Cost effective way for manufacturing a small plastic part

[John MunroeParticipant @johnmunroe13164]

Hi

I'm trying to have about 2000 pieces of this nylon part made:

It's a small rectangular piece with 2 holes in it. Does anyone know of a cheap way for manufacturing? How about laser cutting?

Thanks

Edited By John Munroe on 29/03/2017 07:14:24

[John MunroeParticipant @johnmunroe13164]

[JasonBModerator @jasonb]

I would think that would cost more than manual machining.

Assuming you can get 1" squae bar, I would set a stop on a chop or crosscut saw saw and be able to cut them to length very quickly. Simple locating jig on a drill press (you don't state tollerance on hole) and drill one set of holes, change drill and do the others

[not done it yetParticipant @notdoneityet]

Apart from needing 40mm square bar, I agree with JB, assuming units shown are in centimetres.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by not done it yet on 29/03/2017 09:00:01:

Apart from needing 40mm square bar, I agree with JB, assuming units shown are in centimetres.

.

Interesting assumption

… I was about to ask for confirmation of the units

[having first thought them likely to be millimetres]

I suppose it depends how you think of "small"

MichaelG.

[Chris Evans 6Participant @chrisevans6]

That is not an easy task, is it a regular plain nylon or glass filled ? My concerns are not the cutting and drilling but trying to get the nylon to cut cleanly without leaving a burr.

[John MunroeParticipant @johnmunroe13164]

Posted by not done it yet on 29/03/2017 09:00:01:

Apart from needing 40mm square bar, I agree with JB, assuming units shown are in centimetres.

No, the units are in millimetres.

[JasonBModerator @jasonb]

Ah, now I have blown up the screen that 1 is actually 4, so I'd say its cm but as Michael says there is small and there is small so could be 4mm sq in which case a circular saw would tend to throw the parts about.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Munroe on 29/03/2017 09:08:42:

… the units are in millimetres.

.

Thanks for that important clarification, John

Next question [which Jason has already mentioned] must be

… 'what are the tolerances?'

I think you might have difficulty with a 1.80mm dia. hole in Nylon.

MichaelG.

[Bob n AboutParticipant @bobnabout]

You don't give a tolerance for the part. Assuming you can't find an existing nylon extrusion, I would route the section from 6mm bar. Each part can be guillotined with a Stanley blade, I would drill the blocks in a jig possibly using a 2mm carbide end mill than a drill. You are probably looking at 21m (x7 3m lengths).

If you are likely to make more of these, look into extruding your own section and punch the holes out whilst the nylon is still warm and in the die. Kind of like a giant 3D print head, you're almost at the point of injection moulding.

[Tony Pratt 1Participant @tonypratt1]

Obviously 4mm square stock is the ideal material if you can get it, maybe jig drill the holes then cut off to finished length or cut off to length & drill the holes? Deburring will be tiresome.

Tony

[John MunroeParticipant @johnmunroe13164]

I'm hoping to achieve a tolerance of 0.05mm. Is it too tight?

[richardandtracyParticipant @richardandtracy]

2nd hand hand injection moulder & home made tooling, and sell the moulder afterwards? There is a Gingery book on it to give an idea, but the biggest problem is buying the material to be injected. Well nigh impossible on a small scale.

Hmm seem to be arguing against my own idea.

What value can you extract from each, and is there a possibility of future manufacture? May be more cost effective to pass on the job or let someone else have the agro.

As for the tolerance you are specifying, that's tight enough for a plastic to need to specify the temperature and material water content at which it's to be measured. Some types of Nylon can shrink by 10% when going from saturated to dry.

Regards,

Richard

Edited By richardandtracy on 29/03/2017 10:22:38

[Bob n AboutParticipant @bobnabout]

You can buy Nylon on a roll suitable for 3D printing, feed it through a bean slicer to make pellets for injection moulding.

[HOWARDTParticipant @howardt]

it is probable best to speak to an injection moulding company. They may have ways to prototype parts at lower cost than normal volume parts. It all depends on what you can afford to spend in money or time. If time is not important but money is then cut from sheet and use a jig to drill both holes from one end datum not the middle as drawn. Forget the length tolerance unless it needs to fit into something.

[Bob n AboutParticipant @bobnabout]

Any reason it has to be Nylon and not a castable resin. Spin casting in resin with steel pins you push out after would make small batches at a time.

[Martin ConnellyParticipant @martinconnelly55370]

You can get 4mm square nylon strimmer cord. It comes on a reel but a bit of warmth should allow it to be straightened out before use. Due to the problems of drilling plastics with accurate sized holes what are the material requirements you need to meet, something else may be a better option.

Martin C.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John Munroe on 29/03/2017 10:10:22:

I'm hoping to achieve a tolerance of 0.05mm. Is it too tight?

.

First point is that Nylon is hygroscopic, and the holes will probably tighten-up.

Second is that, as others have now mentioned; Injection Moulding [done properly] would be the preferred method.

In the early 1970s I worked for Kodak, in Stevenage, and it was truly amazing what they could achieve with injection moulding … BUT … they used very big, very expensive, machines and the set-up time was often a couple of days. To achieve the required quality; temperature and pressure need to be right [and very stable!].

An injection mould with two holes at right angles could prove expensive, but I think you might explore the possibility of moulding a precision part with one hole, and then drilling the second hole as a 'second operation'.

I've been away from that business for about 40 years, so can't advise regarding current Suppliers' capability.

MichaelG.

[Brian GParticipant @briang]

Have you tried the estimators on http://www.custompartnet.com **LINK** ?

Brian

Edited By Brian G on 29/03/2017 11:14:32

[Bob n AboutParticipant @bobnabout]

There above is a 10 x 10 x 10 array with 2mm spacing and a 2mm joiner in Z for SLA printing. The whole thing is 60mm x 60mm x 120mm tall. Two of these prints would give you your 2000 parts. In the long run this is probably the quickest and cheapest method.

[Bob n AboutParticipant @bobnabout]

P.S it you buy me an SLA printer I will do them for FREE

Holes should be treated as approximate size.

[Michael GilliganParticipant @michaelgilligan61133]

Joules,

That looks very impressive

Please forgive my innocence in these matters, but: could a 3D Print be reasonably expected to hold the hole diameter to 1.80 +/- 0.05 mm ?

MichaelG.

[Bob n AboutParticipant @bobnabout]

No, it couldn't so each hole would need reaming to final size. Also I doubt the whole print could hold that tolerance. But considering the time saving and the fact an 3D SLA printer can be had for just over £1k it's a pretty good trade off, with no tooling required other than a reamer.

[Tony Pratt 1Participant @tonypratt1]

Ok guys how long to print one of these parts?

Tony

[Bob n AboutParticipant @bobnabout]

One, or the array ?

The array can be printed in several hours and all 2000 in one session to fit the print bed. Resolution is a big issue at 100 micron in XY and 25 micron in Z Then a day or two doing the clean up and reaming/sizing.

So about £0.55 per part.

 

Worst still the resolution in XY is 300 micron (0.3mm)

 

Edited By Joules Beech on 29/03/2017 12:24:24

Edited By Joules Beech on 29/03/2017 12:30:43

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