Where to start?

[keycapsule]

Hello fellow resin addicts,

I've submitted my patient admittance form and I wanted to say hello to everyone. It's amazing that such a community exists and from what I've seen so far, everyone has been incredibly helpful and insightful in these threads. The level of knowledge and mastery that many of you possess is truly inspiring.

With that said, I've gleaned over pertinent threads and have a general understanding of the molding/casting process. However, in terms of the barrier of entry, I have to admit that I am a bit overwhelmed. For reference, I have zero experience in casting but would like to take the plunge as soon as I feel properly prepared.

Full disclosure. The goal of this endeavor is to create keycaps for my personal keyboard collection. Resin casting provides the level of personal expression that no other pre-made keys can do. So where do I start? I've read the tutorial by Paulson Games and understand the basics of casting.

Keycaps by nature are temperamental as they must meet pretty precise measurements to fit into the keyboard itself and function under constant use. As such, I fear that I may need to look into vacuum chambers/pressure pots. Currently, I have bought the following items:

Super Sculpey Polymer
Legos
Wax Carving Kits
Tweezers
Polymer Mixing cups
Precision scale to measure grams
Stir sticks and plastic cups
Magnifier to detail work
3m respirator

I have held off buying molding medium (silicone), resins and dyes as I am not absolutely sure which ones I should purchase. I have also allocated $300 to purchasing proper equipment. The plan is to mold small shapes and designs on existing keycap (PBT). Cure the master in an oven. Create split mold with silicone and cast with colored resin. Based on experience of my fellow artisans, surface bubbles are a huge problem when dealing keycap production.

So here are my questions: (tl:dr)

Given the size of the product I am trying to make, which type of silicone should I be using. I am looking in the direction of Smooth-On products.
How would I go about determining sprue location when creating the mold?
Which would be a better investment with my current budget? Vacuum or Pressure?
Given the small scale of production( 10"X10" - 25cmx25cm lego baseplate), what parameters should I be looking for while shopping for a vacuum/pressure chamber?

I have many more questions to ask and fear that this post may be a little long-winded. I humbly request your guidance. Thanks in advance!

[mangozac]

Welcome to RA, Keycapsule!

So I just did some googling and indeed there is a lot of people casting keycaps but it seems not many get good results. A lot of it looks to be poor material selection though.

It sounds like you are adequately mentally (and financially) prepared for diving into casting! It's great to see that you've already done plenty of research.

Before we advise any further can you give an idea of the kind of quantities you want to produce? Do you want to sell your custom keys (thus volume production)? The best approach may be dependant on your volume. Keys are not complex shapes so for a low volume you might be able to get away with room pressure casting...

[keycapsule]

Hi mangozac,

Thank you for taking the time to reply to my thread. There certainly are quite a few people casting keycaps though the quality of the final product tends to be hit or miss.

I've tried my best to do as much research as I can before diving into any endeavor and I know how frustrating it can be when new forum members ask questions that they can easily find themselves. With that said, although I think I grasp the basic components of resin casting, I am still not entirely sure what materials or setup I need for my own projects.

In terms of my goals. I am entering only as a hobbyist for the time being. I have no grand delusion of making a profit or sustaining myself on resin making. If I become proficient and skilled as some as you are, I may consider profit as a goal. For the time being, I want to hone my skills. If a buyer likes my work, I'd be willing to sell to recoup costs. So for now, the goal is low yield, high quality.

Any advice on setup or materials would be greatly appreciated. Thanks

[mangozac]

If just doing singles I'd suggest giving a go at room pressure casting first. You will want to sprue the part to facilitate resin flow in through the bottom and airflow out the top, so most likely a 2-part mould. Have you read Paulson's casting tutorial ? It's got a lot of good information about part orientation and venting, which become more important as the casting technique simplifies.

Smooth-on products are going to be your go-to for this. Since you're not too concerned about curing time you could try out Smooth Cast 305. It has a 7 minute pot life and that should give you ample time to mix, pour and then de-bubble the mould. Techniques like repeatedly squeezing the mould will help dislodge bubbles. Don't get me wrong; you will still get bubbles. The aim here is to try and avoid having them form on the outer surface of the part. You can then progress to casting under pressure using the same technique, which will remove such bubbles.

Adding vacuum to the process will give you perfect casts every time, but for what you want to do it is added expense that you can get away without...

[Blindhorizon]

Hi, What your doing looks interesting. Keycaps i would have never thought, but everyone has their pleasures. One thing i did not notice that you had as some of your supplies is baby powder(talc), This will help whick the resin into the cracks. It's something i always use, and am sure most here do to, just a light dusting of the stuff on the insides of your moulds will help a bunch. We as a community get very interested on everyone little projects, so pics please! Also pics help us, help you better.

You had said you cure your keycaps in the oven, i might be missing what exactly your talking about in regards to keycaps. Are they the plastic keys from computer keyboards?..... and just googled it, looks very promising for some very cool keyboards. I was thinking so you can skip the oven step you could just use green stuff to sculpt onto the keyboards with and let it cure at room temperature.

Found this link to a thread where a gentlemen is actually making molds and casting keycaps. His master was created using greenstuff.
https://geekhack.org/index.php?topic=68526.0

[mangozac]

Blind's suggestion is good, but there's a pro tip: greenstuff is horrible, especially if you want to try and sculpt any hard edges. I recommend and use Milliput and Procreate putties.

[Blindhorizon]

[keycapsule]

Hi guys,

Thanks so much for the advice. I'll be sure to look into some of the materials you suggested. I was actually looking into getting a pressure/vacuum setup. I have set a firm budget but finding quality parts has been difficult. Some people from other forums have recommended Harbor Freight for pressure pots while others have warned me of the dangers and suggested I get something that is ASME certified like Binks. The problem is the price different is quite significant and out of my price range.

Can anyone recommend a pressure pot that would accommodate my needs without breaking the bank? I'd prefer not to spend more than $300 on a pot that is fairly reliable. Thanks!

[mangozac]

Here at RA we definitely recommend against the Harbor Freight pots. We've had them fail catastrophically on a couple of our members and while fortunately nobody was hurt in either case, there was certainly a lot of potential for serious injury. I personally use a pot of the same design purchased here in Australia, but either I was lucky and got a well built one, or the local sources get them from a different, higher quality Chinese supplier. There are pretty stringent standard they have to comply with here, so I don't know if the same exists in the US.

The C.A. Technologies 2.5 Gallon pot is highly regarded, but certainly not a cheap option.

Honestly, give it a go at room pressure to start with. It's kind of like the natural progression of learning how to mould and cast

[Blindhorizon]

I use this pot, and i know others on the forum use it as well as they are the reason i bought it. With an addition of 20-35 bucks of fittings and some good old fashioned thinking this would be perfect for a garage caster to get a handle on casting without breaking the wallet before moving to the next level.

http://www.ebay.com/itm/2-1-2-Gallon-PR ... 2c8ef61870

I got myself a 6 gallon compressor with 135 psi and it does the job very nicely. I believe this compressor would do the job for you(please someone correct me if i am wrong), or something equal to this should be good.

http://www.homedepot.com/p/WEN-6-gal-Po ... /203579151

Thats the basics, but with the items being so small the waste of resin with misscasts with no pressure would be minimal on cost.

[RTVMagik]