New Mold Making Tutorial Video From E-Wan and I

[MattMunson]

I think this might be my FOURTH mold making video tutorial. This one is actually pretty rich on pro-tips, which E-Wan and I discuss while doing the mold making.

Mold Making Tutorial - Rubber! - YouTube

I'm curious to hear your feedback on this one. There was actually about twice as much pro-tippin', but I edited a lot of it out as there was nothing visually interesting going on while we were talking about tactics and tips.

Would you slog through a video like that, or is this one sort of the right mix??

 

[Kevin Gossett]

The rice tip is simply genius, I'm not sure why I haven't thought of that before... :lol

 

[Contec]

If this is the first piece of the two parts mold (this being the front) It would seem that you forgot to make registrations keys before you poured the silicone.

You could also have talked about the vacuum chamber a little more. Now it was only a quick picture of it and "this is the chamber" But maybe an in dept explanation of how it works/what it's made from, could fit better in another episode.

You could have done a few closeups on the pouring of the rubber (when it crawls over the piece) Just to make the video a little better.

Good work Matt.

The Rice estimate method was good, but you could do an episode were you explain how you can estimate the calculate volume of a shape by measuring the size of an object.
How To Calculate Volume

 

[zorg]

a little dark at the start, too many bleeps.

otherwise enjoyable

 

[bookface]

Nice vid. I kept expecting Dwight to pop up at any moment though.

 

[Sluis Van Shipyards]

I don't know I laughed at the "Mix that s*** right the **** up!" part :lol


I'd also like to see more on the vac chamber. Most of the molds I've done have been small one and two part molds, and for simple parts, nothing really complicated.

 

[MattMunson]

The rice tip is simply genius, I'm not sure why I haven't thought of that before... :lol

I would love to take credit for it, as it seems to be a pretty popular piece of insight, but I must give credit where credit is due. The rice trick came to me from the good folks over at HMS, many of whom are members here.

 

[MattMunson]

If this is the first piece of the two parts mold (this being the front) It would seem that you forgot to make registrations keys before you poured the silicone.

Nope, as per the title of the video, this is strictly a dump mold. If you check out the two videos prior to this, you'll see Ewan and I talking through the molding process, and how we are going to handle the different parts of the prop.

You could also have talked about the vacuum chamber a little more. Now it was only a quick picture of it and "this is the chamber" But maybe an in dept explanation of how it works/what it's made from, could fit better in another episode.

Based on the feedback I've been getting, it seems that the chamber may indeed be due for its own episode. However, there's already a bunch of videos on youtube showing how to build your own Vac Chamber, many of them similar to the one I have. While I'm all for making repeat tutorials and putting the ol' Munson Spin on them, I don't have any plans to build another vac chamber

The Rice estimate method was good, but you could do an episode were you explain how you can estimate the calculate volume of a shape by measuring the size of an object.
How To Calculate Volume

The rice method is infinitely simple, which is what makes it appealing. While calculating the volume of the box would be simple, determining the volume of the prop to be molded would be really problematic. Not only difficult to get it accurate, but difficult to do it right. Rice requires no math, and is highly accurate.

Keep the suggestions coming though! Ewan and I want to do more!

 

[Viking]

Nice tutorial, another great option is pressure degassing of silicone rubber. Unlike vacuum degassing, you don't get the heading (foaming, bubbling action), you can pour and place your molds into your chamber (if they fit) and de-gas. Pressure degassing helps capture very fine details in hard to reach places on the model, reducing voids. You can find pressure pots for under $100.00 at Harbor Freight
Paint Pressure Tank - 2-1/2 Gallon

 

[MattMunson]

Viking, give me some more information on this technique you are describing. Do you mean that by putting the rubber and item into the chamber, it squishes rubber into all the nooks and crannies? To my knowledge, a pressure pot will simply squish the air down in size, but not eliminate it. The problem being that once you take the thing out of the pressure pot, the bubbles expand to their original size.

Don't get me wrong, there's plenty of great uses for a pressure pot, and I had NO idea you could get one from harbor freight for so cheap!! lol. I'm just not certain how a pressure pot would help in the mold making process.

 

[masterjedi322]

As someone who has always wanted to learn about mold making, I thank you for taking the time to document and share this!

As far as feedback, I agree with most of what's been said already. In addition, my personal preference would be for shorter videos (say around five minutes or less?) as opposed to longer ones. You might also consider throwing in some cheesy background music to break up some of the quieter parts.

Thanks again! Looking forward to seeing more episodes!

Sean

 

[FordPrefect]

Great video ! time went by super fast for me so would not shorten the format based on my view. Will check out other videos I like your presentation style.

