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Performance of stock kitchen cabinets and laboratory-produced cabinets based on joint tests.

Abstract

This study determined the deflections at different load levels and the load at failure for three purchased stock kitchen cabinets and nine laboratory-produced kitchen cabinets. The laboratory-produced cabinets were designed and constructed based on an earlier study which tested the effectiveness of different combinations of hot-melt adhesives and joint design. The laboratory-produced cabinets had back panels constructed from particleboard, plywood, and hardboard. A comparison of the deflection results of the purchased cabinets to the laboratory-produced cabinets indicated that laboratory-produced cabinets performed better than the purchased cabinets since they had lower deflections and higher failure loads. Based on the Wilcoxon Rank Sum test, there was no significant difference at the 0.05 confidence level between the purchased and laboratory-made cabinets at relatively low loads of up to 200 pounds for horizontal deflection and 400 pounds for vertical deflection. Significance differences occurred at higher loadings.

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Built-in kitchen cabinets are universal in current North American residential construction. Most cabinets are "stock cabinets" or those which are mass produced in order to keep costs as low as possible.

Maintaining low costs has resulted in two factors that this paper attempts to investigate. The first factor is the use of hot-melt adhesives to attach the back panel to the top, bottom, and side panels. Hot-melt adhesives cure in less than 10 seconds and thus increase the efficiency of the assembly process. The second factor is the construction of the joint between the back panel and the top, bottom, and side panels. Manufacturers have typically developed a design through experience that has been successful in the field and maximizes throughput in their production facility. When structural failure occurs in a kitchen cabinet, it usually results because of excessive loading that pulls the front of the cabinet away from the back panel (assuming the cabinet is well attached to the wall) with failure beginning at the joint between the back panel and cabinet top. As a result, manufacturers are usually not willing to experiment with a different method to attach the back panel to the rest of the cabinet.

Tora, S. (1) and Tora et al. (2) have recently reported on a thorough review of the literature related to kitchen cabinet construction and investigated the shear, tensile, and bending strength of joints constructed with three different hot-melt adhesives. The authors also reported the effect of temperature, use of excessive adhesive, and presence or absence of staples for some of the joints tested. From these results, a suggestion is made on the best way to construct and attach the back panel to the top, bottom, and side panels of a kitchen cabinet.

Objective

The objective of this study was to compare the strength of three purchased stock kitchen cabinets to nine cabinets constructed in the laboratory with dado joints, ethylene vinyl acetate (EVA) adhesive, without staples at room temperature conditions. (2)

Experimental procedure

A survey of major cabinet outlet stores in Lafayette, Indiana, showed that there were two types of joints commonly used in the attachment of the back panel to the side, top, and bottom panels. These were rabbet and dado joints (Fig. 1). Based on this survey, three cabinets were purchased representing the observed construction types. Cabinets C1 and C3 were constructed using the rabbet joint as shown in Figure 1 a and 1b, with the only difference between them being the placement of the top and bottom rail. The materials used for the back panels were either particleboard, plywood, or hardboard. All of the purchased cabinets were constructed with staples and hot-melt adhesives.

[FIGURE 1 OMITTED]

Nine cabinets were constructed in the laboratory and tested. All of the cabinets were constructed with a dado joint configuration, EVA adhesive, without the use of staples. They were maintained and tested at room temperature. (2) Three of the cabinets were constructed with l/4-inch-thick softwood plywood, three with 1/2-inch-thick M-3 grade particleboard, and three with l/4-inch-thick standard hardboard. The sides, top, and bottom panels were all constructed of M-3 grade 1/2-inch particleboard.

Figure 2 shows the laboratory test set-up for the cabinets. The cabinets were securely attached to the studs using six number 8 (3 in. long) flat head screws, three on the top and three on the bottom rails. A strap was passed over the top front of the cabinet and attached to two air cylinders located below and on each side of the cabinet. Two dial gauges were placed at the center of the front frame of the cabinet to record the vertical and horizontal deflections. Vertical deflections at loads up to 600 pounds and horizontal deflections at loads tip to 400 pounds were taken at these points.

[FIGURE 2 OMITTED]

Results and discussion

The results observed for this study are shown ill Tables 1 and 2. This study determined the deflections at different load levels and the load at failure for the three purchased stock cabinets and nine laboratory-produced cabinets. Five hundred pounds is the minimum load required by the ANSI/KCMA A161.1 (3) standard. The average failure loads for laboratory-made cabinets with particleboard, plywood and hardboard back panels were 1,220, 1,360, and 1,373 lb, respectively. The failure loads for the purchased stock cabinets named C1, C2, and C3 were 750, 810, and 850 lb, respectively.

The results from the Wilcoxon Rank Sum (4) test indicated that the laboratory-produced cabinets had a better performance than the stock cabinets. There were no significant differences at the 0.05 level between the purchased and laboratory-made cabinets at relatively low loads of up to 200 pounds for horizontal deflection and 400 pounds for vertical deflection. Significant differences at the 0.05 level occurred at higher loadings.

