Casting issues

General Discussion
1

I’ve tried to cast the castable resin 4 times now with NO usable results.

It appears the burnout isn’t complete.
The resin is cured (after 24 hours in a fingernail salon light box, the resin is very light purple and a bit brittle).
I’ve been using a 1.5" x 2" flask.
I’m using PlastiCast investment.
Burning out schedule: 2 hours at 300 degrees, 2 hours at 600, 2 hours at 1350, then down to 925 for vacuum casting.
I put 5 small holes (approximately 1/4 inch diameter at the entry door of the oven and left it open about 3/8 of an inch during the 1350 degree part of the burnout (I was hoping more oxygen would get into the burnout chamber).

Have any of you had success using an electric burnout oven?
Do you have any suggestions?

Peter

2

Check out the burnout schedule and make sure your investment is compatible with resin based models. From what I gather it isn’t as easy as wax models.

3

Try blue cast…
For dental Framework i use grey V3 and 2°C/min up to 900°C.
Takes a while but I have almost perfect results… I cast 8 everydays 6days a week…

4

Thank you for sharing your results. It does sound like you’re doing the right things – postcuring sufficiently, good investment, increasing airflow – so I’d like to ask a few more specific questions to try and help.

Postcuring: your length of time and color/texture change sounds great. Are you rotating and/or flipping over your parts so that all sides receive the same exposure? And are you curing with supports attached?

Investment: assuming you have followed the mixing and setting instructions for Plasticast, this shouldn’t be an issue. Perhaps just check the expiration or batch date on your investment, to make sure it isn’t too old/degraded.

Oxygen: the holes will help with getting some more oxygen into your kiln. Do you have a venting system or fan running to encourage actual air flow?

Pictures would be extremely helpful in assisting with your issues; we can sometimes diagnose specific problems depending on the casting results we can see. A few additional questions: what metal(s) are you working with? Are these pieces new designs, or something you have cast successfully in the past in other materials?

5

bad casting - Copy.jpg1069×1043 212 KB

Here’s a picture of a piece I cast in silver. It’s about 1/2 inch long.

Somebody on another forum suggested the peak oven temperature should be 1500 degrees. Has anybody tried that?

Peter

6

need to add boric acid to go that high. without it could get investment breakdown

7

Caylee, answers to your questions:
I am curing with supports attached. These pieces are so light, they are curing completely without rotating or flipping.

The oven has a vent hole at the top (approximately .75 inch diameter). The 5 small holes (approx. .25 inches) are in the front bottom edge. And I left the door slightly open during the 1350 degree part of the burnout. No fan running.

I added a pic to show some of the poor casting issues.

I have not cast this design in other materials. The sprue, which were wax, came out correctly.

8

You cannot expect to get good casting results with a 6 hour burnout. Count on it being twice that and a different ramp: https://formlabs.com/support/materials/using-castable-resin/#burnout Your top end temperature is also not high enough, needs more like 1400. Stick to the Formlabs burnout schedule and you will have better luck.