FABRICATION GUIDES
From time to time, you might need to cut your engraving sheet down to smaller sizes. Here is an excellent guide to get started.
Sawing Acrylics
Given the increasing demand for acrylic sheet for a number of applications, most plastic distributors and fabricators will spend a great deal of time cutting it. While there are a number of methods available, sawing is the most frequently used process for sizing acrylic sheet material.
There are three basic types of equipment used for sawing plastic sheet: table saws, vertical saws and automated panel saws. Many table saws and vertical saws are limited to cutting single sheets, while an automated panel saw is designed to process stacks of acrylic sheets. In addition to automating the cutting process, panel saws can provide higher accuracy and better edge quality for acrylics due to machine design and advanced features. In consideration of these points, we will focus this discussion on automated panel saws. Ranging from the thinnest extruded acrylic to the thickest cast acrylic, there are a number of key factors to consider when cutting acrylic with an automated panel saw.
Tooling
We begin with tooling (saw blades) because it is the heart of the sawing process. Someone once said that the world’s best machine is simply a fancy tool holder. This statement holds some truth in that an incorrectly selected or poorly maintained saw blade produces poor results regardless of the sawing equipment. Saw blades vary in tooth geometry, number of teeth, width of blade, rpm speed and other factors depending on the specific job requirements. Selecting a smaller diameter blade that allows for up to a 1.25 inch projection over the top sheet will cost less and produce a slower tip speed which will result in less burning. Saw manufacturers and saw blade vendors can assist you in selecting the correct tool for your specific acrylic needs.
Blade Speed
Using an inverter to control the blade rpm can improve the quality of the edge finish by reducing chipping and melting. In addition, the inverter will enable higher stacks of acrylic material to be cut at faster speeds which will increase productivity. Controlling the tip speed of the blade through blade diameter size on a fixed rpm saw can provide some flexibility if your saw does not have an inverter.
Blade Projection
The height that the blade projects above the acrylic being cut is important to control chipping, “blow-out” and melt. Normally the blade should project enough so the gullets in the saw blade can evacuate the chips to the dust collector. Raising the blade projection to as much as 1” over the material can also help to reduce edge “blow-out” when stack cutting thin acrylics. If your saw is not equipped with variable blade height adjustment, try to control projection through blade diameter size.
Blade Cooling
Heat buildup within the saw blade can create serious edge problems when cutting. A fine mist or blown air is used on some panel saws to cool the main blade during the acrylic cutting cycle. Lubrication helps to produce a smoother, cleaner edge and increases blade life.
Cut Speed
Cutting speed for acrylics can range from below 20 feet per minute to over 60 feet per minute depending on acrylic sheet thickness, stack height, tooling and panel saw features. State-of-the-art panel saws with rpm control, variable blade adjustment, blade cooling and advanced guide systems ensure that you can cut at faster speeds, maintaining productivity without sacrificing quality.
Other Factors
Vibration created within a panel saw can be transferred to the acrylic being cut causing chipping and overall poor cut quality. A solid base design (heavy I-beam type construction) with a smooth drive system (rack and pinion) will deliver the smoothest, most vibration-free cut. Material hold down is also important. A pressure beam providing evenly distributed hold down over the entire material length is critical for a good finish. A pressure beam system with slots can allow the pusher fence with grippers to maintain continuous contact on the acrylic during the cut cycle, ensuring maximum accuracy on the narrowest cuts. This is especially important if you cut small dimension acrylic parts. Using a slotted beam system can improve yield by as much as 6-8%.
Chip and Dust Evacuation
Last but certainly not least, your sawing system for acrylic should include a good chip evacuation system. Acrylic residue remaining in the saw blade gullet, on the saw table or in the saw carriage can cause heat and melting problems resulting in loss of quality and yield. Be sure to provide your sawing operation with adequate chip removal to prevent this problem.
Painting Acrylic Sheets
Painting Acrylic Sheet
The superior clarity and long-term durability of acrylic sheet allow for easy painting and printing of fabricated signs, displays and other decorative items. However, simply choosing to use the material is not enough to guarantee success. With that in mind, the following guidelines and the correct supplies will help you produce high-quality acrylic sheet products.
Paint
A variety of paints specifically designed for acrylics are commercially available. Most are supplied as concentrates and require thinning to obtain the correct viscosity.
As a rule, use mild thinner consisting of an alcohol blend, rather than one containing aromatic hydrocarbons, such as benzene and toluene. Always follow the paint suppliers’ recommendations about the amount and type of thinner.
