THE ENGINEERIST: Designing with Moldability in Mind

Editor’s Note: The Engineerist is a three-part blog series written by Michael Corr, founder of Los Angeles-based manufacturing consulting firm, DuroLabs. This is part three. The first two installments can be found here.

Intelligence does not automatically equate to experience, and in hardware, product development experience goes a long way.

I was recently hired to take over management of an engineering team at an early-stage company. A team of mechanical, electrical, and firmware engineers was already in place, and while I noticed they were younger than most teams I’ve managed before, I was incredibly impressed with their intelligence and creativity. That energy of young and enthusiastic engineers was a convincing factor for me to accept the position.

An Introduction to Manufacturability
Since the team had already released products to customers, I took a passive approach and just observed the established processes while they worked on the next version of the product. I injected comments and feedback on occasion, but trusted them to repeat their existing methods as they prepared for production. However, the more I got involved in reviewing the designs, I realized there was a common theme across the younger engineers—moldability was not factored into their designs. Many of the mechanical prototype parts coming off the Stratasys desktop 3D printer were designed to satisfy the performance requirements, but would at best, be expensive to manufacture, and at worst, impossible.

Adding draft angles to design helps facilitate ejection of a part from a mold, and improves overall moldability. The exact degrees of draft angles are dependent on part geometries.

I took several of the MEs aside and asked a few direct questions challenging them on how they envisioned an injection mold being designed for their parts. Blank stares were the only answers I received. I pointed out that one design had an undercut and another had no draft angles for clean part ejection. Again, blank stares. That’s when I realized that these engineers had become trained on producing parts using 3D printing tools only. While 3D printing has a made tremendous impact in prototyping and even production-grade parts, it also has its caveats. Continue reading

Overmolding: Chemical and Mechanical Bonding

Learn more about overmolding in our free webinar we’re hosting with RTP Company on Tuesday, Nov. 15 at 1 p.m. CT. REGISTER TODAY!

Overmolding is not a new manufacturing technology, but there is still some confusion about how to design for the two-part process. One of the largest areas to consider? Bonding. A number of materials can be used to overmold components together, but without a chemical bond or mechanical interlock, some overmolded parts won’t stand the test of time.

Chemical Bonding
This bonding process involves two chemically compatible materials that are molded together to form a strong bond with each other. It’s important to note that not all materials play well with one another.

The compatibility chart below indicate whether a chemical or mechanical bond is recommended for key thermoplastic and thermoset materials.

mechanical bonding

Three types of mechanical bonding techniques.

Mechanical Interlocking
What happens when your materials are not compatible, the desired bonding strength cannot be achieved, or you want to ensure your materials don’t peel apart from repeated use? This is where designing a mechanical interlock, which physically holds the overmolded material to the substrate, makes sense. There are many ways to design these into parts (see example), so discuss the options with your manufacturer.


Learn more about overmolding in our free webinar we’re hosting with RTP Company on Tuesday, Nov. 15 at 1 p.m. CT. REGISTER TODAY!

If you have further questions regarding rapid overmolding at Proto Labs, contact one of our application engineers at 877.479.3680 or

VIDEO: Lockheed Martin Drone Takes Flight with help from Proto Labs

The drone market in the U.S. is expected to soar to an $82-billion industry in the next decade, the New York Times recently reported. With that robust market in mind, Lockheed Martin, the aerospace, defense, and technology giant, developed a small, fold-up, lightweight drone, the Indago Quadcopter UAV (unmanned aerial vehicle), turning to Proto Labs for quick-turn prototyping and low-volume production.

Proto Labs’ automated design for manufacturability (DFM) and quoting system was especially helpful in taking the Indago from 3D-printed prototypes to injection-molded parts, and getting finished parts delivered in days and weeks. The video tells the story:


Rapid Overmolding: Consider These 3 Elements

Injection molding is a common, cost-effective method for manufacturing parts, but, sometimes, those parts need a little help. Low impact or vibration resistance, slippery surfaces, poor ergonomics, and cosmetic concerns are only a few of the reasons why a second molded part is often added as a grip, handle, cover, or sleeve.

Proto Labs now offers rapid overmolding for parts, including the three samples pictured here.

The process of rapid overmolding will get the job done. This method, which Proto Labs now offers, and is the focus of our October design tip, uses a mechanical or chemical bond (or both) to permanently marry two parts together.

This month’s tip discusses:

  • Bonding: A strong bond between the two materials is critical to overmolding.
  • Materials: This is a key consideration in overmolding.
  • Principles: Overmolding uses the same playbook as injection molding, but with a few quirks.


THE ENGINEERIST: Mitigating Production Risk with Prototypes

Editor’s Note: The Engineerist is a three-part blog series written by Michael Corr, founder of Los Angeles-based manufacturing consulting firm, DuroLabs. This is part one.

Startup companies have limited time and money, and, rightfully so, treat them as precious resources. There is constant pressure to get products out to the market fast, and when cash is limited, there is little margin for mistakes.

As an engineering manager, my responsibility is to ensure that the development processes being used by my team to bring parts to production are reliable, repeatable, and properly mitigate risk. For high-volume production, injection molding is the best option for plastic parts but it can be expensive and time consuming—two factors that can severely impact the success of a product launch if there are mistakes.

Waiting 12 to 16 weeks for first articles off a steel mold can be an eternity for a company pressured to get products into production in a shortened nine-month time frame. Any delays only compound the issue, adding pressure on myself, my team, and the company as a whole.

CAD model

Analysts at Proto Labs prepare CAD models for manufacturing.

Automated Quoting
When I was first introduced to Proto Labs almost 10 years ago, I was impressed with its commitment to leveraging modern technology. Its quoting process was simple and quick due to automated online tools. This allowed me to independently configure part options without having to go back and forth with a sales rep to update quotes and lead times. The automation saves hours, if not days, in evaluating various options. Additionally, the design for manufacturability feedback tools, which automatically highlight problems and areas of concern in the parts, save days to weeks of time and potentially hundreds to thousands of dollars by alleviating the risk of re-spinning due to an erroneous part. Again, with time being a limited commodity and a close watch on development dollars, these attentions to detail were very important to me.

The Case for Milled Prototypes
Prototyping before production is necessary to mitigate this risk but it can potentially cost money and take time to produce parts, so it’s important to choose your prototype runs wisely. One risk-mitigating technique I’ve incorporated into my mechanical engineering team’s process is to always produce a CNC-milled prototype of any part that is identified to be injection molded for production. This seems like trite advice, but I was amazed at how often engineering teams overlook the value of this step. Even 3D printing, another valuable prototyping tool, is often not as effective as a milled part if a move to molding is imminent. The advantage of the milled part is a closer approximation to the final molded material properties—not only in strength but also look, feel, and toughness when handled.

CNC machining

Proto Labs has hundreds of CNC machines, which enable quick-turn milling of functional prototypes and production parts.

I have now built several dozen parts with Proto Labs, so I can attest to the quality and expediency of the parts. In just a few days and not much investment, one can have several milled parts in-hand and ready for evaluation. Proto Labs’ extensive library of material options has also allowed me to select the same exact plastic to be used in the eventual injection-molded parts. This flexibility paired with comparable tolerances and resolution to final injection-molded parts, allows me to reliably use milled prototypes for a full form and fit check. In many cases, I can even use the parts for structural and environmental performance tests, so we can evaluate and make any final tweaks before cutting steel without having to cross our fingers that nothing goes wrong.

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