Port Plastics > Architecture

Acrylic Installation Guide

Cold Forming:

Acrylic sheet may be formed into a simple curve without heat by bending the sheet and retaining the shape in a curved channel or frame. Minimum radius of 250 times the thickness of sheet is recommended.

Thermoforming:

Acrylic sheet can be formed over and into any conventional type of thermoforming mold. When heated it becomes soft and flexible and can be thermoformed into complex shapes using very little pressure. The optimum mold temperature range is 170° to 200° F (80°-95° C) As the sheet cools, it hardens and retains the shape. The cooling time is more critical than the heating time.Extended cooling allows the material to shrink back on the mold creating stress that could crack the part in weak or notch sensitive areas. Forced cooling can lead to warping. Acrylic sheet will absorb moisture when exposed to humid atmosphere. If sheet is found to be wet and cannot be thermoformed, drying at 175° for twelve hours should reduce moisture levels and allow the sheet to be formed

Troubleshooting the Thermoforming Process

Defect	Causes	Corrective Action

1. Blistering	a) Overheating	a) Reduce heater temperature and/or cycle
	b) High moisture level in sheet	b) Per-dry sheet at 175°F (80°C) for 3mm sheet at least 12 hrs drying time required

2. Poor Surface Finish	a) Contact with hot surface	a) Do not allow sheet to contact heater surface

3. Wrinkles	a) Sheet too hot	a-1) Reduce surface temperatures
		a-2) Have hottest surface on outside of bend
	b) Sheet too cold	b) Longer heating cycle
	c) Radius too tight	c) Use larger radius

4. Warpage	a) Non-uniform heating/cooling	a) Provide uniform output from heater
	b) Part removed from bending fixture while hot	b-1) Limit area heated
		b-2) Increase cooling time in bending fixture
		b-3) Machine a radius or "V" groove at bend

5. Distortion	a) Non-uniform heating	a) Provide uniform heater output and spacing from sheet
	b) Part removed from fixture while hot	b-1) Keep support surfaces uniformly cool
		b-2) Increase fixture cooling time
	c) Sheet bend angle too shallow	c-1) Increase bend angle
		c-2) Use counter bowled tool

Free Form Blowing:

Most commonly used to produce spherical domes. The sheet is usually heated in a oven, removed, then firmly clamped to a blow table and formed to a shape using relatively low air pressure. Because the heated sheet will stretch during handling if not supported, a carrier plate which is removed from the blowing table may be used to facilitate the transfer of the sheet from the oven to the blowing table. The carrier place also helps to prevent rapid cooling of the sheet during transfer. To minimize stress during cooling, it is during cooling, it is important to avoid chilling the inner surface of the sheet by the blowing air. Defusing the air flow through felt will help prevent this, but in extreme cases the blowing air may be reheated.

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