October 2005 Design Tip

Getting the Words Right

A picture may be worth a thousand words, but sometimes a few words or lines of text are all it takes to get your point across. If those words are going to appear on your plastic part, there are some important points to keep in mind. First, there are two general considerations. One is that text is usually among the smallest details on a part, so all factors affecting small details apply. The second is that the mould is the inverse image of the part. Raised text on the part is recessed text in the mould, while recessed text in the part is raised text on the mould.

The lower limit on text size is determined by the diameter of the smallest size end mill that can be used. For a part with raised text on a flat easy to reach surface the smallest feature that can be milled is 0.020in. (see Figures 1 and 2). If the text is at the bottom of a deep rib or next to a feature that requires the endmill to “reach” a significant distance, a larger diameter end mill may be required and consequently the text size may need to be larger.

In general, for ease of cutting and ease of reading, particularly at small sizes, bolded sans serif fonts are preferred. Also, whenever possible, add 2 to 5 degrees of draft.

Figure 1: In SolidWorks, Century Gothic/Bold/0.20” high will generally produce text we can mill.

Figure 2: This text is too small to mill.

Finally, because it is easier to polish around text that is recessed into the mould, for cosmetic reasons it is preferable if the text on the part is raised.