Baxter et Al.  identified seven types of qualitative case study: explanatory, exploratory, descriptive, multiple-case studies, intrinsic, instrumental, and collective. In this work, multiple field studies are conducted for explanatory and exploratory purposes. Exploratory, in order to explore distinct situations where Material Handling is differently performed, and to understand what are the factors that provoked these differences and the similarities. Explanatory, to seek thorough answers to the main question: What are the mains challenges of the MHS design process ?
3.1. Field studies design
To understand how Material Handling is performed in industries, five interviews are conducted using a grid analysis. Later on, three steps are adopted to exploit the data; data reducing, data display and cross analysis. This procedure is inspired from .
Table 2 presents general information about the company typology for each case. The objective of the survey is to define Material Handling parameters, and to understand the approaches used for the design of MHS. Various companies have been chosen to observe different practices. The interviews were semi-directed, with additional questions to deepen interviewee’s answers. In most of the cases the interviews were complemented by a plant walk-through.
In order to thoroughly analyze the different cases in terms of LoA, a concept was adopted from the work of Parasuraman et al. . The concept allows to visualize the LoA of different systems through the cognitive and physical aspects. The original concept is used to compare four classes of information functions (information acquisition, information analysis, decision and action selection) and action implementation of different systems. In our case, it is used to visualize the LoA of different cases based on two types of activities; Productive activities and Material Handling activities (see Fig. 1). Figure 1 summarizes the observation made on the visited plant LoA and serves to discuss the observed practices in each case description (Sect. 3.2 to 3.6).
Details about each case study are given in next sections. Each case is described through the following steps:
- Presentation of the case
Presentation of the interviewee
Identification of the competitive priorities and objectives of the company
Description of the existing Material Handling activities
Description of automation (LoA) in productive activities
Description of automation in Material Handling activities
Description of Material Handling design approach
Criteria identification for measuring the performance of Material Handling activities
Criteria identification for MHE selection
Design experiences or general remarks
3.1.1. Case A
The interviewed company in Case A is a construction machinery manufacturer. It is considered as one of the world’s leading manufacturer of construction and mining equipment. The analyzed manufacturing plant is producing bulldozers and mechanical shovels. The productive activities are mainly organized as an assembly line.
The interviewee is a former plant director. He believes that in the context of the production of heavy vehicles, company survival and effectiveness are mainly driven by automation.
The company delivers standard and customized machines to final clients or retailers. Its competitive priorities are :
On time deliveries (OTD)
Quality of products
The Material Handling activities are of two kinds. The first is to move heavy mechanical parts as truck chassis. The second is to guarantee a good line-side supply.
The productive activities are mainly assembling activities. The mechanical assistance of operators is important for heavy parts lifting but many movements are done manually. For the cognitive side, torque control is applied but many decisions are left to operators. More assistance is given for maintenance activities. The LoA of productive activities in this case study is considered just below the medium grade for both cognitive and physical tasks.
The Material Handling activities are done using the following equipment; Forklifts, trolleys and “water-spider” (a train of wagons guided by an operator which passes across different workstations). Cranes and part lifters are also used. The mechanical effort for lifting parts is fully automated, sometimes the mechanical power needed for transportation is mechanized. However, decisions related to picking and placing items, navigation as well are done by a human. Therefore, the LoA of Material activities is considered below the medium grade as shown in Fig. 1.
The Material Handling System design approach used in this case study, is highly directed by corporate guidelines available for all production sites. Their objective is to optimize transport length and number of parts touches. Their second approach is to benchmark the practices of automotive industry.
To measure the MHS efficiency, some key performance indicators are used: Overall Equipment Effectiveness (OEE), Inventory on location, OTD, number of touches, line balance.
For MHE selection, the important criteria are related to the equipment performance (speed and capacity). Return on investment (ROI) and needed skills of equipment.
