Looking into a ballscrew, not sure if I should buy. Help

[bikepete]

Sounds good, you've clearly got an idea what's involved! A few more thoughts:

- Re second hand: if you could find some old 'big iron' for approaching scrap price - e.g. an old planer or planer mill with a table about the right size, that would be a great shortcut and get you a solid basic structure. But it's a long shot as you say.

- Re drives - I'd leave that until you've finalised the structure a bit more and know how much mass you're needing to move, and the details of any ballscrews you may be able to get.

- Re face milling - certainly not difficult but they charge a lot because the difficult bit is them having to pay for the large machine needed to do it... Is the affordable solution you've come across epoxy levelling?

- Re welding - you familiar with idea of residual stress and stress relief to prevent distortion over time?

- Re resonance/vibration - wasn't talking particularly about anything provoked by machine movements or ballscrews. It's the cutting forces as the flutes of the cutter hit the material which will cause the structure to vibrate/resonate.

- Re ballscrews/servos... you've probably already seen but this ebay seller:

items in linearmotionbearings store on eBay!

has a good reputation for ballscrews etc at good prices - might be worth getting a quote for the lengths you need to compare with your local suppliers. Given the size of the machine I very much suspect you will want two for the long axis.

[JAZZCNC]

Don't want to be a Nah sayer and I'm the biggest DIY-er but your not going to achieve the tolerances what your looking for without having parts machined on proper machine and even then I don't think you'll achieve what your looking for easily or at all and it will cost plenty of money.

IMO If you have enough paid work for the machine then I'd look at leasing VMC rather than buying and you'll have it paid for in no time.!! You'll also be up and earning with-in the month.!!

[oldmam4m80s]

Thank you bikepete. I had not taken into account the vibration and resonance of machine tools while machining. I anticipated slow and steady work but I am not lying to myself thinking it would be completely avoided. I have not accounted for that type of vibration/res. How would I go about that? (I may come across it in the pdf's that were posted earlier) I have not yet read them.

As far as leveling: it was not epoxy leveling that I was thinking about more of a setup the linear rails I purchased and perform the operation myself at my home. It would be tedious but I believe it would be possible to do. Is epoxy leveling a better idea than machining the surfaces myself at home? I will have to look up the steps involved for that to be able to decide. Thank you for providing the option/idea.

Welding: I am unaware about stress relief to account for warping over time. I will look up that information to become more familiar with it. Thank you for pointing that out.

I will also check out that ebayer... I believe I may have run across his items a few times. lol, I have been searching everywhere!!

JazzCNC. Thank you for visiting my post. Im glad you can relate as a DIYer. I know the tolerances are ambitious and while they may be unattainable I would like to try. What are tolerances of professional made CNC machines? I believe they have much closer tolerances to .001" If I end up on the higher end of lets say .008-9 I would consider it a success. If I have a .01" tolerance I would still be happy. I just believe that there is a market where I can draw income from with a machine with these capabilities. I do not intend to manufacture items for industry with this initial build but more of a build whatever comes to mind and make a small profit if possible. If I can use the machine to perform operations for some folks I would but I would explain the capabilities of my machine before taking on any work.
Leasing a VMC sounds plausible but I do not want/need the pressure of having to take on jobs to finance the machine at this time. It may turn into that but at this moment it is something I would rather avoid. Thank you for the suggestion, I will keep it in mind. Thank you guys kindly for responding to my post. You are making this endeavor a very good learning experience for me. Things that are being brought up are paramount to the success of the build. I will continue searching and reading and hopefully make some good progress when the time comes to put all this together.

[bikepete]

Gotta say it's worth listening to Jazz. I think what he's partly going on here is that judging by your answers you have a very steep learning curve to get up and also it's not really clear what sort of machining knowledge you have 'in the bank'.

Do you already have a metalworking business and/or workshop? It's just concerning that you don't know e.g. that machine vibration comes from cutting...

Point is, your ambition is admirable but what you're intending to do is to a major project for an experienced, very well equipped machinist who is already up that learning curve. To 'properly' design such a machine to the extent that it will be good enough for commercial use requires degree level understanding of mechanical engineering and manufacturing and measuring facilities which cost serious money.

It's the size of project you might tackle when you're confident of your skills. Not as the first project: it's so big that everything about it, especially any mistakes, will be expensive.

Follow the link I posted to the Milltronics machine and read the PDF brochure and specification there to get an idea of what a commercial machine can do. Bear in mind that this sort of machine will cost as much as a small house... and has many million pounds/dollars of design and manufacturing capability behind it in the company that made it.

Re machining level surfaces 'at home'. What reference would you use to check things are straight and level? What instruments would you use to determine how far off straight and level they are when done?

My suggestion is this: start by making a 1/10th scale model of the machine you intend to build. Or even smaller: make the longest axis shorter than the longest travel on your largest current manual milling machine (you do have one?). This'll make life a whole lot easier.

You'll probably be able to build the whole thing for less than the cost of steel for the monster machine and you'll learn a hell of a lot. A small machine can still make money for you (e.g. engraving nameplates etc) but you won't be spending major sums on something that may not deliver. Go for a stepper not a servo system (so just a few hundred dollars) and just get the damn thing working. Then you'll have a better start point to build the monster machine if you still want to try.

Sorry to be less optimistic this time but there's no shortcuts: if it was easy to build a huge machine like that and start the money rolling in, a lot of people would have done it. Jazz is right to give a bit of a reality check.

[irving2008]

...
I did think about the two screw option on an axis and if I had to the shorter of the axes would be ideal. An Engineer at a manufacturer I spoke to advised I go with only one screw per axis. I called them to ask about pricing on parts and WOW! they were very proud of their parts. I am considering a design with single screws at every axis but if I see the design benefits from two screws at any point I will go with that option.
...

'An Engineer' who has no responsibility for ensuring your design is fit for purpose and certainly won't have considered all the aspects and possibly has no experience of building such a machine. Trust us on this one, there have been enough builds done by people here to prove the point... a Y-axis that wide needs 2 screws on X for machining wood. Yes it might just be possible to be done with 1 but to prevent racking under the sort of cutting loads you'd encounter with machining steel the gantry support bearings would have to be so far apart you'd lose maybe 20% or more of your X travel.


I have to say I'm intrigued by your starting point for this discussion... what is it you do and why did this gentleman with the pressure housings you refered to earlier seem to think you had the capbillity, expertise & skill to re-machine them?