**5.1 Assembly process**

**4.9 Automation equipment**

*Overall value analysis per year.*

*Advanced Functional Materials*

**Figure 21.**

work in process (WIP).

**5. Washing machine**

**306**

**Figure 21**.

**4.10 Overall value analysis**

While tape solution cannot be automated by using equipment, one of many benefits of adhesive solutions is to automate the assembly line. Adhesive solution in this case requires a melting machine and a robot. Melting machine is required to melt the solid-state adhesive into the molten state. The adhesive is then applied in a liquid state onto substrate and as soon as it touches the substrate, it loses its energy quickly and hardens into solid. Robot is required to position (control) a dispensing area and location; currently, a 6-axis robot is recommended to this application for manufacturers. Typical parameters of melting machine and robot are 10 s of adhesive dispensing for 650 750 mm refrigerator door, dispensing speed is 300 mm/s for 15 g/min, pump speed is 103 RPM, application temperature is 130°C,

adhesive bead height is 2–2.5 mm, and bead width is 7–11 mm. These allow

manufacturers to make the assembly line with less manpower, less space, and better

Cost comparison has been done for overall required cost between tape solution and adhesive solution for glass plate bonding for refrigerator door as shown in

The cost for tape was 1,100,000 Euro, which is positive value for adhesive solution, meaning the value they can save by using adhesive solution was 798,000 Euro; and additional cost of adhesive solution was 0 Euro. The total prospect value that the manufacturer can save by using adhesive solution was 1,898,000 Euro. The cost for total adhesive solution was 730,000 Euro, which includes adhesive cost 660,000 Euro + equipment cost (melting machine + robot) 210,000 Euro, and 1 year depreciation cost for equipment is 70,000 Euro. Therefore, the adhesive cost becomes 730,000 Euro (660,000 + 70,000). the ultimate value to manufacturer can be 1,168,000 Euro which was calculated based on 1-year production. The capital investment cost for melting machine and 6-axis robot required when using adhesive solution can be calculated and the pay-back time will be 0.4 (730,000/1,898,000) year.

In this section, we are going to compare polyurethane hot melt solution vs. 1 component room temperature vulcanizing (RTV) silicone solution for top loading

One-component room temperature vulcanizing solution is to apply silicone onto a plastic frame by dispenser with 3 axis robot that is an assembly of bare ABS and chrome-plated ABS that was assembled by mechanical screws (23 s) ! place glass plate on top by 1 operator (2 s) ! put several mechanical clamps or wrap the tape around the assembly for fixture by 1 operator (10 s) ! transfer it to the rack (3 s) ! rack placed in the corner of plant for curing (24 h, space) ! move to next assembly process.

Polyurethane hot melt solution is to apply to a plastic frame that is an assembly of bare ABS and chrome-plated ABS that was assembled by mechanical screws by using an automatic dispensing machine as well as dispensing robot (23 s) ! place glass plate on top by 1 operator and press for 30 s ! assembly is fixtured and then goes to the next assembly process.

Comparing those two solutions, polyurethane hot melt adhesive solution takes a total of 1 or no operator and very compact assembly process time (total 1 min) while existing 1C silicone solution requires 2 workers and complicated and longer assembly process time such as taping 4 corners of cover, clamping or wrapping the assembled parts for curing, and a space for stacked assemblies to cure for 24 h before it moves to the next assembly process [2].

### **5.2 Initial fixture time vs. loading**

Testing has been carried out to measure and compare an initial fixture strength per loading between polyurethane hot melt adhesive solution and 1 component silicone solution. As shown in **Figure 22**, adhesive is applied onto ABS plastic assembly; then, a glass plate is placed on it and pressed for 30 s, and the assembly is conditioned at different interval time, placed upside down; 25 kg weight is placed upon the glass part and then it is observed if the assembled glass remains bonded or falls apart. As shown in **Table 4**, polyurethane hot melt adhesive has no de-bonding even at 1 min curing while 1 component silicone takes a much longer curing time;

**Figure 22.** *Fixture time test condition.*


**Table 4.** *Fixture time comparison.*

therefore, it has a de-bonding even after 10 min of curing time. This explains more compact and process efficient assembly process with less time and less manpower for polyurethane hot melt adhesive compared to 1 component silicone solution.

sharp decrease of bonding strength at 1000 h. Polyurethane hot melt adhesive shows an immediate certain strength initially due to pure hot melt fixturing function, but as time goes by, due to the chemical reaction, the adhesion strength increases to a higher reliable level. The assembly of glass to painted ABS shows a

higher ultimate strength than the assembly of glass to ABS.

*Global Trend of Glass Bonding for Appliance Industry Assemblies*

*DOI: http://dx.doi.org/10.5772/intechopen.90515*

**Figure 26.**

**Figure 27.**

**309**

**Figure 25.**

*Tensile shear strength comparison for glass + painted ABS.*

*Gap change at different corners vs. environment conditions.*

*Tensile shear strength comparison for glass + ABS.*
