Podcast – How Can You Effectively Reduce Warping in Injection Molding?

Injection molding machine with focus on plastic part design to reduce warping
How Can You Effectively Reduce Warping in Injection Molding?
Nov 08 - MoldAll - Explore expert tutorials, case studies, and guides on mold design and injection molding. Learn hands-on skills to enhance your craft at MoldAll.

All right, so if you're listening to this, you're probably dealing with some warping issues.
Yeah.
In your injection molding project.
Definitely a common one.
And that's why we're here today.
Absolutely.
Diving deep into this source we've got here.
Yep. Yep.
How can you effectively reduce warping in injection molding?
Ah, it's a good one.
It's a really great source. It's got a lot of information.
Yeah. Jam packed.
And really arm you with the knowledge to beat this warping issue.
That's the goal.
I think some of the things you learned today might surprise you.
It's funny you should say that, because I think one of the most surprising things is that people always jump right to the machine settings when they have warping problems. They want to tweak the materials when oftentimes the root of the problem lies in something much more basic, and that's mold design.
Really. So we have a go all the way back to the drawing board.
Back to basics.
Wow. Okay.
Yeah. So it's a big deal with mold design. Mold design is like, you know, constructing a building. If you have a wonky foundation.
Right.
You're going to have a shaky structure, no matter how fancy the facade is.
Interesting.
So in mold design, uniform wall thickness is key.
Okay. Uniform wall thickness. So that means that, like, every.
Every single part of the mold, every.
Part needs to have the exact same measurement.
Yeah. That's the starting point.
Okay.
But there's more to it than just that. Because variations in wall thickness caus cause uneven cooling and shrinkage.
Okay.
Which leads to warping.
Gotcha.
So just imagine a product with thick and thin sections. The thin parts are gonna cool faster, right?
It would.
And they shrink quicker.
Yeah.
And that ends up creating internal stress that pulls the product out of shape.
So it's kind of like a tug of war between different parts of the plastic as they cool.
Exactly.
At different rates.
You got it.
This guide also mentions gate positioning. Gate positioning, is that, like, where the plastic enters the mold?
That's exactly what it is.
Okay.
It's all about ensuring that that molten plastic is flowing smoothly and evenly throughout the mold. Makes sense. So imagine, like, your mold is a sink.
Okay.
And the plastic is water.
I like that.
You need strategically placed faucets to fill the entire sink evenly. Right, Right. A poorly positioned gate can create uneven flow. Oh. Which leads to inconsistent cooling.
Okay.
And you guessed it. Warping.
Warping. So it's not just about getting the plastic in there.
Nope.
It's about controlling the flow. It's like a River for a nice, even cool down.
Exactly.
What about the cooling system itself?
The cooling system.
So, like, does a faster cool down.
And less warping while cooling speed does matter.
Okay.
Even cooling is really the most important thing.
Okay.
So think of it like this. When different parts of the mold.
Yeah.
Cool. At different rates.
They shrink unevenly.
They shrink unevenly. You got it. Leading to stress in the part creating those internal stresses.
Yeah.
So a well designed cooling system acts like your body's circulatory system.
Okay.
Ensuring even temperature distribution and minimizing those stress points.
So it's not a race.
It's a marathon, not a sprint to cool down. Exactly.
It's about making sure the whole thing cools evenly.
Evenly.
Now, this guide throws in another element here. Ribs.
Ribs.
What role do ribs play in preventing warping?
Ribs act like internal support beams.
Okay.
And they're especially crucial for thinner sections. They reinforce the structure.
Gotcha.
And resist bending and warping.
So they're kind of like giving it extra strength.
It's like imagine the internal scaffolding.
Okay.
That holds up a building during construction.
Okay.
They provide that extra strength and rigidity.
So we're not just relying on the material itself. We're giving it help from the inside.
Exactly.
It's like we're building a fortress.
A fortress. Against warping.
Against warping. And that brings us to the material itself.
The material.
Right. Which is another big player.
It is.
In this battle against warping.
Absolutely.
I was actually kind of surprised to learn that material selection is about way more than just picking something that's strong.
