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.

TIPS WITH TONY: Prototyping with Soft Metals

Soft metals — aluminum, magnesium, brass, copper — are available in different grades at Proto Labs depending on the 3D printing, CNC machining and injection molding service chosen. Quantities range from 1 to 5,000+ parts in 1 to 15 business days.

Aluminum engine bracket 3D printed through DMLS.

Aluminum
At Proto Labs, we use the industrial 3D printing process of direct metal laser sintering (DMLS) to build parts from soft (and hard) materials like aluminum.

DMLS-built aluminum provides parts with excellent strength-to-weight ratios, temperature and corrosion resistance, and provides good tensile, fatigue creep and rupture strength. With a tensile strength of 37.7 ksi (260 MPa) and a hardness of 47.2 HRB, for example, you are able to have parts produced in nearly any part geometry with features like internal channels or complex undercuts that can’t be manufactured through any other method. And, final parts are still up to 98% dense.

You can also get aluminum parts using CNC machining in 6061 and 7075 grades. 6061 can provide you with improved corrosion resistance and can be welded while 7075 provides you a part that has a higher tensile strength and is harder than 6061.

Do you need a prototype of an aluminum die-cast part? We can mimic aluminum die casting using our stereolithography (SL) process and SLArmor technology. SLArmor uses our DSM Somos (NanoTool) material, applying a nickel metal coating that gives the look and feel of metal without the added strength or weight.

 

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TIPS WITH TONY: Can 3D-Printed Parts Take the Heat?

Here’s a question that’s often asked: How do materials used in 3D printing compare to injection-molded thermoplastics when the temperature rises? To answer that, I’ll briefly dissect the materials used in stereolithography (SL) and selective laser sintering (SLS) processes as these are commonly compared to injection molding.

Stereolithography
SL involves a thermoset resin that is solidified by an ultraviolet laser, followed by a UV post-curing process to completely solidify the resin. As far as material properties, the big takeaway is that SL parts are built from thermoplastic-like resins, so they do break down over time in direct UV light.

SL uses materials that mimic ABS, polypropylene and glass-filled polycarbonate, and they offer an array of material properties still exist. But today we’re concerned with the thermal properties of the materials that are best suited to handle the heat — 3D Systems Acura 5530 and DSM Somos NanoTool. Both are offered in post-cured states and there’s an additional process for thermal post-curing that increases the operating temperatures.

The chart shows optimal heat deflections for SL materials. The other materials offered in SL have a much lower heat deflection ranging from 120˚F to 177˚F.

Material

UV Post-Cure

UV Post-Cure +
Thermal Post-Cure

3D Systems
Accura 5530

85˚C (185˚F)

250˚C (482˚F)

DSM Somos NanoTool

225˚C (437˚F)

263˚C (506˚F)

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