Not an expert. Will the casted housing need machining? How precise must the outcome be? What do you pay for the stock material now? And most important: Based on what is sales doing the forecast?

We were in a similar situation. We had an Aluminium base roughly 6“x4“x2.75” that had to be machined from all sides. It was the housing but carried also all critical functional parts. When we produced the first 300, sales showed up with a forecast of 3000 per year.

We then decided not to do a casting but to invest in the machining: We bought a tombstone where we were able to clamp more parts and do the first and second step in one run. We contacted the tool suppliers for optimizing the process and we also invested in PKD-tools that would finish critical parts in one run. All these measures have cut due time in half plus the machine would run for 4 hours during the night. When this work was running we collected the chips in a clean chip box that was there uniquely for that purpose, to be able to get the best possible price for the recycling. Turned out to be the best decision because we never passed 1000 parts per year and the design was changed in details at least three times since then. The daily unmanned hours have also had a positive impact on the hourly rate.

Die casting requires a very expensive mould.

Sand casting less so. The middle big series you are talking about, that might be the way to go.

Does you housing need to be liquid tight?

the die casting quote always looks better per part right up until someone asks for a cosmetic surface on the cast faces

How big is this housing? I machine tens of thousands of aluminum forgings every year and I have noticed that some visitors, even tool vendors are sometimes surprised at how violently you can rough aluminum. Have you really pushed the rough tools to get the bulk of the material out as quickly as possible? IE we run a ³⁄₄, 3fl EM at 12,000 RPM, 250IPM and ramp down in to pockets at 25 degrees in a roughing operation. We will run thousands of parts on a tool.

Aluminum and carbide are cheap compared to adding another process to the mix. Plus you get money back from the chips. I’m typically making 10% finished stock weight with billets ranging from 28-60lbs. Get your MRR up and it’s a no-brainer.

This is pretty simple, call up some casting places and run some numbers? I mean… this is a simple numbers equation.

I would assume you could tighten up your processes a bit with some other LEAN manufacturing techniques but the casting numbers are easy to game out.

The published numbers say the switch happens at a higher volume than your forecast. Fictiv’s guide treats under 1,000 parts a year as a machining job, 1,000 to 5,000 as neutral, and over 5,000 as a casting job. the break-even for die casting at around 5,000 to 10,000 parts.

Casting isn’t a clean swap. A cast part still needs some machining after casting on the spots that have to be exact, like the surface a seal sits on and the threads. So casting cuts the machine time, but it doesn’t remove it. Xometry quotes 12 to 18 weeks to first samples, and doesn’t take die casting orders under 500 to 1,000 pieces.

With 300 now and maybe 2,000 in 2028, I’d get both ways quoted at 300, 1,000 and 2,000 a year and compare the total cost over three years. How tight are the tolerances on the lid face?

Unless you have a PO for the next few years of orders, going to casting is a huge risk due to the high upfront cost.

How big is this housing?

40 minutes is long for a housing tbh. before you go casting id look at whether a 4th axis or better workholding knocks that down, plenty of billet housings drop under 20 min once you stop flipping them

Foundry pattern maker here. I design a lot of parts using 3D printed foundry sand. The main foundry I work with generally pours A356 and does in house heat treating. The parts have a rougher finish than a regular sand casting but there are a ton of benefits to producing parts with this method.

I would wing it as you are until you simply don’t have the time to machine the required number. Get quotes for casting in the meantime. Bare in mind you can make changes on the fly to a machined billet but not a cast part. I’m not sure what your business model for this part is. Is this your product or a customer’s? If you can remove yourself from any responsibility in errors or changes in the tooling cost for casting, then the threshold number for casting comes down from your perspective.

What machine are you running these on? When I went from 3 vmc’s to two hmc’s my production increased fourfold.

Investment casting would give you better finishes and tolerances than die casting, it typically requires less finish machining. The trade off is the higher cost and some geometry restrictions. 300 a year is hitting enough volume where it might start to justify the setup cost. I’ve worked with some aluminum foundries in the past. If you want to DM me a drawing of the part I could take a look and see if its castable.

A lot of the time, these manufacturing decisions are driven harder by production time than cost savings. When it comes to injected plastics, the switch usually hits at the earliest around 1000 unit batches. Die casting is much more expensive and by the book starts around 10k batches. In my experience, this switch from CNC to die casting hits much later than 10k, and usually follows closer to 30k or 50k batches. If a process is reliable and profitable using CNC, it is very hard to justify the switch to die cast without additional external pressure. Die casting is a huge investment with huge risk. It takes time, barrels of upfront money, and can cost even more if you get it wrong the first time. The push to die casting is usually driven when demand outpaces production capacity, and expansion of CNC operations become inefficient to the point of further decreasing product margins. An engineer would need to demonstrate that a 3, 5, etc. year timeline of CNC production at current rates of expansion would lead to risks of unfulfilled orders or spiraling lead times before the investment into a die casting transition is made.

Size also matters vs the machine envelope. Having the opportunity to machine 5+ parts in one operation would be a nice next step…

Simple formula in algebra gives you the answer.

(Capital cost of diecast) + (cost per dc) * Xpcs = (Capital cost of machined) + (cost per mc) * Xpcs

Solve for Xpcs

That is your break even point.

(Provided you guessed all the costs correctly)

This is how you justify spending $2.8 million to make a 5 cent part.

Edit to add, the cost per part should be the “out the door” cost on both sides

The crossover has more to do with how much of the part you still machine after casting than with the raw count. A die cast housing still needs the sealing face, bores and thread cut, so you pay for the tool and still own a machining setup and at 2000 a year plenty of shops would keep it on the mill. If it does got to casting, keeping the casting and the finish machining with the same supplier saves a lot of datum arguments and quickparts is one that does die casting with post machining as well as CNC.

This is actually a pretty straightforward math question. How much will the castings cost you per piece after everything is figured in, tooling investment, engineering cost, and how much the casting house will charge you for each one once in production. Then compare it to how much you’ll save in machine time and tooling cost for each one. The volume you need to make this a wash or more profitable is dependent on these factors and is different for everyone.

How confident is sales that they’re actually going to hit that number? Is your customer willing to place a PO for those numbers? Will you have to machine the castings after they’re made?

I would either automate it or load them up in something like a horizontal. At 40 mins per part, you’re talking 167 days (give or take). Dedicate it to one machine and just let it run.

Unless your customer is pushing for cost saving per part, take their money and keep machining them.

where are you located? send some our way. would be happy to help you

u/Different_Pain5781 until we know your exact costing no one can even begin to guess.

China is going to be the answer for 300 parts/yr all in house. The US or the EU has to pay skilled laborers living wages. If thats not a moral issue go to china or Vietnam