PDA

View Full Version : Why can nobody do the CNC job I need?



Harry
15-04-2011, 09:36 PM
I've been sending out emails looking for a company to cut my fin model out of polycarbonate

All of the companies so far have said they can't do it as they can't cut the curved surface... surely thats pretty basic?

Do i need to be targeting companies with special machines or something? Certain number of axis?

I have 3 slighty different designs. Two of them are flat on one side and curved on the other. The other is curved on both sides (shown in pic)

If anyone here could do the job for me then feel free to contact me. We are talking quantities of around 500 - 1000 and orders every couples of months or so.

M250cnc
16-04-2011, 06:23 AM
Harry you need to give the overall dimensions.

Phil

Sent from my HTC Desire using Tapatalk

Harry
16-04-2011, 10:33 AM
Harry you need to give the overall dimensions.

Phil

Sent from my HTC Desire using Tapatalk

Max thickness is 6mm. Max width 11cm, max heigh 13.5cm

John S
16-04-2011, 11:37 AM
At those quantities you need to look at getting them moulded.
For a start it's a soft material and doesn't want to cut well and being the shape it is how do you hold it ? If it fills a shape 150mm x 150mm cutting time for curved surfaces could well be over an hour each and at commercial rates that's about 50 to 60 each.

Robin Hewitt
16-04-2011, 12:20 PM
We live in a world of injection moulded plastic, curved surfaces are commonplace and it is easy to start thinking they are easy.

CNC mills do curved surfaces as facets or use custom cutters which will cut one set curve.

There are 2 approaches for this, cut it in 2.5D with a ballnose, cut it in 3D with a flatnose.

The ballnose cuts a round bottom groove so the facets have to be smaller and there is a lot more cutting to do.

The flatnose requires one hell of a machine, an uncommon beastie.

Polycarbonate? Are you hoping these will cut shiny and see through? :heehee:

Harry
17-04-2011, 07:21 PM
Hmm, I'm pretty stuck then if it's going to cost 60 to produce 1 fin!
I just don't know what the best way to go about producing these is. If CNC won't work, I cannot afford the 9k to start injection molding! Any other methods, please help!

M250cnc
18-04-2011, 09:58 AM
There are 2 approaches for this, cut it in 2.5D with a ballnose, cut it in 3D with a flatnose.

3D can also be cut with a Ballnose or a Bullnose but i agree a lot of time will go into cutting.

A simple mold could be made "High Precision Of Course" where a casting resin could be added, then the mold is sealed then the mold is rotated until all the inner surfaces are covered and the resin hardens.

A similar principal is used to make Easter Eggs among other things.

Phil

Robin Hewitt
18-04-2011, 01:44 PM
If CNC won't work, I cannot afford the 9k to start injection molding! Any other methods, please help!

It's a very simple two cavity mould, if you had CNC you could make your own. Set aside a few days to polish it though.

Mould components are fairly cheap. Follow this link and see if you feel way out of your depth...

http://www.dms-diemould.co.uk/

birchy
18-04-2011, 09:13 PM
Taking a different view, have you considered contacting some of the Chinese manufacturers/injection moulding factories? For a regular order, I imagine they'd foot the costs of setup or at least meet you half way...

Robin Hewitt
19-04-2011, 12:49 AM
Last time I had a mould made in Taiwan it was for a little rubber keypad. IIRC the mould was 4k, the keypads were 7p each/5k pcs, which included the contact pills and legend print.

Over here they would skin you for the mould, then skin you again when they squirted it.

Over there they only skin you once :naughty:

birchy
19-04-2011, 12:59 AM
Hmmm. Personally, I think I'd consider liasing with a plastics injection firm. i.e. you supply the moulds (made to suit their machine) and they do the squirtin'.

HankMcSpank
19-04-2011, 02:48 AM
Last time I had a mould made in Taiwan it was for a little rubber keypad. IIRC the mould was 4k, the keypads were 7p each/5k pcs, which included the contact pills and legend print.

Over here they would skin you for the mould, then skin you again when they squirted it.

Over there they only skin you once :naughty:

Forget cockle picking in Morecambe bay...if I was a Chinese "Mr Big", I'd smuggle in a few guys who can whack out an injection mould in short order here in the UK ....."back of the net"!

Seriously, if this Govt want to really want a "march of the makers"...then they'd better sort out a way that "the makers" can get small plasticy bits made without having to donate a kidney.