Our Insight video series will help you master digital manufacturing.
Every Friday we’ll post a new video – each one giving you a deeper Insight into how to design better parts. We’ll cover specific topics such as choosing the right 3D printing material, optimising your design for CNC machining, surface finishes for moulded parts, and much more besides.
So join us and don’t miss out.
Insight: Design Cube
Hi and welcome to this week’s Insight video.
As you know previous videos have dealt with all sorts of design tips and useful advice about digital manufacturing. We‘ve gone into the dos and don’ts for injection moulding, CNC machining and 3D printing.
Which is all great stuff but unless you are going to rewind and watch some of our past episodes, and please feel free to do so, the challenge is remembering all of those tips when you get to sit down in front of your CAD.
All of this brings me onto the subject of today’s video, a really useful aide memoir for those of you who are designing for injection moulding – our design cube. It actually shows you the design dos and don’ts on it.
Okay, here’s mine delivered just the other day.
Let’s take a look. It’s flat packed as you can see, but it’s not exactly rocket science to make it into a cube that can sit alongside you on your desk.
It’s got all sorts of features moulded onto its exterior surface. The leaflet with it explains exactly what you are looking at as you turn it round in your hand. But even if you lose the leaflet there’s still an explanatory note in text on the cube itself.
Now I don’t know about you, but I find that it really helps me to see something when it’s explained so let’s take a closer look at some of these features.
We’ll spin it round and have a look at some of the features on what I think of as its underside. Here we can see both good and bad examples of bosses and through holes.
We have bosses that are too thick, which can cause sink on the other side of the part, and some examples of well-designed bosses. What’s the secret of a well-designed boss? Well let’s look at the design cube again. You can see that they have thinner walls to avoid sink and a top tip - they are tied to walls with a short rib for support.
Turning to the explanatory leaflet it recommends that you should design the wall thicknesses of the bosses and the ribs to between 40 to 60 percent of the wall thickness and that they can be strengthened with gussets rather than using thicker walls.
All good practical stuff and this design cube shows both good and bad examples.
The same side of the cube also warns you how knit lines can form downstream of through holes. Remember them? Well, they might or might not be a problem depending on the purpose of the hole.
Okay let’s flip it round and have a look at some of the other sides.
What have we got here? Let’s start with these ribs. If they are too thick then they can cause sink on the other side of the part – let’s flip open this face and have a quick look – can you see the difference between the different thicknesses?
Okay let’s close it up again.
What else have we got on this face? Well as you can see thicker features can sink, have voids or cause warp. And what have we got here? Well, here’s a good example, here we’ve cored out the thick section and you can see that it is fine.
There’s also a reminder on this face that thinner sections in the mould may not fill properly and cause surface imperfections.
Let’s turn it round and have a look elsewhere. Well, I suppose one thing to point out is that we have living hinges all the way around this cube, it’s what allowed me to convert it from a flat pack into a … well a cube.
And on this face, you will see a whole host of other features including undercuts and if you read the leaflet that comes with the cube, you’ll see how to get it right. We’ve also got a side-action cam and a sliding shut-off.
I think you are getting the idea of how this cube can really help you get your CAD for injection moulding right and avoid some of the pitfalls.
The other two faces of the cube show you some of the typical surface finishes that you can have with injection moulding, which let’s face it can be important for cosmetics; but remember that secondary finishing will obviously add cost to your part – so it’s worth comparing the default finish with the different options.
I hope I’ve shown you what a useful little thing this is. Remember it’s free of charge, it’s not conditional on you giving us business, although of course that would be nice.
So, what are you waiting for? If you don’t already have one then visit our website and send off for one right away.
That’s it for this week. I’ll join you again next Friday for another insight video. Have a great weekend.
With special thanks to Natalie Constable.