Podcast – What Are the Differences in Injection Molding for Thin-Wall vs. Thick-Wall Parts?

Yeah, always a fun one.

Yeah, we do.

It's amazing how something as simple as wall thickness.

Affects so many things.

So many things in your. In your process, your design material selection, how fast you can make a part.

Yeah, exactly. Or a headache, maybe.

So thin wall, Are we talking under a millimeter?

Less than one millimeter. Okay.

Over four millimeters. Sorry.

Gotcha. All right.

Well, it matters because the thickness affects how the plastic cools inside the mold.

The thicker the wall, the longer it retains heat.

Yeah, exactly.

Yeah. A thin one cools down quick.

A thick one stays hot forever.

So that means you have longer cooling times, which means slower production.

Exactly. So thin wall parts, they cool quickly. You can pop them out, you can make more.

There is.

No, you can't make everything thin.

Well, if you go too thin, you risk warping the part as it cools.

So we're looking at, you know, did you have the. The table there with the different thicknesses?

Exactly.

There is. There is definitely a sweet spot in there somewhere. So under 2 millimeters, it's gonna cool in under 10 seconds, probably, which is great.

That's really fast. But you're gonna have warping.

More likely, yeah.

And then if you go over 4 millimeters. Yeah, well, now you're talking, you know, much longer cooling times yeah. So it's gonna slow down your production.

Absolutely. The type of plastic, does that matter? Hugely important. It's like picking the right ingredient for your recipe.

Different plastics have different properties, so. And those properties are critical.

They really matter in injection molding.

So, for example, some plastics are much better at conducting heat than others.

Absolutely. Yeah.

That's a great point. So, like polypropylene. You see polypropylene everywhere.

Food packaging and things like that. Yeah. It's lightweight, recyclable, and its high thermal conductivity means that you can make thin walls, and they'll still cool down quickly.

You get that speed. Yeah.

Advantage.

ABS is a very common plastic. It's used in a lot of electronics, but it's not as good at conducting heat.

You wouldn't want to go too thin.

For a thin wall. Yeah. You're gonna see those cracks if it's too thin. If it's too thin, you're gonna see cracks and breaks.

Yeah.

I guess there is. Yeah. And that's where those data sheets for the different materials are your best friend.

They'll tell you everything you need to know.

About the properties and if it's the right choice for your design.

Injection pressure coming up.

That's a big one.

Injection pressure is all about getting that molten plastic into every nook and cranny of the mold.

And, yes, it's hugely important in both thin and thick wall molding.

Well, with thin walls, you've got narrow spaces.

So you need to fill them quickly before the plastic cools.

So you get to use higher pressure to force it in.

Race against time.

But with thicker walls, you need to use lower pressure.

Otherwise, you risk warping or creating voids.

Voids are just little air pockets that weaken the part.

So it's a balancing act.

Too much pressure can be bad if it's thick. Yeah. Especially with thick walls.

You know, I remember back when I was first starting out, I had a whole batch of prototypes come out warped.

Because I didn't quite understand this pressure dynamic.

Yeah. It was a hard lesson.

They do. They do. Which is great.

That can model the injection molding process virtually.

So you can see how the plastic's going to behave based on the thickness, the material, the pressure.

Exactly.

So you can predict potential problems before they happen.

Yeah, that's really helpful.

You can optimize the cooling, the pressure distribution.

To make sure you get consistent parts.

Whether they're thin or thick walled.

Yeah.

Looking at designing for thin wall parts? There's definitely some guidelines that'll help you avoid disaster.

The most important one. Consistent wall thickness.

Consistent wall thickness throughout the design. Oh. So it can't be.

Okay.

It's like that souffle analogy.

If it doesn't cool properly.

Yeah.

You're gonna have problems.

What's a sink mark?

Oh, okay. Cool.

Gotcha.

Okay. And that makes sense.

Now I'm thinking. Okay, what's the perfect wall thickness?

On the material.

Okay, so we have that other table here. Right. With some suggestions.

Okay.

Okay.

Okay, got it.

What else should we be thinking about?

Draft angles? Yeah. So that's all about making sure the part can be easily ejected from the.

Yeah. So it doesn't get stuck.

Or damaged.

Think of it like a sweater.

It's much easier to pull off a loose fitting sweater.

Yeah. Than a tight one.

Right? Yeah. So we want the part to slide right out of the mold.

Draft angles give it a little bit of a slope.

So a typical draft angle is between 0.5 and 2 degrees.

It depends on the material, how complex the shape is. But it seems like a small detail.

It can make or break your production.

Yeah.

Everything matters.

So another thing you might want to consider is ribs.

Yeah. So ribs are those raised lines.

