DIY or buy Round Rail?

[andycorleone]

I'm buying the bit to build a CNC but I need to decide between build somethign like this:



or buy something like this for the 3 axis



I was thinking in 16mm diameter for X but not sure if the same diameter for all axis


forthe DIY expect to spend around £50 or a bit more

for the buy option is about £130 (Inc 6 x Round Rail, 12 x Supports and 12x Carriages)

[blackbeard52]

You will be more happy with the first if you are not supporting the rail underneath. both have been used on here so there are varied opinions as to which is better. As a DIY the angle is the most widely used of the 2. however, have you considered using another arrangement. It is easier to configure and cost is about the same as the other angle configuration. Joe uses it on his design as well as others...It works pretty darn slick. http://www.cnczone.com/forums/showth...t=51770&page=4 post #39

[Oldmanandhistoy]

Hi Andy,

More information required
To get the best from members (or even just a reply sometimes) you need to give as much info as you can within reason.

Based on the information you have supplied I would say the 16mm rails pictured would be fine for a very light machine with say a 300mm X and Y used for light engraving and PCB type work (I would still go with supported myself). Anything heavier than that and you need supported rails (16mm rails pictured would be ok for a Z axis on a medium machine).

So if your machine is larger and your budget is tight then DIY is your friend.

If your budget can stretch take a look at V bearings and rails as pictured in the link above. If they are too rich for your liking then its a skate board bearing design.

John

[irving2008]

Andy,

My machine (300mm x 300mm x 250mm fixed gantry, moving table) uses 16mm round rails for the table support (X) and Z axis and 20mm for the Y. Currently built from MDF but v2 will be all ally/steel construction. The deflection of 16mm unsupported 500mm long rails for the table is <.05mm under 5kg of load so this is fine for PCB routing, plastic and small ally parts as long as the DOC is light (<0.5mm - I use a 500W Dewalt die grinder as the spindle). The 20mm rails deflect less, equivalent to a 0.08mm sideways movement of the cutting tool when the Z traverse is at the lowest point (that's a 350mm moment at 10kg sideways cutting force) so fine for light ally work with moderate accuracy (better than 0.1mm tolerance). Anything heavier I'd go to 25 or 30mm rail or use fully supported rails but the cost goes up and then the deflection of the MDF becomes significant so the overall construction needs to be beefier.

ps, why not come and join the UK CNC community on www.mycncuk.com