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Make a plastic phone cover using CNC milling

  • This topic has 76 replies, 22 voices, and was last updated 2 years ago by Reter.
Jerry de Vos jerzeek

Make a plastic phone cover using CNC milling

11/11/2017 at 21:32

Hi Guys,
I made an instuction video on how to make this, and in this thread i want to reply on questions that you guys might have!

Why not design the injection point on the inside of the phone cover? – by @jegor-m
This is cause the inside has an insert to mold around, and in general you want to prevent injecting through inserts.

Where does the air go
Yes on big injection machines this is a problem, but here the tolerances are not so thight, one scratch and you will have plenty of ventilation…

What material did you use?
The mold is made out of Aluminum

How much did the mold cost?
We paid €400 for the mold, €50 for shipping

I used Solidworks mainly because i know the program very well and the iPhone can have difficult radii. you can easily use fusion360, thinkercat or any other (free) program, but im still learning those πŸ˜‰

Where to find the mould files?
Mold files are in the download pack:https://github.com/hakkens/precious-plastic-kit/archive/master.zip
In this path:Β Β  5.create -> iPhone 7-8 mould -> STEP files 😃

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21/11/2017 at 21:34

is there a link to the digital files for this mold?

edit: found it! (in the download kit of course)

22/11/2017 at 14:13

Nice! I just watched the video. The end product is very professional looking. I like how you also show the application of the stamp.

When you designed the mould, did you oversize it to allow for any shrinkage of the plastic? Perhaps it’s not necessary, and even creates a tighter fit of the case on the phone.

You don’t mention your choice of plastic, but I note you used PP which will flow better into thin sections and also shrink less than say, HDPE. Though it took the weight of both you and Dave on the injector handle to generate enough pressure, the results are impressive. It’s good to know that the injection machine is capable of producing relatively thin cross section items like this.

Are you going to be selling these phone cases on the Bazar?

22/11/2017 at 14:21

Oh, and… Did you manage to get this to work on the first go or did you have to do a number of trials? How did you determine the minimum thickness you could successfully inject?

23/11/2017 at 13:08

Hi @andyn!

Thanks for your questions πŸ™‚

Did you oversize the mold?
Yes initially i did oversized the mold, 3%. But after making a couple of cases we noticed that the case is still quite loose around the phone… this is because the product is fully cooled down while still in the mold, this way the product cannot shrink much. the files in the download kit are changed to a oversize of 1%, this should result in a better fitting case.

Choise of plastic
Initially i was planning to use HDPE, this is cause its more flexible and doesnt break, but we found that it’s way more difficult to inject HDPE with such a thin product then PP, so from now on we will mainly use PP.

Sell it on bazar?
Not anytime soon, maybe later we can pass the mold to someone else who want to make a lot of them.

First try?
Oke so the first try of the phonecase mold was actually succesfull πŸ˜€ We made a good case, but afterwards the results where a bit mixes, sometimes it wouldn’t fully inject, i would say 60% of the injections give a good phonecase. but before we made different molds(not cnc) and there we figured 2mm is the thinnest we would do πŸ™‚

23/11/2017 at 13:56

Thanks Jerry, for the answers 🙂

26/11/2017 at 23:51

Can you give me the company name who made the mold?
In Mexico there’s no one who make it
Thank you

27/11/2017 at 18:21

If these moulds were available in the Bazar, would you be interested in buying one?

29/11/2017 at 02:44

Don’t want to sound like a know-it-all, but for €450 I think you could have purchased a cheap CNC and a +18.000rpm spindle and make the moulds yourself. Cheap CNC machines are not made for milling metal but if you make the GCODE to mill very slowly, it should work just fine πŸ™‚

29/11/2017 at 16:35

I think 450 euro sounds like a very reasonable, or even cheap, price. Of course you can purchase a cheap CNC but it’s less of a plug and play thing then it might seem. You need to invest quite some time and research to get super clean results with high precision.

29/11/2017 at 17:53

And don’t forget that the mould is made from several sizeable aluminium billets that probably cost 100 euro on their own.

It is possible to buy a cheap CNC router for 450 euro, but I doubt it would give acceptable results and even if it could it would take days or weeks to do it.

14/01/2018 at 21:13

Dear Jerry,

I am a student and also a young entrepreneur. I am currently busy with a project where I want to design my own iPhone cases made of recycled plastic. While brainstorming about this idea I did some research and found your video. I am not very handy so I have no idea how to make a mold or anything that have to do with this. So, I have some questions about the producing process of this and I like to ask them to you.

