CNC Your Own Parts

[volvolugnut]

I believe a quality bearing would required grinding to the final tolerances.
volvolugnut

[Chuck W]

All CNC stands for is "Computerized Numerical Control". It's just pre-programmed movement controls for production equipment.

Any "cheap" CNC mills are going to be very limited in what they can do. You're looking at 4 figures to get a decent, useable 3 (or more) axis desktop/hobbyist milling machine.

[volvolugnut]

Check out these small milling machines. All manual control but cheaper.
https://www.cncsourced.com/rankings/bes ... -machines/
volvolugnut

[MrAl]

All CNC stands for is "Computerized Numerical Control". It's just pre-programmed movement controls for production equipment.

Any "cheap" CNC mills are going to be very limited in what they can do. You're looking at 4 figures to get a decent, useable 3 (or more) axis desktop/hobbyist milling machine.

Hi,

It's hard to say what "limited" means because it depends on what you want to do.
The under $200 USD units seem ok though, for general purpose stuff.
If you want to do metal you have to take small steps removing a little at a time. The bigger the spindle motor the more you can take off in one pass. The base models are 100 watts, but you can get 500 watt upgrade for about $100 and you could do a lot more with that.
For me, I do not have to be in a hurry so I can take several passes.

So far I have not done much though and I got sick after eating at Outback so that has me hanging a bit now.
I did a small Christmas tree, then some practice PCB board etching in wood just for practice and getting familiar with the various parts and workings and what works well.
Then I got side tracked because I wanted to create my own G code generator software. I didn't like what I was seeing on the web, seemed too complicated for some things. I wanted a simple line drawing to G code generator program, so I set out to create one. Turned out it's not as hard as it might seem. I started generating codes for DIP packages from a simple drawing right off, along with the drilling codes. I tested the drilling codes with a larger bit like 1.6mm just to see if it would work, and it did work pretty well it gets the holes drilled accurately enough. Those holes are spaced 0.1 inch apart. The smaller SMD type packages required pads spaced 0.05 inches apart, and I think that should go smoothly too. Getting down lower than that I'm not sure about though, some of those tiny packages can have hundreds of pins the width of a human hair and spaced the same. I am not sure this machine can do that because the bit you use is wider than the pins I think (ha ha), but maybe there are better bits out there (these came with the machine).
Anyway, it's pretty cool to watch it move around with the head going up and down when it has to mill out a strip or bore a hole. I have it going fairly slow for now as I get used to what speeds are acceptable without breaking all my bits too soon.

Some people I talked to really love their 3d printing machines though. They make all kinds of stuff with them.

[MrAl]

Check out these small milling machines. All manual control but cheaper.
https://www.cncsourced.com/rankings/bes ... -machines/
volvolugnut

Hi,

Oh, that kind, yes they are beautiful. I almost got one of them years ago.
The kind you can get now are built a little less ridged but still work pretty nicely, and they are computer controlled through the use of G codes. The way I understand it is G coding is a standard in the industry. From what I gathered so far, for a mechanical part you first create a 3d model using 3d drawing software, then convert it somehow to a file of G codes, then set up the workpiece, then send the codes to the machine. It the carries out most of the work unless you have to switch tools, but some machines will have multiple heads.

The last time I used a big milling machine was over 50 years ago. It was a HUGE thing, must have weighed in at 2 tons maybe more. It had a big table and you could put big bits in the chuck. I used it a few times to mill the bottom of hydraulic pumps used for pressing LP vinyl records. The motors that drove the pumps were gigantic electric motors and they were high speed so the pump shafts had to align perfectly with the motor shafts. I had the job of milling some of the pump bottoms so they fit would be more accurate. The cutting bit was something like 3/4 inch in diameter, and the pump bodies were made of cast iron. The bit would cut through the base like butter, it was amazing. You could easily take out 1/8 inch depth per pass. The surface was then nice and flat too. Truely an amazing machine. It was an old ass thing too, manual x,y,z crank handles, these days they probably make them all computer controlled.

[MrAl]

All CNC stands for is "Computerized Numerical Control". It's just pre-programmed movement controls for production equipment.

Any "cheap" CNC mills are going to be very limited in what they can do. You're looking at 4 figures to get a decent, useable 3 (or more) axis desktop/hobbyist milling machine.

Hi,

Check out Amazon then have a ton of them all different grades and sizes, and of course prices.

[MrAl]

I believe a quality bearing would required grinding to the final tolerances.
volvolugnut

Hi,

Yes that's what they did.
From memory, first the machining to the rough size. Then heat treating in a molten salt vat for some minutes, then quenching. Then there might have been another machining cycle. Then they did 'carbonizing' to the piece, then the final grinding to the final shape.
The carbon adding part I think they call it Carburization.
The heat treating schedule was fairly ridged. The piece went into the molten salt bath and the timer times it for so many minutes then it is removed and immediately quenched. The hardness is then checked on random samples.

[abscate]

Pseudo- random, Shirley

[MrAl]

Pseudo- random, Shirley

Hi Steve,

Yeah I don't remember what the criterion was for deciding when a sample was to be tested. It might have been one from each batch.
There was a chart recorder that would record the thermal cycling of the vat of molten salt so that there would be a record of the time a batch went into the vat and the time when it came out. That was to help to ensure that each batch spent the correct time in the bath.

[ZionXIX]

I believe a quality bearing would required grinding to the final tolerances.
volvolugnut

Hi,

Yes that's what they did.
From memory, first the machining to the rough size. Then heat treating in a molten salt vat for some minutes, then quenching. Then there might have been another machining cycle. Then they did 'carbonizing' to the piece, then the final grinding to the final shape.
The carbon adding part I think they call it Carburization.
The heat treating schedule was fairly ridged. The piece went into the molten salt bath and the timer times it for so many minutes then it is removed and immediately quenched. The hardness is then checked on random samples.

Whoa, molten salt bath? That alone puts it out of reach for the DIY person. Doesn't it take several thousand degrees to melt a salt?