Acrylic sheet’s extraordinary transparency allows for back-painting (i.e. applying paint to the side of the material not exposed to weather). The unpainted outer surface of the sheet provides weather protection for the paint. If you must paint the outer surface, apply a suitable protective coating over the paint.
Spraying Systems
Use any efficient, atomizing spray gun system that uniformly distributes paint. Consult your suppliers regarding the equipment you need for a particular application.
To obtain enough atomizing air, the available line pressure should be in the range of 414 to 621 kilopascals (60 to 90 psig). Use a 7.6-m (25-ft) long, minimum 8-mm (0.3- in.) diameter hose to avoid pressure drops in the line.
The air compressor should be large enough to provide the volume and pressure required for all spray guns.
Water and oil in the atomizing air will spot the paint and cause uneven distribution. To prevent this problem, use water and oil traps in the line.Metal screen strainers at the pressure tank and spray gun will ensure equipment cleanliness, which is also crucial to uniform paint dispersion. Clean these items and the spray gun daily.
Install an adequately vented spray booth that is large enough to house your biggest work piece. Use a light box to judge paint uniformity on transparent plastics. Be sure the light box conforms to building code regulations for a spray painting area.
Fabrication Techniques
Fabricating acrylic sheet using incorrect techniques prior to painting may cause stress in the material. This can result in crazing (i.e. numerous tiny cracks) after painting. You can eliminate crazing by following the manufacturers’ recommendations for fabricating acrylic sheet.
Cleaning
Always clean acrylic sheet before painting. This will remove dust and assure paint adherence.
Use special care in cleaning, as acrylic sheet is sensitive to solvents, such as aromatic hydrocarbons, concentrated alcohols and ketones. Clean parts with a solution of distilled water and 25 percent denatured alcohol.
For stains such as those caused by oil or grease, use stronger cleaning agents, like hexane, aliphatic naphtha or kerosene. Make sure the sheet is fully dry before painting.
Static Neutralization
It is important to neutralize electric or static charges that can accumulate on the sheet’s surface and attract dust before painting. Dust on the sheet causes paint agglomeration and uneven layers.
Since tearing the masking off the sheet will create a static charge, all acrylic pieces should be treated with an ionizing air gun, which safely and effectively neutralizes electric charges. Wiping the sheet with a damp, lint-free cloth or cleaning with a diluted alcohol-water solution is also effective.
Avoid anti-static cleaners. They can leave a residue and cause paint adhesion problems.
Maskants
Acrylic sheet’s paper masking is commonly used as a protective layer while spray painting flat signs. However, paint manufacturers also distribute liquid maskants, which are often used to spray designs onto acrylic sheet.
Maskant is supplied as a thick liquid, consisting of water-soluble latex resins in a solution. It is applied through the use of air (or airless) atomizing spray equipment. Being a water solution, it must be stored at above 0º C (32° F), to prevent freezing.
Clogging may occur, due to dried film mixed with the solution. You can prevent this problem with a special nozzle— available from paint equipment suppliers—that reverses the flow and cleans out the buildup.
Spray the maskant on evenly to a wet film thickness of 250 to 300 microns (10 to 12 mils). It will dry to above 100 to 125 microns (4 to 5 mils).
Maskant Drying
Drying time is usually about two hours. However, it is better to plan for overnight drying to assure complete evaporation.
Using forced-air heating at 43° C (110° F) can accelerate the drying process. Higher temperatures might dry the surface and prevent evaporation of the water in the layers beneath it.
To prevent dust accumulation on the plastic surface, leave the dried maskant in place just prior to painting. Score the design on the film, using an exacto knife, applying just enough pressure to cut the film without scratching the plastic beneath.
After painting, leave the film in place until the paint is thoroughly dry. Otherwise, you will end up with smeared paint and uneven edges.
Painting
Before painting, practice on a few test pieces of acrylic sheet to ensure paint viscosity and air pressure are correct. As a rule, use the lowest possible pressure to obtain the correct results.
Too high a delivery rate will result in an excess of paint and cause paint sag. It can also cause crazing of the sheet, due to too much solvent. Too low a delivery rate, on the other hand, will result in dry spray—i.e. a matte surface caused by too much dusting.
Hold the gun 300 to 350 mm (12 to 14 in.) from the work piece; being too close or too far away will cause the defects listed above
Move the gun at an even pace and in a straight line. Its movements should never start or stop when directly facing the sheet surface.
