Urethane Castings and Moldings

Cast Urethane Parts

Universal Urethane Products has manufactured countless polyurethane parts and products used in many industries worldwide. We provide cast polyurethane manufacturing solutions for high and low volume production. Manufactured using high-performance resins, curatives and additives, our cast polyurethane products can be manufactured in almost any hardness or shape. This is possible through a number of manufacturing processes which employ state-of-the-art technology at each processing step. With experience in highly customized products, we welcome complicated projects and difficult applications. Universal Urethane manufactures custom molded polyurethane products which span a wide range of industrial applications. Our scope of services were developed to handle large-and small-scale design and prototype projects, to high volume contract manufacturing agreements.

Polyurethane Manufacturing Experience

We have over 50 years of experience in custom polyurethane molding. Over the years, we have cast some of the most intricate and difficult products in the Polyurethane industry. We bring a fearless spirit and a long history of outstanding quality, product performance and customer service to meet the ever-changing needs of our customer base.

What are polyurethane castings?

Polyurethane is a type of resin that’s used to make a range of plastic items. It’s end-use is highly versatile; you can create both flexible items that are almost rubbery in texture, and very rigid plastics. Polyurethane castings in the manufacture of short-run, low-volume products such as movie props or bespoke models. It involves pouring the urethane into a mold and letting it cure – but we’ll talk more about the process later. Polyurethane casting is a brilliant low-cost, high-quality way to create parts and whole models. It works well for detailed designs too, creating a high standard finish quickly and without the high price tag of other methods.

Polyurethane Casting Process

Casting polyurethane can be tricky, so we recommend ordering a tester sample before a big order. You’ll be able to get to grips with the process, work out whether you like the resin, and avoid losing too much in failed attempts. Most of us mess up a few times when trying a new resin, so don’t worry if it doesn’t go to plan! The process starts with a silicone mold. In order to create this mold a master model of the parts will be manufactured by 3D printing or CNC Machining, then by pouring the silicone into a tool imprint of the parts will be shaped. You then have to mix your polyurethane, which comes as two separate liquids. You should mix the parts in a 1:1 ratio or as directed on the brand instruction. As soon as you mix the two, a chemical reaction starts that turns them from liquid to solid – this is curing. You may also hear curing being referred to as room temperature vulcanization. It may sound more advanced, but it really is the same thing. If you’re adding a tint to your resin, remember to do it before combining the two liquids. It can take a while to mix the tint so this will give you more time. If you add the tint to the combined resins, the polyurethane may start to set before you’ve thoroughly mixed it. Once you’ve mixed the tint, you can combine parts A and B of your polyurethane. Stir this for between 10-20 seconds. You can then carefully pour it into your mold. Leave your urethane for around 1 hour to cure – although you can follow the brand’s guidance for timing. Remember to always read their safety information, too, and they can tell you more about pot life and pouring techniques. Once the resin is properly cured, remove it from the silicone mold – easy! They can repeat the operation up to 20 times.

Things to Remember When Using Polyurethane

Polyurethane can be affected by many factors. Remember these so that they don’t affect your final parts:

Polyurethane hates moisture – As soon as urethane comes into contact with moisture, it reacts. Even the water in the air can ruin your polyurethane, which would be a pain after you’ve just bought two large jugs. So, always remember to put the caps back on your urethane as soon as you’ve poured it. This will help it to last longer and work better.
Polyurethane is exothermic – An exothermic reaction is when heat is created, and this happens to urethane whilst it cures. Because of this, areas with a higher volume of concentrated polyurethane will cure faster than thinner areas. Just because one area is ready doesn’t mean the whole part is, so be sure to leave it for long enough for everything to dry. The exothermic reaction will also evaporate heat from your mold which can cause damage.
It will shrink – As your resin turns from liquid to solid, it’ll shrink. With urethane casting you expect shrinkage of around 0.15%, which you’ll have to bear in mind when creating your mold.
Your tint will be affected by the base color – The base color of polyurethane is usually white. It can also be black, translucent, or colored. Remember that whatever base color you pick will affect your final color when you use a tint. So if you choose a white base and red tint, for example, it’ll more likely come out pink.

Each polyurethane brand will be slightly different, so always read the advice and guidance from your brand before using it. This will help you get the best finish and make sure your urethane lasts for its full pot life.

Polyurethane Castings vs Plastic Injection Molding

Now you know more about the processes, let’s take a look at some of the other differences you should consider:

Upfront costs – Injection mold can be far more expensive than polyurethane casts as they’re made from metal. This makes this system more of an investment and better for long-term, mass-production. The molds for polyurethane casts can be made for me much less, helping you reduce upfront costs. This makes it better for one-off designs or low-volume batches.
Cost of materials – Just like the molds, the production-grade plastic that you’ll need for injection molds is much more expensive than polyurethane. This includes PVC, ABS, acetal, and LPDE. Once again, this makes urethane the better choice for prototypes and low-volume work.
Lead times – The molds for injection molding can take a very long time to make – sometimes even months! This increases lead times and can prevent quick delivery of products. Urethane silicone molds are much quicker to make. Usually, they can be created with a 3D printer or even by hand, reducing lead times and helping you get your product to market quicker.
Per-part cost – Usually the bottom line, per-part cost will be higher for polyurethane than injection molding. This is because you can only make a few pieces with each mold. On the other hand, the higher volumes produced by injection molding make them much cheaper. This reduces those previous higher costs, like for materials and tools. In this way, injection molding is usually the most cost-effective molding for long-term production.

Which one is better for you?

So, which one’s better for you? That comes down to what you need to make – there isn’t one superior option. The cheaper upfront costs and quicker lead times will always make polyurethane better for porotypes – unless injection molding is essential. Whereas for product runs of larger numbers, you’ll get a much better ROI with injectable molding and the steel molds used will last far longer than the silicone alternatives.

Benefits of Polyurethane

Still not sure if the urethane casting process is the option for you? Let’s run through some of the benefits:

You can test out your design and ensure there is a market for it before going into mass-production. It’s a working prototype that isn’t too expensive. Once your product switches to higher volumes you can change to a different process.
It gives you low-volumes of high-quality, production-grade parts.
You can create very detailed models and have more freedom with your designs. This is ideal for bespoke props and models. You can even create internal, sharp corners, which can be trickier with other processes.
You can bring your product to the market quicker with short lead times.
It can cure to a variety of finishes, from very rigid to incredibly flexible.
It’s available in tons of different texture, finishes, and tints can be added to change the color. This means you can tailor your casting to suit your end-use.
The shrinkage rate of 0.15% is much less than many other processes.
Polyurethane castings can be FDA approved, which is essential if you’re making items for the food, medical, and pharmaceutical industries.

Cast Urethane Processing Technology

We utilize a number of molding process technologies such as: transfer compression molding, spin casting, open casting and vacuum casting to low pressure injection molding. We manufacture products ranging from wheels to wipers in sizes from 1 gram to 2,000 lbs. We use state-of-the-art casting machines with outputs ranging from 200 grams per minute to 125 pounds per minute. We carry a wide array of polyurethane material systems and additives which allow us to not only meet performance requirements of our customers, but accommodate pricing as well.