ACRYLITE® LED sign grade (Resist SG) Fabrication Manual

Introduction

ACRYLITE® LED sign grade is an impact modified acrylic specifically developed to meet the unique needs of the sign industry. It is ten times stronger than standard acrylic so it will resist breakage during storage, fabrication, shipping, and installation. Ideal for any sign application, it offers:

  • Superior light transmission
  • Excellent light diffusion with LED light sources
  • Outstanding weatherability
  • Easy fabrication

Cutting Operations

Cutting With Table and Panel Saws

Generally, straight cuts are made using a conventional table or panel saw. A saw blade specifically designed for acrylic, such as a triple-chip grind, carbide toothed saw blade works best. For a 10 inch saw blade, 80 teeth are recommended. For larger blades, equivalent tooth spacing can be utilized with good results. On a triple-chip grind saw blade, every other tooth has a beveled cutting edge which aids in chip removal and reduces heat buildup.

When cutting our LED sign grade, the blade should protrude 1/2” to 1” above the surface of the sheet, with optimum results usually obtained using a 3/4” blade height. Vibration should be kept to a minimum, either by clamping the sheet to the cutting surface (when operating a vertical saw or panel saw) or providing the proper pressure on a table saw.

Moderate feed rates, in the 15-25 ft/min range, will ensure a proper cut. A chipped edge indicates that the feed rate is too fast or that the material is vibrating too much, while a melted edge indicates that the feed rate is too slow. It is recommended that the feed rate be decreased at the end of the saw cut, especially on thinner sheets. This will prevent chipping and blowout of the exit edge.

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Panel saw cutting

Jigsaw Cutting

Hand held jigsaws work well with our LED sign grade when cutting intricate shapes and letters. Results comparable to those achieved with cell cast acrylic sheet are possible. For best results, use a wavy-set type blade with 8-13 teeth/inch (tpi). This blade configuration will typically chip cell cast acrylic, but will work very well with this material due to the sheet’s inherent toughness. Using a blade with a higher number of teeth per inch, 18-24 tpi, may result in melting along the cut edge. It is also important to ensure the blade is sharp – do not use a blade that has already been used for cutting metal or other materials.

When jigsaw cutting, it is important to minimize vibration by clamping the material to a firm surface. Feed rates in the 8-12 ft/min range will yield the best results.

Bandsaw Cutting

Bandsaws are typically used for quick, rough cuts, as well as intricate shapes and letters. As with jigsaw cutting, the quality of the edge is dependent on the type of blade used. Generally, blades in the raker style with teeth in the 8-13 tpi range will produce the best results. Blades with fewer teeth per inch will leave a jagged, rough edge while blades with a higher number of teeth per inch will yield a smoother edge. If blades with more teeth per inch are used, it is recommended to utilize a coolant such as water, compressed air, or a combination of both to reduce melting along the cut edge. Feed rates in the 10 to 15 ft/min range will yield the best edge.

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Bandsaw cutting is easily accomplished with ACRYLITE® LED sign grade Sheet.

Scribing and Breaking

Our LED sign grade sheet can be scribed and broken similarly to our cast and extruded acrylic sheet. Scribing should only be done on the 0.118” (3 mm) thickness. With the aid of a straight edge to guide the scribing tool, pull the scribing tool across one side of the sheet surface several times until the tool has penetrated approximately 1/16” through the material. Next, position the sheet so that the scribed line is just beyond the edge of the working surface. While holding the sheet firmly in place on the surface near the scribed line, apply a quick, downward pressure to the end of the sheet overhanging the working surface.

Routing Operations

Hand Held and Table Routers

This sign grade can be routed with the same equipment used for routing standard acrylic sheet. Because it's not as stiff as conventional acrylic, particular care must be taken to eliminate the vibration of the work piece during the routing operation. If vibration is present, it can result in a chipped edge. To support thin material, 0.060 and 0.080 (1.5 mm and 2.0 mm) thick, during routing, sandwich the material between stiffer plastic sheets.