Some line-side transportation activities were automated in the past using self-guided vehicles. Then the system was dropped off because its speed movement and reactivity caused a negative impact on the OEE. It has been noticed that replacing the automated guided system by a human was easier to set up and it has been observed that it offers a new communication channel between the workshop and the warehouse.
3.1.2. Case B
This second case is a semiconductor manufacturer, in which two types of silicon wafers are processed. Each type has its own production line. Both lines are organized as a flexible job shop.
The interviewee is an industrial methods manager. He is a proponent of technology and automation, but he considers that nowadays smart robots are still not smart enough when it comes to handling perturbations.
The competitive priorities of the company are based on three main factors:
On Time Delivery (OTD)
The Material Handling activities in the facility are: to transfer the boxes of wafers across different workshops and ensuring a short transportation time.
The productive activities are composed of a set of 600 to 700 steps. All tasks are completely automated, from the production machines to the quality control process. That is why the LoA of productive activities in this case is placed at a high degree for both cognitive and physical tasks.
The Material Handling activities are mainly performed with Automated Guided Vehicles (AGVs) for one workshop and Overhead Hoist Transport system (OHT) for the other. Each equipment is dedicated to handle one product type. The utilization of OHT allows a high layout flexibility for the shopfloor, since the installation of the OHT is done under the ceiling without occupying the floor space. For both of these equipment, human intervention is not needed, except when a breakdown occurs. That is why the physical and cognitive LoA are both placed at a high degree in Fig. 1.
The Material Handling System design approach is based on the definition of the needs and the benchmark of best practices of other industries in the field. After this step, many simulations are done to make sure that the system is able to satisfy the needs. During this phase, lot of factors are considered such as; the capacity of the MHE, the cost of the MHE, the degree of automation, the flow units, the ROI. The performance of the Material Handling system is measured through: number of transports, time of transport, Overall Equipment Effectiveness (OEE), and throughput.
For the MHE selection, the company uses the following criteria: ROI, degree of safety and precision.
The activities done in the facility are measured through a 5 degrees LoA scale that was developed by the interviewee, it considers both of cognitive and physical automation.
Company B tried to introduce new technologies such as Autonomous Intelligent Vehicles (AIVs), but it did not cope with their expectations. The equipment took different paths to reach its destination, which led to increase the transportation time and the risk of collision with operators. The transportation time unpredictability brought by the system was also feared.
3.1.3. Case C
This case addresses the production of drawn wires and stainless-steel fixings. The company is involved on various industrial sectors such as: construction, railway, automotive, food and beverage industry, energy networks and management or solar industry.
The interviewee has been working in the company for almost 9 years and held 2 positions since then; he first started as a Production Manager and now he is a Lean Manager.
The competitive priorities of the company are based on the following factors:
Quality of products
On Time Delivery (OTD)
The Material Handling activities in the facility have to ensure the movement of the materials across different operations. Wire coils of up to one ton are moved and heavy metal boxes of metal parts as well.
The productive activities are done through the physical tasks are automated, but still need to be configured by the operators. That is why the LoA of physical tasks is higher than the LoA of cognitive tasks. The main activity of shop floor operators is to set and control machines.
The Material Handling activities are mainly done using forklifts, pallet trucks, and one automated equipment which is a conveyor system. The mechanical efforts are automated for some equipment, but the company relies mainly on pallet trucks for their Material Handling activities. For this reason, the LoA of physical tasks in Fig. 1 is placed near the medium degree. All material movements are decided by the operators, except the ones made with the conveyor system. Therefore, the LoA of the cognitive tasks is considered at a very low degree.
This company does not have a Material Handling System design approach, but their main concern is to remove NVA activities and increase the availability of operators so they can focus on their main tasks.
For the MHE selection, the main criterion that is considered is the ROI.
An automated transfer cart on rails was used in the past, but the loading/unloading operations were too difficult to be performed by the operators which increased downtime. The company then removed the automated transfer cart and switched to a completely manual MHE: pallet trucks. The railway remains in the workshop, which causes some traffic restriction.