Vary the direction of the spray, both horizontally and vertically, to assure uniform coverage. Four or five passes with several seconds between coats will provide sufficient paint. Using a light box behind the acrylic sheet will help you judge the uniformity and intensity of color.
Screenprinting
When used for high-volume production, screenprinting is fast and economical. For beginners, it is best to purchase a screen from a local screen supply house.
After set-up, apply paint with the squeegee in a uniform and even motion in one direction. The paint will pass through the open screen mesh, transferring the pattern onto the acrylic.
The most important factors are the paint’s viscosity and the size of the mesh openings. These will determine paint flow through the screen and the paint’s appearance on the acrylic.
It is difficult to generalize what these conditions should be. Many different fabrics are used for screens and paint viscosity depends on the application methods and temperature. Consult your paint manufacturer for advice about thinning paint.
Paint Removal
If paint removal from the acrylic sheet’s surface is necessary, it should be performed immediately. Use the paint manufacturer’s recommended cleaner. Apply the paint remover with a rag, then wipe off the paint using another clean rag.
Paint removers contain organic solvents. Therefore, to reduce the chance of crazing, you should minimize the period during which the remover is in contact with the acrylic sheet.
Troubleshooting Guide
ProblemCauseSolution
Maskants
Weak and brittle maskant Air bubbles in film Dilute slightly
Film not thoroughly dry Wait recommended drying time
Maskant film too thin Increase thickness to 3-5 mils (10-12 mils wet).
Too much adhesion Maskant film too thin Increase thickness to 3-5 mils (10-12 mils wet).
Coating exposed to UV Do not store faces outside.
Spray Paints
Poor adhesion Incorrect paint Use paints recommended for use with acrylic
Dirt or residue on sheet Clean sheets thoroughly before painting
Blotches of paint Static electricity Neutralize charges with ionizing gun or wipe with damp cloth
Uneven paint application Apply paint in more passes, using less paint per pass
Paint not applied uniformly Use back lighting to check paint as it is being applied.
Screen Paints
Poor detail Screen mesh too coarse Use a finer mesh screen.
Paint too thin Use less thinner
Worn screen Replace screen.
Paint drying on screen Hot, dry weather.Add retarder to slow paint drying.
Too much time between screening Flood screen between passes.
Crazing Stress from fabrication.Review fabrication techniques.
Flame polishing Flame polish as last step.
From time to time, you might need to cut your engraving sheet down to smaller sizes. Here is an excellent guide to get started.
Sawing Acrylics
Given the increasing demand for acrylic sheet for a number of applications, most plastic distributors and fabricators will spend a great deal of time cutting it. While there are a number of methods available, sawing is the most frequently used process for sizing acrylic sheet material.
There are three basic types of equipment used for sawing plastic sheet: table saws, vertical saws and automated panel saws. Many table saws and vertical saws are limited to cutting single sheets, while an automated panel saw is designed to process stacks of acrylic sheets. In addition to automating the cutting process, panel saws can provide higher accuracy and better edge quality for acrylics due to machine design and advanced features. In consideration of these points, we will focus this discussion on automated panel saws. Ranging from the thinnest extruded acrylic to the thickest cast acrylic, there are a number of key factors to consider when cutting acrylic with an automated panel saw.
Tooling
We begin with tooling (saw blades) because it is the heart of the sawing process. Someone once said that the world’s best machine is simply a fancy tool holder. This statement holds some truth in that an incorrectly selected or poorly maintained saw blade produces poor results regardless of the sawing equipment. Saw blades vary in tooth geometry, number of teeth, width of blade, rpm speed and other factors depending on the specific job requirements. Selecting a smaller diameter blade that allows for up to a 1.25 inch projection over the top sheet will cost less and produce a slower tip speed which will result in less burning. Saw manufacturers and saw blade vendors can assist you in selecting the correct tool for your specific acrylic needs.
Blade Speed
Using an inverter to control the blade rpm can improve the quality of the edge finish by reducing chipping and melting. In addition, the inverter will enable higher stacks of acrylic material to be cut at faster speeds which will increase productivity. Controlling the tip speed of the blade through blade diameter size on a fixed rpm saw can provide some flexibility if your saw does not have an inverter.
Blade Projection
The height that the blade projects above the acrylic being cut is important to control chipping, “blow-out” and melt. Normally the blade should project enough so the gullets in the saw blade can evacuate the chips to the dust collector. Raising the blade projection to as much as 1” over the material can also help to reduce edge “blow-out” when stack cutting thin acrylics. If your saw is not equipped with variable blade height adjustment, try to control projection through blade diameter size.
