The One Where He Talks About Money

A project log for Sexy Gantry

Documentation of my journey to a commercial enterprise around hobby machining, specifically cnc, even more specifically 3d printing.

daniel-graceDaniel Grace 07/30/2022 at 05:470 Comments

I am slowly getting into metal working. I found a local supplier of metal, and noticed that they sold aluminum cast tooling plate, the kind that are often used as build plates for 3d printers. By default they come in some pretty large plates, like 4 feet by 8 feet for around $600 USD. They will cut it for you, but there's a $45 fee (interestingly, it seems to be independent of whether your size necessitates one or two cuts).

The Voron source guide for the 2.4 300mm looks like it's about $50-$60 for a build plate (I'm not counting Fermio's out of stock DIY version, only the more expensive one with holes cut in). If you were to go to my supplier and have them cut 12"x12" (they only operate in imperial, so no exact match for 300mm) it would cost $20 for the material and $45 to cut it, total of $65. You're better off just ordering from Fermio labs.

But wait, what if I just bought the entire 4x8 foot slab, cut them into 300x300mm slabs and sold them? The raw material for that would cost us about $20 (they really don't seem to discount based on volume, just the cut fee makes it effectively a discount to buy the whole slab).

Can we turn a profit selling build plates?

That is what this project log is going to be about. Not the mechanics of cutting a build plate, drilling some holes, and selling it. That's pretty boring.

It's going to be a deep dive into figuring out the actual cost of making a product once you go beyond raw material cost. I expect a lot of labor, packaging materials, and miscellaneous consumables (saw blades, etc.).

For now, I have obtained some "off cuts" from my supplier to do some initial testing with. That's what you see on the current project image. It's not the best quality, there's a sizeable ding in in, and its short dimension is below the 120mm that would make it theoretically a candidate for a Voron 0.1 build plate. But that's okay, I mostly want to use it to validate, and I want to keep it as a trophy rather than sell it anyway. It was supposed to cost $4, but they charged me $3.50. Offcuts are sold by weight, and it weighs exactly $1. Cast Aluminum is supposed to be $4/lb, other aluminum is supposed to be $3.50/lb.

I have also bought an aluminum-cutting saw blade, some drill bits, and a drill press. I am using my father in laws circular saw for the moment, but will likely get my own at some point.

The next steps are going to involve running some more numbers about what running an online business will cost (charging credit cards, etc.) and at the same time, start working on fixturing jigs for cutting to specific sizes.