View Full Version : Linear sliders
17-08-2010, 09:33 AM
Just joined great forum, I am looking to build my first CNC machine for woodworking and came across this site http://www.automotioncomponents.co.uk/products/linear-rails.htm
would these be OK for CNC use?
17-08-2010, 12:56 PM
Welcome to the forum. I had a look at that link and the 'linear guideways' and 'minature linear guideways' are both tried and trusted parts for CNC use. Depends on what you had in mind, but good solutions.
'Easy to install rails systems' would take a bit more care to use. They are like reverse profile rails with the rail on the outside and the rotating part on the inside. Since they use wheels rather than ball bearings, their moment about one axis (local X) was low. Depends on where you wanted to use them on the CNC machine for their suitability. The main advantages were misalignment tolerance and low noise. Given that the machine you make is a one-off, and made by your fair hand(!), you'd hope to make it fairly true. As for noise, when the router or spindle is cutting the bearing noise will probably be inaudible, or certainly acceptable.
Personally I would therefore choose the 'linear guideway' type. Be warned though that all these sorts of bearing things are really for industrial use so tend to be expensive.
Did you have anything in mind from this link? Did you have a CNC design in mind?
17-08-2010, 01:13 PM
Thank you for your reply and welcome, Over the last few weeks I have been trolling through the interwebby look for CNC information, my main use would be woodwork but some plastic and soft ally might be used, I have a workshop at present and most equipment to help me build the CNC, cost is not a great issue, I was thinking of buying a complete unit but I`m weighing this against self/build/cock-up/rebuild, One issue I do have is noise, my shop is in a residential area so some sort of sound proof hood will be required.
I was looking at these sliders with some interest especially the belt drive ones could these be linked to a stepper?
The size of my CNC would be approx 600 x 400mm bed to give me room for bigger work-pieces.
As I have said I am totally new to this but very excited about the possibility it will give my Carpentry work
17-08-2010, 05:27 PM
These guys are 15% more expensive on linear rails (example 30mm, 500mm long) than MarchantDice (http://www.worldofcnc.com/main.asp?category=Profile+Rails+%26+Carriages)and 25% more expensive than ZappAutomation (http://www.slidesandballscrews.com/precision-profile-rails-hiwin-rail-c-40_120.html), but 12 x 3 trapezoidal leadscrew is roughly the same... so I'd do a proper price comparison.
17-08-2010, 06:59 PM
The sliders with the belts inside do not look suitable for CNC, judging by the spec on page 36:
Running parallelism 0.8mm
Repeatability of positioning 0.1mm
I think these are more for moving objects around, say on a production line.
On the subject of belts and motors, they are often geared rather than direct drive. They tend to make more sense on larger machines, although small ones do have them also.
Routers are noisy, due to the use of Universal motors.
Spindles running from a VFD are much quieter.
As a woodworker you'll already know that the limiting factor will be the noise of the cutting tool in the workpiece.
Direct mounting of steppers onto a metal frame, with fairly stiff coupling to the leadscrew will transmit alot of noise into the frame and make it louder. You could experiment with rubber tube couplers (more backlash - but could be OK for woodwork) and wooden mounting brackets for the stepper.
Hoods are useful for noise, and also catch the dust that the extractor missed.
On the subject of cost, you might want to budget for about £2000 as a starter.
17-08-2010, 07:20 PM
Once again thanks for the info, it seems there is a good way of building CNC machines, tried and tested, I will be asking more questions as the build progresses.
This will be a long term project and I intend researching a lot more yet, I see many hours searching through your information here.......... once again thanks
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