A comparison of the deflection results of the purchased cabinets to the laboratory-produced cabinets (Figs. 3 and 4) indicated that laboratory-produced cabinets performed better than the purchased cabinets since they had lower deflections and higher failure loads. There was no significant difference between the laboratory-made cabinets. Evaluating the stock cabinets at the 600-1b level, C2 had 41.1 percent lower horizontal deflection compared to cabinets C I and C3. Vertical deflection for cabinet C2 was 14.2 percent and 17.8 percent lower than cabinets C1 and C3, respectively. Cabinet C2 likely had better performance because of the dado joint that connected the side panel and the back rail.

[FIGURES 3-4 OMITTED]

The method of attachment of the back panels and back rails to the cabinet can be considered a major reason for the difference in ultimate load capacity and deflection. From the present study, it can be concluded that using a dado joint to join the back panel to the side panels is the best method of construction for a cabinet.

Failure type

Three types of failures were observed. The first type of failure (Fig. 5) was in the back rail of cabinet C2, which was also the strongest of the purchased stock cabinets. In this type of failure, the part of the rail forming the dado joint separated from the side panel. The entire cabinet eventually failed, leaving the back panel and the rails attached to the studs. The second type of failure (Fig. 6) consisted of the top, sides, and bottom panels of the cabinet pulling away, thereby leaving the rail and back panel attached to the studs. This type of failure was observed in cabinets C1 and C3. The third type of failure (Fig. 7) resulted in the top and side panels being pulled away from the back panel. This failure was common for the nine laboratory-produced cabinets.

[FIGURES 5-7 OMITTED]

Conclusions

Following the suggestions of a previous study, the authors constructed nine cabinets under laboratory conditions using dado joints and EVA adhesive without staples at room temperature conditions. Based on horizontal and vertical deflection under increasing load levels, these cabinets all outperformed three stock cabinets. The improved performance is attributed to the dado joint used in the laboratory cabinets as compared to the rabbet joint used in some stock cabinets.

Silas Tora *

Eva Haviarova *

Daniel L. Cassens *

(1) Tora, S.G. 2004. Strength and construction techniques for kitchen cabinet back panels. Unpublished MS thesis. Purdue Univ., West Lafayette, IN. 118 pp.

(2) Tora, S.G., D.L. Cassens, and E. Haviarova. 2006. Properties of hot-melt adhesives used in furniture joints. Forest Prod. J. 56(11/12):43-50.

(3) American National Standards Inst. (ANSI) and Kitchen Cabinets Manufacturers Assoc. (KCMA) 1995. Performance and construction standard for kitchen and vanity cabinets. A161.1.1995. ANSI. Reston, VA.

(4) Devore, L.J. 2004. Probability and Statistics for Scientists and Engineers. Brooks/Cole-Thomson Learning. Belmont. CA. pp. 677-682.

The authors are, respectively, Graduate Research Assistant, Assistant Professor, and Professor (stora@purdue.edu; ehaviar@purdue.edu; dcassens@purdue.edu), Dept. of Forestry and Natural Resources, Purdue Univ., West Lafayette, IN. The authors wish to acknowledge the Seemac Graduate Fellowship Award for financial support. They also acknowledge Dr. Carl Eckelman, Professor, Dept. of Forestry and Natural Resources, for his technical contribution. This paper was received for publication in March 2005. Article 10018.

* Forest Products Society Member. [c] Forest Products Society 2006. Forest Prod. J. 56(11/12):51-54.
Table 1.--Vertical deflections of the wall cabinets for loads of up to
600 pounds.

 Vertical deflections (in.)

 Stock cabinets Laboratory-produced cabinets (a,b)
Load
(lb) C1 C2 C3 PB PW HB

200 0.022 0.220 0.019 0.025 0.029 0.02
400 0.053 0.045 0.054 0.049 0.05 0.048
600 0.096 0.084 0.099 0.078 0.079 0.074

(a) Values are the average of three cabinets.

(b) PB = particleboard back panel; PW = plywood back panel; and HB =
hard-board back panel.

Table 2.--Horizontal deflections of the tested wall cabinets for loads
of up to 400 pounds.

 Horizontal deflection (in.)

 Stock cabinets Laboratory-produced cabinets (a,b)
Load
(lb) C1 C2 C3 PB PW HB

200 0.005 0.006 0.006 0.005 0.005 0.004
400 0.022 0.016 0.024 0.012 0.011 0.011

(a) Values are the average of three cabinets.

(b) PB = particleboard back panel; PW = plywood back panel; and HB =
hard-board back panel.
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Title Annotation:Technical Note
Author:Tora, Silas; Haviarova, Eva; Cassens, Daniel L.
Publication:Forest Products Journal
Date:Nov 1, 2006
Words:1697
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