Newbie- Good intentions...

[EliPro]

As so many of you already have, I'm going to build a CNC machine. A
plasma-cutter to be. I've searched the forums for information, wandered
around ebay for parts, and drawn numerous designs, and now I'm finally
content with the setup I have in my mind. Although many questionmarks
remain unanswered...

First up, the design. (all negotiable after recieving priceless information)
- ALUMINUM EXTRUSION (8020 profile system) used for the structural design
- LINEAR BEARINGS for all moving parts




The aluminum profile system, I'll be using that, it's light, strong, and cheap.
I am still looking for a Belgian suplier though. In the rendering you can see
that I'm using Igus Drylin-W and T linear moving parts, I'm hoping these will
do the trick because they are a lot cheaper then steel ball bearings, although
I don't want end up having to buy new rails and carriages after two weeks of
usage, because of accuracy problems.

I'm thinking of skipping the whole Z-axis, If I make a manually adjustable
part I'll still be able to cut great parts, it saves a good deal of money too. I
was looking into bolt-on automatic height adjusters but they are way too
expensive.

Sometimes I think I'm overdoing the whole concept, why shouldn't I use
v-groove bearings and aluminum corner profiles as guides, it will save me a
lot more money, but will I be satisfied with the results?

[FandZ]

I read something negative about those Igus glides, I can't remember what it was though. Maybe it was wear or binding issues. The design is nice all around. I plan to do something similar down the road at some point.

I'm not sure what you mean by skipping the Z axis. They can be a pain in the neck but what's the alternative? Manually lowering your spindle? Solid and pre built Z axis can be had in the 200 to 600 US range.

There have been a lot of successful builds useing V bearings and Steel guides. I would avoid rolling them on aluminum though. Sooner or later dust will get between the wheels and the track and an aluminum guide will become pitted over time. I have some steel and aluminum rails on the same machine. They both got debris under the rollers. The steel one can be scraped clean. The aluminum ones are damaged for life.

What materials do you plan to machine.

[FandZ]

I just reread your post and realized you are making a plasma table. You probably could use a much smaller extrusion for your Y axis, you will not have to deal with any serious forces. Now I can see your logic in skipping the Z axis. I still think you should use one though. Also, I'd go with the V bearings, on steel though, you'll be happy.

[EliPro]

I'm getting all info on prices now, so we'll have a look wich is affordable, I'm looking into precision linear rails too, so I might go for those.
The reason why the Y-axis is so sturdy, is because I might want to double the machine as a router, so I don't have to build two, I'll find a way to easy-clamp the torch, or the router to the Z-axis. I will somehow put a Z-axis on the machine, because I'll need it for Milling, and a THC I'll need to build too...

[rvt]

You are making a plasma table,

so you can easily use V bearings and Steel guides.

Ries