You see them on plastic parts on the parts.

Yeah. They act as reinforcement. So they make the part stronger.

Without adding to the wall thickness.

So you can keep the wall thin.

Exactly.

It can have strength.

Exactly. Like little support beams to a building. Build right in.

Yeah. So good rule of thumb is to keep the rib height less than three times the wall thickness.

And the width, about 60% of the wall thickness.

So it gives you that strength without creating stress points.

There's a lot of math, a lot of science. Science that goes into it, a lot of engineering.

But it's all about making sure that part's strong.

We've covered some of the big ones.

But, you know, material selection.

Gate location optimization.

Surface finish. Surface finish, all of that matters.

But what's gate location?

Oh, okay.

Got it.

Interesting.

So it's all like a puzzle.

You gotta fit all the pieces together.

All right, so let's talk about speed ski.

I wanna know how thick, thin wall molding stacks up against thick wall molding.

Okay. I was gonna guess that.

Why?

Right.

Okay.

Less material.

So it's like a double whammy.

Faster cooling, less material.

It is for sure.

Well, thick wall molding might not win any speed races.

But it's essential for products that need durability. Durability and structural integrity.

So think about, you know, car parts.

Heavy duty containers.

Things that need to be tough. Yeah.

So, yeah.

It really depends if it needs to.

It does. It does.

You got to consider the design, the material, how many parts you need to produce.

So it's a balancing act.

It is.

It is.

There are, right? There are. There are challenges with both.

Specifically with thin wall molding, one of the biggest challenges is uneven cooling.

It all comes back to that, right? Yeah, it all comes back to that.

So those thin walls cool down really fast.

But if different sections cool at different rates, well, then you're going to have.

Going to have warping, you're going to have internal stresses.

It's got to cool evenly.

Well, you got to be really strategic with your cooling channel design.

Yeah.

Cooling channels are essentially pathways.

That are built into the mold.

And they allow coolant, usually water or oil, to circulate and absorb heat.

From the molten plastic.

It's like a little. Yeah. Tiny waterways regulating the temperature.

Exactly. And those simulation tools we talked about, they're great for visualizing this cooling process and optimizing the cooling channels so you.

You can see it before you even build the mold.

Yeah.

So that's really helpful.

That's one of the challenges.

Another challenge is material flow.

Yeah. So getting that molten plastic to flow smoothly through those thin sections.

It's like trying to squeeze honey through a straw.

Yeah. If the material doesn't flow correctly, it's not good. You're gonna have parts of the mold not filling completely, or you're gonna get these surface defects.

Yeah, like flow lines, which are these unsightly streaks on the surface.

Well, you gotta be smart about material selection and gate location optimization.

And need a material that flows well.

And you need to make sure that the gate is positioned in a way that allows the plastic to fill the mold evenly.

There is a lot of tweaking. A lot of testing.

Yeah.

Cracking. Yeah.

They can crack, Especially if they're under stress.

Or impact.

Yeah. So again, material choice is critical.

You gotta pick a strong, impact resistant material.

But it's not just about the material itself. You also need to design the part in a way that minimizes stress.

So adding things like fillets.

Yeah. Fillets are just rounded corners that help to distribute stress more evenly.

And then, of course, testing is essential.

You gotta make sure that part can withstand real world use.

There's a lot to think about. But the key is to approach thin wall molding with caution and creativity. And you gotta be willing to experiment.

And those simulation tools are really helpful.

They can catch a lot of these problems before they become real world headaches.

Yeah. So it's a powerful tool.

Yes.

Injection pressure.

Yes.

It has been.

We've covered a lot of ground, but there's still more to come.

Yeah.

Yeah. Let's look at some real world applications, different industries. See how thin and thick wall molding are used to make all sorts of things.

All Right. Let's do it. Let's start with consumer electronics.

That's. That's where thin wall molding really shines.

Think about your smartphone.

The thin, lightweight casing, the intricate buttons, even a lot of the internal components. Yeah. That's all made possible by thin wall injection molding.

Yeah. It's amazing how much technology it is goes into something that we use every single day.

They do. And more feature packed. So the demand for that's only pushing thin wall molding techniques further.

Manufacturers are always finding new ways to make parts that are even more precise and intricate.

I think that's a good way to put it.

Yeah.

Oh, that's where thick wall molding comes in.

Great. Example is the automotive industry.

Cars, car parts. Yeah.

They got to be tough. They got to withstand a lot of stress and impact.

Think about bumpers, dashboards, door panels, even structural components within the car's frame.

Those are often made using thick wall injection molding to make sure they can handle the demands of the road.

Exactly.

So, yeah. It's not just strength.

