[DMahalko]

I am a hobbyist that wants to build a robot of my own design. It's nothing ambitious really, just a powered exoskeleton.

I am expecting to use steel at first, but probably titanium later to make this as light and strong as possible.

My equipment budget is not high. I have a lower middle class income, so I don't have a huge disposable budget.

It appears that in the long run for machining components for testing, it will cheaper for me to just buy my own CNC hardware and do it myself, rather than pay someone else to make one-off parts for me.


So, what is the cheapest, weakest, and wimpiest CNC mill and lathe that would be capable of machining titanium?

Is a Tormach PCNC about as low as I could expect to go to get the job done in any reasonable about of time?

Is there anything smaller and cheaper that would be capable of titanium?

[djr76]

does it have to be cnc? a decent bridgeport knee mill will cover all your basic milling, drilling, and tapping needs,

[DMahalko]

The difficulty is doing complex sculpted surfaces for compact structural designs. If all you are doing is simple plunge cuts or bevels, then yes, a basic machine tool is fine.

But once you start moving into complex curved surface geometry, it's beyond the ability of hand work. Trying to machine a spheroid surface by hand is basically impossible.

I suppose a halfway mark is an old used Bridgeport plus a CNC conversion.

[ssguy4111]

You would also benefit from looking at used machines online - I have seen decent 3 axis VMC's for about 15K.

[hanermo]

Tormach - yes. Will work fine.
CNC refit - yes. Similar capacity in rigidity for common stuff.

Exceptionally rigid old cheap cnc machines exist.
A Bridgeport boss is one, with the 3 Hp spindle iirc. Coudl run new control & servos. Lack of toolchanger is major pain.

Cheap old cncs .. not really practical, for you, ime, imo.
Hard, expensive parts, expensive hard to get know-how, expensive tools.
Ie its doble, is 5x more productive, but 100-2000 hours work to start, and 2-12 k in unforeseen costs. Plus basic machine.

I could probably restart an old cnc machine and fix it. Take me 200-2000 hours.
Then 2-5 k in tools, minimum.
A control refit == 3000 € and 200 hours. Add new servos (700 /axis) and done.

Refit old machine will not be productive, but might be your best bet.
Also, for 3-5 k, you are running.

[DMahalko]

My general plan is to ignore the built-in drive computer, and do everything from AutoDesk Fusion 360 over serial.

But yeah, I would not buy an old CNC mill if it was not in running condition. I have some vague experience from 14 years ago trying to repair antique CNC mill that wouldn't get out of NOT READY.





"You want $5000 to replace the motherboard??? Which I'm not sure is even the problem...?"

Scrap pile.

[hanermo]

Suggest recalibrate expectations.
A. fusion wont run anything.

Add 500-2500 of stuff first.
Cheap stuff wont be any good, and you will buy 2-3 times.

[handlewanker]

LOL.......a cheap solution is a cheap way of thinking.

Suggest your top budget expectation and someone will sell you their old stuff or you might go Chinese and live to tell the tale on here.......I would no hesitate to think in terms of $10K for what you want.
Ian.

[awerby]

Capable of milling titanium parts that are how big? This is an exoskeleton for what - a gerbil? Generally, "cheap and wimpy" and "titanium" are not found in the same sentence.

[DMahalko]

Size of parts? Well look at the average size of a human body. I expect all parts will probably be within the range capability of a Tormach PCNC 1100.

I am starting to lean more in the new equipment Tormach direction, though all the optional toys like the tool changer / auto drawbar, floor stand, etc will bring this up around $30,000 not even considering a lathe. Plus need to build a heated insulated garage / shop. So, at least $75,000 by the time we're ready to make any parts?

I would look into trying to start a nonprofit Maker Space, if it could help reduce equipment costs. But I live in the middle of nowhere so the likelihood of that working out is low.

[djr76]

You would also benefit from looking at used machines online - I have seen decent 3 axis VMC's for about 15K.

What this guy says, you want some horse power. I think the Tormachs are just to wimpy. You can get a used Haas with 20hp behind the spindle for the 3D sculpting you want to do and the tech support to back it.

