Plastic Injection Moulding (?)

[Flynnwood]

Does anyone have any experience with Plastic Injection Moulding and/or machinery?

I'm interested in tooling costs and potential pitfalls?

Outsource projects or buy machinery? (depends on volume of course.)

Any info would be appreciated.

 

[Sheffield Tony]

I don't, but we do have some parts 3D printed (in nylon), which could be worth a thought if quantities are small. These lot are often plugged by the IET:

https://www.protolabs.co.uk/

 

[Claymore]

The company i used to work for did injection moulding for chocolate moulds and the tooling was very expensive as the machines were as long as a house but for some of the smaller injection moulders they would be cheaper but would think tooling would be £1000+ so not a cheap thing. The 3d Printers might be the way to go but don't know bugger all about them as they are witchcraft lol

 

[AES]

I know nothing about this directly, but before he died a local mate of mine made a highly satisfactory self-employed living designing and making first-off prototypes for the injection moulds used for producing the cases of mobile phones (the actual plastic phone cases, usually in two halves, NOT just outer pocket "carrying cases").

I've no idea how he got those contacts originally, but as all the major phone manufacturers were at that time bringing out new models very frequently, he was always rushed off his feet. As said, he made a very comfortable living (in Switzerland please note!) so a bit like metal casting dies, I've always ASSUMED that these are very expensive tools and can only pay for themselves when production runs of "millions off" are contemplated.

Likewise I know nothing at all about 3D printing, but unless you're looking at "millions off" production runs, from what little I have heard, 3D is a MUCH cheaper/more cost-effective alternative, at least in many cases.

 

[LancsRick]

Whilst I agree with the sentiments here about 3D printing being great for small prototyping, be aware that ALM printing will give a weaker plastic product than injection moulding. From a formal perspective ALM is also not suitable for foodstuffs due to the uneven finish.

It depends entirely on what you're looking at doing this for.

 

[Sheffield Tony]

We have had small runs of injection molded parts made for us. I think if you only want a few, the tooling can be made from easier to work but less durable materials. Possibly by 3D printing the dies ! I assumed the OP was looking at modest quantities, the link I gave say from 25 off.

 

[Distinterior]

A good friend of mine invented a little 2 part threaded adjustable spacer and he had the injection moulding tooling made for himself out in the Far East.
The cost of having the moulds made was in the tens of thousands....!!! This was about 7 years ago and only now, has he recently started to re-coup the cost of his investment after selling 2.5 million of them and started making money.
He has the patent on the spacer here, in the EU and in the USA I believe.

 

[thick_mike]

Injection moulding tools are very expensive (circa £10k+) as they have to withstand very high pressures as the thermoplastic is injected. Reaction Injection Moulding (RIM) is cheaper for tooling as the resin is two component and so has a lower viscosity, so lower pressures needed. The cycle time is longer though because the resin has to be baked to crosslink before it becomes solid.

The above is from my experience with automotive components in the fifteen years ago, so may not apply to what you want to do though.

 

[Flynnwood]

Thanks for all the replies.

3D printing is not an option due to durability.

I have been in contact with a Plastic Injection Moulding manufacturer that told me their minimum quantity would be 250 due to the setting up cost of the mould. That's fair enough, and their price to me would reflect that position in terms of volume. No problem.

Does anyone know what it might cost for the machinery to produce plastic injection moulding? And what does it cost to produce a mould - per square inch/cm?

Roughly?

There are machines on ebay but I don't know enough about this yet.
:?

 

[Eric The Viking]

I don't know about the costs, but I used to operate a small machine (as a teenager - holiday job). You will need:

• Probably three phase power,
• Compressed air
• An industrial oven or heating system for the pelletized stock (nylon in particular is very hygroscopic, which causes serious issues when operating the machines)
• Quite a bit of bench space: the bigger benchtop one we had used a horizontal piston.

The higher throughput units use a steam-heat/water-cooled cycle for the mould halves. There are a few consumables too, such as silicone release agent (might be the same as that used in GRP construction, not sure).

The moulds themselves wear out, particularly if there is any filler material, such as glass strands. If I was confident about the component design, and about a high quantity production run, I'd get two moulds made at the same time.

The injection pressure needed will vary with the mould design - you have to waste a fair bit of plastic in tweaking that and temperatures, to get good results, so I can understand the minimum quantity you got from the manufacturer (seems a bit low to me, actually).

If you switch colours or material, purging and cleaning the machine is noisy, time consuming and potentially rather dangerous. I'd guess you also need to keep it warm overnight.

Hope that informs, but it was state-of-the-art some decades ago!

E.

 

[shed9]

One thing to note if you look to develop a dedicated machine to make the parts is to speak to your local business support. They often have grants to invest in machinery especially if there is an innovative aspect to the project. The UK gov runs Innovate UK who will often be able to help; https://www.gov.uk/government/organisat ... e-uk/about

Some of the funding channels require it be a step change in innovation, i.e. something new in the industry or sector you're in and not just making more of the same. May be nothing but perhaps worth the phone call to see. I'm based in Wales and have helped a number of businesses invest in new tooling (including injection moulders) via these funding support mechanisms. We have a slightly better system than England via Smart Cymru but there are options out there.

PM me if you want more info, if not, no worries. And no, I'm not selling services - I work for the gov and I'm just offering help / advice to another business.

 

[Flynnwood]

Thanks so much shed9! - are grants available for the private sector end user only, which this would be for?

 

[shed9]

Thanks so much shed9! - are grants available for the private sector end user only, which this would be for?

They are generally available to business (registered via companies house). I assume based on the potential high costs that this is a business venture. Does that make sense?

 

[TFrench]

I understand you're being vague because you dont want to let on what you're doing but its hard to get a feel for what you're after. If you want to make hundreds of thousands of a part, its worth investing in the equipment. Anything less than that and I would sub it out. One of our customers started a moulding shop up as part of his business a few years ago (he makes automotive components). He had to get a new electric supply to the factory to power the moulders. There is a lot more to it than just the injection machine - plastic granulators, heaters, chillers etc. Always seems to be something breaking down in there. (possibly because he buys old kit) but there is a lot going on. I have no idea what tooling costs but I imagine it isn't cheap.

 

[Flynnwood]

I am still struggling to understand the art of plastic injection moulding and costs (I'm still working full-time). I wish I could get a job for a month to get "inside" the industry to "get it!" Any more help/advice would be most welcome.

 

[Eric The Viking]

Biggest single take-home is that it's an industrial process, suited to high volume production. Tooling and setup are expensive unless you do high volume runs. It's not suitable for prototyping.

Also, moulds have a limited life, determined by many factors, including the material you are using and the shape/design of the mould, the throughput and the nature of the machine (steam/water cycling can be brutal, as can plastics with fillers such as chopped glass strands).

Finally, you really need to know the physical characteristics you want from the part being made: Does it need very accurate dimensional stability, ability to cope with high temperatures, some sort of mechanical toughness, etc. All these affect the process, and not just the material chosen.

When you know what you need, find a local specialist and go ask them, but don't be shocked at the cost of making moulds, etc.