big budget cnc

[Clive S]

if i was to change the machine 90 °( making the machine 3 meters long and the gantry 1600 mm long) could it work then?

There are a few examples of machines built vertically. Dean (Jazzcnc) has made a few and Neil (njhussey) has done one as well.
Deans are built with the long axis horizontal and Neil has done it with the long axis vertical.

[Boyan Silyavski]

Save some money and buy proper linear bearings, at least round supported. Which in fact are very cheap. What you want to do is like driving on the Autobahn 200km/h with this:

[Desertboy]

I have SBR25 and would recommend that as the minimum for the longest axis and it weighs a ton so I wouldn't want it on my gantry. I'm putting 1.5m 15mm Hiwin clones I got on ebay with 4 carriages for €120 delivered on my gantry to keep the weight down.

I like my supported rail it's lovely and smooth but it's no Hiwin.

[Boyan Silyavski]

I have SBR25 and would recommend that as the minimum for the longest axis and it weighs a ton so I wouldn't want it on my gantry. I'm putting 1.5m 15mm Hiwin clones I got on ebay with 4 carriages for €120 delivered on my gantry to keep the weight down.

I like my supported rail it's lovely and smooth but it's no Hiwin.

Thats what i am talking. Its cheap, its not Hiwin but hey, its supported bearing. Thats what i call the real "budget solution". It will work much better than any V and skate bearings. And i have such small machine /V with skate bearing/ from the time when there were no cheap Chinese bearings or machines. And i am telling you this is one of the things in life that have frustrated me most. I dont wish that to anybody. It will go in the museum of Bad engineering

[Davek0974]

Looking at the dimensions more, i can only repeat earlier comments - this is not a machine for what is called "plates and skates" motion - ball bearings running on steel plates. It works reasonably for small stuff - my first plasma cutter was plate & skate but it jammed a lot due to crud on the plates and it was only 650x650mm, over a length of 3000mm the motion will not track square or level.

This would be a big machine, heavy and expensive I feel, it will need to be if it is to do any sort of work at all. If it were me building big, I would be looking at ball screws, 25mm linear rails, 750W servo motors at least, and a heavy steel frame. I would not even go with the round supported rail at this size. Just my thoughts of course. :)

[Desertboy]

Looking at the dimensions more, i can only repeat earlier comments - this is not a machine for what is called "plates and skates" motion - ball bearings running on steel plates. It works reasonably for small stuff - my first plasma cutter was plate & skate but it jammed a lot due to crud on the plates and it was only 650x650mm, over a length of 3000mm the motion will not track square or level.

This would be a big machine, heavy and expensive I feel, it will need to be if it is to do any sort of work at all. If it were me building big, I would be looking at ball screws, 25mm linear rails, 750W servo motors at least, and a heavy steel frame. I would not even go with the round supported rail at this size. Just my thoughts of course. :)

I'm planning an 8*4 machine next for wood only and I was going to use SBR25 and I'm sure it would be very nice but the price of HIWIN 25mm from cnc4you (About 50% more) means I'll just go with 25mm Hiwin on X&Y and 20mm for the Z.

I costed it at ~£1500 delivered from cnc4you for
2*2.7m HIWIN
2*1.6m HIWIN
2 * 2005 2.6m ballscrews with fittings
1* 2005 1.6m ballscrew with fittings

but I think I would want to fit a minimum 2510 (Or 2520) ballscrew for the gantry and R&P for the long axis (So I can do a dual gantry, independent drive).

R&P gets a bad rap but I've seen some very accurate setups out there certainly on par with the C7 ballscrews I would buy and with ballscrew mapping I'm sure well within any tolerances I would ever need with such a machine.

[Davek0974]

For your HiWin, look into AliExpress, guy called BST Automation, thats where i got mine from.

R&P can be done well and is good on long machines - to get good accuracy look to anti-backlash pinions, they are like two pinions with a spring twisting them apart so the tooth is under tension all the time.

To check what screw, look at the speed/whip rating, longer they go the thicker they need to be, you can also tension the screw to stop whip.

[Boyan Silyavski]

Just as a side note - 20 size Hiwin for all axis is ok. No need for 25 size. Ball screws: 1605 for the Z, 1610 or faster for the X, 2510 or faster for the Y and A long ballscrews and rotating nut setup. I dont see a point for faster ball screws though than xx10 for a Do-ALL-Machine