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Radiation Shielding using 3D Printer Filament

Radiation Shielding Components using GMASS Introduction

GMASS is now for sale on MakerGeeks.com here: GMASS

GMASS is a high-density 3D printer filament designed for use with Fused Deposition Modeling (FDM) printers. It is manufactured using ABS base material that is filled with heavy-metals or metal oxides to add density. These heavy fillers act very much like lead for absorbing x-rays, allowing the user to make radiation shielding components using 3D printers. The fillers are non-toxic, and meet ROHS restrictions for import of hazardous materials into Europe.

There are 2 main varieties of GMASS. Bismuth oxide filled ABS is available in densities up to 2.7 g/cc. This material has a basic yellow/green color, which is light enough that the material can also be supplied in blue or red configurations. It is electrically insulating for those applications where it is near high voltage. The other variety is tungsten-filled ABS, which is available in densities to 4.0 g/cc. Because the tungsten fill material is black, it is not possible to color this GMASS beyond “dark gray.” While not electrically conductive, this material is not as insulating as the bismuth filled material.

The approximate lead-equivalent thicknesses (LE) for radiation shielding applications are shown in Table 1.
(Table 1) Approximate Lead-equivalent thickness of GMASS material.
Note that this table assumes 3D printing at 100% fill density.
Lead (Pb)
Bismuth-filled GMASS
Tungsten-filled GMASS
Density
11 g/cc
2.7 g/cc
4.0 g/cc
Thickness for 1mm LE
1.0 mm
4 mm
2.8 mm
 

The following examples show uses of the 2 materials and provide the user with some design considerations.

Example 1 – Rapid Prototyping

Our first example is a scatter shielding component for a dental x-ray source. In production, the part is injection molded from ECOMASS high density engineered thermoplastic. The manufacturer wanted to make some design changes to the scatter shielding. Before making changes to the injection mold, the design needed to be evaluated with a rapid prototype. The prototype part was manufactured using bismuth-filled GMASS on a Makerbot 3D printer. (See Figure 1)

Following engineering evaluation, the injection mold modifications were performed. Bismuth-filled GMASS was chosen because it most closely matched the
density of the ECOMASS material to be used in the final
product.


There are a number of manufacturers of high density polymer-metal composite materials for injection molding. Some representative examples are shown in Table 2 below. This list is certainly not comprehensive, and is intended to provide guidance on GMASS material selection for rapid prototyping these injection-molding materials.
(Figure 1) Secondary scatter shield made from Bismuth-filled GMASS for a dental x-ray device.
page1image22280
Lead (Pb)
Bismuth-filled GMASS
Tungsten-filled GMASS
Density
11 g/cc
2.7 g/cc
4.0 g/cc
Thickness for 1mm LE
1.0 mm
4 mm
2.8 mm
page1image32328
page2image1440
GMASS Type
Possible ECOMASS compounds
Possible GRAVI-TECH compounds
Bismuth-filled (2.7 g/cc)
4703BI74 (2.6 g/cc)
706BI76 (2.5 g/cc)
GRV-NY-027-SS-BLK-F (2.7g/cc)
Tungsten-filled (4.0 g/cc)
4301TU74 (3.8 g/cc)
GRV-NY-050-CU Natural (5.0g/cc)*
720ZC85 (4.0 g/cc)
(Table 2) Appropriate GMASS configurations to rapid prototype for injection-molding materials. *For radiation shielding applications, higher specific gravity materials can be rapid prototyped by increasing the wall thickness of the prototype part so that the areal density in g/cm2 matches the areal density of the finished part.

Example 2 – Additive Manufacturing
A manufacturer of a medical x-ray system had us 3D print a prototype primary beam collimator from tungsten-filled GMASS. (Figure 2) Normally they would have used lead for this component, but GMASS allowed them to achieve the same level of radiation shielding while working with an eco-friendly material that could be rapid-prototyped.

Another manufacturer of x-ray source assemblies needed a shielding cap to block leakage radiation. Again, GMASS provided the design flexibility to put shielding exactly where it was needed, without added weight by using lead foil in places that it was not needed. (Figure 3) The GMASS reduced the overall weight of the x-ray source assembly. In both these cases the production quantities are low enough that the manufacturers will use 3D printing as the primary production methods for these parts.

Advantages of GMASS
Rapid prototype high density components
Evaluate shielding properties before you go to hard tooling Eliminate lead (Pb) – increased safety and certifications
Design Flexibility – add mass only where needed
page2image30184

GMASS is now for sale on MakerGeeks.com here: GMASS

Comments

  1. Great information getting about the "Radiation Shielding" use of 3D Printer Filament

    ReplyDelete
  2. Hi, I am trying to make a 3D printed anti-scatter collimator, I wonder how did the tungsten filament material perform. It would be easier to evaluate the performance if we knew the components but I suppose because of confidentiality I could not find it on the net. I have three questions:

    1. Is this Tungsten filament the best available filament to 3D-print a collimator or there are other filament that would serve this purpose better than this (higher density than 4 gr/cc)?
    2. How is the performance of this material for shielding?
    3. Does any one know the percentage of the materials used to compose this tungsten filament?

    I really would appreciate any help to find the answer for these questions.


    Thank you so much in advance.
    Maida Ranjbar
    maida.ranjbar@gmail.com

    ReplyDelete

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