This document presents a brief overview of the steps required to exchange
photopolymers in SL equipment which uses the auto refill system. The steps are
necessarily generalized, you should follow the equipment manufacturer's
recommendations relative to specific issues related to handling their
equipment.
Note: If you are changing from an acrylate based material to an epoxy based
material, give special attention to the directions for removing all the
acrylate photopolymer residue before installing the epoxy material. Some epoxy
photopolymers can react adversely with some acrylate components; adequate
cleaning of the equipment before installing new photopolymer is your best
protection against possible cross contamination. Basically, the criteria for
acceptable cleaning is: if it is tacky, then it is not clean. The requirements
for cleaning can be less stringent when changing between compatible resins.
Use adequate personal protective equipment during all phases of the resin
exchange. Neither old nor new resin should be exposed to sunlight or
fluorescent light (actinic UV light) during the resin exchange process.
General Procedure
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Shut off the laser system and the tank heaters.
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Use adequate personal protective equipment to guarantee no skin contact with
the resin during the exchange.
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Shield or cover any components sensitive to resin contamination, e.g., beam
profilers/sensors that may be located near the tank of photopolymer.
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Follow the manufacturer's directions for removing the photopolymer from the
tank.
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Draining presents an opportunity to filter the existing resin, drain through a
screen, cheesecloth, or other filtering apparatus to remove polymerized
material from the liquid.
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The last resin remaining in the tank may be noticeably viscous, especially in
the case of an epoxy. It is best to discard such resin since it can promote
viscosity increase if added to fresh resin.
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The last resin remaining in the tank may need to be scooped from the tank
manually.
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Scrape or squeegee the tank walls, base and other components until as much
resin as possible has been removed. Also scrape away any polymerized residue
that may be adhered to the resin handling components like the tank walls,
elevator arms, etc.
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Wipe the inside of the tank with absorbent paper towels. Pay special attention
to any components that may tend to trap resin.
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Soak an absorbent towel with clean solvent (the same solvent recommended for
cleaning parts should be satisfactory) and wipe the inside of the tank a
second time. Final wiping with isopropyl alcohol (Isopropanol) usually works
well. Because alcohol is flammable, it must be used in a well ventilated area
away from sparks or open flames. Remember, if a surface is still tacky, then
it is not clean.
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Be sure all surfaces are dry before proceeding, then add new resin to the tank.
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Install the vat in the machine following the manufacturer's recommended
procedure.
Tank exchange procedure for the automatic resin refill system
The following steps are intended to be an overview of the procedure and are
not intended to be exhaustive. (Follow the manufacturer's recommendations when
available.)
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Cap the vent on the resin container.
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Remove the front (SLA-5000) or side (SLA-350/3500) and rear covers on the
bottom half of the machine cabinetry exposing the front of the vat and the
auto refill valve.
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Tilt out the container. Drain the hose and valve by activating the refill
valve using the system software or by turning the shaft on the bottom of the
valve manually. (If you turn the valve manually, it may perform an auto reset
if you turn it too far. If this happens, try again.)
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Remove the top cover inside the build chamber, exposing the recoat mechanism
and the vat.
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Once the resin has drained from the hose and valve, remove the hose from the
refill container end and from the valve end.
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On the SLA-5000, remove the shroud covering the valve assembly.
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Remove the inlet and outlet portions of the valve. Remove any seals or
gaskets. Wash all components in solvent.
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Wipe the inside the valve with a towel. Open the valve by using the system
software or by turning the shaft on the bottom of the valve manually. (If you
turn the valve manually, it may perform an auto reset if you turn it too far.
If this happens, try again.)
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Using the controls on the buildstation, lower the vat assembly (~ -4.5 inches)
and remove the vat from the build chamber, by rolling it out the front. (Note:
it may be helpful to align the casters to face forward before they touch the
floor.)
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Place the cover on the vat and latch it closed.
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Wipe all the wet components in the build chamber: platform support arms,
Zephyr blade, level sensor shroud. Once most resin is removed wipe the
components again using a towel soaked in solvent. It may be necessary to use
cotton swabs to clean small enclosed areas like bolt heads. (Note: if it is
necessary to move the Zephyr blade, do so by rotating the shaft coupling
adjacent to the drive motor.)
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Reassemble the automatic refill valve and attach the hose between the valve
and refill container. Be sure all seals are in place.
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Using the system software, move the blade toward the rear, then move it toward
the front until it stops on its own. This finds the Home position for the
blade, allowing the vat to be reinstalled.
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Install the new vat of resin by removing the cover and rolling the vat into
place.
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Prepare to raise the vat by checking the alignment of the lift points. Using
the system software, raise the vat. When the lifts contact the lift points,
wiggle the vat a bit to ensure that it is properly seated on the lift
mechanism.
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Continue to raise the vat checking clearances as the vat comes up. Be careful
for interference with the level sensor, Zephyr blade, elevator arms, etc.
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Once the vat is in place, home the elevator and home the vat.
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Install the new bottle of resin the refill chamber. Be sure the O-Ring goes
smoothly into the mouth of the bottle, you may have to help it along with your
fingers.
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Activate the automatic refill system. Once resin begins to drain into the
tank, then puncture the vent on the bottom of the container. (Note: waiting
until resin begins to drain will prevent any resin from coming back out the
vent hole when it is punctured.)
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Set the Zephyr vacuum as recommended for your particular machine. Typically
this is ~1/2 way up the window on the blade. (Note: some systems have two
valves that can be adjusted using a procedure from 3D Systems. Other systems
have a single valve and a coil of tubing vented to the atmosphere that
replaces the second valve.)
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Install the rim cover inside the build chamber.
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Replace the cover shroud on the valve assembly.
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Replace the covers on the bottom half of the machine cabinetry.
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Update the resin files on the machine and the Ec and Dp in the workstation
style files.
Finishing the Resin Exchange
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Turn on the tank heaters and close the machine.
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Update or create the appropriate resin parameter file and select the new file
as described in your machine operator's manual.
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Update or create the appropriate style files on your prepare station. Note
that the Ec and Dp for the resin are embedded in each style file used by the
Maestro software. These files must be modified manually.
Once the resin is installed in the tank, and the heaters are turned back on it
will be necessary wait for the temperature of the resin to stabilize and the
bubbles formed during pouring to escape. Working curve measurements and
diagnostic parts should not be prepared until the resin has stabilized. If it
is desired to build parts prior to this time, use the parameters supplied with
the material, but realize that the parts will likely contain bubbles and
recoating may not be optimal.
Build Parameters
See the DSM Somos® Resin Specific Build Parameters for detailed information.
Other Resources
3D Systems, Tips & Info Technical Bulletin: Polymer Change and Vat Cleaning
Procedures (P/N 19093-S08-01) which describes the recommended procedure for
exchanging polymer in SL equipment.
For Further Information Contact:
DSM Somos
Telephone: 302-328-5435, Fax: 302-328-5693
