[4]

How to identify die casting vs CNC?

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

NGrimberg

Newbie
Registered
Joined
Jun 6, 2018
Messages
3
Likes
0
#1
Hello! How do you know if a product was made using CNC machining or die casting? For example, a phone back cover. The Google Pixel 2 has an aluminum chassis. How can I tell if that was made using CNC or die casting? Any input would be appreciated!
 

rgray

Active User
H-M Supporter - Gold Member ($25)
Joined
Nov 26, 2012
Messages
1,016
Likes
532
#2
I'm thinking something like that is stamped.
Looking closely at cast parts you can see the parting line if they haven't gone to the trouble to remove it.
Cast aluminum is somewhat brittle so thin parts are likely not cast.
 

Asm109

Active Member
Registered
Joined
Aug 29, 2017
Messages
196
Likes
217
#3
Casting requires draft. ie angles on vertical surfaces so the part slips out of the die easily. Requires a gate where the metal was injected.
Good design strives to keep the wall thickness constant. CNC machining has no such requirement.
Machining leaves cutter marks. Dead sharp inner corners are much more difficult to make No draft required.
Close visual examination will tell you what process made the part.
It could also be a combo. Casting with a bit of machining to hold a critical dimension or two.
 

derf

Brass
Registered
Joined
Oct 3, 2015
Messages
630
Likes
732
#4
Look at the cost. In the case of a phone back, it's a high volume part. That means it will be manufactured the most cost effective way....die cast.
 

RWanke

Active Member
Registered
Joined
Aug 23, 2017
Messages
110
Likes
123
#5
Depends on the phone. I phone X sells for $1000. Supposedly all machined aluminum. Maybe that's why. :big grin:
 

Downunder Bob

H-M Supporter - Sustaining Member
Staff member
H-M Platinum Supporter ($50)
Joined
May 16, 2016
Messages
1,016
Likes
410
#6
Machined parts will usually have some visible mahine marks, unless they have been very well finished. Also virtually impossible to have square internal corners.

Die cast will usually have visible draft, also you can often see the marks left by ejection pins and sometimes sprue gates, and part lines are visible. However if the part is extensively machined after casting, not always easy to tell. A toolmaker who is familiar with die casting dies can usually tell. but for the novice not always easy.

If it's important to know can you post some very clear close up photos from various angles. We might be able to help.
 

mws

Active User
H-M Supporter - Silver Member ($10)
Joined
Jan 26, 2013
Messages
196
Likes
101
#7
Most all small metal electronics cases, particularly phones these days, are machined. The tolerances are such that it doesn't pay to cast such a small part which will then need to be machined anyway. So they just start with a punched blank and CNC the rest, and changes are easy if they need clearance for a different component.
 

Downunder Bob

H-M Supporter - Sustaining Member
Staff member
H-M Platinum Supporter ($50)
Joined
May 16, 2016
Messages
1,016
Likes
410
#8
Most all small metal electronics cases, particularly phones these days, are machined. The tolerances are such that it doesn't pay to cast such a small part which will then need to be machined anyway. So they just start with a punched blank and CNC the rest, and changes are easy if they need clearance for a different component.
High pressure die casting can achieve some pretty good tolerances. Back in the mid 60's when I was working as a toolmaker we made some dies that produced precision parts for a customer that did not require machining.

many said it couldn't be done. but we did it. What they meant was, that they'd never seen it done, afraid to stretch the envelope. Fear is always the biggest hurdle for achievement. I admit however, that nowadays, with high speed CNC it's probably just cheaper.
 

mws

Active User
H-M Supporter - Silver Member ($10)
Joined
Jan 26, 2013
Messages
196
Likes
101
#9
High pressure die casting can achieve some pretty good tolerances. Back in the mid 60's when I was working as a toolmaker we made some dies that produced precision parts for a customer that did not require machining.

many said it couldn't be done. but we did it. What they meant was, that they'd never seen it done, afraid to stretch the envelope. Fear is always the biggest hurdle for achievement. I admit however, that nowadays, with high speed CNC it's probably just cheaper.
Indeed! I suppose, given some of the external features I've seen on some cases that might be an option. All the ones I've opened show milling marks internally with no ejection pin marks. No doubt, the volume of these throw away phones produced would cover the price of a few moulds in short order. There's a fellow, Paul Hamler, on you tube that does some pressurized lost wax casting "at home". It's pretty neat. Where's there's a will...
 
[6]
[5] [7]
Top