UL 94 is a plastics flammability standard released by the Underwriters Laboratories (USA). The standard classifies plastics according to how they burn in various orientations and part thicknesses from the lowest flame-retardant to most flame-retardant in six different classifications.
UL 94 Rating
Definition of Rating
| Slow burning on a horizontal part.
| Burning stops within 30 seconds on a vertical part allowing for drops of flammable plastic.
| Burning stops within 30 seconds on a vertical part allowing for drops of plastic that are not inflames.
| Burning stops within 10 seconds on a vertical part allowing for drops of plastic that are not inflames.
| Burning stops within 60 seconds on a vertical part with no drops of plastic allowed but may burn through the part.
| Burning stops within 60 seconds on a vertical part with no drops of plastic allowed and cannot burn through the part.
We recently hosted a 30-minute webinar on: Choosing the Right Rapid Manufacturing Method for Plastic Parts. If you missed it, no worries. You can still watch it on-demand HERE.
What did you miss?
We discussed the benefits of rapid manufacturing for plastic components and how to select the correct manufacturing process:
- 3D printing, machining and molding processes and specifications
- Material selection and properties for each process
- Advanced molding materials like thermally conductive plastic and liquid silicone rubber
Top 3 Questions Asked
How long will you keep a mold and do you inform the customer if you’re going to get rid of it?
We’ll store the mold for one year from the last order unless it is requested to keep in storage, and we’ll notify the customer of inactivity to if they would like the mold disposed of or retained in storage.
Is there any limit on volume for injection-molded parts?
No, you can get injection-molded parts in quantities of 25 to 10,000+ with several molds even surpassing 100,000 parts. We have the ability for single and multi-cavity molds dependent on size and complexity.
Can Proto Labs be used for light pipe assemblies in PC, PMMA and silicone?
Yes, we have molded countless parts in those materials for light pipe assemblies. Mold finish should be polished to a SPI-A2 with special attention made to the mold build for ejector pin location, gate location and parting lines.
Look for additional technical webinars throughout the year on various 3D printing, CNC machining or injection molding topics. The next webinar will discus how to navigate through Proto Labs’ design for manufacturability (DFM) feedback.
Did you know that living hinges are possible with 3D printing? Here are a few things areas to keep in mind when designing hinge functions so your part’s functionality and integrity remain intact.
We offer two processes for 3D printing thermoplastic or thermoplastic-like materials: selective laser sintering (SLS) and stereolithography (SL). But only SLS will produce parts with the functionality required for a living hinge.
An SLS part with living hinge functionality.
Anytime we see the potential for a living hinge in a 3D-printed part, we will strongly guide you to SLS. SLS uses nylon thermoplastic, primarily PA 850 Black, which is a nylon 11 material. PA 850 has an increased EB of 14-51% followed by ALM PA 650 with an EB of 24%.
However, you can’t take a part that was produced in PA 850 or ALM PA 650 and expect it to function as a living hinge without a secondary process first. When you have a living hinge, we need to know what direction or the range of motion in which the hinge may function. This is critical as we anneal the part by heating it to 250-275°F and flex the hinge in the intended range of motion. This extends the life of the living hinge by stretching the material instead of fracturing the links of resin.
SL offers thermoplastic-like materials, but they are not be recommended for living hinge applications. Somos 9120 is our most flexible material of all SL resins with an elongation at break (EB) of 15-25%.
To decrease weight and potentially cost, you can replace metal with plastic on certain parts through 3D printing and injection molding. At Proto Labs, we use industrial 3D printing process stereolithography (SL) to produce thermoplastic-like parts that have a nickel coating on the surface. This offers the increased strength of aluminum die-cast components, without the weight. With injection molding, the introduction of thermally conductive plastics has broken new ground when looking for heat dissipation of expensive heat sinks.
Stereolithography parts built with SLArmor have a metal coating applied over a thermoplastic-like base.
SLArmor involves a ceramic-filled DSM Somos material, which has a metal coating applied to achieve the look, feel and, most importantly, comparable strength of aluminum without added weight. SL is a cost-effective prototyping method for initial parts that mimic metal before moving to higher volumes of die-casted parts.
The material properties of SLArmor are greatly improved in regards to heat deflection, tensile strength, elongation at break and elasticity. The chart below shows exactly how the material relates to die-cast aluminum in three different thicknesses that can be applied based on geometry of SL parts. Note that the thickness of the nickel plating may vary on each part due to the ability to apply the coatings.
The big lighting and optics show, Strategies in Light, starts today in Santa Clara, California. We’ll be talking with designers and engineers over the next three days about how industrial 3D printing, machining and injection molding processes can help them develop well-designed, more efficient products and devices. Track us down at booth #102.
One topic that is certain to dominate the conversation is the relatively new thermoset material, optical liquid silicone rubber (LSR), which has many advantages during lighting development versus plastics like polycarbonate and acrylic.
Optical liquid silicone rubber prototype from automotive company MagWerks LED.
Optical LSR is changing the lighting industry with its superior material and optical properties that improve:
- heat resistance
- UV stability
- light transmission
In addition to ongoing optical LSR discussions in the booth, we’re co-hosting a presentation with Dow Corning on prototyping with optical moldable silicone on Wednesday, March 2 at 1 p.m. in the presentation theater. Proto Labs’ global segmentation manager Jeff Schipper and Dow Corning senior application engineer John Nelson will cover why optical LSR works well for prototyping and low-volume injection molding and the results of recent research on implementing aluminum versus steel tooling when molding with optical silicone.
We hope to see you at the show!