**4.8 Initial creep resistance vs. load**

Testing has been done to measure a creep resistance of adhesive solution after applying onto substrate. The assembly test method was to hang 150 g weight to bonded specimen for max 10 min and measure the creep at each different fixture time. This weight and bond area are representations of actual glass bonding for refrigerator when the bonded assembly is put in upright position after bonding at horizontal position; then the glass, due to its weight and gravity, tends to move downward. The adhesive solution has to grip the glass in place after a certain fixture time at horizontal position. As shown in **Figure 20**, "1 time" means the same weight condition as actual glass load (glass weight/bonding area). "2 times" means 2 times more weight that was used to measure the creep. It has no creep in 5 min of fixture time and this is a severe condition. "5 times" means 5 times more weight that was used to measure the creep. It has no creep in 10 min of fixture time and this is a very severe condition. For "1 min" condition, 5 kg weight has a 2.5 mm creep at 15 s of fixture time, but as fixture time goes further, the creep reduces and at 4 min fixture time after assembly, it has no creep at all. This is the time that customers have and use in their assembly line. Anyway adhesive solution has a good fixture time with 4 mins of bonding after which bonded glass plate is placed vertically in such short amount of time and there is no creep that is adopted by various manufacturers, mostly their time is longer than 4 min. This explains the efficiency and durability of adhesive solution for process consideration when the refrigerator is put in upright position.

**Table 3.**

**Figure 18.** *No gap with adhesive.*

**304**

**Table 2.** *Thermal cycle.*

*Advanced Functional Materials*

*Higher thermal cycle.*

**Figure 20.** *Initial creep resistance vs. load.*

type that used to use a folding plastic top cover which changed to an ink printed glass cover for better appearance and high-end image as a value sold in the market place. The application area is for bonding of glass plate to ABS plastic frame for top

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

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

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

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;

**Solution 1 min cure 3 min cure 5 min cure 10 min cure** PUR HM No de-bonding No de-bonding No de-bonding No de-bonding 1C silicone De-bonding De-bonding De-bonding De-bonding

loading washing machine cover [2].

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

*Global Trend of Glass Bonding for Appliance Industry Assemblies*

goes to the next assembly process.

**5.2 Initial fixture time vs. loading**

before it moves to the next assembly process [2].

**5.1 Assembly process**

assembly process.

**Figure 22.**

**Table 4.**

**307**

*Fixture time test condition.*

*Fixture time comparison.*

**Figure 21.**

*Overall value analysis per year.*

#### **4.9 Automation equipment**

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 work in process (WIP).

#### **4.10 Overall value analysis**

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 **Figure 21**.

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.

### **5. Washing machine**

In this section, we are going to compare polyurethane hot melt solution vs. 1 component room temperature vulcanizing (RTV) silicone solution for top loading type that used to use a folding plastic top cover which changed to an ink printed glass cover for better appearance and high-end image as a value sold in the market place. The application area is for bonding of glass plate to ABS plastic frame for top loading washing machine cover [2].
