PMMA (Acrylic)

CNC Machining / Light Weight + Corrosion Resistance

Introduction

PMMA, also known as acrylic, is a transparent thermoplastic. One of the most widely used plastics in the world, PMMA demonstrates good chemical stability, mechanical properties and weather resistance. The material is also easy to process and to dye.

Because of its transparency, PMMA is often used as an alternative to glass and is popular in the interior design, construction and chemical industries. It is also regularly used in advertising to fabricate signage, lightboxes and billboards.

Surface Finish

Bead blasting

Bead blasting results in parts with a smooth surface with a matte texture. Used mainly for visual applications and can be followed by other surface treatments.

Painting

Painting the surface of a part improves its aesthetic appearance and can provide brand recognition to consumers. In addition, painting can have a protective effect on parts.

Polishing

Polishing is the process of creating a smooth and shiny surface, either through physical rubbing of the part or by chemical interference. The process produces a surface with significant specular reflection, but in some materials is able to reduce diffuse reflection.

Manufacturability

Tolerance

- Standard: (+/-) 125 µm -Achievable: (+/-) 100 µm , (+/-) 50 µm

Wall Thickness

- The minimum wall thickness should be at least 1 mm for machined parts. - 2 mm is suggested for better strength and 2.5 mm for a rigid wall.

Pocket depth

- Pocket depth should be up to 3 times the diameter of the end mill

Engraving

- Engraving is preferable to embossing - For the clear, legible text consider fonts such as Arial or Gothic - Design letter strands with a width of at least 2 mm

Internal Radii

- The minimum internal radii possible is 1 mm - In general, internal radii dimensions depend on the depth of pocket being milled

Holes

- Use standard drill bit sizes - Minimum of 1 mm in diameter

Threads

- Use standard metric inserts - Smallest threaded insert possible is M2

Design Recommendations

Min Wall Thickness

0.5 mm (0.01 in)

Min End Mill Size

0.8 mm (0.03 in)

Min Drill Size

0.5 mm (0.02 in)

Max Part Size

1200 x 500 x 152 mm [(x,y,z] (mill) 152 x 394 mm [d,h] (lathe)

Undercuts

Square profile, full radius, dovetail profiles

Radii : Depth

Depth must not exceed 12x drill bit diameter. For end mills, depth must not exceed 10x drill bit diameter.

Engineer's Pro Tips

PMMA has the highest transparency of any plastic. Though its strength is not as high as other thermoplastics on the market, it is over ten times stronger than ordinary glass, making it a popular alternative to glass.
It should be noted that the material does have low impact resistance, meaning it cracks easily. It is also susceptible to scratching and visible wear and has low heat resistance (up to only 80 °C). It does, however, have good weather resistance, and is unlikely to change color or transparency in extreme climates.