Injection Moulding Quote Calculations

[Marc_Bloke]

Hi there,

Can anyone shed some light on how an injection moulding company will compile a quote for a certain part?

I have no experience working within and Injection Moulding Company but using some logic this is where I'm at at the moment (please correct me wherever my logic was in fact illogical):

- I have part price per unit
- I know the price of the material so by subtracting the material cost from part price per unit I am left with what I'm calling the processing cost
- Within this processing cost I would imagine there to be a price per hour cost of the actual injection moulding tool (based on repayment of the tool) and then a cost for packaging the parts

Considering a few rough rules of thumbs I've gathered:

- Mould cycle time ~ 20 seconds per mm thickness of part
- Tool clamping force ~ 2-3 tonnes * surface area of part (inches)

From this I have some hourly rates of machines of varying tonnages.

PP 30%GF seems to have a much lower processing cost than PA6 30%GF - is this is generally true?

Apologies for rambling nature of this post. To be concise: I'm trying to ascertain what are the major cost drivers when designing parts for injection moulding without having to go back and forward to Injection Moulders requesting quotes, wasting their time, when I could have a much better idea myself.

Thanks,
Marc

 

[hendersdc]

This is a useful tool for cost estimation and includes a lot of the process costs you are looking for. I have found the numbers to be fairly accurate when compared to North American suppliers, China, not so much.

[URL unfurl="true"]http://www.custompartnet.com/estimate/injection-molding/[/url]

 

[MikeHalloran]

what are the major cost drivers when designing parts for injection moulding without having to go back and forward to Injection Moulders requesting quotes, wasting their time, when I could have a much better idea myself.

Do not be bashful about using molders' time. You are not likely to have any better ideas than they do until you have decades of experience.

The second quote from a given molder, submitted in response to a revised drawing implementing all of their suggestions, will be lower than the first quote, perhaps by a lot, and the parts will be better.

You should get very different quotes depending on quantities, and different materials. Some molders like to run huge quantities in hard tooling; some specialise in lower volumes in soft tooling. Optimal parts for large or small volumes are often different from each other, almost always in draft and thickness.




Mike Halloran
Pembroke Pines, FL, USA

 

[Marc_Bloke]

Thanks for your replies!

My intention wasn't really to get a better idea than the moulder - just to educate myself a bit further.

What I would like to know is if there is a typical way that moulders will price the part.

Example: if I am quoted a unit cost of $1.00 - and I know that material cost is $0.25 - that leaves $0.75 - how is this $0.75 calculated?

Thanks,
Marc

 

[MikeHalloran]

My molder friends might privately say that the difference is none of your business, and they might add another $0.50 just for you acting like a Supply Chain Manager.

If you continue focusing on the financial elements of their businesses, you will never have molder friends, only adversaries.

IMHO, it is better to develop friendly relationships with molders, so that there is some chance of you working together to resolve technical issues that arise along the way. I have had small, and not so small, design changes, made over a weekend in response to a faxed drawing change, with a phone quote that amounted to a few hours of overtime.

Molders are different from commodity suppliers in the degree to which you are co-dependent on them.



Mike Halloran
Pembroke Pines, FL, USA

 

[Marc_Bloke]

With all due respect I think most industries would consider their 'processing costs' whether in manufacturing or otherwise to be none of the customers business.

I'm not for a second trying to second guess the moulder, or haggle them on price or create any enemies - in fact we currently use a moulder who we have a very good relationship with who often make changes like mentioned above. I'm just trying to understand their processes better in order for us to work better together.

I just can't accept that the moulder plucks a number out of thin air for the processing cost. There has to be a calculation involved which includes, but is not limited to: tool payback time, tool running cost, electricity, man hours, cycle time, etc. I am just trying to find out what are the main drivers in this calculation.

Thanks,
Marc

 

[John2025]

I would expect: material cost + expected scrap + setup time + hourly rate times the expect production rate.
The amortization of the setup and setup scrap will make low volume runs expensive. As Mike said, years of experience go into the mix.

 

[Pud]

We always add on a percentage of the cost of material. How many businesses buy something and then sell at cost? Madness. That's not including allowances for wastage.
Processing cost (e.g. hourly rate) is based on a)knowing your customer* (i.e. how much you can get away with, b) batch sizes c) fully auto or man on press - or even sorting parts off a family tool.
There is also a minimum order value which is equivalent to 8hrs production.

*Defence jobs are nice....

H

www.tynevalleyplastics.co.uk

Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Marc_Bloke]

Thanks for your responses!

