Casting Sending a BJD 3D print to a Casting company - how do I prepare?

I've been sculpting and casting for a few years now, and here's what I've found:

1. every tiny detail/imperfection will show on the final cast, so you want to make sure that as you prime him you sand any printing lines or imperfections--get him as smooth as possible! This means that you need to spray, sand, and spray until he is smooth.

2. As long as you spray in thin coats, the logo should be fine. Make sure that you don't put the coats of primer on too heavy, just a light coat then let it cure- repeat, just until you can't see the resin underneath. If you end up having to spray more, you can always cover the logo with some sticky tack once it has a good coat of primer.

3. As long as you use a good primer and spray in light coats, you shouldn't lose a lot of detail. I would go with Mr Surfacer 1000, or 2000 if you have especially tiny details (2000 has a finer spray). Also, be careful when sanding so that you don't get scratch marks (I would use a sanding sponge with a super fine grit).

Edit: I would end with a final coat of primer to make sure all sanding marks are gone, and this gives it a nice finish as well!

I would particularly make sure that there is no resin showing underneath as 3D-printed resin can inhibit the cure of the mold.

The casting company could have more specifications, but this is what I have found at least when casting my heads.

Hope this helps!

 

Ray Vel gives excellent advice. The only thing I would add is to make sure you talk to the caster about what primer to use before you spray anything on to your print.
Some materials doesn't like each other, so if the caster have a prefered brand of primer you kind of have to work with that, even if it's expensive or hard to get or not your prefered product to work with.
If you have a different preference you could probably send your caster a sample of that and they may be willing to test it for you to see if it works (I have done that in the past), but talk to them first before you do anything.

Personally I would not leave the last layer pf primer unsanded unless the caster specifically asks you to. Unless you have a very good spray set up and a fair bit of skill, it's very likely that the spray goes on a little bit uneven and that will show (typically a bit of texture difference behind ears and in other "shaded" areas). Sanding last gives much better control over the surface.
The last steps of sanding is done wet with a very high grit so as long as you haven't taken any short cuts in finishing before that, there is little to no risk for visible sanding marks or scratches.

 

Glad to be of help!

Yes, Mr surfacer is a grey color that shows up very nice on white. as you sand, this will help to identify the areas that need more work.
The lips and ears are definitely a challenge! I usually end up taking a cotton swab with acetone and 'melt' the tiny imperfections in those crevices before I start priming, but this can take away detail, so that may not be the best option for your sculpt. For the mouth I usually take the edge of some normal sand paper and gently sand out that bit.
You should be able to get in the inside of the head with the sanding sponge, as they are quite flexible.
https://www.amazon.com/gp/product/B01F7Y384S/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 <<these are my favorite sanding sponges. they come in a variety of different grits.
Yes, the curing time of Mr Surfacer is about 30 mins to an hour. It definitely needs a warmer environment and low humidity much like MSC.
Casting dolls is all trial and error I have found, especially when doing it yourself! Sending it to a caster is probably the best way for success if you want a really nice quality doll first go.
But the priming process is, in my opinion at least, the easiest, if not the most tedious part.
Unless the company sands the seam lines, you may have to sand those. But what your master looks like is basically what you will get! You definitely want to take the time to make the master as perfect as possible.

That all being said, this is what i found to work, but isn't the end all be all. If you are printing the head yourself, I might suggest printing a spare one and doing some test runs so that you can experiment some.

 

I would say just thick enough where everything is fully covered and smooth. The details will begin to fade if you put too many coats. I would make sure you rotate him with each coat to make sure all of the crevices are covered.

I wish you all the best with your dolly!

 

You will be able to see the detail inside the head that you are worried about.
You can sand it away with a coarse grit. Then smooth it with the fine grit that you have.
Then you can prime that part again

That said, it's inside of the head. It does not have to look perfect in there and I have had many dolls with less than perfect interior finishing. In my opinion, it's not worth fussing over.
The likelihood of your customer noticing is low and likelihood of them caring is even lower.

 

Yes, it will show in the cast. This is a What You See Is What Will You Get kind of situation. I agree it's not much to worry about unless the caster whants you to remove it. There are plenty of rough insides out there, so as long as it is not bad enough to trap bubbles or to cause unneccesary wear on the mold it's fine to leave it. If it is bad enough to cause a problem with the casting, the caster will be able to tell at a glance when they have it in their hands.
Speaking of... Have the caster seen the inside of the head? There does appear to be a rather large ovehang under the magnet socket. Keep in mind that it has to be possible to pull the inside part of the mold out of the head back. Silicone is flexible and small overhangs are usually ok, especcially if they are at a bit of a soft slope, but this looks like a sharp shelf. You may want to double check this with them, if you haven't discussed it already.
If it was me casting that head, I would suggest letting the socket continue straight down to meet the inside of the head cap.