Blade Cooling
Heat buildup within the saw blade can create serious edge problems when cutting. A fine mist or blown air is used on some panel saws to cool the main blade during the acrylic cutting cycle. Lubrication helps to produce a smoother, cleaner edge and increases blade life.
Cut Speed
Cutting speed for acrylics can range from below 20 feet per minute to over 60 feet per minute depending on acrylic sheet thickness, stack height, tooling and panel saw features. State-of-the-art panel saws with rpm control, variable blade adjustment, blade cooling and advanced guide systems ensure that you can cut at faster speeds, maintaining productivity without sacrificing quality.
Other Factors
Vibration created within a panel saw can be transferred to the acrylic being cut causing chipping and overall poor cut quality. A solid base design (heavy I-beam type construction) with a smooth drive system (rack and pinion) will deliver the smoothest, most vibration-free cut. Material hold down is also important. A pressure beam providing evenly distributed hold down over the entire material length is critical for a good finish. A pressure beam system with slots can allow the pusher fence with grippers to maintain continuous contact on the acrylic during the cut cycle, ensuring maximum accuracy on the narrowest cuts. This is especially important if you cut small dimension acrylic parts. Using a slotted beam system can improve yield by as much as 6-8%.
Chip and Dust Evacuation
Last but certainly not least, your sawing system for acrylic should include a good chip evacuation system. Acrylic residue remaining in the saw blade gullet, on the saw table or in the saw carriage can cause heat and melting problems resulting in loss of quality and yield. Be sure to provide your sawing operation with adequate chip removal to prevent this problem.
Painting Acrylic Sheets
Painting Acrylic Sheet
The superior clarity and long-term durability of acrylic sheet allow for easy painting and printing of fabricated signs, displays and other decorative items. However, simply choosing to use the material is not enough to guarantee success. With that in mind, the following guidelines and the correct supplies will help you produce high-quality acrylic sheet products.
Paint
A variety of paints specifically designed for acrylics are commercially available. Most are supplied as concentrates and require thinning to obtain the correct viscosity.
As a rule, use mild thinner consisting of an alcohol blend, rather than one containing aromatic hydrocarbons, such as benzene and toluene. Always follow the paint suppliers’ recommendations about the amount and type of thinner.
Acrylic sheet’s extraordinary transparency allows for back-painting (i.e. applying paint to the side of the material not exposed to weather). The unpainted outer surface of the sheet provides weather protection for the paint. If you must paint the outer surface, apply a suitable protective coating over the paint.
Spraying Systems
Use any efficient, atomizing spray gun system that uniformly distributes paint. Consult your suppliers regarding the equipment you need for a particular application.
To obtain enough atomizing air, the available line pressure should be in the range of 414 to 621 kilopascals (60 to 90 psig). Use a 7.6-m (25-ft) long, minimum 8-mm (0.3- in.) diameter hose to avoid pressure drops in the line.
The air compressor should be large enough to provide the volume and pressure required for all spray guns.
Water and oil in the atomizing air will spot the paint and cause uneven distribution. To prevent this problem, use water and oil traps in the line.Metal screen strainers at the pressure tank and spray gun will ensure equipment cleanliness, which is also crucial to uniform paint dispersion. Clean these items and the spray gun daily.
Install an adequately vented spray booth that is large enough to house your biggest work piece. Use a light box to judge paint uniformity on transparent plastics. Be sure the light box conforms to building code regulations for a spray painting area.
Fabrication Techniques
Fabricating acrylic sheet using incorrect techniques prior to painting may cause stress in the material. This can result in crazing (i.e. numerous tiny cracks) after painting. You can eliminate crazing by following the manufacturers’ recommendations for fabricating acrylic sheet.
Cleaning
Always clean acrylic sheet before painting. This will remove dust and assure paint adherence.
Use special care in cleaning, as acrylic sheet is sensitive to solvents, such as aromatic hydrocarbons, concentrated alcohols and ketones. Clean parts with a solution of distilled water and 25 percent denatured alcohol.
For stains such as those caused by oil or grease, use stronger cleaning agents, like hexane, aliphatic naphtha or kerosene. Make sure the sheet is fully dry before painting.
Static Neutralization
It is important to neutralize electric or static charges that can accumulate on the sheet’s surface and attract dust before painting. Dust on the sheet causes paint agglomeration and uneven layers.
Since tearing the masking off the sheet will create a static charge, all acrylic pieces should be treated with an ionizing air gun, which safely and effectively neutralizes electric charges. Wiping the sheet with a damp, lint-free cloth or cleaning with a diluted alcohol-water solution is also effective.