Think about safety features too. Love airbags and child safety seats.

Those need thick, robust plastic components.

That can perform reliably when it matters most.

It is. It's a versatile technology.

It's not limited to just consumer electronics and cars.

Thick wall molding is also used in industrial machinery, medical devices.

Household appliances, you name it.

Yeah.

Makes sense.

It is. And the choice really comes down to what you're trying to achieve.

With the product.

What are the requirements? What does it need to do?

How does it need to perform now?

Sustainability. Yeah.

That's a big one these days.

It's the major focus in pretty much every industry.

And injection molding is no exception.

Well, well, there are a few things happening.

One is the increased Use of recycled plastics.

So more and more manufacturers are incorporating recycled materials into their products.

Yeah.

Less waste. Exactly. It helps reduce reliance on virgin plastics.

Another big one is lightweighting.

So as we talked about, thin wall molding uses less material, which automatically means a lower environmental impact. So manufacturers are constantly looking for ways to further optimize designs to use even less material without sacrificing strength or functionality.

Exactly. It's a win win.

Less material means lower cost for manufacturers.

And a smaller environmental footprint.

Biodegradable plastics. Yeah, that's.

Kind of in the early stages.

But they have huge potential.

So biodegradable plastics are designed to break down naturally over time.

Which means less plastic ends up in landfills, so it just decomposes.

Yeah.

Yeah. It's a really exciting area of development.

It seems like there's definitely a growing awareness of the environmental impact.

And manufacturers are responding with some innovative solutions.

The applications.

Sustainability.

It's been a fascinating exploration. Yeah. I hope our listener has a deeper appreciation, I'm sure, for this process.

Good, good.

All the engineering, the design that went into it.

Yeah. It's incredible.

The wall thicknesses, the ribs.

All the little detail.

It is.

It has.

We did.

Yeah.

Okay.

Design. Okay.

We have.

The design perspective is so important.

It's where the artistry comes into play.

That's a great question. We could probably do a whole other deep dive. We probably could just on that, But I can give you a little glimpse.

Into the Mind of a designer.

They're thinking about how they gotta think in three dimensions.

They gotta visualize how that molten plastic is going to flow.

And solidify within the mold.

So they're not just designing a shape. They're designing a process.

They got to consider the properties of the material, the wall thickness, the placement of ribs, all the other features.

And, of course, the overall esthetics and ergonomics.

How's it going to look?

How's it going to function?

It is a lot. It's a constant balancing act, pushing the boundaries of what's possible while still staying within the limits of the manufacturing process.

It is a delicate dance. Yeah. Between creativity and technical expertise.

Yeah. And that's what makes designing for injection molding so exciting.

Especially when it's something that's useful that people want.

Oh, really?

Okay.

That's cool.

This deep dive has been amazing.

I feel like I have a new appreciation.

For how much goes into it.

It is.

All right, so before we get to our final part. Oh, yeah. I want to leave our listener with a thought.

We've explored the technical side.

The applications, the design process. But we've talked about how designers balance form and function.

But how do they actually approach those challenges, specifically with thin wall molding? Ooh.

Right?

Because it seems like there's a whole other level of complexity.

Let's unpack that. In part three, there is.

So where do you even begin?

Okay.

Right.

It's that honey through a straw analogy again.

The gate position, the shape of the.

The material? Yeah.

So material really matters.

What else is a challenge?

Warping. Okay.

So you have to come up with features to minimize that risk.

Exactly, yeah.

Ribs are great because they add strength without increasing the wall thickness too much.

Designers also use things like gussets and fillets.

Yeah. Gussets are these triangular supports.

And fillets are those rounded corners.

Yeah. So they help to distribute stress more evenly.

Yeah. It takes experience to know what's going to work.

Well, surface finish is another one.

You want it to look good, right?

But a smooth, glossy finish.

It might not always be practical or cost effective.

Exactly. Might not matter. And some finishes require extra steps.

Like texturing or polishing.

Yeah. So it's all about balancing the look. You want the functionality and what's possible.

It's a lot.

Designers have to wear a lot of hats.

They have to be creative. They have to understand engineering. They have to understand manufacturing.

It is. It's a challenging field.

But it's also really rewarding. I bet when you see that final product.

And you know you were a part.

It is. Yeah. And this field is always changing.

Always evolving. Yeah.

New materials are being developed all the time.

New technologies, new design trends.

It's an exciting time to be in this field. Yeah.

It has.

The future of it. Yeah.

Good, good.

Right. Think about all the thoughts, the engineering.

Design that went into. You went into it creating those everyday.

Yeah. You have a deeper understanding of into it.

It is. It's a hidden world that we don't often think about.

Right.