This fabrication bulletin addresses basic thermoforming of
DuPont™ Corian® solid surface sheet.
Molds can vary greatly depending on application and
desired mold lifetime. Surfaces should be smooth and the
mold material should not cool the formed part rapidly.
Thermoforming is a process by which Corian® solid surface
sheet is heated until it softens, then formed into a two or
three dimensional shape and cooled. Applications with
simple two-dimensional bends can be fabricated fairly easily,
while complex three-dimensional shapes can be fairly
complicated to fabricate and are beyond the scope of this
document. A key principle is to favor compressing the solid
surface over stretching it. Thermoforming can be an iterative
process, with the mold design, the shape of the blank to be
formed, and the forming conditions all important.
Protective equipment
Both the ovens and heated sheet have the potential to cause
serious burns. In addition to standard protective
equipment, insulated gloves are required. Inspect the gloves
before use as thin spots, holes, adhesive or moisture can all
reduce insulation resulting in burns. If forming multiple
parts consider having multiple gloves per person as sweat
will reduce the effectiveness of the insulation. Gauntlets are
recommended to protect arms if long sleeves aren’t worn.
Leather gloves should be worn for handling room
temperature sheet and molds. Eye protection and steel-toed
shoes should be worn at all times.
A vacuum membrane press is often used with single-sided
Molds can also serve to hold parts for trimming operations.
Temperature Measurement
There are a variety of methods to measure temperature. For
sheet temperatures, infrared thermometers are very useful
as they can read temperatures by simply pointing the
thermometer at the sheet or the membrane of a vacuum
press. There are also indicator strips, which change color to
indicate the maximum temperature reached. While
cheaper, these are not as accurate.
Infrared thermometers however, are not as effective for
determining oven temperatures as the accuracy of the
measurement is affected by the cleanliness and oxidation of
the metal surface. A contact thermocouple is best for
measuring platen temperatures. A standard thermocouple is
best for air temperatures in an air circulating oven and
internal sheet temperatures. Digital thermometers are
available that accept multiple types of thermocouples.
A clock or stopwatch may suffice, but it is best to have a
timer that will alarm after a set time period.
Dual platen ovens are preferred for their consistency and
speed of heating. Air circulating ovens may be used, but it
may be more difficult to obtain uniform sheet temperatures
and heating takes approximately five times as long as a
platen oven. The ovens should be capable of reaching
200°C (392°F). Temperature uniformity is a key to
consistent forming. If the lower platen of an oven does not
slide out and reaching into the oven is required the upper
platen should be blocked so it cannot close while someone
is reaching for a part.
Variable room conditions will cause variable results. Ideally
the room with the oven and molds will be temperature
controlled. If air currents are an issue, consider installing
curtains in the thermoforming area to minimize
temperature variation.
Thermoformability varies by aesthetic. The limits provided
here are the best performing colors. Solid, lighter colors will
perform better than darker colors and colors with larger
particulates. It is important to understand the characteristics
of the aesthetic to be formed. Prior success with a different
color is not a guarantee of success.
Page 1 of 8
Table B-1 is a guide to the minimum inside radius for two
dimensional bends. Three dimensional forming is much
more complex, but local elongation should not exceed
10%. A simple way to evaluate whether a part can be
formed on three dimensional molds is to use kraft paper.
Try forming the paper over the mold. Areas with excessive
wrinkling will be potential problems. Consider forming in
multiple pieces and seaming to address these areas.
Table B-1
Sheet Thickness
Minimum Inside Radius
25 mm (1")
12 mm (1/2")
76 mm (3")
127 mm (5")
6 mm
19 mm
The shape of the blank, or piece to be formed, can be a critical
factor in successful thermoforming. For two-dimensional
forming the blank will be close to the final dimensions. Some
excess should be allowed for trimming. The edges will not
be square after forming due to deformation.
For three-dimensional forming it is often desirable to have
as little excess as possible. In many shapes the maximum
deformation is near the edge of the part and there will be a
strong tendency to wrinkle.
When developing prototypes it is often useful to mark a grid
on the DuPont™ Corian® solid surface before forming. The
deformation of the grid will help you understand how the
material deforms and what the blank shape should be.