3.1.4. Case D
Company D is considered as a global leader in fastening and assembly solutions. It is involved on various industrial sectors e.g. automotive, energy networks, construction, and agriculture.
The interviewee has been working in the company for 20 years and held several positions, and now he is a “Factory of the future” coordinator. His role is to manage the transition to a factory which integrates more technologies related to industry 4.0.
This company has the perspective to increase automation in its processes using robots, and cobots by the end of 2030 as stated by the CEO. Its competitive priorities are :
On Time Delivery (OTD)
The Material Handling activities guarantee the routing of materials across the whole manufacturing process. These activities are whether manual, semi-automated, or fully automated. They consist in moving boxes of very small parts and heavy bulk of raw materials.
The analyzed plant is composed of 2 production workshops; one for the production of metal fastening solutions (D₁), and the other for the production of plastic fastening solutions (D₂). More investments were done for D₂, since the plastic fastening solutions were and still are a highly competitive market according to the interviewee.
The productive activities for both D₁ and D₂ are done by a fleet of automated production machines. Some machines still need manual configurations and settings, thus the LoA of cognitive tasks is not as high as the LoA of physical tasks.
The Material Handling activities in D₁ rely on non-automated equipment such as: forklifts, electric stacker, and pallet trucks. However, the navigation is done by the human, which is, according to the interviewee, time consuming. While in D₂, the equipment are completely automated and does not need interventions from the operators.
The Material Handling System design approach is based on making the material flow simple as much as possible. Environmental aspects (carbon footprint) are considered as well.
A value stream mapping is used to follow MHS efficiency with three main KPIs; Intermediate storage time, cost of work-in-progress (WIP), and cycle time.
For the MHE selection, the company relies on 3 main criteria; total cost of ownership (TCO), ROI (ideally less than 2 years), and finally the suppliers’ reputation and location.
Autonomous Intelligent Vehicles (AIVs) are used in another plant that belongs to the same company, the interviewee affirmed that the equipment takes short time to transport materials. It is integrated to the information system of the plant, which allows the operator to supervise the movement of the equipment through a screen.
3.1.5. Case E
Case E is a plant of a metal wire special parts manufacturer, in which a variety of custom products are made in small and medium production. The productive activities are organized as a job shop.
The interviewee is the CEO of the company for 34 years. He is a proponent of technology and automation, and constantly tries to integrate new sort of technologies to the plant.
The competitive priorities of the company are based on two main factors:
The Material Handling activities in the facility are done through transferring the materials across different operations, the transport time is not an important constraint in company E.
The productive activities done in the workshop are: production of bent curved and shaped wire parts, production of wire grids, productions of hooks and displays, assemblies and sub-assemblies. Most of these activities are automated, but there are still some activities that are manually done. That is why the LoA of physical tasks is placed at a medium grade. The LoA of cognitive tasks is below the medium grade because the machines need to be configured by the operators.
The Material Handling activities are done using the following equipment: forklifts, pallet trucks, electric stacker, and cobots which are used for some pick and place activities. Some of these equipment allow the automation of the mechanical effort but the decisions related to moving the materials are left to the operators. That is why the LoA of physical tasks is placed above the medium grade and the LoA of the cognitive tasks is at a very low degree.
The case E does not have a Material Handling System design approach, but they focus on removing the NVA activities.
For the MHE selection, the company relies on 6 criteria; ROI, ease of implementation, cost of implementation, cost of the equipment, time needed for the implementation and suppliers’ location.
Cobots were brought to the workshop to remove the non-value-added activities performed by operators (pick and place activity). This equipment was not accepted by the operators at first. Once the operators started to make use of the cobots, the interviewee noticed that some of the operators appeared to get attached to the cobots. In the company, it is felt that automation is drastically reducing costs.