 

[Viking]

Do you mean that by putting the rubber and item into the chamber, it squishes rubber into all the nooks and crannies? To my knowledge, a pressure pot will simply squish the air down in size, but not eliminate it. The problem being that once you take the thing out of the pressure pot, the bubbles expand to their original size.

Don't get me wrong, there's plenty of great uses for a pressure pot, and I had NO idea you could get one from harbor freight for so cheap!! lol. I'm just not certain how a pressure pot would help in the mold making process.

Correct, using pressure squeezes the trapped air into an undetectable micro size bubbles (bubble free to the naked eye) while forcing the material into voids and smaller areas within the mold. This works great for silicone as well as resin. This is great for casting clear resins into closed molds (multi part molds) to get a crystal clear finish on the completed part. Vacuum degassing does a great job, but just pouring the degassed material into the mold introduces air back into the mix due to the viscosity of silicone rubbers. Both ways do work, but in closed molds you can only use pressure due to the heading (bubbling of material).

The problem being that once you take the thing out of the pressure pot, the bubbles expand to their original size.

The mold stays in the pot under pressure till fully cured.

 

[MattMunson]

The mold stays in the pot under pressure till fully cured.

I'm still not convinced that would work, as the air would expand once the pressure was removed on the cured silicone. I'll check this out, but I must confess I'm skeptical. Do me a favor and make a tutorial video of your process!!! :lol

 

[Viking]

I'm still not convinced that would work, as the air would expand once the pressure was removed on the cured silicone. I'll check this out, but I must confess I'm skeptical. Do me a favor and make a tutorial video of your process!!! :lol

Just Google pressure casting.:facepalm

Edit: Here is a video of the process

http://www.youtube.com/watch?v=rVFsNBv2MPA

 

[garybarth]

Hey Matt,

Nice tutorial vid. This is the first one I've seen, so you may cover this in other vids, but you may want to talk about making the mold dam (you can use clay, hot glue and foamcore, old baking pan, etc.). Also, in some cases, you might want to talk about anchoring the item you are molding since a lot of people are molding very light items they are making on their Makerbots and cutting them out of foam on their rapid prototype machines. On a one piece, flat sided mold, you don't want a foam item floating in your silicone. Lastly, you might want to talk about the joys of mold release.

G

 

[MattMunson]

Gary!

Super glad to see you still lurking these halls, and thanks so much for the post.

Fortunately, almost all of those topics are indeed covered in other videos. What this thread has revealed to me is that I need to get into the habit of popping up links in my videos to my OTHER videos.

The first two videos in this series directly address making the mold dam AND what I use to adhere the item to the box. Heck, I'll post links right here in case anyone is curious.

Mold Making Tutorial - Introduction - YouTube
Mold Making Tutorial - Box Building - YouTube

I've also found, in response to an earlier comment, that the length of the video varies wildly. The most recent video is high on chatter, BUT it's trimmed down from almost twice its original length. Some videos go really quickly, as the steps are just not that complicated, and don't require much explanation.

 

[robn1]

A follow-up on pressure molding. I wanted to try it, so I made a small block mold the other day, about 2x3 inches. I didn't vac the rubber (I don't have the tools yet), I just poured it and pressurized at 50psi. The rubber was slightly compressed, but it retained this form after pressure was released (I'm using Smooth-Sil 945). I got sharp details with no voids. I even sliced it open and there are no bubbles anywhere inside, it's smooth and solid all the way through. A non-pressurized mold I sliced looked like a sponge :lol

So it seems that air bubbles will not reappear after releasing pressure, the rubber will retain it's size and form after it's cured.

Obviously this won't work in all cases though, you'll have to determine if your master can withstand pressure. Something hollow and/or delicate can be crushed by the pressure.

 

[coofunkcurly]

I'm still not convinced that would work, as the air would expand once the pressure was removed on the cured silicone. I'll check this out, but I must confess I'm skeptical. Do me a favor and make a tutorial video of your process!!! :lol

I will vouch that it works. We have used this process countless times.

You do need to pressure the mold if you are going to pressure the resin castings though. If you did a regular silicone mold without pressure and then poured resin in and tried to pressure it, the resin will be forced into any micro voids in the silicone and you end up with fuzzy looking castings.

 

[NormanF]

I like watching rubber boil, so I was disappointed that was not shown. Also, let's face it: some people will not read directions. In the future you might want to mention that the rubber you were using mixes in that ratio but other rubbers use different ratios. Like that Smooth-On trial kit in the background that mixes 1:1 by volume.