Construx

[TripHazard]

Hi everyone. I'm just learning about injection moulding. I was wondering how these would have been moulded since they look to have undercuts on all 6 faces of a cube. I've seen example of how threads are moulded but the only way I could see this working would be a 6 part mould and I've never seen any examples of that. https://www.google.co.uk/amp/s/www.mnn.com/earth-matters/energy/blogs/amp/heirloom-toys-construx-for-the-win

Thanks in advance for any info

[MTUHusky]

Hey Trip,

A close-up picture would help but it looks like it would be a combination of slides, lifters (sliding, hinged or spring lifters) and horn pins. So essentially you would have the detail on two sides coming from the A and B side of the mold and then each cavity would have 4 slides for the other 4 faces of detail. This is slightly over simplified but it will get you started in the right direction.

Husky

[TripHazard]

wow sounds complicated! i thought it would be because it even looks as though the under cuts have under cuts haha. yeah i couldn't find any better pictures. ive got a similar design in mind for a product and couldn't find an example of anything else being injection moulded like it, until i came across those "fisher price construx", which gave me hope it was possible.
i guess the mould cost, machine cost and cycle times would be extremely high on something like that? i did do a quote on that "proto labs" website but its all automated it just came back at around 4000 for the mould and told me i needed to get rid of the undercuts... are there some companies on here that could take a look at the design and give me a proper quote? or any suggestions for companies that dont just have an automated response. im quite new to all this and just learning. i know some of the basics but, its all youtube and google-fu.

[MTUHusky]

Hey Trip,

$4000 sounds extremely low for an injection mold. If 4 slides would be good enough (and it probably won't), just to have a machine shop cut the 4 slides would cost you $4000 or more and that's just for one cavity. Maybe they quoted you a single cavity aluminum mold but that would be for just the prototype and very low production. Just a guess off of the top of my head, an 8 cavity tool may cost you between $50k and $100K to be made out of nice S7 tool steel. If you get lucky and have a material that is not very abrasive, you may be able to make it out of a cheaper steel.

The slide concept is actually pretty simple. The part detail is part of a moving slide. The slide is set into motion by a pin (horn pin) on the other half of the mold that is at an angle. When the horn pin mates with the hole in the slide, the angle causes the slide to move along the pin until it shuts off at the parting line of the part. When the mold opens the slide moves along the horn pin and opens the slide, clearing any under cuts. Now it sounds like you would need a spring loaded slide within your slide to make the second undercut. All of this can be done and any competent mold builder should be able to do it. The cost is the question.

Good luck with your venture!

Husky

[TripHazard]

yeah i thought 4000 a little on the cheap side as well. 50-100k is more what i was thinking. looks like its back to the drawing board for me since there isnt just the cube in the set, theres 12 shapes total. i wish i had that kind of money, but sadly i don't haha. thanks a lot for all the help Husky.

[MTUHusky]

Well don't let the different pieces scare you off. If the different parts share like dimensions and features you may be able to have a mold made using different inserts for different part numbers. So lets say you have an 8 cavity tool and are making 8 of these cubes per shot. Now the run is over and you want to make long rectangular pieces. Well the mold gets pull (or in some cases the inserts can be changed right there in the machine) and you pull the cube inserts and replace them with the rectangular inserts and now you are running a 4 cavity mold making a different part number. Just something to think about, instead of buying two or more $100k molds you just have one mold that may run you an extra 10k for the different inserts.