A miniature fiber Bragg grating sensor for inner stress measurement in powder compression molding

Powder compression molding is an important manufacturing technology for medical tablets, powder metallurgy, and explosive forming. Necessary monitoring means are lacking for inner stress measurement in the compression process. To solve the problem, a miniature fiber-optic pressure sensor for inner stress sensing is proposed. A femtosecond laser-inscribed fiber Bragg grating sealed into a miniature stainless steel capillary was used as the stress sensing element. An inner stress as high as 250 MPa was successfully monitored in the compression molding of sodium sulfate. A high pressure sensitivity of -2.33 pm/MPa and a linearity of 0.999 were achieved in the compression molding process. The sensor may find applications in powder compression molding of various industrial manufactures.