A recent customer of 3D Print Western was concerned with the heat deflection capabilities of 3D printed plastics. He was rapid prototyping a 17” diameter by 20” tall part that needed to remain stable while operating under high heat conditions. My marketing and finance textbooks did not cover heat deflection let alone the properties of each plastic. I had to do some digging. Below is some information I found from the internet and our team of engineers.  

My search started, like most people, with Wikipedia:

Heat deflection temperature is the temperature at which a polymer or plastic sample deforms under a specified load. This property of a given plastic material is applied in many aspects of product design, engineering, and manufacture of products using thermoplastic components.”

Wow, that was a mouthful! Essentially, a stress is applied on a sample’s outer edge through 3 point bending. The sample is then heated by 2 °C/minute until it reaches the temperature that cause the specimen to deflect a set amount (0.125” unannealed in our material’s tests). The temperature at the specified deflection point is then recorded. This material property is important to compare different plastics, and to know the maximum stable operating temperature in load-bearing parts.

If that is still confusing here is a YouTube video demonstrating a heat deflection test.

In my customer’s case, our first reaction was to use ULTEM 9085 as it has incredible thermal and corrosive resistance (something we like to call The ULTEM Advantage). ULTEM 9085 is a perfect material for inhospitable environments such as oil & gas or aviation. However, upon further review, ULTEM was a little overkill for this situation. Instead we opted to use Polycarbonate (PC) which is widely used in fields like automotive and medical.

The end result was a cost-effective part for my customer that met the heat deflection properties he required. Our customer was able to demonstrate his prototype to his end-user and in the end he won the contract. ULTEM 9085 is a great material but was a little excessive for this particular application.

If you are curious for specifics: here are common heat deflection properties of FDM 3D Print material using test method ASTM D648 (unannealed 0.125” deflection).


Material Heat Deflection @ 66 psi Heat Deflection @ 264 psi

ULTEM 9085

N/A 153° C
Polycarbonate 138° C

127° C

ASA 98° C

91° C


96° C

82° C

NYLON 12 97° C



Heat Deflection of 3D Printed Materials. FDM 3D printing material specifications. Additive manufacturing specifications for FDM thermoplastics under standardized heat deflection tests.