Beyond The Sprues

Modelling => Tips, Tools & Techniques => Topic started by: Kerick on May 04, 2021, 11:20:44 AM

Title: UV casting resin
Post by: Kerick on May 04, 2021, 11:20:44 AM
Over on Whatifmodelers site there was a thread about epoxy resin cured by UV light. Usually used by craft and jewelry makers this looked like a probably useful tool.
I gave the UV resin a try and here is what I came up with. First of all the bottle I bought at Micheals craft store was $16.99. Not super cheap but not bad either. Also a pound of modeling clay for a mold. I cut a pill bottle in half to hold the modeling clay so it wouldn't deform later.

(https://live.staticflickr.com/65535/51157642180_e0fc050ef5_c.jpg) (https://flic.kr/p/2kWChHs)

I made "feet" to hold the pill bottle half from rolling around with Aves epoxie sculpt.

(https://live.staticflickr.com/65535/51157642265_818219210b_c.jpg) (https://flic.kr/p/2kWChJV)

I had to make the mold extend beyond the pill bottle to fit the length of the fuel tank half. Actually making the mold in the modeling clay was easy. I just had to make sure clay was pushed all the way up to the edge of the tank to get a proper complete shape of the mold. Detail was very good except where clay didn't get pushed into the corner where the fin met the tank. If I did this again I would push a little clay into these type of spots before pushing the tank into the clay. As I wasn't going to use the fins anyway it didn't matter here.

(https://live.staticflickr.com/65535/51157320009_86dcfb94cb_c.jpg) (https://flic.kr/p/2kWACWM)

I took the mold and the UV resin outside in the full sun and set up on an overturned trash can. All set to go and I thought I should have a mold release agent. I grabbed a can of WD-40 spray oil. One little squirt was more than enough to coat the mold. Probably too much. I tipped the mold up to get as much to run off as possible. I stared to fill the mold with resin and it started to harden almost immediately. It took a couple of passes to fill the mold and just a tad more to make sure it was filled all the way. I had scribbed a line around the top of the tank half for a fill line. I turned the mold about once a minute for five minutes. More than enough time but I wanted to be sure.

(https://live.staticflickr.com/65535/51155868312_e23ff9086c_c.jpg) (https://flic.kr/p/2kWtcpw)

After it was hard I removed the part by prying under the end of the tank with a model knife. It was a little stubborn but came out in one piece and didn't destroy the mold. I'm not sure if the WD-40 made much difference. I would have to try a new mold without oil to see for sure. I refilled the mold for a second part and it came out nearly as good as the first. Not bad for modeling clay.

(https://live.staticflickr.com/65535/51156534551_a633926cfc_c.jpg) (https://flic.kr/p/2kWwBsp)

The mold didn't look too good after the second part was removed. I blame it on the WD-40. After lots of sanding these should be usable parts.
Of course, by the nature of the UV resin you can only make one sided parts. If I were going to make more than a couple parts I would use a silicon type mold material that would be more durable. The biggest advantage I see here is the curing time of only a few minutes in direct sun and very clear resin material.
Title: Re: UV casting resin
Post by: Jeffry Fontaine on May 04, 2021, 11:30:16 PM
Thank you for sharing!
Title: Re: UV casting resin
Post by: Frank3k on May 04, 2021, 11:51:27 PM
Looks good for a first attempt. If it's like most of the "clear" resins used for 3D printing, it will yellow (slightly or a lot) over time as the interior cures.
Title: Re: UV casting resin
Post by: Kerick on May 05, 2021, 01:30:28 AM
This resin is meant for making crafts and jewelry so is supposed to stay clear. As it will be painted that doesnít matter in this case.
Title: Re: UV casting resin
Post by: GTX_Admin on May 05, 2021, 02:26:04 AM
 :smiley:
Title: Re: UV casting resin
Post by: apophenia on May 05, 2021, 05:50:01 AM
Cool technique ... thanks for sharing.

If the resin yellows as it cures from the inside, could that curing process effect paintwork? If so, how long would it take until the resin was completely cured?
Title: Re: UV casting resin
Post by: Frank3k on May 05, 2021, 11:58:49 AM
I'm sure the resin is cured - it's just that exposure to UV tends to affect the clear resin (extra curing?), turning it yellow.
Title: Re: UV casting resin
Post by: Kerick on May 05, 2021, 01:09:46 PM
Unfortunately when I glued the resin parts I made to the plastic part I used as a master the resin part appeared to have shrunk a couple of millimeters. Something to keep in mind during future use. Itís usable but will require more PSR than I had hoped.
Title: Re: UV casting resin
Post by: apophenia on May 06, 2021, 07:45:57 AM
... Something to keep in mind during future use...

That sucks but, as you say, let's you know how to plan around shrinkage in the future.

Frank: Thanks for the explanation. So, once painted over, no more UV concerns  :smiley: