The TRUE COST of CNC machining!

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How much does it cost to make a CNC machined part? The answer depends on a number of variables like the material type, part quantity, dimensional tolerances, lead time, and surface finish. We demonstrate this using the two shock bottom brackets we CNC machined for the landing gear on the DarkAero 1 prototype. They were made in house on our Tormach from 7075-T6 aluminum. Quoting tools from Xometry offer a quick and easy way to see the cost of machining these parts if we were to outsource them. We uploaded a 3D CAD file of the shock bottom bracket to Xometry and then looked at the instant quote numbers to see where the cost might land in production.

Links to tools we use for CNC machining:

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00:00 - Intro
00:36 - Machining
04:37 - Cost

[GermanTopGameTV]

The saying in engineering goes: If you can't make it precise, make it adjustable. This video gives you a great insight into why there are so many parts in mass production that allow for adjustment. Assembling 100 parts on a wide tolerance margin and then turning some set screws to get everything to fit together properly makes a huge difference in cost.

Great video!

[TheeAthis]

33 years as a manufacturing engineer in I can only dream of design engineers understanding what you just demonstrated, and we're just talking about the basics here. very well explained guys.

[nerfburger]

I ran across your video by chance, and I enjoyed the demo... however, as a former CNC machinist/programmer I saw a few things during the machining process that could have sped up your process, as well as created a perfect bore through the part without having the chance of a mismatch. When working with aluminum, don't be afraid to hog out more material during roughing at a higher feedrate... it's the best material to machine (metal-wise) and rip through without loading your spindle torque and tool deflection. Many times you can cut your cycle time in half by bumping up the D.O.C. along with a slight increase in feedrate and it will throw a better chip (both drilling and milling). Also, if you have access to a boring head, I'd suggest utilizing it to finish your thru bore if it requires tighter tolerances on diameter and concentricity... it will give you a consistent microfinish while holding your tight tolerances and it only takes 1 operation to finish. It also gives you the option to use an arbor fixture for securing the part while finishing the outer profile. Just some tips from an old machinist and a new subscriber!

[jaredfaustino]

as a small CNC business i really appreciate how you broke this down so simply. nobody realizes the amount of time and effort that goes into making A "SIMPLE PART", let alone the amount of time it takes to get to a high level of manufacturing to produce parts of any size and complexity. This video helps shine a little light on it. thanks

[townsendliving]

I randomly got this video in my feed, but one of the reasons I like to have a CNC is how many times I can screw up or change the part or scrap the whole idea and move to a differnt idea in prototyping. Material is cheap, screwing up on a design you had a shop make and had to redo is horrendous and it hurts, plus doing the work on your own makes you a better designer and have a better understanding of things, I'm fairly new to all of this but I figure 10 more years amid practice I'll be pretty decent

[SwordandShield]

I am so glad that you tube recommended me this video and this chanel

[box]

If you look at this part, it's a perfect shape for an aluminum extrusion. If we talk mass production. The extrusion production be outsources cheap and easy. The part just needs minimal CNC treatment and less material is wasted.

[pxwjuvr]

I'm an 8yr Navy vet, current engineering student, lifelong aviation enthusiast and maker.... It gives me genuine inspiration seeing you all do this.

[logannewman]

Leave stock in the bore on the first side then finish the bore thru while finishing the second side. Eliminates any blend issues.

[russellpurdie]

Cost analysis was really interesting, I started looking at this as 'weld two plates on a pipe 'but I was wrong :)

[taiwanluthiers]

One tip to reduce the machining time (because those 3D profiling is really unnecessary on your part): Using MasterCAM as an example: Draw out 2D profiles of the part. Top and side. Machine the top using 2D tool paths. Flip it over, repeat. Then lay it on its side, and machine the sides.

The top and bottom machining would have established the roundness and the big bore in the middle. Then machining from the side would take care of the rest of the dimensions.

Machine TWO part per vise. Your video may be a demonstration but machining 2 parts would have seriously increased your efficiency especially if you want to mass produce it (but since your machine does not have an ATC, the point is moot)

If you have 3 vises on your machine (very common in a CNC environment) you will be able to machine top and bottom on vise 1, side A and side B on vise 2. And then you will be able to basically mass produce the thing. This is probably why making 100 costs so much less than making 2.

Try to produce more parts per cycle if you can. Reloading vises every 2 minutes is VERY tedious especially when you need to make lots of parts. a 40 minute cycle is much more relaxing. You can basically kick back and relax while the machine is doing its thing.

Which is why a ATC, even if it only has a limited number of slots, is so crucial in CNC.

Though honestly would have found a used VMC for very little money if I were going to play around with CNC... but making youtube videos with sponsorship from Tormach may not be easy if that were the case.

[apollolux]

The true cost of CNC machining also includes the price of the machine and the cost of the labor involved in designing the part(s) in the first place.

[ratoneJR]

I asked a 6 year CNC guy to face off a 4" piece of 1020 round bar . Then drill a 1" hole 2" deep in it, then drill a 1/8' hole in the side.
He did not drill the 1" hole deep enough. Broke the 1/8 bit in the side, welded it up to cover his mistake. And went too fast facing it off and left a poor finish. He said he was unable to use his CNC equipment, and did the best he could. BTW... The piece was discarded
The moral of the story, you may ask? The true cost of CNC machining is ...the creation of a workforce unable to do the simplest of jobs, with out the aid of a $100K+ computerized work station.

[azzamaddas]

Excellent video because it explains what you do in DarkAero I, in-house versus outsourcing and cost versus economy is scale. Can't applaud you enough.

[rogerfroud]

Personally I'd have made that from round bar using the 4th axis hold the stock horizontally. That way you can machine around all of the sides with the exception of the end, all without fixtures and having to keep setting up. It's way more accurate and I use it all the time. Then I'd part it off and hold it in the vice with some packing in the gap to clean up the end.
You'd do it in much less time and without needing any tooling.

[metaldawg-americanmanufact]

Dude, fantastic work. I started out with a Tormach 770. Those Tormachs are a great way to get started .

[jimwhipple]

I've owned a CNC shop for nearly 40 years.
That part is two ops and flip it to remove the excess. Wheel cut the slot You could use two vices and get two parts off at every push of the green button.

[wernerdanler]

When I worked at Boeing as a machinist they told us once that due to tolerances a 707 could vary 7 feet in overall length.
I ran an electronic tracer and had tolerances on two parallel surfaces over a 6" span of +0.0/-.005 on a titanium part refueling nozzle. Every part I made passed inspection.
Management came down on me once for making less parts than the first shift guy till I pointed to all his reject tags.
That shut them up. Lol

[qyrgntl]

I got an eye roll when I made 2 custom RC plane parts overnight and only charged $20.

[bobdixon]

There are other costs you are not considering or did not mention, like the amortized cost of your machine. Most job shops will take on a fixed cost to an order to cover part of the expenditure for the machine that will be used. Again, like set up costs and tooling costs, this will be spread across the number of parts in the order. The more parts made, the cost per part drops. You have that cost in house as well, and you need to track it so you know when you have "paid for" your machine by spreading the purchase costs over a number of jobs. This also helps when considering the depreciation fo the machine for tax purposes. You can recoup some of your costs through tax savings if you keep track of things like this.