Study on Complexity of Precast Concrete Components and Its Influence on Production Efficiency

Table 2

Open coding process.

No.	Initial category	First-order concept (interview and observation)
1	Component size (surface-to-volume ratio)	01 Currently, the standardization level of PC components is low. Some components have large surface-to-volume ratios and the component structural design is very complicated. The specific production processes and manufacturing techniques may not be fully considered in detailed design stage. Such components need a long production duration. 09 Different kinds and sizes of components increase production cost and time of molds. Some large and complex components require 3-4 days to produce.
2	Number of openings, number of sections	08 Some components are designed with many openings, unique shapes, and many sections, which increase the difficulty in mold production and the time of mold assembly.
3	Number of embedded parts	01 Normally, the numbers and location of embedded parts directly affect design and assembly complexity of molds. 10 Some components need redesigning and reproduction due to the inappropriate placement of embedded parts in PC components, which does not meet the construction requirements.
4	Reinforcement ratio	03 Steel rebar is the main material of a PC component and the amount of rebar contained directly reflects the structural complexity. For components with a larger amount of rebar, the time required for binding and processing is comparatively long.
5	Waiting time in production line	01 There is a waiting time for inspection and warehousing after mold removal. The waiting time for rebar binding is another circumstance. These all lead to inefficiency. 06 Assembly lines mainly produce components of laminated panels and in-line walls in factories. The degree of automation is relatively high. However, different production processes for these two main components can cause waiting time when demand is high.
6	Material consumption	06 Generally, components with more materials require longer production time and face greater production difficulty which results from production complexity.
7	Abnormal production status	05 Force Majeure factors, such as equipment failures and water and power outages may occur in the production process. That will increase the production complexity and inefficiency. 07 In Beijing, Force Majeure factors are, for example, haze, low temperature, lower production efficiency.
8	Improper delivery time	10 Components produced ahead of schedule may not be able to be shipped in time, resulting in the accumulation of finished products in factories. That may affect the production cycle.
9	Stocking	02 The backlog of finished components increases the stock, disrupts production plans, and causes inefficiency.
10	Mold turnover rate	08 Low reuse rates of molds are common today. The customized molds increase the management complexity in component production. 09 The turnover time of fixed vibration platforms, such as for exterior walls, stairs, and balcony panels, is relatively long, resulting in decreases in reuse rates of molds.
11	Repair rate (quality defect)	03 Some factories are in short of component supply causing rush work; therefore the proportion of products returned to the factory or scrapped (due to quality issue) is quite large. Complex components are prone to crack, contain bubbles, and have unqualified dimensions. A repair area is required for those components, increasing the complexity in the production arrangements. 04 If the finished products are identified as unqualified ones in the test before delivering, they will need reproduction. This may disrupt the original production plan.
12	Mold manufacturing accuracy	04 Currently, component molds are outsourced to mold factories to produce. The manufacturing factories conduct accuracy inspections before mold use. A low accuracy level will cause severe damage in production. Those molds with large errors cannot be used and need reproduction. 05 Some manufacturing factories may produce all the molds by themselves, which can achieve high mold accuracy and avoid the cost and waste caused by insufficient mold accuracy.
13	Mold assembly time	10 Mold removal is typically carried out manually, and this takes a long time, especially for complex components. 01 The mold assembly time for complex components is different, which may affect production efficiency.
14	Degree of automation of production line	01 Automation equipment is out of use in some PC component factories, resulting in an increased reliance on manual operations. A large number of manual operations will extend the production duration and lower production efficiency. 07 Automation levels of assembly lines in PC component factories today are relatively high. However, stairs and sandwich wall panels are normally produced on fixed vibration platforms. Some processes such as mold removal and mold assembly are still manually operated. If full automation can be achieved, production efficiency can be significantly improved and the complexity in production management will be reduced.
15	Operating proficiency of workers	09 Workers in PC component factories are hired from labor service companies. Their operational proficiency of workers will directly affect production efficiency. 02 Managerial and technical personnel in PC component factories are usually qualified, whereas others are sometimes new migrant workers, which increases the difficulty in training and management.
16	Information management level	11 Intelligent information management system is adopted in many PC component factories. However, some data and information fail to upload in time, and this increases the management complexity in component production. 03 Most of the data in factories are still recorded using a paper-and-pencil method, meaning that data can be easily misplaced. Moreover, some information is not recorded in time, resulting in delayed information transmission and increased management complexity.