So you want to get a tool made? Given the high cost of injection moulding tools, it’s important to get things right – especially if this is your first time. Here are a few simple injection moulding tooling tips I can offer to avoid getting caught out, in no specific order:
1. Know (approximately) what polymer you’ll be using.
It will greatly help your toolmaker if you know what polymer you’re using before starting the tool. Different polymers have different flow-rates so the point of entry will need to be broader or narrower if you decide on one or the other. It’s not 100% essential, but it’s a good idea if that’s the case. If you decide on one material then change your mind, there’s a good chance we’ll be able to change over without any modification. If we do have to, then the mods are pretty simple.
Polymer choice is down to a bunch of different attributes – price, heat resistance, chemical resistance, shrinkage, flame-resistance, tensile strength, flexural strength etc. I’ll post something about polymer choice in the coming weeks.
2. Know what machine you’ll be using.
You’ll also need to have an rough idea of what machines you’re running the tool on – though it’s not essential, you’ll be asked about tie bar size and nozzle size/shape as well. Tools are mostly interchangeable and most tools, unless they have special features like auto two-shot moulding or core-pulling, they will work on most other injection moulding machines. At AV, we work with a lot of Boy machines: 22, 30, 50 & 80 tonnage on the smaller side of things, to deal with larger parts, we use a Oima 230 and a Battenfeld 260.
3. Make sure you’re aware of the lead time.
Make sure you don’t get caught out. Often, the lead time quoted is from GA (tool layout drawing) approval to T1 samples (first samples off the press). Assuming you have a injection moulding-ready design, there’ll be a week at least to do the GA drawing, then once you’ve had the samples, they’ll sort out any polishing you need to do – and any other stuff like making things fit more snugly, so there’ll be a week or two even after that. If it’s getting made in the Far East, then you’ll have to wait 5 weeks for shipping – or pay extra to have it air freighted. Then your injection moulder will need to make samples for your approval. So a 5 week lead time for T1 samples + GA drawing (1 week) + finishing etc (1-2 weeks) + shipping (5 weeks) + production sampling (1-2 days with sample shipping) = 12-14 weeks or more until production starts. That’s all assuming you’ve got a finalised design.
4. Get the specification and design right in the beginning.
Make sure you specify everything you want up front. Getting the design optimised for injection moulding is probably the single most important thing you’ll do aside from getting the marketing and sales right. Describe intimately the function of the part and which parts need to fit together and how well they need to do that – if you’re getting a drawing done, this’ll be set up as tolerances. Your toolmaker and ourselves should have these to work to for QA. If your toolmaker/ourselves have the spec up front, they should make a product that makes that part to how you want it. Don’t expect them to make any changes for nothing if you get the part and don’t like this edge or that fit – if you haven’t specced it before. Sometimes this can be a painful process as you may end up with a huge bill to pay making minor tweaks when the part hasn’t moulded correctly. If we’re helping you get a tool made, we and our toolmaker will guide you through that as much as possible, but the buck stops at you.
As well, if you’ve asked for a part to have a certain spec and it hasn’t, don’t pay anything extra. If a toolmaker has committed to making a part, then they should see it through to the end.
5. What you expect from your tool determines what material to use.
Generally we recommend steel moulds. There’s a lot of work in making a tool – in any material – and softer materials (like aluminium) are a little cheaper to use, but don’t represent a massive saving (up to 20%). The risk of damage is quite high. If a part doesn’t eject properly and gets stuck in the tool, then the tool may be rendered unusable. As long as you’re aware of this risk – and it is your risk – then you can make a decision about the material.
The expected lifetime of the tooling tends to determine the material used. So if you’re expecting 1000 parts/year for 5 years then finish, then a softer steel will be recommended. Many tools we have at our facility have been running for over 20 years, and there’s no reason that if you choose a good grade of steel, yours won’t. Remember, the longer the tool runs, the more profitable it is. It’ll likely pay for itself after 10,000 parts, then everything else is a much higher profit margin.
What polymer you use will also affect material choice: for example, if you want to make parts in PVC, then we’d recommend a stainless steel tool due to it’s corrosive nature.
6. Expect an injection mould tool to be expensive, but you may be able to get the price down.
As mentioned elsewhere here – IM tooling is expensive, but production is cheap. You’ll need decent figures to justify the cost of the tooling. There are some ways to get the price of tooling down somewhat. As mentioned before here and here – the tool material (grade of steel/aluminium) will effect the price; if cycle time isn’t important (ie prototype tool – not production) then reducing the number of cooling channels may reduce the price; design may make a difference – sometimes taking a feature out and making the product more simple changing it from having side-actions to just a regular open-shut mould can reduce the price by £1000s.
Some moulders have modular tooling systems. If the part is very simple, you might be able to get away with just getting an insert made to fit into a ready-made bolster.
3D printing is a new technology for injection moulding tooling. There’s a limited lifespan, but you may be able to get a tool insert made for under £1000 that will be able to produce a few thousand parts. Watch this space for more news on that front. It’s very much an untested technology at the moment for us, but very promising for the low-volume requirements.
7. Once the tool is made, you’ll need to approve samples, then pay the final bill.
If you’re using an engineering material, your toolmaker may send over samples in a commodity polymer grade as they don’t have access to the engineering grade polymer. Be aware of this probability.
When the tool arrives at AV, we’ll make parts in the material you chose, with the colour and any additives you specified. You’ll need to check the samples and see that they conform to your requirements for material properties and dimensions, then give the go ahead for production. We normally keep the tool in the machine, while waiting for approval, so your speedy response is appreciated in this case.
For the tooling, you’ll probably be asked to pay a maybe a 30-50% deposit, then 25-30% when the samples arrive, then 25-30% when the tool is delivered and approved to be working. Obviously, don’t pay the whole lot up front otherwise they’ll have no incentive to do a good job. Make sure you thoroughly read through the terms and conditions your toolmaker has set out so you don’t get any nasty surprises. If you don’t agree with any, ask them to change them – or find another toolmaker that satisfies your needs. If there are any specific requirements or changes, get as much of it as you can in writing – even by email.