Viability of injection molding phone cases

General
1

Hi all,

Just a thought… I’ve currently got my eye on the Kite phone project, which is a 4G phone delivered as a build-it-yourself kit. The kickstarter project isn’t live yet, but there’s a draft of it here.

Crucially, it comes without a case, you 3D print that yourself.

Right now I’ve got a ZTE T83, and @vk4mdl gets by with the slightly newer T84. My phone largely works, but is stuck at Android 4.1, which is getting a bit long in the tooth now, some of the software on fdroid.org is now seemingly for Android 5 or later, so I see supporting this OS is going to get harder moving forward.

The T84 @vk4mdl has is better in that it runs Android 5 and has higher specs, but there’s a catch: its cellular transceiver performance is rubbish compared to the T83. We just did a trip down to the Snowy Mountains, and there were times I was holding both phones in my hand, my phone would report a strong 4-bar or better 3G signal, his would report “limited service - emergency calls only”, or worse, “no network coverage”. External antenna made no difference in these cases.

Looking in the Telstra shop today, the staff there couldn’t explain the discrepancy, and I noted none of their current crop feature the external antenna connectors of these two devices.

Thus, we’re both looking at the Kite. We can 3D print cases for these, but then I thought, there’s an injection moulder here, why not use that? Especially if a few others are interested, we could put an order in for a couple, and injection-mold a few cases in one go.

What’s the steps involved in producing a design to be used with the injection molding equipment?

2

Not to sound like a broken record. But may be better of with silicone molds and PU.

Alan will chime in and correct me if I am wrong, but I think that Boy machine is going to have a hard time with something as large as a phone case.

(more surface area that shot size being a problem)

3

Fair point, and I’m open to other options, especially as in my case, I want something that’s reasonably resistant to water ingress (good enough to survive a decent shower, don’t need to go swimming with it) for use on the bicycle.

I enquired not knowing anything about the machine’s limitations. :slight_smile:

4

Well, they’re idiots, because they should know the answer to this one. Phone models vary in the frequency bands they support, and the T84 is missing the one that covered that area. Looking at the specs, the T83 supports the 700MHz LTE band and the T84 doesn’t.

5

True that, we walked in there fully expecting the outcome we got. :slight_smile:

They gave us a phone number to chase things up. I’m not holding my breath. Telecom Australia was an Engineering firm… Telstra is not.

I’ve just dug up the other T83 we have laying around (bricked by an OTA update), and it seems I’ve had it off the charge too long. Phone refuses to fire up off a charger, which is odd because cracking the thing open (and these things are built like bombs… 6 screws, lots of hidden catches, and some glue on the rear speaker), revealed the battery was sitting at a moderately healthy 4V. So it looks like it’s going to join its maker and I’ll have to make the one I have last.

The fact is both advertise 3G support, and the newer phone should have fell back to using 3G when it couldn’t access the 700MHz LTE band, and didn’t.

The Kite also does not have 700MHz LTE, but should be able to operate on 3G networks. At least though if something is wrong, I have more latitude to fix it.

6

Actually, looking at the product pages:

T83:

  • 4G LTE: 1800, 2600 MHz with 100Mbps data
  • 3G UMTS: 850, 2100 MHz with 42Mbps data (HSPA+)
  • GSM: 900, 1800 MHz

T84:

  • 4G LTE: 1800 (Band 3), 2600 (Band 7), 700 MHz (Band 28) with 150Mbps downlink, 50Mbps uplink
  • 3G UMTS: 850, 2100 MHz with 42Mbps DL (HSPA+)
  • GSM: 900, 1800, 1900 MHz

That suggests the newer one should have worked.

7

the injection molder that @alandonnelly7 has acquired only has a shot capacity of 30grams. This weight includes all sprues/runners required to fill the part. for reference this is about 10 standard lego bricks by weight. A good indicator is weighing something similar to what you wish to make. if it’s over 20 grams, it’s ~probably~ not possible on this machine.

8

I heartily approve of the use of LEGO as a unit of measurement. :+1:

1 Like
9

@Wixted, do you know what kind of surface area the clamping force of the machine is good for.

A phone case is likely very thin walled (to be light), therefore not likely to hit the shot size limit. But it may exceed the ability of the machine to hold together the mold haves well.

10

There is also this project that may interest you
https://shop.fairphone.com/en/spare-parts
Yes the boy probably wouldnt be the best option for a phone case as it would be quite large. The biggest mold size is 250mm square but you would lose some of that space because of the mold design. If you want to have a chat im sure il be down there tuesday?

Its a 15 tonne machine, the simple way you work out if the machine has enough clamping force is to roughly calculate the area in inches… say a part is 2"x1"=2… and then use the magic number of 2.5 to multiply it by… so a part 2"x1" will need 5 tonnes of clamping force! :wink:

Its what they used in the factory, they weren’t sure why they used 2.5 when asked ha but it has worked for them for the past 30 yrs

Clamping force isnt everything however the part actually needs to fit in the mold template, with space for ejectors etc… I have a 150mm square mold which might have a workable area of 80x90mm.

I dont have the 250mm square mold but it could possibly do the job. How big is your part?

11

No idea yet … I haven’t even gone that far, it was a hypothetical question: “can it be done?”

By the looks of things, it is better suited to smaller components. Nothing wrong with that of course. :slight_smile:

12

No nothing wrong with that but if I can help you with it, and try to make it possible let me know. Mainly id need to know exact sizes

13

Okay, now having seen and used the phone up close, I’m getting some better ideas. This is Kite v1.

That device is about (since we’re using imperial) 6"×3", so perhaps a little big. I’m actually giving thought to using thin wooden sheets, either manually cut or lasercut, glued together.

In any case, WICEN has a meeting Monday night, and on Tuesday night, two of us will be rigging up bicycles to provide communications for the Yarraman to Wulkuraka bike ride… I’ll have the Kite with me then for people to have a look.