Strength is important. Of course.
Of course. Yeah.
But it's just one factor to consider.
Right.
You also need to think about thermal stability.
Thermal stability.
Which is how well a material maintains its shape.
Okay.
Under temperature changes.
That makes sense.
And also shrinkage rates.
Right. Because things shrink differently.
Different materials shrink at different rates during cooling.
Yes.
And that can absolutely lead to warping.
So it's like picking the right wood.
Exactly.
For a project.
Some woods are strong.
Right.
But they're going to warp like crazy. They're going to warp if you don't treat them right.
For sure.
Exactly.
You wouldn't use, like, a moisture sensitive wood.
Right.
To build outdoor furniture. Good point. And there's a great example in this guy.
Okay.
They initially chose this ABS plastic, which is known for impact resistance.
Okay.
But they ran into warping.
Oh, no.
So they switched to a PC ABS blend.
Interesting.
Which has better thermal stability and a more suitable shrinkage rate for their mold.
Gotcha.
And guess what?
What?
They Significantly reduced warping.
Wow. So just changing the material.
Material matters.
Made all the difference.
It really does.
So material choice is about matching the properties of the plastic. Yes. To the demands of the design and the molding process itself.
That's all connected.
What other factors are important with materials?
Moisture content is another big one.
Moisture content.
Yeah. Especially for materials like nylon.
Okay.
Which are hygroscopic, which means they act like sponges, basically absorbing moisture from the air.
Oh, wow.
Expanding and potentially warping.
So it's like making sure your cake ingredients are dry before you bake.
That's a great analogy.
You don't want to add a soggy bag of flour. You don't want to do that to the mix.
Yeah.
So pre drying hygroscopic materials like nylon is essential.
Okay.
It's like wringing out the material before you use it.
It's amazing how much we take for granted with these everyday materials.
I know. Right?
Now, this guide mentions fillers and additives. What are those all about?
Fillers and additives are like.
Yeah.
Think of it like adding spaces to a dish.
Okay.
You know, they enhance certain properties of the material.
So, like, if you want a stronger plastic.
Exactly. So, for example, you can add glass fibers.
Oh, wow.
To plastic to increase its strength and.
Rigidity, and that would help reduce warping.
And that helps reduce warping. You got it.
So it's like fine tuning a recipe to get this flavor, texture, flavor and texture you want.
That you want.
We've talked about mold design.
Yep.
We've talked about material selection. We have what's next in our quest to conquer warping?
Now we get into the heart of it all. The injection molding parameters.
Okay.
That's where we fine tune the machine settings.
Gotcha.
To really dial in and get the best results.
Sounds like we're about to get hands on with the machinery.
We are.
Stay tuned as we explore this fascinating world of injection molding parameters.
Part two.
In part two.
Welcome back. So we've laid the groundwork we have with mold design material selection. Now let's dive into the heart of the process itself.
Okay.
The injection molding parameters. Right.
It's like we're stepping into the control room.
Exactly.
Of this whole operation.
That's a good way to put it.
So what are the key parameters? Okay, so we need to understand.
First up, we have injection pressure and speed. These guys work together to control how the molten plastic flows into the mold.
Gotcha.
So injection pressure is the force that's pushing the plastic.
Right.
While speed determines how quickly the mold Fills up.
Okay. So more pressure. More pressure means faster filling.
Well, not necessarily.
Okay.
It's about finding the right balance.
Right.
For your specific material and mold.
Okay.
Too much pressure can cause the plastic to flash.
To flash.
Which basically means you get this excess material, while too little pressure could result in the mold not filling completely.
So it's like finding that sweet spot.
Exactly.
Between filling the mold completely. Yeah.
Got it.
But not overdoing it.
That's it.
How does speed play into this balancing act, then?
Well, injection speed determines how quickly that mold cavity fills up. Faster speeds mean you're more efficient.
Right.
But they can also create problems.
Okay.
If the material doesn't have enough time to properly distribute itself.
So if it's going too fast.
Too fast. Yeah.
You can't quite. Like.
