Mustang Forming

Cold Bending

Although no plastic sheet should be cold bent to any severity, a bend in MUSTANG can be achieved without applying heat. A minimum radius of at least 100 times the initial thickness of the sheet is required.

Brake Bending

Brake bending is not recommended when fabricating plastic sheet. However, if this type of fabrication is necessary, do not perform on MUSTANG sheet >0.100" (2.5mm) thickness. Heat bending should be used on thicker gauges. Brake bending creates high levels of stress in the bend area, and could result in cracks and breakage during this process, or at a later time.

Line Bending

Line bending, also known as strip heating, is a technique used for forming sharp bends in the plastic sheet. When heated properly, MUSTANG lends itself well to this type of fabrication. The radius of the bend can be controlled by the width of the heated area. The temperature of the side opposite of the heat source should be heated to 250 degrees F prior to bending. This will assist in eliminating the residual stress that can form when bending at a temperature that is too cold. Thicker sheets should be heated from both sides to achieve a uniform heating through the sheet. Heat perpendicular to the manufacturer’s extrusion direction to reduce the possibility of warpage in the heated areas. Always stabilize the sheet by clamping during the heating and cooling processes.

Oven Heating

MUSTANG sheet should be heated in a horizontal oven. It is not conducive to use with vertical ovens.

Thermoforming

The term thermoforming refers to the process of heating a plastic sheet to sufficient temperature to form a shaped article. MUSTANG sheet excels in this area, offering a unique combination unmatched by polycarbonate. MUSTANG sheet can be thermoformed without pre-drying, forms at lower temperatures, has faster heating and cooling cycles, has excellent material distribution characteristics and processes consistently. Deep draws and intricate part definitions are achievable with MUSTANG by using simple vacuum forming techniques.

The entire cut to size sheet is typically heated to forming temperature inside an oven. The forming temperature depends on the thickness of the sheet and the shape or complexity of the mold. For less intricate molds, heat MUSTANG sheet on the lower side of the temperature range. For deeper draws and more complicated mold designs, heat to the middle to upper side of the temperature range. Because MUSTANG sheet exhibits great detail, care should be taken when manufacturing the mold. It needs to be smooth. MUSTANG sheet will form to the details of a rough mold (mold mark-off).

The radii of the finished part should be greater than or equal to the initial sheet thickness. This will greatly reduce stress molded into the part due to sharp radii. Sharper corners increase the localized stress, which could lead to micro cracks, and then to possible part failure.

During the cooling process, a thermoformed part should be fully supported as additional shrinkage may occur. The extrusion direction of the sheet is the most susceptible to shrinkage. Supporting will reduce the possibility of warping of the final part, especially in the flange area.

Free Blown Forming

This is done by clamping the heated MUSTANG sheet and blowing upward with compressed air similar to blowing a bubble. The reverse can be accomplished by drawing the sheet into a chamber using vacuum pressure

Availability And Transportation

MUSTANG is available in flat sheet or roll stock. If cutting from reels, do not re-roll to less than 50" diameter. Sheet should be handled standing on edge. Protect the entire sheet from scratches with shrink wrap or other protective source.

Forming And Annealing

MUSTANG sheet cut from reels can be thermoformed without annealing. However, if a flat sign will be manufactured from Mustang cut from rollstock, annealing is recommended. Annealing can be accomplished by placing the sheet in a forced air oven at 165º F for 2-3 hours and allowing it to cool to at least 120º F prior to use.

Selection of Sheet Thickness

Determining proper sheet thickness is based on the short dimension of the sign and the specified maximum wind load in pounds per square feet (PSF) (see Figure 6). The sign is required to meet a specified wind load determined by building codes of your area. Approximate wind loads in relation to wind velocity can be seen in Table 3.

Sheet Size

Expansion and contraction allowances must be taken into consideration when fabricating signs for outdoor applications. Mustang sheet, like all plastics, must be allowed to move within the confinements of the sign channels to prevent bowing or dislodging. The coefficient of linear thermal expansion (COTE) is 3.9 x 10-5. This number can be used to calculate the necessary dimensions needed to allow the necessary movement of the plastic sign face. A simple rule of thumb is to allow 1/16" per linear foot in each direction (width and height).