Your table tennis Mechanics of the arm-swing with a quiet shoulder is the secret of controlling blade angle to eliminate unforced errors.
Your upper arm is attached to the shoulder in a round socket, therefore it is impossible to (swing straight) back or forward; when you swing your elbow to shoulder (upper arm) forward your blade angle will automatically open the blade (in proportion to length of the upper arm travels forward to and through the ball contact. This is the exact opposite of what's best.
Try this for yourself: Grip your blade and let you playing arm hand and blade hang relaxed below your shoulder: Move your upper arm and elbow forward and your blade will automatically open, move the elbow back and it will automatically close the blade and/or Move your upper arm away from the body and your blade will automatically close. Move the upper arm in towards the body and it will automatically open the blade. Therefore, controlling the upper arm and shoulder movement during the stroke is the key to blade angle control.
When you start your forward arm-swing towards the incoming ball, at about 6 to 8 inches from the ball without moving the upper arm, pull your blade forward to and through the ball contact with elbow rotation to close the lower arm to the upper arm and body and your blade angle will automatically move from open to close in proportion to the amount of (length of blade travel to the ball). Blade open to close action is the ideal action for the blade angle to follow the contour of the ball and this closing the lower arm to the upper arm adds the accelerated blade speed needed without moving the elbow forward.
The best action for blade control is an open to close action as you contact the ball. The desired blade action (the open to close blade angle) is achieved by: rotating the forearm at the elbow and swing out towards the incoming ball, which starts the blade to close, then when your blade is within 6 to 10 inches of the ball close your lower arm to your upper arm by using your bicep to pull your blade through the ball contact for better control, power and blade acceleration.