Mold Max 14NV 25 or 30?

[ChickenMacNugget]

Hi all,

I've been playing around with casting for about 3 months now. Got myself a pressure pot for pressure casting silicone and resin. I don't have a vacuum chamber, and so far with the pressure pot I don't know if I really need one.

I've been using Smooth-on products to get in to casting small resin parts that I've scratch built, and want to multiply for games like 40k, so the details are really small.

I've used OOMOO 30 as my silicone, and SmoothCast 305 as my resin (which I really like). The problem I've been having with the OOMOO is that, my pieces regularly have undercuts, and OOMOO seems to be VERY delicate. I use mold release and it still tears, sometimes even coming away with the master on the undercuts, no matter how careful I am. I've been looking around and heard good things about the strength of MoldMax from smooth-on, so I'm thinking of moving to that, as my OOMOO has just about run out anyway.

The tree MoldMax products I've heard of are 14NV (a non degas silicone with low viscosity, but low tear strength also), 25 (a medium viscosity, high strength silicone) and 30 (higher viscosity again).

I was wondering which of the 3 I should get really. I was originally going to get MoldMax 25 but the company I've been looking at in europe (FormX) only has 1kg kits, not the 5kg I'm looking for.

14NV looks great for casting, and has a short (4 hour) cure time, but I'm worried about the low tear strength, and the 30 I'm worried about being too viscous, leading to reduced detail, and also the 24 hour cure time, over which I think my pressure pot will leak from 40 psi probably down to 20 or less, possibly deforming the mold due to air pockets.

TL;DR - Should I get MoldMax 14NV or 30 for high details, 2 part molds, with more strength than OOMOO 30?

Also, anyone knows of good suppliers in europe that sell moldmax 25 5kg tubs for around €100 (it would be around 100 on FormX if they stocked it) please let me know!

[mangozac]

Hi ChickenMacNugget, welcome to RA!

I appreciate the well written first post and particularly the fact that you've already done plenty of your own research

I personally feel that anything above ShoreA 25 hardness is getting a little bit too hard for casting smaller model parts, so I don't think the Mold Max 30 will be suitable. But then again the Ooomoo 30 you've been using is that hard so maybe you're used to it! I've recently tried out some ShoreA 28 silicone and it's right on the borderline I think.

I had a look at the 14NV datasheet. With a ShoreA hardness of 15 it is very soft. Maybe even too soft (more likely to cause mould slip and part warping), especially coming from the Oomoo 30. The strength isn't super low (tensile strength is only about 5% lower than the silicone I use, although admittedly I wouldn't mind a stronger silicone).

Really, the Mold Max 25 would be the best option. It's good a nice hardness and good strength properties. The next best would be the Mold Max 30. I don't think the 14NV is suitable.

Whatever you do I would still buy a 1kg sample quantity first to try it out. One thing that is hard to get a feel for from datasheets is how well the product will degas in practice.

Keep us posted!

[ChickenMacNugget]

Hi Mangozac!

Yes, I was lurking in the shadows as a guest, checked out a lot of the threads, especially about pressure casting. It definitely helped a lot getting started!

I think at this point I'm getting so frustrated with the OOMOO tearing that I'm just going to have to go for 25 or 30. 14NV sounds nice for the demold time and viscosity, but as you said, I don't think it'll make high fidelity molds that won't warp.

I was originally wanting to get the MoldMax 25 anyway, it's just the annoyance that this company doesn't do 5kg tubs. I've got a pretty big backlog of pieces I've made now that the OOMOO has let me down on, and I'm desperate to cast fast, so getting a 1kg tub, it'll be gone in a day haha. I might have to do as you suggested though and get a small tub to see how it goes.

Well in the mean time before pay-day I guess I'll try to find somewhere that does the bigger kit, and order the small one if all else fails. I think I'll refrain from using the MoldMax 30, as it is just at the upper limits of usability, and maybe if I had more experience, I might be able to get use from it, but not currently.

