You ever get a quote for a plastic part that made your eyes water?
I have. Years ago, I needed 50 little housings for a gadget I was testing. A big injection molding shop said, “Sure, that’ll be $12,000 for the mold alone.”
I almost choked on my coffee.
That’s when I learned about repmold. And honestly? It saved my project.
Let me walk you through what repmold is, why it matters for smart manufacturing, and how you can use it for rapid prototyping without selling a kidney.
So, What Exactly Is Repmold?
Repmold is a manufacturing process that uses silicone molds to cast plastic parts.
Here’s the simple version:
You make one perfect master part. Then you pour silicone around it to create a soft mold. Once it cures, you cut the mold open, remove the master, and start casting polyurethane resins.
You can get 20 to 100+ parts from a single silicone mold.
The term “repmold” comes from “replication molding.” Some folks call it urethane casting or silicone molding. But the idea is the same: fast, affordable, low-volume production.
I think of it as the secret weapon for product designers who aren’t ready to spend tens of thousands on steel tooling.
How Repmold Fits Into Smart Manufacturing
Smart manufacturing is all about doing more with less. Less waste. Less waiting. Less money tied up in inventory.
Repmold checks every box.
Low upfront cost – Silicone molds cost a few hundred bucks, not ten grand.
Fast turnaround – You can have parts in 7–14 days.
No minimum order drama – Need 10 parts? Great. Need 80? Also fine.
I’ve seen big factories waste months on hard tooling for parts that ended up changing anyway. That’s not smart. That’s expensive stubbornness.
Repmold keeps you agile. You test, tweak, and iterate without crying over sunk costs.
Why I Fell in Love With Repmold (A Short Story)
Back to that $12,000 quote.
I was building a wearable device. The housing needed to be durable but lightweight. I had maybe $3,000 left in my budget.
A friend in the hardware space said, “Dude, just repmold it.”
I had no idea what he meant. But after a quick call with a prototyping shop, I sent them my 3D-printed master. Two weeks later, I had 60 perfect parts in my hands.
Total cost? $1,800.
That’s when I became a repmold evangelist.
Now, every time a client tells me they’re about to drop a fortune on injection molding for a first run, I stop them. “Hold on. Have you looked at repmold?”
Repmold vs. Other Prototyping Methods
Let’s get real for a second. There’s no single “best” process. But repmold wins in specific situations.
Repmold vs. 3D Printing
3D printing is great for one-off parts. But it’s slow for batches. And the surface finish can feel rough.
Repmold gives you injection-molding-like quality. Smooth surfaces. Consistent dimensions. And you can run multiple parts at once.
Winner for 10–100 parts: Repmold.
Repmold vs. Injection Molding
Injection molding is the gold standard for high volume. Think 10,000+ parts.
But the tooling cost is brutal. A simple mold can run $5,000–$20,000. Complex ones go way higher.
Repmold skips the steel. You pay for the silicone mold and the resin. That’s it.
Winner for low volume (under 500 parts): Repmold.
Repmold vs. CNC Machining
CNC gives you strong, precise parts from metal or plastic. But it’s wasteful (lots of chips) and slow per part.
With repmold, once the silicone mold is done, each casting takes minutes. You can make a dozen parts while a CNC machine is still finishing one.
Winner for speed and material efficiency: Repmold.
When Repmold Doesn’t Make Sense
I’m not here to sell you snake oil. Repmold has limits.
High temperatures – Silicone molds start breaking down above 200°C (about 392°F). If your part needs to survive a hot car dashboard, repmold resins might not cut it.
Thousands of parts – After 100–200 casts, the silicone mold wears out. For mass production, go with injection molding.
Super tight tolerances – Repmold is accurate (typically ±0.1mm), but CNC or hard tooling is better for micron-level precision.
Be honest about what you need. Repmold is a tool, not a miracle.
The Step-by-Step Repmold Process
You don’t need to do this yourself (most people outsource it). But understanding the steps helps you talk to shops like a pro.
Create a Master Pattern
You need one perfect part. Most people use a 3D printer or CNC machine for this.
The master gets sanded, polished, and coated with a release agent. Every scratch or bump will transfer to your castings, so take your time here.
Make the Silicone Mold
The master is suspended in a container, and liquid silicone is poured around it.
Once cured (usually 24 hours), the silicone block is carefully cut open. The master comes out, leaving a cavity shaped exactly like your part.
A good mold maker will add sprues and vents – little channels for the resin to flow in and air to escape.
Cast the Parts
The two-part polyurethane resin is mixed, degassed (to remove bubbles), and injected into the mold cavity.
