Moldworx develops automated process for molding and assembly of hypodermic needles

MoldworxMoldworx LLC (Gilbert, AZ), a custom injection molder that designs and builds molds and automation systems, takes special pride in optimizing manufacturing for medical device OEMs. Its latest innovation involves automating the production of hypodermic needles using the over-molding process to reduce cost and improve productivity. Moldworx designed and built tooling to inject medical-grade plastic around stainless-steel needles as small as 0.012 in. (0.305 mm) and developed the automation for this project.

Asked by a medical device OEM to develop a single-cavity injection mold to over-mold a needle that had been glued in place, Moldworx began by designing and developing an A-Series, single-cavity injection mold with slides. The needle initially was hand-loaded into the mold by an operator, then molded to a finished assembly to test the design. 

“This allowed us to over-mold the needle, eliminating a step in the current manufacturing process and reducing overall production time and cost,” said Moldworx President Jim Taylor. “We encountered some unique issues in the process, including the additional challenge of making this all possible in a horizontal press, not a typical vertical press.”

The next stage was designing a production mold and automation that would robotically feed the needles into the mold cavity, thus eliminating the operator. “We designed the mold to integrate with the automation and the automation to work in unison with the mold,” explained Taylor. “In an effort to accelerate the timeline, the entire automation cell was built in parallel with the mold.”

One challenge that Moldworx had to overcome was "singulating" thousands of bulk-packed delicate, tiny needles. To do this, Moldworx designed and developed a “singulator” with a “hopper” that would introduce one needle at a time to the assembly line cell. Each needle is picked up by a robot affixed to the injection molding machine and indexed in front of a set of high-resolution inspection cameras to ensure it is not bent or otherwise damaged, which would cause the needle to be rejected.

The needle is then placed into the mold and the mold closes for the injection cycle. When the mold opens, the robot removes the molded assembly and places a newly inspected needle into the mold. All these actions require inspection and verification, and tolerances must be exact.

After successfully completing the single-cavity mold and automation system, and after customer testing and approval of the parts, Moldworx built a multi-cavity mold with the required integrated automation cells. The four-cavity production mold will quadruple automated cell production to keep up with required demand.

“This is a prime example of the benefits of working with Moldworx,” said Taylor, who founded the company in 1995. “We partner with our clients to deliver innovative, automated plastic injection molding manufacturing solutions.”

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