aaronreichmenberliner commented 7 years ago

Need to draft experimental methods for implementing an epoxy Infiltration of Chamber/Floor using BJB epoxy resin (TC–1614) as described by Stratasys

aaronreichmenberliner commented 7 years ago

These two documents are very helpful.

aaronreichmenberliner commented 7 years ago

@luzlab

Epoxy Infiltration Methods Take 1

Summary of Epoxy Infiltration From Stratasys:

BJB epoxy resin (TC–1614) penetrates the surface of porous and semi-porous parts. FDM parts are immersed in the resin and a vacuum is drawn to infiltrate the epoxy into the part. In addition to a vacuum chamber, an oven is needed to pre-heat and cure the epoxy. Epoxy infiltration offers an airtight and watertight seal up up to 65 psi (448 kPa). Parts sealed by this method also withstand high temperatures and are chemically resistant. The sealing process is straightforward and can be completed in less than three hours but is somewhat expensive due to the cost of the epoxy. When care is used in the infiltration process, there is little change in the part’s dimensional accuracy. BJB TC–1614 may be used on any of the currently available FDM materials.

Background

We will use epoxy filtration to seal the Crucible Chamber and Floor components. The chamber and floor are subjected to temperature and pressure extremes from -80,40ºC and 10 kPa to 101 kPa. As a result, the chamber and floor must be watertight along cooling lines and vacuum tight within the chamber when exposed to near vacuum lines.

Material Sourcing

TC-1614 A/B
Vacuum chamber
Industrial oven
Large/X-large ziplock baggies
Hanging wire
Disposable Cups/Tray trey

Methods

Measure some set of dimensions. Weigh 3D printed parts to determine initial mass. Compare with calculated mass from CAD by subtracting the measured mass from the calculated mass to get mass of porosity mp. Calculate the volume of porosity Vp using the mass of porosity mp and material density rho. Determine infiltration time t from porosity Vp and infiltration time X.
Heat TC-1614 A/B epoxy in separate containers to 37ºC in a temperature controlled industrial oven. This will lower viscosity and increase the absorption rate of epoxy into the part
Heat 3D printed parts to 40ºC. This will aid in epoxy infiltration. Avoid distortion of part.
Add TC-1614 A/B epoxy to ziplock bag. Mix. A bag that is too large will require more volumetric amounts of epoxy. Squeeze out as much of the extra air in the bag to assure part is fully submerged and coated with epoxy then seal bag.
Add 3D printed parts to ziplock bags and place in heated oven at 40ºC. Soak for 20 minutes.
Remove part from bag. Place in vacuum environment for calculated time.
Hang parts in oven at 40ºC with wire over a cup or bucket to allow continued drainage of excess epoxy. Wipe off any areas of pooled epoxy with a gloved finger or brush. Monitor any sags or drips for the next hour or until epoxy has gelled.
Weight epoxy-treated parts to determine final mass. Calculate the increase in porosity. Measure dimensional change by remeasuring some set of dimensions.

Questions

Do we submerge the part then place the part in the vacuum or do we leak the part submerged in the vacuum?

aaronreichmenberliner commented 7 years ago

gdrive source

aaronreichmenberliner commented 7 years ago

Part Modeling for Testing

Making crucible chambers can get expensive if we have to make many. Testing is also complex. So we will make test parts to evaluate the effectiveness of the sealant in terms of air and liquid sealing.

Parts modeled in Autodesk Fusion 360 and loaded into Clean Crucible A360 repo.

Test part wall thickness and shape are comparable to Crucible chamber. Test part connectors will fit the 1/8" brass fittings as with Crucible chamber.