When compared to feed rates for routing standard acrylic sheet, our sheet's feed rates are noticeably faster. LED sign grade is less prone to chipping than standard acrylic sheet, particularly when entering and exiting a cut. Both materials are notch sensitive. Any notches in an edge can propagate into a crack under load conditions.

During plunge cutting, the cutter has a tendency to grab as it penetrates through the sheet. Take special care to hold the sheet firmly. Exit the material slowly to avoid chipping or cracking during plunge routing. A safer option to plunge routing is to drill an adequately oversized hole and begin routing at this location.

Carbide tipped, 1/2 diameter, two-flute, straight bits are recommended.

CNC Routing

As with all routing, it is important to ensure that the material is firmly held and supported to prevent vibration. This is even more critical with CNC routing because tool speeds and feed rates are usually much higher than with handheld or hand-fed routers.

In general, much higher feed rates are possible with our sign grade sheets than with standard acrylic sheets. When using bits that are 1/4 in diameter or larger, rotational speeds of 18,000 RPM and feed rates of 200 in/min will produce good results on most equipment. On large, stable, well maintained machines with very solid fixturing, feed rates of up to 600 in/min are possible.

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routing

For smaller diameter bits (1/8 and 1/16), rotational speeds of 20,000 RPM coupled with feed rates in the 150–200 in/min range are recommended provided that the router bits are cooled. Coolants such as compressed air or mist cooling systems can be used. In addition, consideration must be given to the depth of cut. For best results the cut depth should be no more than 1.5x the bit diameter. For deeper cuts, multiple passes should be made. Using coolant and minimizing cut depth helps to reduce melting caused by heat build-up and/or inadequate chip removal.

Two-flute, spiral-up, and O-flute design bits made from solid carbide are recommended for most applications.

Rotational speeds of 16,000 to 18,000 RPM’s and feed rates of 100 to 300 in/min will produce the best results with 3/8” and 1/2” diameter bits. For smaller bits rotational speeds of 18,000 to 20,000 RPM’s with feed rates of 100 to 200 in/min range will produce the best edge and tool life.

It is important to note that dust/chip collection systems as well as coolants such as compressed air, mist coolants and cold air/vortex tube technology, will greatly reduce the heat build up and improve the quality of the edge and life of the tool.

Laser Cutting and Engraving

This LED sign grade can be successfully laser cut and laser engraved. Typically CO2 lasers are employed in sizes ranging from 25 watts to 400 watts per laser head. The primary benefit of using a higher powered laser is to increase cutting speed. Additionally, larger lasers often come equipped with an air or gas assist and a vacuum table. Both of these options help to remove vapors generated during the cutting operation leading to improved results.

When laser engraving, ACRYLITE® LED sign grade, start with the same operating parameters as used with continuously manufactured or extruded acrylics. The resulting engraved designs will have a relatively clear appearance (the same as with continuously manufactured and extruded acrylic sheet). The engraved images will not be as white as those achieved when engraving cell cast acrylic sheet.

When laser cutting, it is especially advantageous to have a vacuum table and gas assist option. The gases generated during the laser cutting operation can deposit on the edges of the LED sign grade and form a tacky film. Efficient removal of vapors minimizes this problem. The tacky deposits can be removed by wiping the laser cut edges afterwards with VM&P naptha, which can be obtained at most hardware stores.

Drilling Operations

Because it's not as stiff as conventional acrylic sheet, it has a tendency to lift off the machining table when drill bits exit the hole. To compensate, clamping devices need to be placed as close as possible to the hole being drilled, carefully allowing for clearance of the rotating spindle and cutter. Several hold-downs may be required to firmly hold thinner stock flat to the machining table. Wherever possible, the sign grade should be drilled on stationary equipment. Portable electric hand drills should only be used as a final option and for small diameter holes only.

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Modification of metal working drill bits for plastic.

Twist Drills

It drills cleanly with high-speed steel (modified for plastic) twist drills (see illustrations above). On large diameter holes, it is recommended to pilot drill first before enlarging the hole to the final dimension. Adjust speed and feed rates so that a controlled chip is produced with no melting of the plastic. Continuous chips are not readily produced when drilling the sheet, nor are they required for excellent drilled-hole finishes.

