Thread: Taking The Next Step (Casting)

Bugger ! was going so well I was talking to one of our fellow members at the markets today who has one of these "big toys" lol, his suggestion was to set it to run as you would a standard router ,eg depth of cut equal to dia of cutter but those small cutters would flex for sure on that 19mm depth cut ,even high speed stell drills will bend if not carefull .
I will get some tubes prepared for casting in the meantime lol. Cheers ~ John

Let me ask what may be a silly question but I'm going to ask it anyway.
Before I go buy expensive moulds has anyone tried plastacine?

I have a big block (house brick size) that I used to make silicone moulds in the past and I'm wondering if I could use it PR casting.
Easy to pick apart after to get the blanks out and can make any width, length I like.
I would get some proper moulds if this casting thing works out.

You can make silicone molds fairly cheap.

Originally Posted by _fly_

Let me ask what may be a silly question but I'm going to ask it anyway.
Before I go buy expensive moulds has anyone tried plastacine?

I have a big block (house brick size) that I used to make silicone moulds in the past and I'm wondering if I could use it PR casting.
Easy to pick apart after to get the blanks out and can make any width, length I like.
I would get some proper moulds if this casting thing works out.

Originally Posted by qballizhere

You can make silicone molds fairly cheap.

Not in "ozzie" lol, thats why we buy ready made molds from the US even with postage its still a lot cheaper than the raw materials here .

As to Plasticine it may react to the polyurethane ,I don't know for sure, also a fair amount of heat is generated by the casting process as it reacts while setting,may be enough to upset the mold. You can get about 500 ml for around $20 at Bunnings ,enough for a heap of trial casts ,give it a go , I would freeze the plasticine for a while before pouring the mix to help harden it a bit cheers ~ John

As John says, I suspect the resin would either bond with the plasticine, or react with it and destabilise the mould. Could be wrong though. I have used Blu-Tac to plug the end of tubes, and when I cut into after the resin ahd set, it was very gooey. I know Polymer Clay bonds to resin, or I'd have been using that, as I have a ready supply. Plasticine is oilier though, so try it and let us know

Russell.

OK, I'll give it a try. seeing its such a big block (brick size) I'm hoping any expansion won't be much as I'll only cast 2 blanks in it. Shouldn't be a problem as we take it down anyway or I'll make a small wooden box to help .

I'll do one normal and one chilled in the fridge.

Silicone moulds, I remember when I made made them for lead castings it was about $60 for 1 litre of goo and hardener. Silcone was rated for 300 degrees and lead has a MP of 305. So the moulds do suffer, harden and split.

Give me few days and I'll get back to ya.

Plasticine can be used for a mold, but they are a one off and you need to make it up for each pour. It would also be useless for the purpose these molds are being made for, repetitive SS costing on 10" tubes. Plasticine is perfect for molding small pours on bowls etc, just watch it doesn't stain your timber.

Unfortunately silicon in Aus has gon up rapidly in the past few years. I used to make my own, but it is cheaper to buy them ready made (if they suit your needs) from USA, than buying the raw ingredients here . I still do my own few odd specials, plus a few plugs for the tubes, so usually have some pourable silicon on hand

Neil / John,

I have made changes for the second mold by extending the troughs a further 2mm I have also changed the spacings as requested Neil giving the mold more meat around the perimeter. I also left the centre strip wider also which should give the mold some rigidity through the centre also.
I set up the second slab on the cnc later this afternoon and started to cut however cutting more material out was a bit noisier so had to stop. Might do the rest on the weekend, and hopefully my other carbide bits turn up

Cheers
Tony.

Doin well Tony (I think Neil has some of those cutters I cast a stainless 10" tube yesterday in the vertical tubes ,was hard to remove ,so looking forward to trying the open molds Cheers ~ John

Neil, John,

The mold that I extended another couple of mm in length was completed today. I had a couple of power outages today causing a few issues, Not 100% happy with the job however I have soldiered on and completed the mold.
The material appears to bow significantly after it has been cut and I release the holding down screws so I think it may need to be screwed down to something solid when casting.
My other carbide bits did not turn up so I have cut the roughing and the finishing cuts with a 6mm ball nose Carbide 2 flute cutter.

Looks good to me. Bowing won't be a problem, can easily screw it down to some ply.

Cheers

Done well tony ,next phase is to see whether it releases ok or needs release agent Cheers ! John ( I am sure as Neil says a support board will be no problem .)

Hi All,

Decided to cut out and make a little vertical tube casting stand today. I have recessed the tubes into the base of the stand which is a nice snug fit.
The tubes will be sealed off on the bottom with something prior to pushing the tube into the recess, then they will be ready for pouring in the resin.

Hopefully it should all work ok

Next on the list is another little stand which I would like to have provision to insert a tray of hot water under with a couple of cut outs on top to take the resin mixing cups. That way I can heat the resin whilst I am mixing in the pigments but keeping the resin away from any chance of water splash.

I also need to make some molds for the pressure pot so that will be later once I get these out of the way and working.

Cheers
Tony.

You read my mind lol! Mine are for 10" tubes Turned Delryn plugs for the bottoms a neat fit don't leak and don't stick .You are certainly getting geared up in a big way lol. Good stuff indeed . Cheers ~ John