When creating blanks that require a tight dimensional
tolerance to work successfully it is important to track the
original orientation of the blank within the sheet it is cut
from. The sheet retains some residual stress from
manufacturing that is relieved during thermoforming. This
results in a very slight reduction in length and growth in
width and thickness. Alternatively the sheet could be
annealed before cutting. Annealing is performed by heating
the sheet to thermoforming temperatures and then cooling
very slowly and evenly, typically by just turning the oven off.
This process does take hours and generally isn’t necessary.
Corian® solid surface is sensitive to notches when formed.
Any notches or defects at the edge of the sheet can lead to
tearing. Remove any rough edges from cutting. It is also
recommended that the edges be eased slightly.
Molds can be a significant part of the overall cost of a
project, particularly for large molds that only need to be
successfully used once. Mold material selection can vary,
taking into account the number of parts needed, shape
required, surface finish required, etc.
Wood-based materials (MDF, plywood, pine, hardwood)
are commonly used for low cost, rapidly manufactured
molds. Wood-based materials do have disadvantages. Grain
may leave a pattern on the molded surface. Sap or glue may
leave residue on the surface. Longevity is also limited, as
water in the mold heats up rapidly it damages the mold
over repeated cycles. The molds are also heavy. Aluminum
filled epoxy paint applied to the surface of the mold will
create a smoother surface and extend the mold lifetime.
Synthetic mold materials are also available. These materials
machine well and last longer, but are heavy and expensive.
Both wood-based and synthetic molds are most commonly
made using a CNC, though they may also be fabricated
by hand.
For high volume molding, composite or metal molds may
be attractive. They provide a good finish and long life, but
are much more expensive and require skill and equipment
that most fabrication shops may not have. Metal molds do
have special requirements. Due to the high heat
conductivity and heat capacity, metal molds can cool the
solid surface too rapidly. In many cases metal molds should
be heated to allow slow cooling of the molded part.
Other Design Considerations:
Molds may be male, female, a combination of both, or
two-sided. A two-sided matching mold with both male and
female sections is shown in Figure D-1. To reduce the risk
of wrinkling when molding deep shapes, a male mold is
preferable to a female mold. If a piece is to have a surface
texture imparted by the mold, the mold is determined by
the convexity/concavity of the surface to be textured: a
textured concave surface requires a male mold, while a
textured convex surface requires a female mold
Many molds have features to help locate the blank on
the mold.
Do not attempt to form seamed sheet. If seams are required,
the sheet must be formed, trimmed, and then seamed.
Page 2 of 8
DuPont™ Corian® Solid Surface Fabrication/Installation Fundamentals
allow the material to get caught over a sharp edge. This is
shown in Figure D-4 where excess material is trapped
between the mold and the membrane, preventing it from
drawing into the cavity.
Figure D-1
Part release is another consideration. A deep and/or steep
piece formed over a male mold will shrink around the mold
as it cools and may stick to the mold. Incorporate a
5-degree (minimum) release angle into the mold (See
Figure D-2). If a negative draft angle is required, a
multiple-part mold that comes apart to release the solid
surface is required.
Figure D-2
“Helper pieces” can be used in addition to the mold to do
some initial shaping before vacuum membrane is activated
or work with the vacuum membrane to help forming in
difficult spots as shown in Figure D-3.
DuPont™ Corian®
Figure D-4
Steps to completion:
Figure D-3
When using a female mold, bevel the cavity edges to
prevent the material from being trapped between the
forming membrane and the edge of the cavity. Make sure
nothing inhibits smooth motion of the material as the
membrane presses it into the cavity. This will allow the
material to move fully into the mold. Above all, do not
1. Drill a 1/32" (0.8 mm) diameter hole halfway into a test piece
of Corian® sheet. The sample should be at least 6"x 6" (150 mm
x 150 mm). Put the hole near the center of the sample.
2. Insert the thermocouple wire into the hole, bend it to fit and
tape it in place.
3. Insert the thermocouple wire plug into a digital thermometer.
Turn on the thermometer; which should now show the
temperature of the sample.
