This flow pattern is mainly caused by the uneven melting of toner in TPU melt. Because the molding speed of TPU is slow, low injection temperature can help molding when producing large parts, but low temperature can not plasticize TPU well, resulting in uneven dispersion of toner, so there are so-called flow lines. The solution can be to provide the processing temperature of TPU as much as possible, or to speed up the screw speed when preparing materials, which is helpful to the uniform dispersion of toner. At the same time, it is necessary to reduce the mold temperature, which is helpful for cooling and setting. Either choose TPU with high fluidity or choose TPU model with fast molding speed.