Powder supplying and spreading device for 3D printer

The invention discloses a powder supplying and spreading device for a 3D printer. Powder supplying and powder spreading are finished in one mechanism, so that the size of the overall printer can be set according to the actual requirements; a scraper is set into a form of a scraper blade; metal 3D printing powder can also be scraped to be smooth even if the scraper blade is damaged due to long-term use or collision by external force; the powder spreading quality is ensured; the powder is supplied according to the requirements by controlling the rotating speed of a powder spreading shaft; the automation degree of the overall powder spreading device is relatively high; fore-and-aft two-way powder spreading can be achieved by virtue of a bilaterally symmetric structure; the work efficiency is high; and a powder level induction device is arranged, so that real-time detection on the amount of the powder in an inner cavity can be carried out; and automatic supply of the metal 3D printing powder in the inner cavity is achieved according to the detection information of the powder level induction device.