PSU GlassWorks
Sponsor: Pittsburgh Plate Glass
PPG is a world leader in the production of automobile windows. We have been asked to help improve on a machine that is used in the production line for automobile side glass windows. The machine is a roll cart that is used to transfer side glass windows from the forming press to the quenching room. The roll cart must be the same shape as the windows being made, that is it must have the same vertical and horizontal radii as the side glass window. The vertical radius is formed by multiple bent shafts that have rotating donuts to move the glass, and the horizontal radius is formed by moving the shafts for the vertical radius up and down. To accommodate the different shapes PPG has many different carts creating a problem with dedicated tooling and the man hours required to change the carts. To elevate these problems PPG created a prototype roll cart that could be adjusted vertically and horizontally to accommodate different radii. PPG's prototype implements titanium shafts with sliders that compress the shafts rather than steel shafts for the vertical adjustment to accommodate a greater bending range. Horizontally the prototype uses a cam shaft that pushes the vertical bars up and down. Our project is to improve on the design of PPG's prototype. Even with the titanium shafts the prototype does not have the vertical adjustment range needed and it does not adjust horizontally due to forces created by the vertical adjustment. The slider that rides on the cam shaft for the horizontal adjustment binds and does not move due to the vertical adjustment.
• Identify improvements to the current method of horizontal and vertical radii adjustments. Horizontal radial adjustments need to accommodate a range of flat to 600 inches. Vertical radial adjustments need to satisfy a range of 39 to 90 inches.
• Identify shaft materials and shapes that will generate precise and repeatable vertical radii adjustments. New design must alleviate current binding problems of the slide mechanism.
• Build a bench scale model,sectional prototype (a one
to three roll section), or generate detailed drawings which incorporate new
concepts.
Vertical Radius Adjustment
• Implement a flat bar.
• Use smaller diameter bars.
• Pull down from the center rather than pushing from the
sides.
Horizontal Radius Adjustment
• Use a spring to push down on the slider to keep contact with the cam.
• Implement an eccentric cam shaft with followers that would pull down on the slider.
• Use power screws rather than a cam shaft.
Vertical Radius Adjustment
• For the vertical radius adjustment we are performing analysis on flat titanium bars and smaller diameter titanium bars to determine the optimum shape and size for bending..
Horizontal Radius Adjustment
• Horizontally we are designing eccentric cams with followers. The cam shaft passes through the center of the center cam lobe and is offset for the cams to the right and left of center. When the cam shaft is rotated the offset cams raise the slider in a radius. Because the cams are round, a follower can be placed around the cam. This will pull down on the slider just like it pushes up on it, elevating any binding problems.
Diagram of a cam that is to the left or right of the center cam. Notice the location of the shaft is off-center.
• The final cam design consists of two cam shafts each with 11 cam lobes. We found that a diameter of 5 inches is optimal for the cam lobes. At this diameter we are able to obtain the full range of radii, with a maximum error of .0056 inches. The prototype will need minor alterations to transplant the cam shafts due to the increased size of our cam lobes.
Cam shaft with cam lobes. Shaft and lobes are notched to ensure rotation.
• The prototype also needs to be modified by attaching a follower to the slider. The follower will alleviate any binding caused by the vertical adjustment in the slider. The final design is very similar to PPG's current prototype, but we believe the solutions we have developed will only improve the roll carts adjustability and performance.
Slider with follower, and fully assembled roll cart.
PPG Sponsor: Mike Fecik