[hanermo]

No, this is, for him, NOT what he wants.

1. He wont have the 20 kW feed to his garage. It will cost 10-20.000$ to install.

2. He cannot fit the 3 m high machine in his 2.5 m sized /typical garage.

3. It wont fit in the door.

4. The tool holders cost 50-200$ each. 24 needed.
The tools cost 50-100 $ each. 24 needed.
The inserts for only 10 cutting tools (end mills, a few face mills) cost approx 2000-3000 dollars.
So, 6000-9000 $ for industrial tooling start up costs.

The industrial tool is 5x more productive, yes.
BUT, he wont need the productivity, and needs to have the extra capital, space, power and NEED for this, to make this make sense economically .

I have sold over 50 Haas machines... and am quite familiar with them.
Factory training, and all.
And they are good machines, for what they are.
So are many others (Brother, Mori, et al).

That is it NOT the point.

The point is smallest machine at low cost.
There are 10-30 small, tiny, industrial machines that will fit in a garage.

They cost 30-60.000$ each, and have the drawbacks of tooling costs mentioned.
None is appropriate.

I saw the Kolibri 5 axis cnc mill, size of desk.
Made in Finland- spoke to the guys, and have a nice 5 axis demo part machine on all 5 sides.
100k each.
Not approprirate, again.

Details matter, a lot.

What this guy says, you want some horse power. I think the Tormachs are just to wimpy. You can get a used Haas with 20hp behind the spindle for the 3D sculpting you want to do and the tech support to back it.

[DMahalko]

Yes, thank you Hanermo, you do have the right idea.

This is absolutely not volume production. Basically look at the human body. If I am making limb actuators for a robot, I need at MOST one left side and one mirror copy right side.

I would just be making a few one-off components, but with complex geometry needing CNC capability.

Since there is no time limit for getting this done other than my own mortality, speed of machining is not really too critical. Basically start the machine, and in the same room have a comfy recliner and a TV, or a computer to play Minecraft.

Though also my desire is to just "get it done", and not be constantly fiddling with the machine to change tools, etc, which is why I'd ideally want an auto tool changer, with an automatic tool indexer. Preferably I'd like to just start the machine, and not have to constantly baby it and fiddle with it all through the part production cycle.

(E-stop and an overheard camera view of the CNC table, by the comfy chair...)

,

The main thing that a professional machine tool would provide is greater rigidity. I do not know how beneficial that is for machining titanium more quickly. Seems you want to go slow with tons of coolant and peck your way along anyway, or it will work-harden on you and break your tools, regardless of how rigid the machine tool is.

(Currently we have single phase 200A out on the farm. We could get 3-phase. It's available about a mile down the road, though I'd have to get the meter / panel service upgrade, etc.)

[DMahalko]

As I may have mentioned, I have a lower middle class income. I am not interested in going into deep debt over this.

I am not planning to run a business selling my CNC machining services. While I fully understand a big professional CNC would permit that, that just doesn't interest me. So I'm not planning to "turn" a profit with this. I will probably start a business though, so I get tax exemption and can write off all the money I'm throwing into this research hole in the ground.

What I mainly want to do is try to patent and manufacture a one-off prototype, wear it to Comic-Con or something, and maybe pull in interest from DARPA,, or find some big university to get involved with this.

(Making the prototype with titanium probably isn't required, but it would be a useful machining capability to have.)

[ger21]

Buy a $3000 router that will let you make wood molds, and make your parts from carbon fiber or epoxy/glass cloth.
Will save you tens of thousands of dollars, and have a much shorter learning curve.

[handlewanker]

Hi, unless you are going to make the parts for the market out of Titanium, anything that represented the part for a demo use would suffice.........making them out of easy to machine plastic for a pattern and then getting them investment cast is another option as it can be replicated over and over again.
Ian.

[inthebay]

I agree with what Handlewanker said. This is a huge problem with startups too, who try to get funding for something they want to make all grandiose and light and amazing. Hack an exoskeleton out of whatever you have lying around and get it to function half as good as you want it to. Find the weak points, refine the design, then go to something slightly better. Iterate iterate iterate. If you're not incredibly ashamed of your first prototype you've waited too long to get funding/exposure.