4. If not using an infrared thermometer, apply a temperatureindicating label near the end of the wire.
DuPont™ Corian® Solid Surface Fabrication/Installation Fundamentals
Page 3 of 8
1”x1” (25 mm x 25 mm)
Piece of Aluminum Tape
Push In
These times may vary with oven design. Follow the oven
calibration procedure to determine the proper heating
times. Note that the time for heating may vary with the size
of the part and the rate at which the oven returns to its
temperature set point after the sheet is inserted.
Cut Away for
Clarity of
1/ ” (0.8 mm) Diameter Hole
Sketch Only
DuPont™ Corian® Sheet
Figure E 1
5. Set the oven to the intended temperature and allow the oven
to come to a stable temperature for at least 20 minutes.
6. Put the test sample in the oven and start the timer.
7. When the temperature on the thermometer reaches within
10°F (5°C) of the oven set point temperature write down the
timer reading and remove the piece from the oven.
8. Read the surface temperature with the infrared thermometer
or inspect the temperature-indicating label and note which
dots turned black.
The surface temperature should be approximately the same as
the oven temperature. If not, check the calibration of the
temperature monitoring equipment.
9. Place the hot sample into the mold, and allow the piece to cool
until the thermometer reads 180°F (82°C).
10. Note the timer reading. This is how long each piece should be
cooled in the mold. This is the minimum time that parts
should be cooled. If multiple parts are formed the cooling
time will be extended as the mold warms.
A platen oven has heated plates that will heat sheets much
more quickly than an air circulating oven. This results in
higher productivity. The platen press must be capable of
uniform heating up to 200°C (392°F).
The upper platen is hot and heavy. If the design requires
reaching into the oven the upper platen should be
blocked when adding or removing sheet. This will
prevent the oven from closing on someone who is
reaching for a part.
The platen oven should be set to the desired sheet
temperature. Place the DuPont™ Corian® sheet into the
preheated platen press with the heat setting between 300°
and 325°F (150° and 165°C). A rough guideline is that the
sheet should be heated one minute for every millimeter, so
6 mm (1/4") for 6 minutes, 12 mm (1/2") for 12 minutes.
Page 4 of 8
The heating times provided assume the sheet is at typical
room temperatures. Temperatures well above or below room
temperature will affect heating times.
If sheet is not stored in a climate controlled building, consider
bringing it into the shop the day before so it conditions
Steps to completion:
1, Preheat the platen oven to the desired forming temperature.
Make sure the temperature is stable.
2. Have everything needed (safety equipment, thermometer,
mold, etc.) ready and accessible.
3. Wearing thermal gloves and gauntlets place the blank in the
platen oven. If you are forming a small sample insert spacing
blocks if necessary.
4. Close oven and start timer. Generally 6 minutes for 6 mm
(1/4") sheet or 12 minutes for 12 mm (1/2") sheet.
5. When the blank has been in for the designated time, open
the oven. If the platen oven has a sliding lower surface it is
good practice to scan the surface with an infrared
thermometer to check that the sample is the correct and
uniform temperature.
6. Transfer the blank to the mold.
7. Follow the instructions in the following sections for the
specific type of mold used.
Corian® solid surface is very rubbery at thermoforming
temperatures and larger blanks may be difficult to handle.
Make sure enough personnel wearing proper protective
equipment are available to help transfer the blank safely.
Burns will result if sheet makes direct contact with bare skin.
Make sure the oven is clean. Any dirt or residue will transfer
to the sheet and may become embedded in the surface,
requiring additional sanding to remove.
If thermoforming small pieces, use some scrap samples evenly
spaced in the oven so the platen lowers evenly on the part to
be formed.
DuPont™ Corian® Solid Surface Fabrication/Installation Fundamentals
If writing on the on the sheet to identify parts, be aware that
the ink can transfer to the oven platens and onto future
sheets. Consider removing labels before heating sheets.
Air circulating ovens can be used successfully, but it is
important to understand the oven. Heating is much slower
than in platen ovens. It will take approximately
5 minutes per millimeter (6 mm [1/4"] - 30 minutes, 12 mm
[1/2"] - 60 minutes) in order to uniformly heat sheet to the
oven temperature. It is important to calibrate and
understand the characteristics of the oven.
