The aim of this project was to create a viable furniture product using the various stages of the product development process. An important conclusion of the project was the benefits of lean manufacturing and the importance of the product development process in the design of a new product.
PLANNING
Market Research
Some examples of multi-functional furniture pieces on the market today include a convertible chair futon, which can be rolled out into a double bed, or a set of tables that can be stacked in a cabinet. In addition, there is a bookcase that converts into two chairs and a table, a coffee table that extends upwards into a dining table, and an ottoman that converts into five chairs [10].
Initial Idea
Multifunctional furniture prices can range from $15 to $150 at retailers like Target, while options at big furniture stores like Wayfair range from $20 to. Preliminary fabrication operations included a table saw to cut all the required panels shown in Figure P0-2, a drill to drill holes for screws, screwdriver to install the screws, wood glue to ensure good adhesion, and wood stain to finishing the unit.
![Figure P0- 2: Furniture solution product concept: digital sketch #2 [8]](https://thumb-ap.123doks.com/thumbv2/123dok/10463011.0/14.918.242.735.105.706/figure-p0-furniture-solution-product-concept-digital-sketch.webp)
Product Pitch
CONCEPT DEVELOPMENT
Initial Concept
Customer/Target Market
A line of communication with the target group was maintained throughout the entire part of the engineering design process that was dedicated to product design. This communication was critical to the design of the prototype as it helped develop some of the key features of the final product.
SYSTEM-LEVEL DESIGN
- Alpha Prototype: Design
- Alpha Prototype: Cost Estimates
- Alpha Prototype: Customer Considerations
- Gamma Prototype
- Delta Prototype: Design
- Delta Prototype: Time Study
- Delta Prototype: Cost Estimates
- Delta Prototype: Customer Considerations
After the initial assembly of the alpha prototype, the finishing work for the SS&T product had to be considered. See Figure P2.4 for an image of the corner pieces added to the alpha prototype before it was painted. See Figure P2-5 for an image of the completed alpha prototype as it was presented to customers.
The results of the time study for the delta prototype can be found in Table P2-2. This was due to the modification of the finishing process, which was more extensive for the alpha prototype. The last change in the costing of the delta prototype was to reduce the profit margin to 20%.
The customers were excited that the cost of the unit was driven.
DETAILED DESIGN
Final Design
Layout A: Process Considerations During Prototyping
Once the unit was assembled, the corner brackets were sent to the final assembly and finishing station along with the unit. The unit was then given a final inspection, during which holes in the exposed edges of the plywood were filled and the unit was sanded and cleaned. Once assembly was completed and the unit was sealed, it went to the finished goods department where it awaited shipment.
When cutting the panels, the table saw left burn marks on the edges of the plywood. In addition, the drying times of the SS&T manufacturing process were a concern for the takt time of the process.
Production Cost Considerations
Although there were several possible areas of investigation to mitigate the burn problem, such as the sharpness or rotational speed of the saw blade, the decision was made to focus on adjusting the feed rate and how the wood was guided through the table saw. . On the other hand, obtaining the necessary equipment for the purchase would require obtaining a loan, and the company would remain in debt even at the end of the 5-year depreciable life of the equipment. In fact, it would take eight years for SS&T to become profitable if they bought the equipment instead of renting it.
Since leasing the equipment was expected to provide $15,495 in additional revenue over the 5-year analysis timeline, leasing the equipment was the chosen method to investigate further. The presentation included a demonstration of the final product design, preliminary production layout and cost information, as well as a discussion of the design process, lessons learned from the process, how obstacles were overcome, and what the next steps would be for the product.
![Table P3- 2: Equipment Purchase Price vs. Yearly Rental Cost [25]](https://thumb-ap.123doks.com/thumbv2/123dok/10463011.0/39.918.239.737.367.548/table-p3-equipment-purchase-price-yearly-rental-cost.webp)
TESTING AND REFINEMENT
Layout B: Process Considerations Prior to Production Trial
Layout B can be seen in Figure P4-1 and a detailed list of process steps can be found in Table A-2 in the Appendix. Since Layout B was the first physical production run for SS&T, process times were broken down by station rather than by individual process steps within each station. When we compare the 40-minute cycle time for Layout B shown in Table P4-1 with the 75-minute cycle time for the delta prototype in Table P2-2, it can be seen that there was a 35-minute improvement in cycle time from delta prototype in the production process of Layout B.
In addition, it showed that layout improvements were an effective way to save time and eliminate motion loss by streamlining the process. Based on the time studies in Table P4-1, it was determined that four operators had to achieve the target clock time.
Layout C: Process Considerations After Production Trial #1
Since the table saw was removed from the layout, this organizational device was placed between the panel saw and the assembly station and can be seen in Figure P4-8. Each different color of sticky note indicated a different size that needed to be cut with a saw. In addition, a standard work drawing has been added to further assist the panel saw operator.