It's like if you were pouring in there.
Right.
A really thick batter into a cake pan.
Yeah. Too quickly, you'd have problems.
You might end up with air pockets.
Right.
Or, like, an uneven distribution.
Okay. So it's not just about getting the plastic in there. It's about making sure it flows nicely.
About the flow.
Yeah.
Yeah. Smooth and even.
To prevent those issues.
Exactly.
Okay. And I imagine the ideal speed. The ideal speed is different for every project.
It can vary. Yeah.
Depending on.
Depending on the material.
All sorts of things.
The mold, how complex it is.
Yeah.
And like the properties you want in the final product.
This guide recommends starting with moderate settings and then adjusting from there and seeing what happens. Yeah. It's like fine tuning a musical instrument.
Exactly.
You gotta make those little adjustments. Weeks to get the perfect sound, to.
Get it just right.
What's next on the parameter checklist?
Okay, next up, we have holding time.
Holding time.
This refers to the amount of time the pressure is maintained in the mold.
Okay.
After it's filled.
So you're giving the plastic a moment.
Yeah. Kind of like giving it a chance to settle in, to relax and really take on the shape of the mold into that mold. Yeah.
Okay.
So too short a holding time.
Too short.
Yeah.
What happens?
Well, you can get sink marks.
Sink marks?
Where the surface kind of dips inward.
Oh, wow.
Because there wasn't enough pressure.
During cooling.
Yeah, during cooling. Or you could even have incomplete filling.
Oh, wow. So it didn't even.
It didn't even fill all the way.
Totally fine.
On the other hand.
Yeah.
If you hold it too long.
Okay.
That can increase the cycle time, which means less efficient. Less efficient. Exactly.
Okay.
And the part might become too dense, which increases the risk of warping.
So another balancing act.
It's all about balance.
Enough time to solidify.
Yeah.
But not so much that it creates other problems.
That's right.
Now, what about cooling time and mold temperature?
All right, so cooling time and mold temperature, they go hand in hand.
Okay.
Cooling time is basically how long the part spends in the mold.
To cool down.
Yeah. To cool and solidify. While mold temperature actually influences how quickly that happens.
So a lower mold temperature.
Lower mold temperature.
It's a slower cooling process.
And slower cooling. Exactly. Oh, and just like withholding time, there's a sweet spot for cooling. Yeah.
Okay.
Too rapid. Cooling Too rapid can trap those internal stresses, making it more likely to warp later on.
It's like quenching.
Yeah.
A hot sword in cold water.
That's a great analogy.
You know, it might make it hard.
It might make it hard, but it.
Could also make it brittle.
Brittle, right. Exactly.
And then it breaks.
It can snap.
Yeah. So if the cooling time's too long, on the other hand, if it's too long, it's less efficient.
Less efficient. Yep.
So the key is to find that balance.
It's all about balance.
To make sure it cools evenly.
Even cooling is key.
This guide mentions a technique called multistage injection molding.
Multistage injection.
What is the advantage of that approach?
Multi stage injection is a more, like, controlled way to control the flow and.
Pressure of the plastic.
Of the plastic.
Okay.
So instead of a single constant injection, it's broken down into stages.
Okay.
To give you more control over the pressure and speed.
Okay.
Throughout the whole filling process.
So it's like a chef. It is carefully layering ingredients.
That's a good way to put it.
Instead of just dumping everything in the pot at once.
Yeah. You don't want to do that.
That makes sense.
This way you can minimize air pockets.
Right.
Get a more even distribution.
Yeah. Reduce the stress, which all helps prevent warping.
It all leads to less warping.
So multistage injection, molding, multistage. It's just a more sophisticated approach, more refined approach. It gives you more control over the process.
That's the idea.
Well, we've covered a lot of ground here. We have with these injection molding parameters.
We've been through a lot.
What is the final stage? All right, so in our quest to.
Conquer warping, the perfect mold design, the perfect material.
Right.
And even if you've, like, totally nailed those parameters, there can still be some, like, residual stress hiding inside the part.
Interesting.
