Mold Redesign Delivers Lower Costs & Lead Times

Application

A 4-cavity injection molding tool was transferred to Nicolet Plastics for production. The mold produced gas valves for welding torches.

• Part: Gas valve knob for a welding torch
• EAU: 56,500
• Mold: 4-cavity mold with hand loaded inserts, pressure sensitive label applied to finished part (label indicated direction to turn the knob to open gas valve)

Challenge

After approximately 6 years, the aged injection mold produced low quality product and needed repair. The old mold wasn’t as efficient as it could be, nor did it make the best use of the operator’s time. A brass insert was molded into each part as follows: Operator threaded a brass insert into a hand-loaded insert, then the set threaded inserts were placed into the mold during each molding cycle. At the end of each cycle, the operator unthreaded the finished part from the hand-loaded inserts. The labor was a significant component of the piece price.

Solution

Nicolet Plastics suggested a mold redesign instead of repairs. Experience and design for manufacturing principles lead Nicolet Plastics to implement several changes to bring down piece price, labor, and cycle time:

• Changed mold design to eliminate an extra step in the handling of inserts
• Increased new mold to 8 cavities to better leverage the operator’s time.
• Replaced pressure-sensitive label with engraved the text into the mold so it appeared in the finished product.
• 8 parts produced every 45 seconds versus 4 parts every 53 seconds
• Piece price reduced 11% (brass insert is high percentage of piece cost)
• Annual savings of over $5800 per year
• Manufacturing lead times cut in half

Due to the design change, it was no longer necessary to thread the brass insert, then unthread the hand-loaded insert from the finished molded part. The pressure-sensitive label was also eliminated. The labels purpose was to instruct which direction to turn the knob to open the valve, which was perfectly suitable for lettering directly on the part during the mold process. The new mold produced high quality parts and cut the press run time and labor requirement to less than half of the old mold.