Initial diy cnc build questions

[JackAPE]

Hey guys and gals,

For several reasons I've set my sights on building my own cnc machine. This is just an idea for now and I'm trying to figure out the scope for something like this.
I used to be a TIG welder and mechanical engineer, but in a very specific field (stainless steel piping for the pharmaceutical and semi-conductor industry) so I'm lacking some insights. I'm a quick learner though.

I have a few constraints here and I'm trying to find my way with them.

One of them is the fact that I live in a rural area of Vietnam. I can get farming supplies everywhere, but nothing for this kind of project. I can order stuff, mostly from China, but importing is a major pain in the behind. So making or doing things myself is preferred for all things.
On a positive note, Misumi does operate in the country.

My two main questions are related to each other. Keep in mind that I have all the time in the world for this (retired), but not all the money.

The first would be about making my own ways.
I can find linear guides at Misumi, but the ones I think I would need are a big hit to the budget. So my idea switched to getting ways milled and scraping them myself.
I fully realize this takes a lot of elbow grease and is a huge learning curve, but I'm still attracted to the idea.
Looking around on youtube I stumbled across the three bars method. This sounds great for me as a precision block is another one of those big hits to the budget.
Does anyone have any experience with this method? Any advice?

The second question is about making a lathe mill combo.
Because ideally I'd love to have both machines and making ways or buying linear guides are a big part, I thought why not use those efficiently. Same goes for all the other stuff like controls and motors.
Adding one more axis is much easier than building a second machine. And since I'm designing this from scratch I might be able to keep the compromises between the two to a minimum.
I've read on this forum that the chinese built combo machines aren't very popular for a number of reasons. But I think some of these could be overcome.
Is that my wishful thinking?

Any questions, ideas or advice are welcome!
Thank you for your time.

 

[markba633csi]

Much of the problem with the combo machines currently on the market is that the carriage makes a poor milling table.
It's not large enough, and isn't really very stable without some downforce applied to it.
The combo machines with the milling head as part of the headstock are the worst- top heavy, poor access, limited articulation and rigidity.
Plus all the benefits of Chinese manufacture- NOT!

Better are/were the Emco-Maier machines from the 70s like the Compact 8, 10 and Super 11 with the milling attachment mounted to the
center of the bed
To me a CNC milling machine would be far more useful than a CNC lathe- but that's just me.
I believe the Canadian company Standard Modern once made an interesting combo machine, and there was a (I think) Swiss model called
"Scintilla" that had a unique design- Check out the website www.Lathes.co.uk for more info

 

[matthewsx]

Having built my own CNC mill/drill I can definitely say you have a project ahead of you if you want to build the machine from scratch.

First thing you’ll need to do is decide what level of precision you’ll be happy with since this will inform a lot of the decisions you’ll need to make.

My first thought is would it be possible to make a trip to an industrial area of your country to search out used machines? Often industrial CNC machines are sold for scrap once they are no longer profitable or reliable. That would give you a much better platform to start with provided you have the space and power to accommodate one.

If you do decide to build from scratch linear rails are the way to go IMHO. I’ve bought used ones from eBay quite reasonably. Look into epoxy granite for a base, you can weld one up like I did but getting it as flat as you like presents a challenge for even experienced welders.

As for a combo machine look into running a 4th axis. It should give you the versatility you’re looking for and probably eliminate the need for dedicated lathe hardware.

Those are my thoughts for now. I look forward to seeing what you come up with. There have been some very cool multi machines build from old engine blocks and the like in places even more remote than you are I’m sure.

John

 

[JackAPE]

Thanks for the replies! Very helpful already.

The projects I have in mind would require a lathe, mill and cnc router if I were to buy machines. That seemed to be combinable to me, and a lot more fun to build haha.
I don't expect to be working with microns, but I'd like to be able to get close to 0,01mm tolerances.
Unfortunately buying a second hand machine is problematic due to our power supply and available space here.

My idea was initially to build the milling axis in the middle of the ways, just like the Emco-Maier machines Mark mentioned above. The newer Chinese combo machines have a similar layout.
But then I found the Shopmaster 3 in 1 machine and their layout makes sense too. The overhang is less or non-existent, which is less harsh on the ways or linear guides for that axis. It just requires building two columns, which is a bit trickier with levelling I would guess. And probably two ball screws, one for each side.

For the guides I have two options. From Misumi, which seem to be made in Vietnam, or try to get some from China. The ones from Misumi I can afford are on the cheaper end with only light preload. I guess I can minimize the precision loss by trying to mount the blocks as far apart as possible.

Adding a 4th axis sounds interesting. Is it possible to fabricate axles with that? I'm looking to work with/make turbines, so it would have to be quite precise.
Does this have any big disadvantages compared to having an actual lathe?

 

[JackAPE]

Just watched some videos on epoxy granite. Very interesting!