And that's where post processing comes in. Post processing, it's like giving the parts a spa treatment.
Okay.
To relax and Relieve that tension.
So even after it's out of the.
Mold, even after it's done.
It's not quite done yet.
There's one more step.
What does this spot treatment entail?
Stay tuned for part three.
Right.
Where we're going to uncover the secrets of post processing and wrap up our deep dive into the world of warping.
Looking forward to it. So we've explored mold design, we've looked at material selection, we've covered a lot. And we even fine tuned those injection molding parameters.
It's been quite a journey.
Now we're at the final stage. Post processing grand finale in our quest to make those work. Free products.
The final step to victory.
So it's like we're giving our molded parts that last little checkup, a little TLC to make sure they're in tip top shape.
Exactly. And make sure everything's settled just right.
What are some of the techniques then?
Okay.
That are used?
One of the most common ones is annealing.
Annealing.
Yeah. And that basically involves heating the part to a very specific temperature and then cooling it down really slowly.
You're like, giving it a chance to relax.
Yeah. You're relieving that internal stress to its final form and improving that dimensional stability.
Without all those internal tensions.
Exactly.
Pulling it out of whack.
It's like imagine you have this, like, tightly wound spring.
Okay.
And kneeling is like, you're gently releasing that tension.
Right.
Letting it go back to its natural relaxed state.
That makes sense. Are there. Are there other post processing techniques that we can use?
Oh, yeah. For sure.
To prevent warping.
Humidity adjustment is another important one. Humidity adjustment, especially for those hygroscopic materials.
Right. Like nylon.
Like nylon. Exactly.
Which soak up the moisture.
They love that moisture from the air.
Which can cause all sorts of problems. And warping, of course, warping being a big one.
So humidity adjustment is about keeping them dry.
Yeah. Maintaining that dryness even after they're out of the mold, Even after they're all done.
So we talked about drying them before.
Tree drying is key.
And now we're talking about.
And then you got to keep them dry.
Maintaining that.
A two part process.
Yeah.
So this could mean like storing them in a special environment.
A controlled humidity environment.
Yeah, yeah, exactly.
Okay.
Or even like using a coating to.
Block out that moisture to seal them.
Off from the moisture.
It's like giving those parts a little protective shield.
It's like a little raincoat for your.
Parts to keep them happy.
Exactly.
And warp free.
Happy and warp free.
That's the goal it's amazing how much detail goes into all of this.
I know. It's really fascinating.
It's not just one thing.
It's a whole process.
It's like you said, it's multifaceted.
It really is. You got to think about all these different stages. Every step matters to get that perfect product.
That's the key takeaway.
And if you're out there struggling with warping issues.
Yeah. Don't give up.
This guide that we've been talking about.
It'S a great resource.
How can you effectively reduce warping in injection molding?
Keep it handy.
Is a great place to start.
It's got all the answers.
It's been an amazing deep dive.
It has been fun.
I feel like we really unlocked the secret. I think we crack the code to success here.
We did it.
What is the most important piece of advice?
Oh, that's a good question.
That you would give to someone. I would say struggling with warping.
Don't get discouraged. It's a common problem.
It is.
And sometimes it takes a little trial and error.
Yeah.
To figure out what works best for you.
Absolutely.
Use what you've learned from this deep dive. From this deep dive, don't be afraid to ask for help.
There's lots of resources out there.
There's a whole community and experts who are ready to help you out.
Who've been there.
Exactly. We've all been there.
They've done that.
We've all had those warping woes.
So you're not alone.
You're definitely not alone on this journey. We're all in together.
We're all in this together. That's right.
And as you get more experience, you'll.
Be able to make amazing things.
You'll be a warping master, and you'll.
Be able to unlock new levels of creativity.
Your designs will be unstoppable in your designs. That's the exciting part.
Well, that brings us to the end.
It does.
Of our deep dive.
It's been a good one.
We hope you feel empowered. We hope you feel ready to tackle your warp challenges. Go forth and conquer and create those amazing products.
Make us proud.
Thanks for joining us.
Thanks for being here.
Until next time.
Happy molding.
Happy