Re: Looking for information to help buy my first CNC machine
Quote:
Originally Posted by
boldford
Your obviously unimpressed with these far eastern machines. What would you recommend for a similar sized machine where the budget is limited
Argh this is the problem and why these chinese machines have appeal.? . . .It's very difficult, infact I'd say not possible, in this country or EC to buy a machine off the shelf that's specd the same but built properly without the weak area's for the same amount.
This is why so meny build there own machines, DIY is about the only way you'll get near a correctly built machine with a similiar spec for around the same money, even then it will be close call sub £1500 if you want all the trimmings like 4th Axis.!
Re: Looking for information to help buy my first CNC machine
Options for lower budget Machines include:
Steel box section as while weight increases which makes moving the beastie a problem the rigidity also increases which aids in accuracy.
Down sides is that it requires very accurate cutting (but that is a common to all materials); it is required to be coated with something to stop oxidation from getting a start; may require welding which then brings it's own problems.
Up sides is the weight it brings for a base helps decrease vibration massively; has a low expansion rate to temperature changes (not non just low); With a little bit of looking and shopping around can be gotten for a lot less then profile or Ali' box section.
Recycled Profile, IF you can find some one or some where that deals in break down of machines that are past their useful lifespan you can get good profile on a discount. Upside it is profile which is light compared to steel and yet retains the rigidity needed for repeatability/accuracy.
Down side is that it will most likely have some work hardening in the section and the will be drill marks and such. Which mean you have to be a bit careful in choosing what you want to work with.
Also starting with an air cooled spindle like a Kress or something a bit better (again look around for folks selling on equipment in good condition). That or save up and get a water cooled unit though realize a good a good VFD is not cheap nor the proper wiring and in line filters to have it work at it's best.
Depending on what you are doing with it Trapezoid Screws with spring loaded anti backlash nuts can be as accurate as you might need. This is where a serious sit down and looking at what you are going to be doing in real world here and now terms can help massively. It is why my second machine that Jazz is building is custom and built towards a goal of specific usage. The frame and structure of a machine is from what I have experienced only about 40 to 50% of the overall cost. Steppers/Servos, drivers, BOB, computer, spindle, vacuum for cleaning, and many more add up quickly and from personal experience are equally important.
Another option entirely is start haunting the equipment auctions and chatting with a few folks here who know where there are auctions of equipment. Go and look a few times and get a feel of what you are looking for. See if one the folks here is heading to one that you can go with. You would be surprised what you can get used industrial machines for at times. Depending on what you plan on doing, refurbishing an older machine might give you an affordable answer to your goal. Yes most of them are heavy as heck and will need work on them. Look around and talk to folks here and at model engineer swap meets and other places the similar minded people meet (robot war groups come to mind) and you might fins what you want exactly or so close that it does not matter.
Good luck and keep asking questions.
Michael
Re: Looking for information to help buy my first CNC machine
Quote:
Originally Posted by
JAZZCNC
This is why so meny build there own machines, DIY is about the only way you'll get near a correctly built machine with a similiar spec for around the same money, even then it will be close call sub £1500 if you want all the trimmings like 4th Axis.!
That's what I was about to say. The only way is to either do the research and DIY, or give someone who knows what they're a clear specification and get them to design and make it for you. I think DIY is the best option as in making the machine you'll learn more about how it behaves and what to look out for.
Quote:
Originally Posted by
m.marino
Down sides is that it requires very accurate cutting (but that is a common to all materials); it is required to be coated with something to stop oxidation from getting a start;
Cutting accuracy depends on how you're joining it. If it's just welded then you can make sure it's clamped accurately and rigidly whilst you weld and small gaps can be filled. For my frame I started off milling all the ends nice and square and milling a chamfer on. Then when I started welding it I realised it's a bit of a waste of time so I just cut it with my metal bandsaw (same as Jazz's), which at the time was cutting quite square and nipped the burrs off. Either way it helps a lot to have a milling machine and metal bandsaw. Frame cost me about the same as steppers and drivers.
