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

‘Strange Lenses’ Art Project Captures Cool Idea! Award

Call it digital manufacturing meets art.

Proto Labs’ latest Cool Idea! Award grant helped artist and engineer Robb Godshaw create the art installation “Strange Lenses.”

The project uses injection-molded optical liquid silicone rubber (LSR) lenses—designed by Godshaw and manufactured by Proto Labs—to create geometric distortions of people’s faces (similar to funhouse mirrors) when viewed from the other side. At the same time, the lenses created connections between strangers when they viewed each other through these distortions at the Strange Lenses art installation.

Photos Courtesy: Strange Lenses

Strange Lenses was a part of The Market Street Prototyping Festival, which occurred earlier this month in San Francisco, and will remain on display on the streets of San Francisco for two years as part of a public-art installation.

The Proto Labs award allowed Godshaw, who is also an Artist in Residence at Autodesk’s Pier 9 in San Francisco, to create the LSR lenses quickly, efficiently, and in time for the prototyping festival.

“I had tried 3D printing some lenses with other manufacturers, but the optical quality just wasn’t there,” Godshaw said. “When I met Proto Labs, I was blown away by its optical LSR—especially the speed and clarity.”

In addition, Godshaw said, “Optical LSR is robust and durable. You can’t scratch it, crack it, or melt it, so it’s perfect for my installation and for the millions of people who will interact with it over the next two years.”


THE ENGINEERIST: Fail Fast, Succeed Faster

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 two.

Certification testing is expensive, especially when your product fails.

I was managing an engineering team several years ago when we submitted a new product with an injection-molded enclosure to UL for certification testing. The tests included a mechanical stress test with some rather extreme impact forces. This product was a deviation to a predecessor and therefore had legacy requirements which constrained our design options. With the time pressure we had to get the product to market, the mechanical engineering team and I were hoping a few modest changes to the existing legacy injection mold would be sufficient to pass the new certification testing and go into production. They weren’t.

Logo Image: PR Newswire

Prototype Prep Before UL Testing
After a humbling blow to our egos and sizeable invoices from both the molder and UL, we took another approach. The ME team reviewed the points of failure of the plastic enclosure and came up with a few design improvements. But we didn’t want to risk failure again, and UL required testing parts fabricated from the actual production mold. It would be too expensive and risky if we were to modify the tool and fail again. Continue reading

Webinar: Designing for Selective Laser Sintering

This is the final part in our series of “Designing for 3D Printing” webinars. Just as we’ve looked at stereolithography and direct metal laser sintering in previous webinar, this presentation will provide insights into how to design for selective laser sintering (SLS), a discussion on material options, and recommended applications for SLS.

Post build

The presentation will include the following:

  • Comparison of SLS materials
  • Design guidelines for functional prototypes and production parts
  • Moldability considerations for effective development
  • Open Q&A session

TITLE: Designing for 3D Printing: Selective Laser Sintering
PRESENTER: Eric Van Roekel, SLS production manager
DATE: Thursday, October 27 at 1 p.m. CDT
REGISTER: Click here to sign up  

Can’t make it that day? You can still register and we’ll send you an on-demand version to watch when convenient. Also, feel free to forward this invite to your colleagues.