Pud - so we're talking something along the lines of:

part cost = (material cost + X% margin) + (machine hourly rate (dependent on various factors) + X% margin) + (setup costs (dependent on various factors)

In the event that a machine is full auto would there be a fixed cost per part associated with packaging etc? Or would that be included in the machine hourly?

Thanks again!

 

[Pud]

We don't charge for set-up although a local competitor charges £300, which I think is outrageous.

Otherwise your costing formula is about right. It's the unknown to you variables that are important. E.g. hourly rate (for it's not a fixed rate for allcomers)

We tend to use recycled boxes for packaging. Not specifically costed in as it gets messy when you can get 10,000, or 5000, or 250, etc.in the same size box. And when you divide the box cost by 10,000 you're down to rounding errors for accounting. Specialist packaging such as sterilised pallets for export are supplied by customer.

Cheers

www.tynevalleyplastics.co.uk

Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Compositepro]

Some big factors that you have not yet considered are:

How busy are they? If their shop is at capacity they will only be interested in business that makes better than average profit.

Are competitive shops busy or slow. If all shops are busy there is less competition to keep prices down.

Do they like doing business with you? The best way to get rid of problem customers is to charge more so that you go away, or the profit is attractive enough to make you a good customer.

 

[Pud]

Compositpro: spot on!

Some of our most profitable work is from customers whose previous moulder couldn't achieve the required quality requirements. After e.g 12 months of poor/no supply to the end user, they are happy to pay whatever it takes.

Marc_Bloke: If you think no moulder plucks from thin air, you are a bit naive.

H









www.tynevalleyplastics.co.uk

Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Marc_Bloke]

Thanks for the information!

Okay, I can totally understand that a number from thin air is plucked from thin air (based on the moulders years and years of experience), but not before you know how much it's going to cost you to do the moulding, right? It's not based purely on something arbitrary like how many goals Newcastle scored at the weekend??

 

[Pud]

It's not based purely on something arbitrary like how many goals Newcastle scored at the weekend??

Certainly not! It'd be zero mostly!

www.tynevalleyplastics.co.uk

Politicians like to panic, they need activity. It is their substitute for achievement.

 

[Compositepro]

The cost analysis establishes a rock bottom price, although even then, if business is really slow you might go below that and only cover variable costs because overhead cost will be incurred whether you take the order or not. And you might even try to buy your way in with a new important customer by doing a first order for free.

The important rule in business is that suppliers and customers should both be satisfied (or happy) in doing business together, because they are both making acceptable profit. Large businesses often sell the same product to different industries at vastly different prices because the product is far more valuable to some industry. As a buyer you can save a lot if you discover this and buy the product that is targeted for the low cost industry. The salesman's (or Marketing's) job is to try to get the highest price by targeting these industries in different ways and "maintaining differentiation".

 

[Pud]

Adding to Comopositpro's comments above, as a supplier you have to realise that buyers like an easy life. Moving tools is a nightmare to them, so annual price increases of a moderate % are rarely ever a point of negotiation.
I did mention to one of our customers after they complained about a late delivery of parts off a crappy tool that we are looking to "rationalise our customer base". Had the managing director on the phone within 15mins practically begging not to be ditched.



www.tynevalleyplastics.co.uk

Politicians like to panic, they need activity. It is their substitute for achievement.

 

[MikeHalloran]

Pud hit a nerve there.
Moving tools IS a nightmare, not just for buyers, but for engineers too.

Supply Chain Managers think it's no big deal, but they are really good at oozing out of the blamefest that results when a tool gets moved to save a few pennies, and the new molder demands thousands of dollars to adapt the mold to his process and make repairs to it.

All of my experience is with medium to low volume molds, a business that seems to attract independent thinkers who do things in nontraditional ways.

My favorite molder started with a very small machine. Many of his molds would not actually fit in it; they projected outside of the clamp area. This was not a problem, because the molds comprised stacked aluminum plates, clamped to each other with capscrews. Ejection comprised removing the mold from the clamps, using an impact gun to remove the capscrews, and knocking the mold laminae off the part with a mallet, all done with a certain rhythm, which was the primary thermal control. Draft was unnecessary to him, and he charged extra if you really wanted it. As his business matured, he bought fancier machines and built traditional molds for them for high volume jobs, but his low-volume molds would confound any other molder.

In my small world, molds do not really interchange among molders, and buying a complete new mold is usually cheaper than moving a mold from one molder to another. Plus, if your SCM doesn't completely piss off your original source (the usual result), you could end up with two sources.









Mike Halloran
Pembroke Pines, FL, USA