Hebei hemisphere head manufacturer, quality hemispherical head plant http://www.hebftc7.com/ Phone 0317-8210122, phone 13722724665 hemisphere head plant bulge reasons: (1) mold size of any gap gap and how uniformity; (2) the size of the pull ring fillet radius and die stamping, surface condition and lubrication conditions; (3) the level of the heating temperature of the sheet and the uniformity of heating and the final temperature of the hot stamping control; (4) __ sheet diameter and thickness; (5) material weld and fight the weld wrong side-tolerance.