Surface Texture Chart

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The Agie Charmilles (CH) scale originates from the Electrical Discharge Machining (EDM) process, where surface roughness is defined by the energy and duration of each spark. Higher discharge energy produces a coarser texture (higher CH number), while fine finishing passes create smoother surfaces (lower CH numbers). The scale provides a practical EDM-based reference for correlating process parameters to surface finish.

Textured surfaces require additional draft to prevent drag or scuffing during ejection. As surface roughness increases, more draft is needed to allow smooth part release and protect both the molded surface and the texture detail.