After 15–60 minutes, the resin cures. You open the mold, pull out your part, and repeat.
One mold can be cast dozens of times. I’ve seen shops get 150 good parts from a single silicone mold.
Post-Processing
Each part might need minor trimming or sanding. Some resins can be painted or glued.
But honestly? Repmold parts often come out looking like final production pieces. No heavy finishing required.
Materials You Can Use With Repmold
This is where things get fun.
Polyurethane resins come in different flavors. You can mimic:
ABS – Tough and impact-resistant (great for enclosures)
Polypropylene – Flexible and chemical-resistant
Rubber-like – Soft-touch or grippy surfaces
Clear – For lenses or light pipes
High-temp – Up to 150°C for under-hood applications
You can also add glass beads for stiffness, aluminum powder for a metallic look, or even glow-in-the-dark pigments.
Last month, a client needed a part that felt like soft-touch silicone. We used a shore A 60 resin. It felt exactly like the real thing.
How Much Does Repmold Cost?
Let’s talk money. Because that’s probably why you’re here.
Master pattern – $50 to $500 (3D printing is cheap these days)
Silicone mold – $200 to $800 depending on size and complexity
Per-part cost – $5 to $50 each, based on resin type and volume
So for 50 parts, you might pay:
$300 (master) + $500 (mold) + ($10 x 50) = $1,300 total.
Compare that to injection molding at $12,000. See why I got excited?
Prices vary by shop and location. But the math almost always favors repmold under 200 parts.
Tips for Getting Great Repmold Parts
I’ve made enough mistakes so you don’t have to. Here’s what works.
Design for Mold Release
Avoid deep undercuts. The silicone mold is flexible, but extreme shapes make demolding a nightmare. Add 1–2 degree draft angles where you can.
Watch Your Wall Thickness
Thick sections take longer to cure and can sink or warp. Aim for uniform walls between 1.5mm and 5mm.
Use Fillets, Not Sharp Corners
Sharp inside corners concentrate stress. A 0.5mm fillet makes your part stronger and helps resin flow.
Ask About Lead Times
Most repmold shops deliver in 7–14 days. But if you need parts faster, some offer 3–5 day rush service. You’ll pay extra, but it’s worth it for urgent prototypes.
Repmold and Sustainability (Yes, Really)
Smart manufacturing isn’t just about speed. It’s about not being wasteful.
Injection molding often requires running thousands of parts to justify the tooling cost. Those extra parts sit in a box. Maybe they sell. Maybe they become landfill.
With repmold, you cast exactly what you need. No excess inventory. No “we’ll sell it someday” promises.
Plus, silicone molds are non-toxic and can be recycled in some programs. And polyurethane resins have come a long way – many are now bio-based or low-VOC.
I’m not saying repmold is perfect for the planet. But it’s a lot lighter footprint than mass production.
How to Find a Good Repmold Shop
Not all shops are created equal. Here’s my checklist.
Ask for sample parts – Any decent shop will mail you a casting from a previous job.
Check their lead time – 2 weeks is standard. If they say 4+ weeks, keep looking.
Talk about your resin – Do they have experience with the material you need (clear, flexible, high-temp)?
Get a fixed quote – Some shops add surprise fees for mold design or post-processing. Ask upfront.
I’ve worked with shops on Makexyz and Protolabs (external link). Both are solid. But smaller local shops often give better prices and more personal service.
Common Questions People Ask Me
Can I repmold metal parts?
Not really. The process works for resins only. For metal prototypes, look at lost-wax casting or CNC.
How strong are repmold parts?
Strong enough for functional prototypes and even end-use parts. Some polyurethanes have tensile strength similar to ABS or polycarbonate.
Do I need a vacuum chamber?
For bubble-free castings, yes. Most shops degas the resin before pouring. DIY repmold without a vacuum chamber will give you pinholes and weak spots.
Can I repmold overmolded parts?
Yes, but that’s advanced. You’d cast a rigid core, then place it in a second mold for the soft outer layer. Expect to pay more.
Final Thoughts: Is Repmold Right for You?
Here’s how I decide for my own projects.
If I need:
1–5 parts → 3D print them
10–100 parts → Repmold
500+ parts → Start looking at injection molding
Repmold sits in that beautiful sweet spot. Low risk. Fast feedback. Quality that doesn’t embarrass you.
I’ve seen startups blow their entire seed round on hard tooling for a product that wasn’t ready. Don’t be that person.
Try repmold first. Validate your design. Sell some units. Then, when you’re ordering 10,000 pieces, you can smile knowing you made the smart choice.
