## 1 Introduction  
Medium-density fiberboard (MDF) is the second most popular (12.3 million m\({}^{3}\) in 2017) wood-based composites in the manufacture of furniture and interior decoration in Europe [1], and is an excellent alternative to a range of natural wood panels due to the excellent mechanical properties and desired physical features. In the production of MDFs, wood fiber and glue at 640-800 kg/cm\({}^{3}\) density are used [2]. The production of MDF involves the application of hot pressing using various heat processing temperatures (155 \({}^{\circ}\)C, 165 \({}^{\circ}\)C, and 175 \({}^{\circ}\)C) for different time durations (2.5 h, 3.5 h, and 4.5 h) [2]. With the introduction of the continuous hot-pressing (CHP) technology in Germany in the beginning of the 1970s, productivity was increased, and good surface qualitieswere achieved [3]. Hot pressing is the most crucial process in the production of MDF [4], and it is essential to achieve the required quality of MDF. CHP is a process wherein the raw wood board is subjected to the application of temperature and pressure in order to achieve moisture evaporation, while in the process, the density increases, the glue solidifies, and the raw material undergoes physical and chemical changes. As a result, the bonding force between fibers is formed [5]. The MDF slab is pressed to a required thickness under pressure. The resulting quality of the MDF depends on the slab formation. Due to steam pressure during CHP, thickness deviations can arise as in thicker MDF slab areas, the steam cannot be released under the constant pressure [6]. Thickness is the principle element of achieving high-quality MDF. As a result, multiple research efforts are done to solve the thickness control problem for MDF CHP systems [7; 8; 9]. A continuous flat press is the core equipment of the entire MDF production line [10]. Quality control is an essential part of the manufacturing process [11; 12]. The production capacity and product quality of the entire MDF production line are directly affected by the accuracy and reliability of its operation and control. The needs to support the requirements of scale and manufacturing intensification, as well as to maintain the quality control of the board thickness deviation of the continuous flat pressing (CFP) process and to ensure the continuous and reliable operation of the press have become a core issue of the MDF manufacturing industry. The MDF hot press forming process is to compact the fluffy mat of fibers by applying pressure; at the same time, the adhesive is solidified, and a compaction and adhesion point is formed between the fiberboard by heating, thereby forming a certain thickness [5]. FMEA is a reliability management method generally employed in different industrial applications to assure the security and reliability of systems and services [13]. FMEA is more arbitrary for the analysis of the level of the failure mode of MDF. The result is not very accurate [14]. This will cause the failure mode analyzed to be too one-sided and difficult to correct [8]. To overcome these problems, this paper proposes to fuse the original FMEA method through the theory of fuzzy mathematics and obtain a new fuzzy FMEA method to judge the deviation grade of MDF accurately. It relies on consistent judgment of the deviation pattern of the sheet surface. The data used in this paper are sampled data from laboratory sensors. The FMEA system is analyzed by fuzzy mathematics and the fuzzy matrix method, and different FRPN values are calculated. FRPN is the fuzzy risk priority number according to the FMEA's judgment standard; the RPN is the only criterion for judging the FMEA failure mode level [9]. In view of the above problems, this paper starts with fault diagnosis control and uses the failure mode and impact analysis (FMEA) to analyze theoretically the possible failure mode of the continuous flat press.