Infrared or radiant ovens are commonly used for heating
unfilled plastics. When used with unfilled plastics the
infrared radiation can partially penetrate the sheet, heating
uniformly. Filled polymers, such as DuPont™ Corian® solid
surface, do not transmit infrared radiation and all the
energy is absorbed at the surface. The ability to heat the
surface faster than the interior can transfer heat often
results in thermal damage at the surface with a center still
too cool to form. Infrared ovens are NOT recommended
for heating solid surface materials.
Air circulating ovens rely on air circulation to maintain
uniform temperatures. This air circulation will be disrupted
by the thermoforming blank. An oven that heats uniformly
with small samples may have poor temperature control if
the blank is near the size of the oven.
Corian® solid surface should always be uniformly heated
and cooled to minimize stress in the final part. Spot heating
will create stress within the material. This stress may lead to
failure in later processing steps or in use. Spot heating is
NOT a recommended practice.
Fabricators will often set the oven temperature higher than
the desired sheet temperature to reduce the heating time.
This is feasible, but it’s important not to set the temperature
above 400°F (205°C). The sheet itself should not be
allowed to exceed 350°F (177°C) as there is a risk of
overheating. The sheet temperature will not be uniform
when removed from the oven. The blank should be allowed
to “rest” 1-2 minutes so the center and surface temperatures
can equilibrate. Careful calibration studies should be done
to develop an understanding of the proper times and
temperatures (note this may vary with blank size) if setting
the oven to a higher temperature.
Steps to completion:
1, Preheat the air circulating oven to the desired forming
temperature. Make sure the temperature is stable.
2. Have everything needed (safety equipment, thermometer,
mold, etc.) ready and accessible.
3. Wearing thermal gloves and gauntlets, place the blank in the
air circulating oven.
4. Close oven and start timer. Generally 30 or 60 minutes (for
6 mm [1/4"] and 12 mm [1/2"] sheet, respectively) will be
The forming process will vary depending on the mold
type. It is important to remember that the thermoforming
blank starts cooling as soon as it is removed from the oven.
The amount of time that one can work with the material
will vary based on the room conditions and the mold type
and temperature.
The mold should be ready before beginning to heat the
sheet. If using lubricants such as wax or talc, apply them
before starting the heating process. Sometimes it is
desirable to have the mold heated before forming. If
forming multiple parts sequentially the mold will warm up,
increasing the cooling time of the part and perhaps
changing the results. Preheating the mold before the first
part will aid in having a consistent process. More time is
available to work with the blank if the mold is warm.
Placing the blank in the correct place on the mold is
important. One can also start to shape the blank in the
mold using hands (using proper thermal gloves). If
forming using a vacuum membrane press, forming can be
assisted using hands pressing on the membrane. This helps
control wrinkling.
5. When the blank has been in for the designated time, open
the oven. It is good practice to scan the surface with an
infrared thermometer to check that the sample is the correct
and uniform temperature.
6. Transfer the blank to the mold.
7. Follow the instructions in the following sections for the
specific type of mold used.
DuPont™ Corian® Solid Surface Fabrication/Installation Fundamentals
Page 5 of 8
Apply Hand
During Early
DuPont™ Corian® Sheet
Figure J-1
Steps to completion:
1. Remove the hot blank from the oven.
2. Position on the mold. Having alignment features built into
the mold facilitates proper positioning.
3. Do any hand preshaping or use auxiliary forming pieces
4. Depending on the mold, the blank should be clamped in
place, the mold closed, or the vacuum membrane lowered.
5. Allow the part to cool to 180°F (82°C). The time required to
cool will depend on the room temperature, mold temperature
and the mold construction. Expect up to 30-45 minutes for
12 mm (1/2") sheet. Some parts can be cooled to room
temperature, but if a male mold is used a part can be difficult
to remove if completely cooled. If using a vacuum membrane,
an infrared thermometer can be used to read the temperature
of the membrane. It will generally be a few degrees cooler
than the sheet. For other molds, use scrap pieces with
thermocouples to establish cooling times.
Figure K-1
Thermoformed parts will generally need some trimming
and finishing. The edges of the formed part will no longer
be square. If precise dimensions are required the part needs
to be trimmed after forming. Some times the mold can be
used to hold the part for finishing. Other times a dedicated
fixture will be required.
