About Tony Holtz

Tony is a technical specialist at Proto Labs with more than 10 years of experience ranging from CNC mill operator to mold designer to customer service engineer. While his formal education is in industrial machinery operations, he has extensive knowledge and experience in both traditional and advanced manufacturing processes and materials. Throughout his tenure at Proto Labs, Tony has worked with countless designers, engineers and product developers to improve the manufacturability of their parts.

TIPS WITH TONY: LSR Offers Design Flexibility

There are many reasons why you should be looking at liquid silicone rubber (LSR) — I’ll highlight a few big ones in order to get you thinking about this versatile thermoset.

For a deeper dive into LSR and how it’s used in the lighting industry, please attend my free tech talk webinar hosted by Tech Briefs.

LSR Molding
LSR parts are formed in process similar to that of conventional plastic injection molding with one main difference. LSR is a thermoset material that compounds two liquids together, which is then heat cured in the mold to produce a part. The material delivery system is cooled and only the mold is heated. This is unlike thermoplastic molding, which begins with the melting of plastic pellets that are injected into a heated mold.

Optical LSR is highly flexible and can replace glass in many lighting applications.

LSR Advantages
LSR parts are strong, elastic, chemical resistant, serializable and biocompatible, and have a range of operating temperatures. The benefits of LSR lend itself well to the automotive, medical and lighting industries where gaskets, seals and lighting lenses are frequently used.

LSR parts have a very good temperature resistance, ranging between -49°F to 392°F; they are non-yellowing, UV stable and optical LSR has up to 94 percent light transmission; they offer good vibration control and offer up to 400 percent flexibility along with excellent part memory.

The chart pretty much speaks for itself when comparing LSR to PC, PMMA and glass when looking at replacing the traditional materials with LSR.

Design Flexibility
Traditional thinking of part design needs to be considered, but many can be broken:

  • Part thicknesses greater than 1 in. and less than 0.020 in. are achievable with little to no concern of any unsightly sinks or internal voids.
  • No ejector pins are used to remove parts from the mold as they are all hand-removed.
  • Gates are nearly invisible, barely thicker than flash. LSR flows like water, so the gate needs to be very shallow, but wide.
  • Negative draft angles or increased undercuts are a possibility with up to 400 percent part flexibility and part memory.
  • Ability to fill fine details or voids.
  • Ability to combine components reducing number of parts to assemble, e.g., combining a lens and seal for lighting applications.

For more information on LSR, please download our white paper or listen in to my tech talk presentation mentioned at the top of the tip. You can also visit our website at protolabs.com or contact one of our customer service engineers at customerservice@protolabs.com or 877.479.3680 with additional questions on any of our services.

TIPS WITH TONY: Top 5 FAQs for CSEs

Proto Labs has a knowledgeable support staff able to answer nearly any manufacturing question you toss their way. If you haven’t already spoken to them, you should get to know our customer service engineers (CSEs) who can help guide you on your next additive manufacturing, CNC machining and injection molding project.

This is Tony from the popular blog series, Tips with Tony. He was a CSE for years and is now Proto Labs’ go-to technical specialist.

It’s challenging to assemble the top five most frequently questions asked — it should be more like a top 100 questions asked on a daily basis. But, I whittled it down to the top questions our CSEs are most frequently asked.

5. How many parts can you produce and how fast can I get them?

Additive Manufacturing
SL, SLS and DMLS:  1 to 50+ parts in 1 to 7 days

CNC Machining
Milling and Turning:  1 to 200+ parts in 1 to 3 days

Injection Molding
Plastic: 25 to 500 sample parts in 1 to 15 days with low-volume production of 10,000+ parts available

Liquid Silicone Rubber (LSR): 25 to 500 sample parts in 1 to 15 days with low-volume production of 5,000+ parts available

Metal: 25 to 100 sample parts in 10 to 15 days with low-volume production of 5,000+ parts available

Magnesium: 25 to 100 sample parts in 15 days with low-volume production of 5,000+ parts available

Please note that lead times are dependent on part size and current workload. As such, not all parts are eligible for a one-day turn and expedite fees may be applied turnaround times faster than standard delivery.

4. What manufacturing method(s) should I use?
First, let me ask you these questions to help you decide:

  • How many parts do you need?
  • Are these functional, cosmetic or just something to hold in your hand?
  • Do you know the material you want?
  • What type of finish do you need?

If you have a part total in mind, you can begin narrowing down the manufacturing method to either injection molding (for higher volumes) or additive manufacturing or machining (for lower volumes). Identifying the material you need will then allow you to narrow down your decision even further. Beginning with any one of these questions will start you down the correct path towards the proper manufacturing method.