Rotational speeds in the 500-1000 rpm range, combined with feed rates in the 3-12 in/min range will usually give good results.

Standard twist drills can also produce satisfactory holes in the sign grade. To avoid sheet notching, securely clamp the material to the machine table and apply slow entry and exit feeds.

Proper backing material such as plywood or another piece of acrylic should be used when drilling ACRYLITE® LED sign grade sheet. The backing material will help prevent chipping of the bottom surface. When drilling stacks of sheet, it is a good idea to utilize a coolant such as water or kerosene. This will minimize heat build up and create holes with smooth walls.

Spade Bits

Spade bits with side spurs (i.e. IRWIN 2000 Speedbores) produce satisfactory holes in our LED sign grade. The drilling is done in two steps with reduced machine speed for large diameter bits. Step one: Drill one face of the sheet to lightly score the perimeter of the hole. Step two: Flip the material and complete drilling from the opposite face of the sheet.

CAUTION:The original Speedbores, without side spurs, are not recommended for drilling ACRYLITE® LED sign grade.

Circle Cutters

Circle cutters can be used for cutting large diameter holes in the LED sign grade. Sharp cutters along with multiple hold-down devices are essential. A single clamping device is inadequate for circle cutters; should the cutter grab, the sheet can pivot and dangerously kick-out towards the operator. For thinner gauge material (.098” or less), lightly score the perimeter of the hole from one face, then flip the material to complete drilling from the opposite face of the sheet. This practice will eliminate notching on the edges and grabs, to which thinner stock is prone.

Hole Saws

Hole saws also produce acceptable holes in the sign grade. Although less smooth than other hole cutting means, best results are achieved with sharp hole saws tipped with carbide. Because of the high friction produced by these cutting tools, a coolant solution of detergent and water or kerosene will help to minimize melting of the material.

Countersinking

Countersinking in this sign grade is best done with a non-fluted (Weldon) countersink design. The large land of this cutter combined with the oblique hole forming the cutting edge of the tool, results in a controlled cut with little chatter and plenty of chip clearance. Pilot drilling is necessary when using the countersink design. The pilot hole should be oversized with reference to the shank of the fastener.

Edge Finishing Operations

The same edge finishing operations that work well with standard acrylic sheet can be used to obtain excellent edge finishes with this sign grade. However, care must be taken in certain edge finishing operations, such as flame polishing, to ensure the best edge quality. This section will cover proper techniques to ensure an edge finish of the highest quality.

Wet Sanding and Scraping

Wet sanding will yield a smooth, matte-finish edge and is suitable for use prior to flame polishing. Dry sanding is not recommended as it will lead to a highly stressed and melted edge. To obtain the smoothest edge, start with a 240 grit “wet and dry” sand paper and use plenty of water. The use of water will keep edge stresses to a minimum by acting as a coolant. Finer finishes can be obtained by sanding with 240 grit, then stepping up to 400, 600, and 800 grit, depending on the desired finish.

The use of belt sanders may result in melting and high stress. If using a belt sander, it is important to use light pressure when sanding. Excessive pressure will increase frictional heat buildup causing the edge to melt and gum.

Hand scraping is an alternative to sanding for preparing the edges of a sheet for polishing. The sheet can be scraped with almost any type of sharp, flat metal edged tool. Holding the scraper vertically, at a 45° angle to the edge, scrape the sharp edge of the sheet by drawing the tool across the edge with firm but steady pressure. A continuous strip should peel as the tool is drawn along the edge. There are tools available that will reduce the sharpness of both edges at the same time. It is important to note that scraping will not provide the smoothness of a sanded or polished edge.

Jointing

Jointing of our LED sign grade will produce a smooth, machined edge. Knives made from high-speed steel or carbide will work well. Blade height should be set to remove approximately 1/32” from the sheet. The most important aspect of jointing is controlling the feed rate. It is important to use a steady, even feed rate while holding the sheet material firmly to the guide fence. Excessive feed rates will result in a chipped, highly stressed edge.