Avoid anti-static cleaners. They can leave a residue and cause paint adhesion problems.
Maskants
Acrylic sheet’s paper masking is commonly used as a protective layer while spray painting flat signs. However, paint manufacturers also distribute liquid maskants, which are often used to spray designs onto acrylic sheet.
Maskant is supplied as a thick liquid, consisting of water-soluble latex resins in a solution. It is applied through the use of air (or airless) atomizing spray equipment. Being a water solution, it must be stored at above 0º C (32° F), to prevent freezing.
Clogging may occur, due to dried film mixed with the solution. You can prevent this problem with a special nozzle— available from paint equipment suppliers—that reverses the flow and cleans out the buildup.
Spray the maskant on evenly to a wet film thickness of 250 to 300 microns (10 to 12 mils). It will dry to above 100 to 125 microns (4 to 5 mils).
Maskant Drying
Drying time is usually about two hours. However, it is better to plan for overnight drying to assure complete evaporation.
Using forced-air heating at 43° C (110° F) can accelerate the drying process. Higher temperatures might dry the surface and prevent evaporation of the water in the layers beneath it.
To prevent dust accumulation on the plastic surface, leave the dried maskant in place just prior to painting. Score the design on the film, using an exacto knife, applying just enough pressure to cut the film without scratching the plastic beneath.
After painting, leave the film in place until the paint is thoroughly dry. Otherwise, you will end up with smeared paint and uneven edges.
Painting
Before painting, practice on a few test pieces of acrylic sheet to ensure paint viscosity and air pressure are correct. As a rule, use the lowest possible pressure to obtain the correct results.
Too high a delivery rate will result in an excess of paint and cause paint sag. It can also cause crazing of the sheet, due to too much solvent. Too low a delivery rate, on the other hand, will result in dry spray—i.e. a matte surface caused by too much dusting.
Hold the gun 300 to 350 mm (12 to 14 in.) from the work piece; being too close or too far away will cause the defects listed above
Move the gun at an even pace and in a straight line. Its movements should never start or stop when directly facing the sheet surface.
Vary the direction of the spray, both horizontally and vertically, to assure uniform coverage. Four or five passes with several seconds between coats will provide sufficient paint. Using a light box behind the acrylic sheet will help you judge the uniformity and intensity of color.
Screenprinting
When used for high-volume production, screenprinting is fast and economical. For beginners, it is best to purchase a screen from a local screen supply house.
After set-up, apply paint with the squeegee in a uniform and even motion in one direction. The paint will pass through the open screen mesh, transferring the pattern onto the acrylic.
The most important factors are the paint’s viscosity and the size of the mesh openings. These will determine paint flow through the screen and the paint’s appearance on the acrylic.
It is difficult to generalize what these conditions should be. Many different fabrics are used for screens and paint viscosity depends on the application methods and temperature. Consult your paint manufacturer for advice about thinning paint.
Paint Removal
If paint removal from the acrylic sheet’s surface is necessary, it should be performed immediately. Use the paint manufacturer’s recommended cleaner. Apply the paint remover with a rag, then wipe off the paint using another clean rag.
Paint removers contain organic solvents. Therefore, to reduce the chance of crazing, you should minimize the period during which the remover is in contact with the acrylic sheet.
Troubleshooting Guide
ProblemCauseSolution
Maskants
Weak and brittle maskant Air bubbles in film Dilute slightly
Film not thoroughly dry Wait recommended drying time
Maskant film too thin Increase thickness to 3-5 mils (10-12 mils wet).
Too much adhesion Maskant film too thin Increase thickness to 3-5 mils (10-12 mils wet).
Coating exposed to UV Do not store faces outside.
Spray Paints
Poor adhesion Incorrect paint Use paints recommended for use with acrylic
Dirt or residue on sheet Clean sheets thoroughly before painting
Blotches of paint Static electricity Neutralize charges with ionizing gun or wipe with damp cloth
Uneven paint application Apply paint in more passes, using less paint per pass
Paint not applied uniformly Use back lighting to check paint as it is being applied.
Screen Paints
Poor detail Screen mesh too coarse Use a finer mesh screen.
Paint too thin Use less thinner
Worn screen Replace screen.
Paint drying on screen Hot, dry weather.Add retarder to slow paint drying.
Too much time between screening Flood screen between passes.
Crazing Stress from fabrication.Review fabrication techniques.
Flame polishing Flame polish as last step.