In general, some finishing will be required. The degree of
finishing required will depend on the color formed and the
quality of the mold surface. A solid color with a high
quality mold surface may need only to be touched up with
a non-woven pad. Colors with particulates or formed on a
rougher mold will need to be sanded smooth.
Vacuum membrane presses are very useful, but the silicone
membranes are prone to tearing and are expensive to replace.
A little extra care in mold design and forming techniques can
greatly extend the life of the membrane. Some tips are:
Developing an economical and reliable thermoforming
process takes advance planning and attention to detail. It
will be important to keep good records to understand
which techniques give the best results or to aid in
troubleshooting. Thermoforming, more than most
processes, can be affected by external factors. Something as
simple as a door being left open that creates a draft in the
thermoforming area could affect results. An example
process record is listed below. Depending on the goal,
different data would be recorded. One shop may be looking
at mold economics and want to know how long a mold
lasts. Another may be trying to understand why they are
having inconsistent results, only to find that they always
have problems for the first few parts on Mondays and
institute a practice of preheating molds.
• Eliminatesharpcornersonmolds
• Lookforplaceswherethemembranewouldhavetobridge
a gap and stretch significantly and fill that space.
• UsehelperpiecessuchasinFigureD-3.Themembrane
will not have to stretch as much.
Selectively thinning or rebating the blank is useful in some
designs. Impact resistance will be lower in the thinned
sections. Thin the material using a router. It is important to
have a 1/4" (6 mm) radius at the transition between the two
thicknesses. An example is shown in Figure K-1 where a
deal tray is being formed in a horizontal top. Make sure the
routed area is smooth. Any variation in thickness may
telegraph to the top surface.
Page 6 of 8
DuPont™ Corian® Solid Surface Fabrication/Installation Fundamentals
Example Process Record
• Material(colorandgauge)
• Operatingprocedure
• Blanktemplateorprogram
• Oventemperature
• MoldID
• Moldtemperature(beforeandafter)
• Heatingandcoolingtime
• Trimfixtureorprogram
• Numberofpartsproducedonmold
• Day/Time
• Ambienttemperature
• Operator
• Successorfailure
• Processaidsused(talc,wax,etc.)
Having a written operating procedure helps ensure
consistency and also helps identify changes in techniques
that occur.
There is no “best” way to form parts. A shop that does
custom, one-of-a-kind parts will have different considerations
than one trying to manufacture many identical parts.
The following is a list of considerations for process and part
design, optimization, and troubleshooting.
Process Development/Optimization
• Ifthegoalisincreasingyourproductionrate,whatisthe
limiting factor? A platen oven can provide blanks for several
molds as heating is faster than cooling. But an air circulating
oven may only be able to provide blanks for one mold.
• Formingbroadarcs?Formatalowertemperature.The
increased stiffness will help form a natural arc.
• Minimizedeformationasmuchaspossible.It’spreferableto
have the material slide across the mold versus stretching. Also,
compression is preferable to stretching.
• Understandthetrade-offsinmoldmaterialdesignincluding
cost, lifetime, quality, etc.
• Theremaybeaslightcolorshiftwhenheatinglightercolors.
If the thermoformed part will be seamed to a flat sheet it is a
good idea to heat the flat sheet as well.
DuPont™ Corian® Solid Surface Fabrication/Installation Fundamentals
• Whiteningiscausedbymanysmallfailuresinthepartthat
scatter light. Possible causes include:
• Temperatureisn’thighenough–possiblecausesinclude:
wrong set point, oven not operating correctly, sheet not
heated long enough, or sheet was excessively cold going
into oven.
• Surfacecooledoffbeforeforming–possiblecausesinclude:
too much time from oven to mold or too much time
positioning on the mold.
• Exceedingmaximumdraws–possiblecausesinclude:too
tight a bend, too much elongation, or the blank may be
trapped during the molding process and unable to move
relative to the mold.
• Wrinklinggenerallyoccursinareawherethematerialis
compressed and it is easier for the sheet to buckle than
compress. Possible causes include:
• Excessivecompression–makesurecompressionisunder
10%. It may be necessary to break the part into multiple
pieces and seam after forming. Kraft paper can be used to
predict where the material will begin to buckle.