Edge Finishing Machines

Commercially available edge finishing machines offer a fast method of obtaining smooth edges without sanding or scraping. Finishes will range from smooth, matte-finish to almost polished edges, depending on the design of the machine and cutting tools used. Edge finishing machines are ideal for preparing sheet for subsequent edge finishing steps, such as flame polishing and buffing, or fabrication steps such as cementing. Care should be taken to adjust the feed rate to eliminate chipping and melting of the material. Fast feed rates will result in chipping while slow feed rates will result in melting. In general, faster feed rates can be used for edge finishing our LED sign grade than for standard acrylic sheet.

Buffing

Buffing the edges of this material will produce a high luster finish. It is recommended that the edge be scraped, then wet sanded prior to buffing. A stationary buffing wheel or portable polishing head can be used. Loose stitched, bleached muslin wheels, used in combination with a medium to fine buffing compound will provide a high luster edge in a short time.

Removal of Whitening

Whitening within our LED sign grade occurs under extreme impact or if the material's edge or face is mechanically stressed. This whitening can be removed by heating both sides of the affected area at approximately 185°F. Apply heat evenly and long enough for the full thickness of sheet to reach the desired temperature. Overheating will cause distortion. A heat gun or an industrial oven can be used for eliminating whitening. Heating the sign grade with a torch is not recommended.

Note: Hazing is noticeable during the heating cycle. When the sheet returns to room temperature, the hazing disappears.

Flame Polishing

Highly polished edges can be obtained by flame polishing using the same techniques used with standard acrylic with slight modifications. When flame polishing LED sign grade, a cooler flame should be used than with standard acrylics. This is best accomplished using MAPP gas.

Another option is to use a hydrogen/oxygen welding torch. Make sure to reduce the oxygen content to produce a flame that is bright orange/red in color, as opposed to the bluish, almost invisible flame typically used with standard acrylics. It has a tendency to turn a milky white color when overspray from the flame contacts the surface of the sheet. It is important to minimize this contact by using a quicker feed rate than would normally be used for standard acrylics. Hold the torch at an angle and draw the flame along the edge of the sheet. Practice will help you to estimate the speed and distance. If the first pass does not produce a completely polished edge, allow the piece to cool,and then try a second pass. For optimum edge finish, wet sand the edge or pass the sheet through an edge finishing machine or jointer to remove any tooling marks from previous operations prior to flame polishing.

Cementing Operations

The LED sign grade can be easily and quickly cemented to itself, other acrylic materials, as well as to trim cap, creating strong bonds in applications such as channel letters. It offers faster setup times than cell cast acrylic sheet products. Acrylic cements such as ACRIFIX® solvent cements work well on this material. Generally, techniques used to cement standard acrylics can be used with success on ACRYLITE® LED sign grade.

Trim Cap

When making channel letters, make sure all areas are in contact with the trim-cap, and apply a generous amount of cement around the perimeter of the letter. For additional strength, a bead of viscous cement such as ACRIFIX® 1S 0116 can be applied to the perimeter of the letter.

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Cementing

Acrylic to Acrylic Joints

Edge finished, jointed, or clean saw-cut edges will yield the best results. Avoid cementing sanded or scraped edges because these operations tend to round the corners of the edge, leading to inconsistent surface contact and air bubbles in the joint.

Note: Never cement flame polished edges. This operation creates high levels of internal stress in the material and could lead to crazing.

Due to its formulation, this sign grade tends to absorb more solvent cement than standard acrylic sheet. To compensate for this, make sure to apply a liberal amount of cement to the joint. This can be accomplished by tipping the vertical piece about 1° so that more cement flows into the joint. Alternatively, 0.002” shims can be used to elevate the vertical piece slightly. Shims should be removed after 45-60 seconds.

Initial setup time will vary between 5-60 seconds, depending on the type of cement used and the shop environment.

Guidelines

To achieve the best results when capillary cementing with typical methylene chloride-based solvent cements or cyanoacrylate based cements, the following recommendations should be followed:

  • Insure a smooth, clean, low stress edge.
  • Apply cement along the entire length of the cement joint. Unlike with standard acrylic sheet, the cement will not flow to the ends of the cement joint if the application of cement is started or finished more than ¼ - ½ from the ends. Failure to fill the entire length of the cement joint greatly reduces strength.
  • Apply a generous amount of solvent cement to the surfaces being joined by: tipping the vertical piece slightly so that its edge can accept more cement; using a larger diameter applicator tip for increased cement flow; or providing space at the joint by shimming (0.002- 0.004).

