Rapid Prototyping Service

Urethane casting vs injection molding

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Henry

15 years of experience in prototyping and manufacturing.

When comes to a project, engineers always want to know which process is the better about Urethane casting vs injection molding, this is because that Urethane casting and injection molding can be both used for low volume manufacturing plastic parts. This blog will help to compare these two processes in terms of all the factors of a project such as volumes, cost, lead time and design considerations inlcude material, precision, wall thickness and more.

Urethane casting vs injection molding

What is urethane casting?

Urethane casting creates plastic parts by pouring liquid urethane into a mold cavity which is typically made from a soft material such as silicone. the liquid urethane cure with the mold in a heated chamber to form the part.

Urethane Casting

What is inejction molding?

Injection molding make plastic products by injecting molten plastic material into the cavities of a mold which is made from steel. the molten plastic material rapidly cool down in the mold and form the plastic parts. it’s an ideal process for large-scale manufacturing operations.

Injection-Molding-Animation

Compare between urethane casting and injection molding

MOLD

The mold for urethane casting is made of soft materials such as silicone while the mold for injection molding is made of metel such as steel or aluminum which is much more durable than silicone.

The mold for urethane casting is created base on a master pattern which is made by CNC machining or 3D Printing, Use liquid silicone surrouding entile master pattern to cure and set, then form the mold.

The Mold for injection molding is made from CNC machining and electric discharge machining (EDM) on a proper size metal block direclty.

Lead time

When compare the lead times of these two processes, we need to compare two factors that mold making lead time and plastic part making time.

Time of Mold making for injection molding takes from 4 weeks to 2 months, it is much longer than that of urethane casting which only take from one to two weeks.

Time for plastic part making by injection molding takes only few seconds, it is much shorter than that of urethane casting which need hours to cure the urethane material.

Cost

the cost of these two processes both include mold cost and part cost.

the mold cost of injection molding costs range from $2000 to $100000 which depends on the complexity of the mold. in contrast, the mold cost of urethane casting is much cheaper which only cost range from $100 to $1000.

Regrading the part cost, Urethane molding part costs range from $20 to $100. while inejction molding costs range from $1 to $10. this is becasue urethane molding is a much more labor intensive process, while injection molding can be more automated.

But, for the machine investment of these two processes, Injection molding machine costs much higher then urethane casting machine.

Volumes

Urethane casting is commonly used for prototyping and low-volume manufacturing from 1 to 100 parts.

Injection molding can be used for both low-volume and high-volume production from 100 to 100,000 parts by using different steels with different hardness.

Design Consideration

When we compare the urethane casting and injection molding, we also need to know the part design according to the reqiurements of these two processes so that you can choose the right one for your project.

Part materials

Urethane casting uses polyurethanes which simulate the injection mold grade production plastic with different hardness. while Injection molding uses the actual production plastic materials with more widely choices. they both can make customed color or textured parts.

Precision

Injection molding parts have better precision because of the hard steel mold. injection molding part tolerance start at +/.004”(0.1mm) for the first inch, and +/-.002”(0.05mm) for every inch afterwards.

While, Urethane casting parts tolerance start at +/-.01”(0.25mm) for the first inch, and +/-.005”(0.125mm for every inch afterwards.

Wall Thicknesses 

The wall thickness of Urethane casting parts generally between 1 mm (0.04 inches) and 5 mm (0.20 inches). While the wall thickness of injection molding parts generally between 0.5mm to 4mm.

Design flexibility

Urethane casting parts have more design flexibility such as undercuts, small draft angle than injection molding parts design. this is because Urethane casting use flexible silicone molds which can accommodate undercuts and draft angles more easily. 

Mold Lifespan

Urethane casting mold last between 10 to 25 runs due the soft silicone material. it will lost part quality if over runs. when you need more parts over 25 pieces, you need to make more silicone molds.

In comparison, Injection molding mold made of aluminum or steel can last between 1,000 to 100,000 shots with a good maintenance condition.

Pros and Cons

Here we sumarize a table for you to understand the pros and cos of urethane casting and injection moldingm, then you can find how to choose for your project.

Urethane CastingInjection Molding
Best used forRapid prototypes and manufacuring Low volume less than 100 pieces1. mass production
2. Low volume from 100 pieces to 1000 pieces
3. Prototypes need same materials as mass production
Pros1. Cost is cheap when the parts volume is less than 100 pieces.
2. Fast to get the parts
1. High efficiency to make parts when the volume is high
2. High precision of the parts dimension
3. Pieces come out ready for use.
Cons1. Need much time for setting up for every part
2. Mold life time is short and need replacement
3. Parts require post finishing such as polishing and trimming.
1. Mold cost is high
2. Mold making time is long

How to get the Molded Parts You Need?

Urethane casting and injection molding are both manufacturing processes which require expertise and investments. KUSLA engineers can help you choose the right process for your projects and help you save your cost with high quality molded parts. Contact us or find more about KUSLA Urethane Casting Prototyping Service and Injection Molding Prototyping Service.

FAQs

Is casting cheaper than injection molding?

Not really. this depend on the volume of your project. for part cost , casting is more expensive than inejction molding due to more labor cost. for mold cost, casting is cheaper than injection molding.

How to choose between urethane casting and injection molding?

it is better you check with a professional rapid prototyping and manufacturing supplier as KUSLA, we will provide feedback base on your project needs.

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Gang Liu

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Employees of Kusla.

Hua Liu

Project Manager

Employees of Kusla.

Yiyang Zhao

Project Manager

Employees of Kusla.

Lu Wang

Technical Sales

Employees of Kusla.

Anming Li

Technical Sales

Employees of Kusla.

Xiaoli Wu

Technical Sales

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Request A Quote

Get in touch with our professional team today, and we will respond to you within 24 hours.

Employees of Kusla.

Gang Liu

Marketing Director

Employees of Kusla.

Hua Liu

Project Manager

Employees of Kusla.

Yiyang Zhao

Project Manager

Employees of Kusla.

Lu Wang

Technical Sales

Employees of Kusla.

Anming Li

Technical Sales

Employees of Kusla.

Xiaoli Wu

Technical Sales

Please enable JavaScript in your browser to complete this form.
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