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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WEBINAR: How to Choose the Right Thermoplastic with PolyOne

With thousands of thermoplastics on the market, selecting the right material for a run of injection-molded parts can be intimidating. To help make the process more manageable, we’re teaming up with the plastics industry leader, PolyOne, to host a webinar with tips on choosing the right thermoplastic material for your application.

TITLE: Thermoplastics: How to choose the right material for your application
PRESENTER: Jeremy Bland, Technical Dev. Engineer, PolyOne
DATE: Thursday, September 22 at 1 p.m. CDT
REGISTER: Click here to sign up

The presentation will include the following:

  • Factors in thermoplastic material selection
  • Overview of common thermoplastics including the effects of additives
  • An open Q&A session

Busy that day and can’t make it? Not a problem. You can still register and we’ll send a link to a recording that can be watched on-demand. As usual, feel free to forward to a colleague know if you think he or she will be interested in attending.

Injection Molding: Aluminum vs. Steel Tooling

Aluminum molds are milled in rapid CNC machines.

Conventional injection molding typically uses steel tooling capable of producing millions of parts, however, it often takes months to manufacture a mold and a capital investment of $50,000 or more. But what if production demands call for smaller quantities? That’s where aluminum tooling is ideal. Here’s a quick look at the differences between steel and aluminum tooling.

Low-Volume Production with Aluminum Tooling

  • Mold production AND parts within 15 days or less
  • Low manufacturing costs with molds beginning around $1,500
  • Production quantities of up to 10,000 parts or more; depending on material type and geometry, some molds are capable of producing hundreds of thousands of parts
  • Simplified mold designs decrease manufacturing time and cost
  • Single and multi-cavity tooling: 1-, 2-, 4- and 8-cavity molds are possible depending on part size and complexity
  • Thermoplastic and thermoset materials identical to that of high-volume production materials; more than 100 different materials can be used including ABS, PC, PP, LCP, POM, and liquid silicone rubber
  • No maintenance fees and lifetime replacement of mold if damaged
  • Improved heat dissipation and without the need for messy cooling lines
  • Inexpensive mold-safe tooling modifications

High-Volume Production with Steel Tooling

  • Lower part cost when quantities increase
  • Part production in the millions
  • Multi-cavity tooling greater than 8 cavities
  • Part complexity can be increased
  • More finishing options

If you part volumes don’t stretch into the millions, if you need on-demand production parts within days, and if you’re looking to avoid risky tooling investments before your part design is truly validated, low-volume injection molding with an aluminum tool might be good option.

Once an aluminum mold is ready, part production begins almost immediately. This allows manufacturing to finish every order in three weeks or less.

At Proto Labs, we include a free interactive design for manufacturability (DFM) review within a few hours in every injection molding quote. In the time it takes to get the initial quote from a high-volume production molder, you can have several design reviews and a mold already in production.

If you have any further questions about rapid manufacturing at Proto Labs, check out protolabs.com or contact one of our application engineers at 877.479.3680 or customerservice@protolabs.com.

TIPS WITH TONY: New Silicone Rubber Materials

We’ve expanded our selection of liquid silicone rubber (LSR) materials, which have some distinct elastic and optical advantages over certain thermoplastics. In addition to three durometers of general-use Elastosil LSR, and medical- and optical-grade Dow Corning materials, we now have two new durometers of Elastosil and a fuel-resistant flourosilicone material at Proto Labs.

Elastosil LSR
Elastosil LSR is a great general-use material that has good moldability characteristics, a good overall appearance and is transparent until colorant is added. Shore A durometers of 40 and 60 have been added our current offering of 30, 50, and 70 durometers.

Technical specs:

  • 40 durometer Elastosil has a tensile strength of 10.0 N/mm² with a tear strength of 33 N/mm and an elongation break of 610%.
  • 60 durometer Elastosil has a tensile strength of 9.40 N/mm² with a tear strength of 27 N/mm and an elongation break of 340%.

THE SHORT LIST: 4 Ways to Leverage Rapid Overmolding

Rapid Overmolding is the latest addition to our injection molding service. Now, you have a fast way to create injection-molded parts with two different materials. We use a pick ‘n place method.

rapid overmolding services sample

That means we follow a two-step process. First we mold the substrate part. Then we place the substrate part into the mold and a second material is injected to form the final, two-material part.

Here are a few benefits of rapid overmolding.

Vibration dampening: Dampen vibration by adding liquid silicone rubber to parts made of hard plastic, like ABS, or if it’s a handhold device (think toothbrush), it can even be used to improve grip.

rapid overmolding services sample orange partMulti-color aesthetics: Add a stylistic flair to your product with overmolding. Using two materials, means two colors for high-quality looking products and can enhance your product’s design.

Fast, flexible volumes: Often, manufacturers will not process low-volume overmolding orders, but now you have the ability to manufacture 25 to 10,000+ overmolded parts within just a few weeks.

Simplify multi-part assemblies: Reduce cost and save time spent assembling parts by combining two materials in one molded part.

For information on rapid overmolding like designing mechanical interlocks or understanding chemical bonding compatibility, visit our rapid overmolding service page to see overmolding design guidelines and get free DFM feedback.