Thanks for your very helpful post I'll definitely be sticking around, and I'll let you know how it goes!

[mangozac]

No, 1kg doesn't last very long at all, but better than being stuck with 5kg of silicone that doesn't suit!

It's not lack of experience why I don't recommend the Mold Max 30, it's just that damaging the parts during demoulding is much more likely with a harder silicone. ShoreA 20-25 is the optimal range

[Fleafa]

I hate to sound like a stuck record, but the MM30 with silicone thinner would be great. The thinner is a Smooth-On product, so you may be able to get it from your supplier.

[mangozac]

Hahaha still trying to recruit for the church of silicone thinner

Doesn't it reduce the strength of the silicone though?

[Fleafa]

It reduces the viscosity, hardness and tear strength. It's a compromise.

[ChickenMacNugget]

I actually had a little bit of a snoop and found out that the FormX prices I was looking at were excl VAT, so they weren't as well priced as other distributors as I thought anyway.

There's a place in the UK ( that does SmoothOn stuff, and they stock the 5kg MoldMax 25 for a good price, only problem is shipping is of course astronomical from the UK as always ¬_¬ £35 (£12 if I lived in the UK, but I'm in Ireland, next door)

Looks like I might be able to get my hands on the 25 then after all, though I'll have to figure out something about the shipping.

Two other notes actually while I'm on the subject.
1. Does anyone have any experiences with casting small minis, and prefer another brand to smooth-on? I'd have to be EU or UK based.

2. I've noticed that my SmoothCast 305 part A has a lot of flakes in it of sediment. I've transfered it to a condiments bottle (bought new for the purpose) and that's how I can see it. It doesnt seem to effect the cast when there is some of the flakes in the mix. I'm just curious if this is normal after having the resin for a few weeks, or if maybe it's reacting with the walls of the bottle.

[Fleafa]

[ChickenMacNugget]

Thanks Fleafa, always nice to ask around. I'm always hearing about SmoothOn, and from time to time one or two other products, but it seems SmoothOn has at least been used by almost everyone at least once.

Ah right that makes sense. I doubt my containers are HDPE, I might look around for one or two of them for future use.

[mangozac]

[Fleafa]

[ChickenMacNugget]

I think I'll stay away from messing with fillers and thinners for now at least Still getting the hang of casting in the first place.

I've noticed a lot that I get a lot of air bubbles at the top of casts because of trapped air, even when the pour spout is at the top of the piece. I've been making gravity pour casts, so the resin entry hole is the same as the air exit hole. Is the best way around this to do vacuum right after a pour, followed by pressure while it sets?

I'm also thinking of having a pour channel go under all the pieces, and have the resin flow up into them from below, with an air escape hole at the top of the pieces. I'm afraid this will mean I won't have as much of a reservoir of resin above the pieces for the pressure casting, as I know the pressure reduces the volume of the resin.

[mangozac]

Yep, vacuum and pressure will definitely help with getting rid of air pockets like that.

One other thing you could try is to squeeze the mould a few times after pouring the resin in. This helps expel the trapped air and suck more resin back into the cavity. The downside is that the squeezing action can cause mould slip and flash issues.

Having the pour channel under the parts is certainly beneficial if you're doing only pressure casting, but it makes the moulds far more complex, which in turn takes far longer to make. Agile mould making is the way to go - that's why so many of us use single part split moulds in combination with vacuum and pressure

[ChickenMacNugget]

Yeah I've heard Vacuum is good, I just think it'll be pretty pricy! The pressure pot system was expensive enough to set up (nearly €600 total). Are pressure pots suitable to use for both pressure and vacuum? If so I could setup a quick release and have my pot do both. It'd mean I'd only have to buy a vacuum pump.

Here's the pot I'm currently using

I would try to use manipulation of the molds after pouring, but I put the molds between two pieces of MDF with a rubber band surrounding it to keep the whole thing flat. When I used rubber bands on their own they significantly distort the mold. What do you normally do to keep the two halves of a mold together?