Joint set-up time will vary depending on the exact formulation of the cement and the temperature and humidity of the cementing environment. Cement joints made with our LED sign grade will obtain initial soft strength approximately 30 minutes after application of the cement. They will begin to harden about 3 hours after cement application, but will not approach full strength for 24 - 48 hours. As a general rule, set-up time will be slightly longer than is normally required with conventional acrylic sheet.

With cyanoacrylate-based cements, the chemical reaction that hardens the cement joint is triggered by moisture in the acrylic sheet and the atmosphere. Therefore, the rate of the curing process is dependent on the rate at which moisture in the air and in the sheet can diffuse to the cement joint. Usually 48 hours is required for the cement joint to reach full strength at which point it will be as strong as the material itself. Extra care should be taken when handling parts to avoid cement smudges. The resulting white marks can usually be removed by wiping with kerosene followed by rinsing with mild soap and water.

Painting Operations

It can be easily painted and silk-screened using the same paints and techniques as ACRYLITE® cast and extruded products. However some paints, due to their brittleness, may result in lower overall impact strength.

Surface Preparation

Paper masking may leave a latex residue on the sheet. This residue can result in poor wetting of the paint on the surface of the sheet and poor paint adhesion. If this is a problem, clean the surface of the sheet prior to painting using a dilute mixture (50% or less) of isopropyl alcohol in water. Rinse thoroughly with water and dry using a soft cloth or chamois. Particles on the surface of the sheet can also cause adhesion problems. Therefore, it is important to remove dust and particles on the sheet surface by neutralizing static charge using an ionized air gun. Leaving the masking on the sheet or using a removable spray-on maskant may help to minimize exposure to overspray.

Painting

It is important to note that the overall impact strength of a painted sheet may be lower than an unpainted sheet. This is due to the lower impact strength and tensile strength of the paint itself. The actual impact strength reduction will depend on the paint used.

Vinyl Graphics

The use of vinyl films for graphics and backgrounds is highly recommended, no reduction in garder impact.

Paint Removal

Spray and screen paints can be removed using recommended paint removers. To reduce the chances of crazing the surface of the sheet, minimize the amount of time this sign grade is in contact with these solvents. Even with the complete removal of paint from the surface of the sheet, a phenomenon referred to as “ghosting” often occurs. A hazy outline of the original images may remain and become visible upon application of new paint.

Thermoforming Operations

This sign grade can be thermoformed into a variety of finished parts and sign faces. Its forming temperature range of 270-350°F offers faster cycle times than can be achieved with conventional cell cast acrylic sheet. This wide range of forming temperatures allows for greater versatility in thermoforming operations.

In most cases, excellent results can be achieved using forming temperatures of 310-320°F. (Up to a draw ratio of 3:1) Parts that contain more detail or have a deep draw need to be formed at the high end of the forming range, 320-350°F. Parts should be left in the mold after forming until they have reached a temperature of approximately 180°F. It is important to preheat the mold to approximately 160-180°F. If the mold is not preheated, the formed part will cool too quickly, resulting in internal stresses in the thermoformed part. Draft angles of 2-3° will allow for easy part removal.

Due to its method of manufacture, ACRYLITE® LED sign grade will be oriented in the manufacturing direction. Manufacturing direction can be determined by looking at the label or printed masking on the sheet. As you read the label or masking, the manufacturing direction is from top to bottom. The sheet may shrink up to a maximum of 5% in the manufacturing direction when heated. Be sure to allow for shrinkage when cutting blanks for thermoforming.

During the heating cycle, colorless sign grade will turn a translucent white color. After the sheet is formed and allowed to cool to room temperature, it will regain its high light transmission, losing its milky white appearance.

