Dan,
Part geometry dictates the procedure for thermal post-curing. To achieve higher temperature characteristics, the entire mass of the part must be held at the specified temperature for the specified time. In the case of SL 5410, the part should be held at 80C for 2 hours. What's not accounted for here is the ramp up and cool down times. A part of large mass will take longer to warm and cool than a part with a smaller total mass. Hence, you need to estimate your total oven time (2hrs + ramp up time + cool down time = total oven time).
When estimating cool down time, be generous. As thin features will cool faster than thick features, a fast cool down could allow internal stresses to force distortion and even crack the part. With an 80C curing, this is probably not likely. However, be forewarned.
Another factor for consideration is feature sagging. During the oven cycle, the SL part softens and may sag based on geometry. For a flat slab, no sagging can occur. For overhanging geometries and thin wall/features, you can expect sagging. There are a number of approaches to minimizing sagging: leaving the parts and supports on the platform, fixturing, and suspension. You should choose your approach based on the critical dimensions and of course...geometry. Curing the parts on the platform will create extra cleanup and may not support some geometries well (i.e. thin vertical walls,etc.) Fixturing will require serious thought to maintaining geometric fidelity and fabrication to create the fixtures may require signficant effort. Suspension can be done in a variety of materials, including sand, vermiculite and I've even heard of someone using silicone oil. Suspension in oil may not restrain internal stresses and the part may distort.
One last factor, your method of maintaining geometry may require extra oven cycle time to ensure the part sees the required profile. This is especially true if you decide to use a suspension technique.
Now I have a question, what ovens are currently being used for thermally post-curring SL parts? What do they cost?
Best regards,
Bob Kruger
Product Manager, Rapid Modeling Group
Ciba Specialty Chemicals
5121 San Fernando Road West
Los Angeles, CA 90039
818.265.7206
> owner-rp-ml@ltk.hut.fi wrote:
> > Hello all,
> >
> > Does anyone out there know the procedure for thermal post-curing SL
> > parts? I'm using SL5410 resin if it makes a difference.
> >
> > Thanks.
> >
> >
> > Regards,
> > Dan Davis
> > Head, RP&M Division
> > PROTON Berhad
> > Hicom Industrial Estate
> > Batu Tiga, PO Box 7100
> > Shah Alam, 40918 Selangor MALAYSIA
> > +60 3 515-2380
> >
> > For more information about the rp-ml, see http://ltk.hut.fi/rp-ml/
>
>
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