according to FEA result its value is 0.0012493 mm.The result of the simulation is shown in Figure 8.The von Mises stress distribution value is 4.4312 MPa, which is less than the yield stress of the material.So, it can be concluded that the structure can sustain the given value of the load applied.Results are shown in Figure 9.

Digital Manufacturing Technology
Fatigue analysis: When the applied load on the structure is less than the yield stress then fatigue analysis is done to evaluate the long-term effect on the structure.
In this case, the minimum life cycle for a tooling system is 10 6 .It means that the tool can bear an infinite life cycle with this amount of load.The simulation result is shown in Figure 10.

Conclusions
The adapter design can successfully attach to different fixtures to accommodate different geometrical shapes of workpieces.
The theoretical stress value is 1.38 MPa which is less than 4.4312 MPa.The main reason for this difference is internal threads which acted as a stress raiser and intensified the stress value around the threaded portion.Still, the maximum value of von Mises stress is less than the yield stress.So, there will be no plastic deformation.
The design of the tooling system is functional according to requirements and easy to handle.
In future work, we can upgrade the design of the hold by considering the complex shape and bigger size workpiece samples.Further, detailed design can be considered as a future task.

Figure 1 .
Figure 1.Characteristics of smart factory a.The design of the tooling set should be simple and transportable through AGVs.b.It can be loaded and unloaded through robotic grippers.c.It should hold the workpiece during CNC machining operations such as the drilling and milling process.d.It should accumulate multi-shape workpieces having a size of 150 mm × 150 mm base area.

Figure 2 .
Figure 2. List of considered workpieces

Figure 5 .
Figure 5. Workflow of tooling solution

Figure 6 .
Figure 6.Isometric view with dimensions

Figure 7 .
Figure 7. Isometric view with dimensions

Figure 8 .
Figure 8.Total deformation σ v is von Mises stress, σ 1 , σ 2 , σ 3 are principal stresses and σ y is the yielding strength of the material.If σ v ≥ σ y , then the structure collapse.

Table 1 .
Mechanical properties of AISI 304 and AISI 430

Table 2 .
The mechanical properties of steel