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TIPS WITH TONY: Behind the Scenes with File Formats

Why can’t you read my CAD file? Wrong file format? What formats do you accept? In our latest tip, I’ll cover what file formats work best with each manufacturing service at Proto Labs and discuss common questions that occur.

Simply put, we accept several different file formats, but some work better than others. To begin, here’s our list of formats that can be uploaded to our website:

CAD Programs:

  • Solidworks (.sldprt)
  • Autodesk Inventor (.ipt)
  • AutoCad (3D .dwg)
  • PTC ProE/Creo (.prt)
  • CATIA (.catpart)
  • SpaceClaim (.scdoc)
  • SketchUp (.skp)

Neutral File Formats:

  • IGES
  • STEP
  • ASIS (.sat)
  • Stereolithography (.stl) — only available for additive and machining

Proprietary Software
We use proprietary software that is able to read or translate the file formats above. If you submit a format not listed, you’ll receive a no-quote and will need to upload a new file from the list of approved file formats in order to receive a quote. But if you submit a file from the list and you still receive a no-quote, there is a good possibility that the file was either corrupt or unable to be translated properly. In this case, we would suggest trying another file format, or multiple file formats, so we have options for translation. Or, reach out to one of our customer service engineers at customerservice@protolabs.com or 877.479.3680 to discuss a solution.

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TIPS WITH TONY: Mold Flow Analysis

Last week we discussed wall thickness by resin types, where we learned the importance of uniform wall thickness and provided a guideline on thickness based on your material selection. Another very useful resource in selecting materials is a mold flow simulator, which tests different resins and how they fill using accurate molding pressure.

Melt Flow Index
All materials have a different melt flow index (MFI), but what does this exactly mean? MFI is a measurement taken on how well a material flows at a high temperature through a specified diameter during a 10 minute test. This measurement for MFI is calculated into grams per 10 mins. Typically, higher numbers mean you have a much better flowing material that can fill thin wall geometry easier. But that doesn’t tell the entire story as a higher MFI doesn’t always mean that you won’t encounter any issues on thin part geometries. All materials have varying melting temperatures, so compare MFI between different families of materials such as polyethylenes and polypropylenes, which have about a 40° difference in testing temperatures.

Knowing the Material
Work with Proto Labs’ customer service engineers (CSEs) as soon as you begin quoting your parts and tell them what material you are considering having the parts produced in. Having this information early allows them to properly analyze part geometry for appropriate wall thickness using the MFI of the selected material. Often times, a part that is too large or has features that are too thin for a selected material will require an increase in wall thickness or an alternative material to be chosen.

Simulation
How does a mold manufacturer know the selected material will work? This is where the software takes over. Proto Labs uses a proprietary ProtoFlow® fill analysis program that is truly unique to our molding technique. We have several available materials that can be tested using a resin’s MFI and your CAD geometry.

The ProtoFlow simulation shows the resin fill of a part through a single gate location at the end of the part and the color represents the part filling through to completion.

After your CAD model has been uploaded, gate location and quantity of gates are selected based on your part’s geometry and material. A simulation is then run by our mold designers to review:

  • gate location
  • knit lines
  • incomplete fill
  • balanced fill
  • and most importantly, fill pressure

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TIPS WITH TONY: Wall Thickness by Resin Type

Knowing the material your parts are going to be manufactured in early on in your development process can save you time, money and a lot of frustration. You should work closely with your manufacturer during design, so they can help you identify potential material issues before any parts are actually molded. Because some part geometries inherently work better with certain resins, your manufacturer can help guide you toward the appropriate material options.

Issues that can result from selecting an incorrect material:

  • Warp
  • Sink
  • High fill pressure
  • Poor cosmetic finish
  • Shorting or burning
  • Brittleness

Uniform Wall Thickness
With injection molding, we talk a lot about how uniform wall thickness helps improve mold fill versus thin features that can restrict the material and create a number of the aforementioned issues. Having connected walls that are too thick and too thin can affect how a part cools, thus creating sink and warp. Furthermore, the same issues can arise if your entire part is too thick or thin.

 

Watch rib-to-wall thickness ratios. To prevent sink, rib thickness should be about half of wall thickness.

This is why the appropriate rib-to-wall thickness ratio must be followed. The appropriate thickness for a rib that is extruded from another surface is approximately half the thickness of the adjacent surface. This is the optimal part design to provide strength while at the same time reducing your chances for significant warp or sink. Learn more on uniform wall thickness in plastic parts on our website.

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