Forming Cycles

It can be heated by a variety of methods including infrared heaters, circulating air ovens, and other conventional heating methods. Generally, when heating the sign grade in an air circulating oven, the heating times will be similar to ACRYLITE® extruded. Heating cycles when using infrared heaters tend to be much shorter than oven heating cycles.

The following table illustrates approximate heating times for 0.118” (3 mm) LED sign grade sheet. Testing was done on a thermoformer equipped with ceramic heaters positioned approximately 2.5 to 3 inches above the sheet.

TimeApproximate Temperature
120 Seconds 260F
180 Seconds 310F
210 Seconds 350F

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Ideal thermoforming temperature is between 310 - 320°F. Many thermoformers judge readiness by the sag and the feel of the sheet.

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Immediately after thermoforming, the sheet will appear a milky white color. Cooling cycles can be reduced by using cooling fans or applying compressed air.

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The resulting sign will have excellent light transmission, clarity and mold definition.

It is important to note that actual times will vary for each individual thermoformer due to various parameters such as the type of heater (convection oven, radiation, etc.), distance from the sheet, and single or dual side heating.

This material offers outstanding thermoforming definition at reduced cycle times, compared to standard acrylic and polycarbonate sheet. The following graph illustrates its typical performance.

As can be seen from the graph, it offers excellent part definitions at temperatures lower than those of conventional cell-cast acrylic sheet and polycarbonate sheet.

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Line Bending

Our sign grade can be easily line bent using standard bending equipment. Line bending should be performed when the core temperature of the sheet is in the range of 270-290°F, which is slightly lower than line bending temperatures for extruded acrylic sheet and much lower than line bending temperatures for cell cast acrylic sheet. As a result, shorter cycle times can be expected with ACRYLITE® LED sign grade. It is important not to bend it at temperatures lower than 270°F because this leads to high internal stresses. These internal stresses can lead to crazing of the material should it come in contact with incompatible solvents or aggressive chemicals.

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As the temperature of the colorless sign grade rises, the material will turn a milky white color in the heated region. It will return to its original colorless, high light transmitting state as it cools back down to room temperature.

ACRYLITE® LED sign grade has a manufacturing direction. This direction is identified by looking at the masking label. As you read the label from left to right, the manufacturing direction will run from top to bottom. On longer line bends, i.e. greater than 36 inches, a slight warp or bow across the sheet may be evident. This effect can be reduced by orienting the bend so that it is perpendicular to the manufacturing direction.

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Trouble Shooting

Cutting Operations

ProblemCauseSolution
Chipping Excessive Vibration Ensure pieces are properly supported and clamped to working surface
Excessive blade run-out Check blade collar, replace if run-out is greater than 0.002"
Improper blade height Set blade height at 1/2” to 1” above work pieces
Improper blade type For table saw cutting, use a triple-chip blade. (2.5 teeth per inch of circumference). For jigsaw cutting, use a wavy-set style blade (8-13 teeth per inch)
Feed rate too fast Decreased feet rate
Melting Dull blade Replace or sharpen blade
Feed rate too slow Increase feed rate
Improper blade style For jigsaw cutting, use a wavy-style blade with 8 to 13 tpi. For all purpose table saw cutting, use a triple-chip, carbide tipped blade, 2.5 teeth per inch of circumference (i.e. 80 teeth for a 10 inch diameter blade)

Drilling Operations

ProblemCauseSolution
Chipping Feed rate too fast Use feed rates in the 3-12 ft/min range
Vibration Ensure pieces are properly clamped to work surface
Incorrect bit For best results, use a “modified-for-plastic” drill bit
Blow Out Insufficient back support Use backing material such as plywood or acrylic
Melting Feed rate too slow Use moderate feed rates in 3-12 ft/min range
Rotational speed too high Reduce rotational speed. RPM’s in the 500-1000 range will yield the best results
Inadequate cooling Use air or water mist
Incorrect bit Use a “modified-for-plastic” drill bit. Smaller bits may require cooling
Bit is not true Replace bit

Bending Operations

ProblemCauseSolution
Bowing from a long bend Uneven cooling of the bend Make sure there is enough clearance to allow air circulation over the entire length of bend, including the underside
Design a reverse “bow” in the cooling jig