An important note to the values in Table P4-2 was the panel saw operating time, which was 210 seconds for all three cutting operations. This time reduction proved that the panel saw was a more efficient method of cutting the stool and bottom panels, and the change was considered a positive improvement to the layout.
Layout D: Process Considerations for the Final Production Trial
When comparing this time to the original table saw time for cutting the bench and base panels (372 seconds), the panel saw provided a time reduction of 162 seconds or 56%. Another important conclusion that can be drawn when comparing the values in Table P4-2 with the values in Table P4-1 was the increase in efficiency of the assembly operations as additional equipment was added to the assembly to assist in the assembly of the units. In Layout B, the total assembly time was 959 seconds, but there were times during the assembly process in Layout B where a second operator stepped in to assist the assembly operator with the unit.
In Layout C, this time decreased by 105 seconds to a total assembly time of 854 seconds (153 seconds stool assembly, 303 seconds stool corner assembly, 398 seconds bottom assembly), and the assembly operator performed all assembly operations without a second operator helper. This showed that the additional fixtures improved the layout in two ways: first, by eliminating the need for a second operator to assist with certain assembly steps, and second, by eliminating 105 seconds (1.75 minutes) of process time.
Layout D: Initial Process Flow
After the base unit was assembled, Operator 2 took the base unit to the polyurethane and finish station and returned to the assembly station to assemble the corners to the bench unit. After the bench corners were assembled, Operator 2 took the bench unit to the polyurethane and finish station and returned to the assembly station to begin assembly of the next base unit. A description of the mounting part of the base unit of the mounting station can be found in Figure P4-22.
Once the base unit was clean, a roller, a paint brush and wipes were used to apply the polyurethane to the entire unit. Then Operator 3 returned to the polyurethane and finishing station to repeat the sanding, cleaning and polyurethane application processes on the chair unit.
Layout D: Improved Process Flow
After the discharge unit received a coat of polyurethane, it was also placed in the finished goods area and Operator 3 returned to the polyurethane and finishing station to repeat the process. Since Operator 1 and Operator 2's processes appeared to match well during the initial process flow, their processes and handoff points were left the same for the enhanced process flow, except for the addition of the grinding operation to Operator 1's process.
Layout D: Improved Process Flow Results
For example, adding the sanding operations to each of the cutting operations resulted in a total time increase of 131 seconds for Operator 1's processes, but this time addition corresponded to a time reduction of 155 seconds for Operator 3's processes. According to Figure P4-24, operator 1's time increased compared to the time shown in Figure P4-18, bringing a more coordinated process flow closer. These were expected results, as the process flow changes primarily moved the sanding portion of the process steps from Operator 3 to Operator 1.
The decrease in Operator 3's time did not exactly match the increase in Operator 1's time, as the sanding was easier to perform on the flat panels and Operator 1 did not take as long as Operator 3. To alleviate the situation, more quality Controls can be added to each operator's process (90 seconds for operator 1, 52 seconds for operator 2, 63 seconds for operator 3) to help eliminate defect waste and bring process times up to date .
Layout D: Final Cost and Rent vs. Buy Analysis
Operators can either move to another process line for the remaining 40 minutes of the 8-hour shift or simply work a reduced-time shift. This analysis was performed for the original production estimate of 200 units used in the lease. Comparing Table P4-7 with Table P3-3, it can be seen that the 5-year profit forecast for the final production was greater than the profit forecast for prototype in Table P3-3, doubling for the purchase scenario and increasing by five times for the lease scenario.
The profit in the rental scenario also had the added benefit of lower costs, which was the reason for the dramatic increase in profit expectations. Nevertheless, for the low production quantity of 200 units, it would have been better to rent the equipment.
RAMP-UP AND WRAP-UP
Future Considerations
If the unit can be reworked instead of being considered defective, rework should be attempted unless it would be cheaper to just scrap the material. For example, in some parts of the process the edges may be sanded or wood filler may be added to edge gaps to make the unit usable. For the process layout, some further adjustments can be made as the production ramp unfolds, such as adding a table next to the panel saw for the sanding operation or optimizing the organizational unit in the middle of the process area.
Finally, in the future, the discrepancy between the clock time and the time of each operator should be taken into account. The gap must be filled moving forward; otherwise overproduction waste will occur and adversely affect SS&T's profits.
Conclusions
Five of the seven lean manufacturing wastes were addressed during the product development process: transportation, movement, waiting time, inventory, and overproduction. Waiting waste was eliminated with the reorganization of operator processes to create a rhythmic process flow that went from one operator to another as seamlessly as possible. In addition, handover points were added between the operators if problems occurred that affected the synchronization of the processes.
Another possibility is that waste due to inventory and overproduction was not directly addressed or eliminated during the project. Excessive production of waste was discussed in terms of tact time and the urgency of ensuring this.
Tables
![Figure P0- 1:Furniture solution product concept: digital sketch #1 [8]](https://thumb-ap.123doks.com/thumbv2/123dok/10463011.0/13.918.165.815.739.1048/figure-p0-furniture-solution-product-concept-digital-sketch.webp)
