A common design feature seen in injection molded parts is the use of lettering and logos. Designers use this feature for many reasons; to illustrate a brand identity, convey important end user instructions, aid in assembly, or display a part number or legal warning. The injection molding process allows lettering and other surface decorations to be easily incorporated into plastic parts. Once the lettering has been incorporated into the mold, each part will display the feature with few or no extra steps. This can save a significant amount of money by eliminating the expense of adhesive or painted labels.

Recessed vs Standoff Lettering & Logos

When applying lettering or logos to a mold, you will need to indicate whether you want your lettering to appear as recessed into the part or raised off of the part (also known as stand-off). This decision determines how your mold will need to be cut. For economic reasons, lettering is generally engraved into the mold which appears as raised letters on the parts. This enables the mold to be polished which provides a better finish on the surface of the parts. Engraving into the mold also extends the life of the mold since you do not have raised small features that wear faster than others. 

The Rules of Lettering & Logos

Engraved lettering or logos in the mold, if not done properly, can cause imperfections in the final part such as streaks, tear drops or flow marks around the features. These defects are usually caused by improper material flow into the letters. The following rules will help you to avoid these problems in your molded parts:

Rule of Thumb #1: Apply a radius to all sharp corners of the lettering. Deep, sharp lettering can lead to defects from air trapping in the mold.

Rule of Thumb #2: Limit the depth or height of lettering into or out of the part surface to approximately 0.010”. Letters and logos raised higher than 0.010” are unnecessary as they seldom wear out during the life of the part.

Rule of Thumb #3: Don’t forget to draft your features. The letter or logo sidewalls should have a draft angle of at least 3o to ensure proper fill.