I am from the Netherlands and I love to meet you if it is possible. I hope you could help my further with the problems that I now have.

Kind regards,
Scott van den Berg

14/01/2018 at 22:45

Really really thank you that you are gave the solidwork files for free!
I am trying to mill the case mold with my cnc machine..

i would like to ask you @jerzeek?
why are they made the mold so huge??

*the price is cheap and the result looks totally professional!

15/01/2018 at 22:28

Easiest is to ask the questions here or in a direct message, if you want we can also meet sometime, but that would mean that you have to go to Delft πŸ™‚

15/01/2018 at 22:31


Cool man that you are trying to mill it!
yeah, about the size… i basicly had no clue when designing it, it could have been a whole lot smaller.
But, it does help to cool down the product quicker πŸ˜‰

15/01/2018 at 22:39




I’m sure that a 450 euro mill won’t be able to mill this.
Maybe you can mill easier and smaller molds. But then you still need time and materials.

Appearently 3D hubs did up their prices lately so it isn’t 450 euro anymore…

16/01/2018 at 14:21

Thankyou for your quick respond. At this moment I am unavailable to come to Delft because I just had a knee surgery. Is there any moment in February that will fit you to have us over?

Hope to hear from you.

Kind regards,
Scott van den Berg
Mees Bakers

23/01/2018 at 14:24

Dear Jerry,

Could you provide me with your email, so I could sent you some more information about our project and maybe make an appointment.

Kind regards,
Scott van den Berg

23/01/2018 at 18:14

My milling progress according to @jerrzeek plans!

23/01/2018 at 18:38


Looking good! How long did it take you to mill that?

23/01/2018 at 20:01

took around one and half hour each.. the third one is much more difficult ….

15/02/2018 at 23:17

Could you tell us the volume of the case? So we know what kind of stroke would be required to make such parts.

20/02/2018 at 01:10

I manage to finish the phone case mold!
As you can see on the pictures below the result is not 100% professional like Jerzeek cases but for me to mill such a complex mould with 3axis cnc it was challenge!
Once more i would like to thank again @Jerzeek who share the files for free!

22/02/2018 at 14:11

Awesome work @stampro01 ! I will try to make one for fairphone “Γ  la Johe” with the fonderie technic.

23/02/2018 at 00:05

Hello!I tried days ago the lpde (4) for my first time! i found it perfect for the case ! soft goes everywhere with not so much pressure like pp

09/03/2018 at 22:24

Hi Jerry,

Is it possible in any way to manufacture it using extrusion.

My concern in current process is mold opening and ejection is pretty time consuming.

I would like to somehow use it for mass production.

By the way, thank you so much for all the information. I really appreciate what you guys do.

Thanks a ton.

26/04/2018 at 17:54

Hey @jerzeek,

me and my friend just started recycling station with a shredder and an injection machine. We ordered the mold for the iPhone 7-8 with the drawings from your download kid and also ordered it from 3dHub but we got this here.

The groove and lip fit perfectly but when we put the insert mold inside then it doesnt fit anymore as you can see on the picture. Id really love to get a fast answer because of the problem is with the drawing then we cant say to 3dHub that it was their fault. So could you just take a look if its in the middle of the aluminum box on the drawing.

thanks Manuel

26/04/2018 at 18:39


Looking at the CAD files there does appear to be a discrepancy. The recess for the insert is exactly centered within the lip/groove, however the cavity of the phone itself is off centre by approx .75mm and the top and bottom halves are displaced by this amount in different directions, giving 1.5mm overall error which probably explains why it won’t fit together with the insert in place.

Out of interest how much did 3dHub charge to make the mould?

26/04/2018 at 18:48

To illustrate the problem here are the cad files with the mould halves assembled:

26/04/2018 at 23:02

He @manuelmaeder and @andyn,

Yeah, uhm…..
I am pretty sure the fault is in the files. πŸ˜₯
somehow something somewhere went wrong, the wierd thing is that our mold fits perfect, and that over the last 6 months more than 5 people specifically looked at the files and somehow didnt see it.

I am really sorry to find this out after your huge investment.

I reworked the files and updated them in the download kit, I added a date to the filename:
Topside mold 26-04-2018.STEP
Underside mold 26-04-2018.STEP
Insert mold 26-04-2018.STEP (only renamed this one)
I would really appreciate it if someone could review the files.

27/04/2018 at 05:15

I just payed 535 Euros with shipping for this mold, which doesnt work..
i could burst in tears. shit

thx for your fast reply.

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