• Molddesigndoesn’tprovideresistancetobuckling
during forming, but changes to mold design may be
required such as moving to matched molds, switching from
female to male molds, etc.
• Blankhasexcessmaterial–thegreatestcompressionis
often at the edge of the part. Optimize the blank geometry
to minimize excess material.
• Tearingcanhavemultiplecauses
• Ifthetearstartsattheedgeoftheblankorifmultiplesmall
fractures are visible then check the quality of the blank
edge. A rough saw cut or nick can cause failures during
forming. Edges should be smooth and eased slightly.
• Theblankmaybepinchedbythemoldorbythevacuum
membrane, preventing it from moving. Try preforming by
hand or with a helper piece. A lubricant (talc or wax) may
help the part slide.
• Theparttearsinoraroundparticulates.Thecapabilityof
the color may have been exceeded. Colors with large
particulates do not form as well and some may require radii
of 6" (150 mm) or more. Better success may be obtained
by lowering the temperature slightly. Rebating in the
formed area is also an option.
Page 7 of 8
• Thesurfacerequiresexcessivesanding
• Iftheshowfaceisagainstthemold,checkthemoldfinish.
• Colorswithlargerparticleswilltendtoberougher.The
roughness will be greater if the show face is away from the
mold during forming. If possible, form the show face
against a smooth mold.
• Inconsistentresults–thisiswhereagoodprocessrecordis
• Ifconsistentsuccesschangestoconstantfailuredouble
check your equipment. There may be problems with the
oven (either heater, or calibration). Verify that the part is
coming out of the oven at the correct temperature and that
thermocouple to check the internal temperature.
• Ifresultsbecomeerratic,trackthemoldtemperaturebefore
and after forming, as well as the ambient temperature. Is
the sheet always the same temperature going into the oven?
Has the thermoforming area temperature changed? Is there
a new airflow pattern (i.e. a door is open creating a draft)?
Are there problems with the first part of the day, or do
problems develop as the mold warms up?
• Differentpersonnelgetdifferentresults–Thereisabitof
art involved in forming that is gained by experience and
may not be captured by formal procedures. Observe
personnel closely. One may be positioning the blank slightly
differently or assisting by hand where the other is not.
This information is based on technical data that E.I. du Pont de Nemours and Company and its affiliates ("DuPont") believe to be reliable, and is intended for use by persons having technical skill
and at their own discretion and risk. DuPont cannot and does not warrant that this information is absolutely current or accurate, although every effort is made to ensure that it is kept as current and
accurate as possible. Because conditions of use are outside DuPont’s control, DuPont makes no representations or warranties, express or implied, with respect to the information, or any part
thereof, including any warranties of title, non-infringement of copyright or patent rights of others, merchantability, or fitness or suitability for any purpose and assumes no liability or responsibility
for the accuracy, completeness, or usefulness of any information. This information should not be relied upon to create specifications, designs, or installation guidelines. The persons responsible
for the use and handling of the product are responsible for ensuring the design, fabrication, or installation methods and process present no health or safety hazards. Do not attempt to perform
specification, design, fabrication, or installation work without proper training or without the proper personal protection equipment. Nothing herein is to be taken as a license to operate under or a
recommendation to infringe any patents. DuPont shall have no liability for the use of or results obtained from such information, whether or not based on DuPont’s negligence. DuPont shall not be
liable for (i) any damages, including claims relating to the specification, design, fabrication, installation, or combination of this product with any other product(s), and (ii) special, direct, indirect
or consequential damages. DuPont reserves the right to make changes to this information and to this disclaimer. DuPont encourages you to review this information and this disclaimer periodically
for any updates or changes. Your continued access or use of this information shall be deemed your acceptance of this disclaimer and any changes and the reasonableness of these standards for
notice of changes.
© E.I. du Pont de Nemours and Company 2012. All rights reserved.
The DuPont Oval, DuPont™, The miracles of science™, and Corian® are trademarks or registered trademarks of E.I. du Pont de Nemours and Company (“DuPont”) or its affiliates. K-25297 7/12
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