TIPS WITH TONY: Replace Metal with Plastic to Save Weight, Cost

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.

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TIPS WITH TONY: High-Temperature Thermoplastics

We offer two high-temperature thermoplastics: PEEK and PEI. Both high-performance materials can be machined and injection molded, and produce parts that can withstand extreme temperatures.

PEEK
PEEK parts contain excellent mechanical and chemical resistance during high-temperature applications. Its mechanical properties consist of tensile modulus strengths of 90-200 MPa and a melting temperature of 662˚F (343˚C). Some grades of PEEK have operating temperatures around 482˚F (250˚C).

Because of its robustness, PEEK is commonly used in applications for mechanical and medical instruments. PEEK is also used widely in the aerospace, automotive and chemical industries due to the insulating properties and creep resistance of any dimensional changes in high-temperature applications.

PEI
Like PEEK, PEI (often called by its trade name Ultem) offers outstanding elevated thermal resistance, high strength, stiffness and chemical resistance. PEI consists of tensile modulus strengths of 96-190 MPa and with a melting temperature above 420˚F.

PEI is available in transparent and opaque colors including glass additives for improved mechanical properties. Unlike other thermoplastics, PEI provides optimal strength and resists stress cracking when the material is exposed to hydrocarbons, alcohols and acids that makes them ideal for automotive and aerospace applications.

Which Manufacturing Process is Best?
If you’re in need of small quantities (up to 200) of PEEK and PEI parts, we can machined them in less than 3 days. For increased quantities in the thousands, rapid injection molding can produce parts in 15 days or less.

The physical properties vary little between processes, so please test out one sample using machining before moving to injection molding if you are unsure if your parts design is complete or not.

Contact us if you have any further questions about high-temp plastics and specific questions regarding PEEK or PEI. We have a full staff of customer service engineers who can be reached at customerservice@protolabs.com or 877-479-3680.

TIPS WITH TONY: The Material Properties of Machined Plastic

If your ultimate product development plan involves a move to injection molding, CNC machining offers a material selection conducive to a transition into increased molded quantities. Proto Labs has more than 30 engineering-grade thermoplastic materials with various benefits.

To illustrate the material properties better (Figure 1), we took four frequently used thermoplastics — ABS, polycarbonate (PC), polypropylene (PP) and nylon polyamide (PA) — and compared the maximum heat deflection, tensile strength and elongation at break that occurs within injection molding, machining and 3D printing.

ABS Molded

ABS Machined

ABS-like SL

Heat Deflection

215°F

214°F

138°F

Tensile Strength

6,091 psi

6,100 psi

7,800 psi

Elongation at Break

30%

40%

6-20%

PC Molded

PC Machined

PC-like SL

Heat Deflection

280°F

280°F

482°F

Tensile Strength

10,442psi

8,000 psi

11,300 psi

Elongation at Break

100%

50%

1.0-13%

PP Molded

PP Machined

PP-like SL

Heat Deflection

203°F

210°F

142°F

Tensile Strength

5,801 psi

4,800 psi

7,250 psi

Elongation at Break

100%

14%

7-25%

PA Molded

PA Machined

PA SLS

Heat Deflection

410°F

370°F

370°F

Tensile Strength

16,500 psi

10,000 psi

6,946 psi

Elongation at Break

60%

25%

14-51%

Figure 1: Thermoplastic material properties compared between different manufacturing processes. Properties are dependent on actual material selected, part thickness and geometry. Please review each material data sheet individually as these are estimates.

Translation: CNC machining is ideal for functional prototyping and end-use production parts, and readies your design for an eventual move to injection molding. We have a full staff of technical experts that can answer any machining questions you have at customerservice@protolabs.com or 877-479-3680. For more information on 3D printing, CNC machining or injection molding at Proto Labs, head over to protolabs.com.

TIPS WITH TONY: Mixing It Up with Plastic Colorants

Proto Labs’ material selection and available color options for thermoplastics can be found online at protolabs.com.

You may require colored resin or transparent coloring for your injection-molded parts, but exactly how much colorant is added and what consistency can you achieve?

Salt-and-Pepper Mix
Proto Labs offers colorant at no charge to most natural, white or clear materials. In most cases, we do this by adding a 3 percent salt-and-pepper mixture of colorant based on weight to the base resin, but on occasion, less colorant is added to transparent resins like polycarbonate.

A 3 percent salt-and-pepper colorant mix is typically used.

 

Since we hand mix the colorant and base resin, you may have a higher or lower concentrate of colorant throughout the order. The injection molding press does a good job of mixing the colorant and base resin when it melts and grinds the resin in the barrel before molding, but it isn’t 100 percent.

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TIPS WITH TONY: Prototyping with Hard Metals

Last week we discussed prototyping with soft metals like aluminum, copper and brass, so this week we turn our attention to hard metals and processes (3D printing, CNC machining and injection molding) used for rapid prototyping in low volumes.

 

SS 316

SS 17-4

SS 304

Nickel Steel

Steel Alloy

Titanium

Inconel

Cobalt Chrome

DMLS

X

X

 

 

 

X

X

X

CNC

X

X

X

 

X

 

 

 

MIM

X

X

 

X

X

 

 

 

Hard metals that are offered in three different manufacturing processes at Proto Labs: direct metal laser sintering (DMLS), CNC machining (CNC) and metal injection molding (MIM).

Stainless Steel
Stainless steel (SS) is one of the most widely used metals in our material library and is available in three different grades and all three services: 3D printing, machining and molding.

  • 304L is only available for machined parts and offers a higher tensile strength and good corrosion resistance while offering a slightly lower price than other stainless steel materials.
  • 316L is available in machining, industrial 3D printing through direct metal laser sintering (DMLS) and metal injection molding (MIM). 316 offers an improved corrosion and chemical resistance over 304 while offering a high temperature tolerance.
  • 17-4PH is also available in all three manufacturing methods and offers a higher yield and tensile strength with good resistances to corrosion. 17-4 also offers a higher magnetism of all our SS offerings.