Routing Operations

ProblemCauseSolution
Bit Breakage Excessive heat buildup in bit due to inadequate chip removal

Used compressed air to clear chips

Use bit designed for chip removal (twist up)

Plow routing using fast feed rates Reduce feed rate
Dull Bit Replace or sharpen bit
Excessive load on bit Make multiple passes
Melting Feed rate is too slow Use faster speed rates
Dull bit Replace or sharpen bit
Inadequate heat removal

Use a larger diameter bit

Use a coolant such as air or mist

Rotational speed too high Reduce RPM’s. May need to be coupled with faster feed rate
Inadequate chip removal

Use a twist-up bit

Use a slow helix angle removal rather than a fast helix angle

Consider multiple passes

Use compressed air to aid in chip removal

Incorrect number of flutes on bit Decrease number of flutes on bit
Chipping Feed rate too fast Decreese feed rate
Vibration

Make sure pieces are adequately supported

Use a larger diameter bit and/or a bit with shorter cutting length

Incorrect number of flutes in bit Increase the number of flutes on the bit

Edge Finishing Operations

ProblemCauseSolution
Dull edge after flame polishing Not enough heat/missed spots Allow piece to cool, than make another, slower pass to cover these areas. Ensure the edge is fully submersed in flame, but with minimum overspray onto the sheet.
Charred edge after flame polishing Too much heat Use MAPP or propane rather than Hydrogen/Oxygen mixture. If MAPP gas is unavailable and Hydrogen/Oxygen torch is used, make sure flame is bright red/orange rather than invisible blue
Dirt or contamination Make sure edges of sheet are free from dirt or contamination prior to flame polishing
Blisters on edge after buffing Too much heat See above recommendations
Rough edge after buffing Improper edge preparation Make sure all tooling marks are removed by wet sanding edge finishing prior to buffing
Melting from edge finishing machine Feed rate too slow Increase feed rate
Chipping from edge finishing machine Feed rate too fast Reduce feed rate

Cementing Operations

ProblemCauseSolution
Crazing Cementing flame polished or buffed edges Avoid cementing after these edge finishing steps
Bubbles Uneven edges, allowing air to flow into gap Edge finish or rout edges prior to cementing
Premature weight application Adjusting timing of weight application so that the application of weights will not cause the cement to flow out of the joint
Removing weights too soon Allow longer cure time
Incorrect weights Weights should be 1-2 lb per square inch of joint area
Cement applied too quickly Make sure to stay behind the front of the cement stream. This will prevent gaps from forming in the joint
Weak joint Insufficient cure time Allow part to setup for at least 15 minutes before moving and 24 hours before performing subsequent fabrication steps
Not enough cement in joint Use an applicator with a large diameter tip. Apply cement slowly to ensure joint is completely filled with cement. Tilt the piece slightly to allow cement to flow into the joint. Scrape one side of edge to allow cement to fill the joint better
Bad cement Ensure cement is fresh and container is closed tightly when not in use
Hazy joints Humidity too high

Try another cement

Try to work in a less humid environment

Try adding acetic acid in small concentrations (3-5%) to slow the rate of evaporation of the cement

Thermoforming Operations

ProblemCauseSolution
Blistering Surface temperature of sheet is too high Reduce heat time, oven temperature, or increase distance from sheet to heaters
Inadequate part definition Sheet temperature below optimum forming temperature For high definition parts, heat to the higher end of the forming temperature i.e. 320-350°F

Painting Operations

ProblemCauseSolution
Inadequate paint adhesion Dust or other particles on surface of sheet Remove particles prior to painting using an ionized air gun
Improper paint mixture Make sure mixture is at the right proportions
Residue left on sheet from paper masking Clean sheet using up to 50% IPA solution in water. Rinse thoroughly with water
Ghosting or hazing effect Use of incompatible paint remover If using paint removers, make sure to minimize the contact time on the sheet
Crazing Incorrect Paint See recommended source of supply in this fabrication manual for approved paints.
Paint contacted sheet in areas of high stress Make sure sheets are fabricated with minimum stresses