Taking The Next Step (Casting) - Page 6

_fly_ · #76 16th Feb 2012, 10:10 PM

Thanks for the quick reply Russell,

Glad I didn't know before... I got a lot done in the shed today.

But now I'm going for a look.

Peter

BoomerangInfo · #77 16th Feb 2012, 10:17 PM

No worries. I should probably throw a caveat in there, that resin is a temperamental thing sometimes. When you want a slow set, it'll gel before you can poor, and when you want a rush job, it'll still be sticky 24 hrs later. 30 mins would be the least, probably at least an hour is best though. If it hasn't gelled after an hour, you have more problems than bubbles

Also note, in winter, set times are drastically extended, and it's anybodies guess.

Russell.

gawdelpus · #78 16th Feb 2012, 10:17 PM

Quote:

Originally Posted by BoomerangInfo

Fair enough, so how much mess was there with the paintbrush and your fingers(?) with all that raw resin slopping around?

Russell.

Hehe! no sticky fingers ,not even gloves, I have little wooden handles out of the tubes,I simply stood the blank up held the top wooden bit and painted with a half inch brush,mix was like honey so no drips

AuS MaDDoG · #79 16th Feb 2012, 10:23 PM

Hi Guys,

Good to see some success

the castings look good John. Maybe some mold release may help or oil the mold prior to casting.
Do you think if the sides of the molds had a slight taper from top to the curved bottom it may make them release easier ??

Were those ones from the first mold or the second one?

Cheers
Tony.

BoomerangInfo · #80 16th Feb 2012, 10:30 PM

Quote:

Originally Posted by AuS MaDDoG

Hi Guys,

Good to see some success

the castings look good John. Maybe some mold release may help or oil the mold prior to casting.
Do you think if the sides of the molds had a slight taper from top to the curved bottom it may make them release easier ??

Cheers
Tony.

I've tapered mine as my first mould cast I had to destroy the mould to get it out, but then, it was wood also

But even so, given the CNC does not make a "perfectly smooth" surface, I think all the little ridges probably act as a key for the resin as well, given it extra "cling".

Russell.

AuS MaDDoG · #81 16th Feb 2012, 11:23 PM

It will be interesting to see how the second mold releases as I used a 2.5mm ballnose for the final passes which ended up making the inner recess of the mould fairly smooth.

Keep us posted John.

Cheers
Tony.

gawdelpus · #82 17th Feb 2012, 01:34 AM

Quote:

Originally Posted by AuS MaDDoG

Hi Guys,

Good to see some success

the castings look good John. Maybe some mold release may help or oil the mold prior to casting.
Do you think if the sides of the molds had a slight taper from top to the curved bottom it may make them release easier ??

Were those ones from the first mold or the second one?

Cheers
Tony.

Tony this was the first mold ,now I have tried it I can see where I need to go with the next lot of casts, I will smooth the mold a bit with sandpaper and use some sort of mold release ,slight taper of side walls would help I am sure but might not be so easy to achieve even on the cnc hehe. Cheers for now

John

_fly_ · #83 17th Feb 2012, 09:01 AM

Hi, what are you guys using as a mould release agent?

I did my first cast last night, all went well.
Solid was fine, although didn't get as much mixing as I hoped for.
Glitter sinks.
Gum nuts must be harder as that didn't work.

I thought best to use something for release so I used canola kitchen spray.
Sprayed it in, it foamed up. I then used the airgun to blow most of it out. It obviously leaves the thinest of coats inside and they basically dropped out of the conduit tube when I took them out of the pressure pot.

Had a leak in the pressure pot (that wasn't there the night before). repaired it and it still leaks. Not keen on the air taps BGS sell. Think i need to get some compound to seal it instead of teflon tape (its a good one, not the cheap stuff).

Plasticine worked well as a plug and did not stick in any way to the resin.
Peter

AuS MaDDoG · #84 17th Feb 2012, 09:54 AM

Peter,

Using the conduit, you should only require a timber dowel and a small hammer to tap the blanks from the tubes. They should release easy for the first few castings and then after that you will need coat the tubes with some form of release agent/oil as they do eventually get harder to release.
The conduit seems to have some kind of film applied to the inside during manufacture which aides the release for the first few times of use.
Re glitter, glue the glitter to the tubes first then coat them in a thin layer of resin prior to casting.

Cheers
Tony.

_fly_ · #85 17th Feb 2012, 10:04 AM

Thanks Tony,
I am not up to casting tubes yet.
First batch I did were solid ones in 20mm conduit.
Bit thick but if I use smaller conduit I won't drill them straight enough to use them.
Might try a label and a glitter one next with tinted clear over the top, now that I know plasticine works as a plug without sticking to anything.
If I get badly bitten I would get a proper mould.
Peter

Dorno · #86 17th Feb 2012, 10:47 PM

Fly
You should have no trouble drilling them straight if you drill them using your lathe instead on drill press.

Thats just my 20 cents worth

Cheers Ian

AuS MaDDoG · #87 17th Feb 2012, 11:09 PM

Fly,

As Ian says if you drill them in your lathe should not be an issue as it will drill centre.

However if you are using a drill press one of those self centering chucks are good for both square and round blanks

and if you do not have one of those use a drill press vice and use the edge of the drill bit to get the blank straight before then tightening the vice. You can then move the blank to the centre of the drill and drill very carefully.

Cheers
Tony.

AuS MaDDoG · #88 17th Feb 2012, 11:17 PM

Hey,

Picked up my new bandsaw the other day and spent the rest of the night setting up the table and the fence and getting everything spot on. I gave it a bit of a run tonight chopping up some pine cones

so no accuracy check needed here. Just had to make sure all ten fingers were well and truly a safe or as safe a distance as I could away from the blade.

Touch wood hehe!! all fingers still in tact. I now have a few pine cones almost ready for casting.

Now where is John and Neil when you need them

Cheers
Tony

_fly_ · #89 17th Feb 2012, 11:37 PM

Hi Guys, Thanks Tony, Someone at mens shed today showed me how to true up against the bit in the press. Works well. Anyone want to see the ugliest castings ever? think god needed to vomit with these ones. Left is gumnuts with inside painted red (looks ok). Second is an ugly one with inside painted green and the third is one painted white. Last 4 are as cast and not drilled. Thought I'd also finally put in some pictures of finished stuff. I think I'm getting there.

Peter

dai sensei · #90 17th Feb 2012, 11:42 PM

I assume you are casting them in tubes. Pour your resin in to half way up the tube, then put you cone in slowly whilst twisting. After they are in, top up with more resin as necessary, ensuring you overfill the tubes. You may also need some ice-cream sticks or similar to hold the cones in the mold, held down with gaffa tape or similar. Then into the pressure pot to cure.

I only hope the cones are dry. Slightly green cones make a mess with the resin.

Make sure they are set before you remove the molds from the pot, I tend to leave overnight. Under pressure the temperature reduces thus setting takes longer in the pot than outside.

Cheers