Sort out a machine last, make something that kinda works first. Then get back to us

[DMahalko]

Oh, I will be quite ashamed of the prototype, no need to worry about that.

Structural design of the exoskeleton comes first, unpowered and only with hinges and connecting linkages. Deal with powering stuff later.


I've talked about this in more detail on the web in other places. In general I am trying to build a fully 3D VR haptic interface. Basically a flight simulator but wearing an exoskeleton to physically walk, run, climb, and fall through a simulated 3D space. The wearer could climb inside and sit in and drive a simulated vehicle in the 3D space.

So this is not a freestanding "Iron Man" armor suit, it's "only" a full-body haptic force-feedback system capable of resisting user motion and supporting them in any position whether lying down on simulated ground, or sitting in a simulated cushy chair, all driven by a 3D physics engine, simulating collisions and force feedback. Though it could also be used as the feedback driver for a larger real machine, like the Aliens movie powerloader.

It's nothing ambitious for a home-built project, you know. Really, I have no hope of getting very far on my own as a hobbyist, but that's why I'm focusing exclusively on designing the exoskeleton first. I think someone with deep pockets like DARPA and the US Military would love this for combat simulations.


Example of a full-motion platform that this would use: (jump to 1:55 to see it move)
Sega R360 Wing War - Video #1 - YouTube

Though making the 6-axis motion / sphere platform myself will be a challenge. Probably will need to pay someone to bend the spherical tubing frame. And then there's the problem of avoiding gimbal lock.

I expect I will probably need quite a large garage to contain the motion platform, so that it can freely move on any axis about 2 meters in any direction from center to simulate falling off a cliff, hitting the ground really hard, etc.



And getting back on topic, titanium would be preferred, to get the internal driven mass as low as possible to reduce drive inertia and weight suspension requirements.

I know aluminum is another lightweight option, but I'm concerned about its sudden stress failure and microcracking problems that could lead to injury if structural components in the exoskeleton frame suddenly crack apart under strain.

[hanermo]

You are the perfect candidate for a refit manual cnc mill, or new electrics (all) on an old bridgeport boss cnc mill.

You really want a cnc mill, if possible, as it already has the very good and rigid ballscrews, mounts etc. that cost more money than you want to pay, and wont be able to make, reasonably.
So, a bridgeport boss series 2 cnc mill, or similar, approx 1000$-2000$.

Toss motors and drives (ebay might get some something, 100€ for all).

Add ac brushless servos, 290€/axis, pulleys (1:2 HTD 5/15 mm wide, 100 for 3), PSU (200), Pokeys CNCaddon (120).
1300 €, done.
1 week.
You have a 9x42" INDUSTRIAL machine of good rigidity, excellent repeatability, great accuracy.
Easy to work on, easy parts, not expensive.
Add VFD for 200$.

No tooolchanger (so you wont be able to do jobshop work in production, repair/one offs yes).

The above recipe is ideal for you, in your situation.
It will have no problems re titanium, that needs heavy cuts, slow rpm, lots of torque, heavy mount/bed vice etc.

Add mist coolant. 200$ or so, for homeshop self built.
No mess, and makes things work really well, without big-compressor noise.
Small low-noise compressors about 3-500$.

You are running for 5-6k, with some basic collets/tools.

Here is an excellent example off feebay.
Bridgeport Series I CNC Mill R2E3 with Updated Control | eBay
This is what you really want.
Bridgeport Series ll CNC Mill Model BMC 7845 w GE Mark Century 2000 Control | eBay
Again 1-2 is good price.
The dealers may sell for 2-3k.
They only paid 500-1000 for it.

I shippped some old machines to big machinery dealers- and paid the money to my customers, so my prices are based on personal experience.
A Bp is 200-1000$, in replacement value.

These are worth 1-2k, as-is.
The 2300 $ is not out of line.
The old electrics are worthless.
Use the pendant, and re-wire as you learn.

The second type real CNCs are very much better.

[43220]

My $.02 - why not just contract with someone here (or local in your area) to make the parts for you? Later on if & when you need more then perhaps you can afford to tool up.