PTI Tech - Advancing the process of MIM prototyping with metal binder jetting

The Challenge

PTI Tech is a global manufacturer that specializes in producing precision injection-molded components using engineered polymers and metal injection molding (MIM). In MIM, powdered metal is mixed with a binder and then injected into a mold cavity under high pressure. To produce high-quality, high-density metal parts, the "green" parts require a debinding and sintering process.

PTI Tech focuses on creating complex, high-precision parts for industries that require mission-critical components, such as aerospace, defense, medical devices, and high-end industrial applications. Before production, the company runs its customers' part designs through a design for manufacturability (DFM) process to ensure that the parts can be cost-effectively produced using plastic or metal injection molding.

Recently, a major elevator manufacturer faced a problem with its button caps and button bodies made of stainless steel with a plastic over-molded assembly. The cleaning process with strong disinfectants was causing the plastic threads to crack and deteriorate. To solve the problem, the manufacturer needed to redesign the button body and cap as a more durable all-metal assembly using 316L Stainless Steel.

The elevator manufacturer needed to bring these parts to market quickly, so they could be retrofitted to existing elevators in the field. The button body design required a pair of flexible retaining tabs that needed to be thin enough to be flexed by hand but retain their shape without cracking.

To finalize its design before production tooling was built, PTI Tech needed a manufacturing technology that could produce a series of production-representative parts that its client could use for testing and design validation. These parts needed to be similar in processing and physical characteristics to MIM-produced parts.

“The shrinkage and final density that we achieve with binder-jetted parts are very similar to metal injection-molded parts.”

– Gaetano Mariella Chief Technology Officer

The Solution

Metal binder jetting and metal injection molding are two sintered metal powder processes that produce parts with similar mechanical properties, according to a report by PTI Tech. They also exhibit similar shrinkage behavior during sintering.

PTI Tech used Markforged binder jetting to create a series of elevator button assembly prototypes for their client to test. The parts produced had similar shrinkage percentage during sintering, density, and surface finish to those produced using metal injection molding. The flexible tabs and thin-wall features met the durability requirements, ensuring that they would not break off during in-field installations.

Without metal binder jetting, PTI Tech would have had to create a series of pre-production molding tools to test different tab thicknesses and other part design variables. This process would have taken up to 16 weeks, with a new tool needing to be fabricated for each iteration. With metal binder jetting, PTI Tech was able to conduct a thorough DFM process and still deliver several rounds of 275-300 pre-production parts to the client for testing without any tooling in just four weeks.

The customer's engineering team was able to perform functional and destructive testing and make tweaks to the prototype parts' structural performance, aesthetics, and dimensions without investing in fixed tooling. Once the design was finalized, the customer could order the MIM tooling with greater confidence.

Using binder jetting to produce functional prototypes eliminated several steps, saving PTI Tech over six figures in cost savings and several months in development timelines. This rapid development process met the manufacturer's need to deliver retrofit parts quickly and reinforced PTI Tech's reputation for delivering high-quality parts in short timelines. It also gave the customer greater confidence in PTI's ability to deliver production parts to meet its urgent deadline.

The Future

PTI Tech frequently receives assignments that require a lot of problem-solving and deep thought to manufacture parts successfully. However, the team at PTI Tech can quickly build a series of MIM representative prototypes to test their ideas and find a solution much faster than machining parts or creating pre-production MIM mold tools.

This process also gives the team greater confidence in their mold design before investing in steel to fabricate a metal production tool, which helps to reduce risk.

With the ability of metal binder jetting to provide pre-production-ready parts so quickly, PTI Tech believes that it will soon be used instead of machining to build prototype parts for many of its clients. Binder jetting can also be used for limited bridge production runs so that customers can start assembly while production tools are being made. Furthermore, it can produce lower volume end-use parts where the cost of tooling for metal injection molding may be cost-prohibitive. According to PTI Tech, considering the time and cost savings from the elevator button project, there is no doubt that binder jetting represents a significant competitive advantage for PTI Tech and its customers.

“Binder jetting enables us to reduce our development time and test multiple ideas in parallel, finalize the part design, and go straight to production tooling.”

– Neal Goldenberg President