Newbie- Designing and building a cnc

[motas]

Hi,
I'm new to cnc and this forum so be nice. Btw I like the smilies
Anyway I am looking at building a machine about 2mx2m and having it very repeatable so it is the same everytime but only need to be 0.1mm acurate or less it doesnt really matter as long as the lines are straight. I am about to start a simple drawing in sketchup and have a bidget of probably <$5000 AUD. Also could someone list the main parts I need for it and where I can get them in Australia? I would like to have it cut aluminium up to 10mm and that would be abuot the hardest thing. Would mostly be using it for wood, acrylic and aluminium and sometimes steel. I have heard that using a drill motor and parts will work and connecting that will make it alot easier and cheaper but not as much control. Would this be strong enough? Has anyone got a good guide for building one exactly like this?
Thanks for any help and if ive forgoten any details please ask.

[vishnu]

Its up to you to plan, because once you design and manufacture the frame of the machine which should finish 50% of the total work. You have lot a designs available on the lathe & mill section. But real sturdy frame is required if you are machining metals. Else you can opt for converting manual machines, which would be lot more easier than designing a full machine. There are lot of build based of RF & seig machines.

[motas]

The frame is easy enough for me to design. I think I know what type I want after doing some research and ill post a quick drawing later. I am more asking about the parts of it other then the frame like motors and steppers and bearings and stuff. Can you buy the controller pre programed and just plug in the motors etc and have it work or do I need to program it?
Thanks for the quick reply. Also I was planning to use steel. Good bad?

[motas]

Did a quick sketchup of it. Not acurate and i relise it wont slide well on steel squares. It was just to show you what I mean. Would that work and are parts to build that readily available for a resonable price?
Thanks.
forgot the pic
Click to view full size!

[njhussey]

Motas,

Like you I am new to CNC machines and I have also been doing research as I want a CNC Router to make parts for RC Planes.

For a start you seem to have your X, Y & Z axis mixed up from what I can see. Your X should be the Y axis, your Y is the X and the Z goes where your spindle is going to be mounted.

With regards to main parts you will have to decide how much money you want to spend on the individual bits. For the rails you can go for anything from square tube with skate bearings up to supported precision ground rails & linear slides. It is up to you to decide. I am doing mine on a very tight budget and am using 1" nominal bore Sch40 CS pipe and skate bearings (search for Skate-o-rail on here) This is because the bearings are £4 ($8 AUD) from eBay and the pipe I can get from my work. Similarly I am using 40x40x3 steel for the frame as again I'll get it from my work. I'll upload a PDF of mine when I get home tonight as I was busy last night drawing it up. You will need to beef your frames up to cope with the cutting forces you will generate, again look on the forum for designs, jgro, joe2006 and upwards etc...

There is a wealth of information on here for calculating the power you need for your stepper motors etc, you just have to look for it. As I'm only cutting balsa and ply I've gone for Nema 23 steppers out of old Lexmark printers (again off eBay $40 AUD) I've got a cheap TB6560 stepper controller board ($80 again off eBAy...see a pattern emerging here?!! ) which runs my stepper fine as I only need 24V and 10A max (my steppers are 1.5A per winding so 10A is plenty enough) a 24V 10 power supply ($40 eBay) and Mach3 software to run it all. My set up is here... YouTube- First run of Stepper motors, 3-axis TB6560 controller and power supply. Again you will need to decide what you want to spend which will be dependant on the size of stepper you want to control and if you want to future proof it for running bigger and better machines after you've built this one!

Not sure if this was any help?

Neil

[motas]

Everything is help. I get confused between x and y but at this stage is irelevant. Where do the stepper motors and lead screws go? How I see it for the supported axis which I think is x axis it runs on two bearings of whatever type I choose on each side and ha a stepper or servo with a lead screw in the middle correct? Then the y axis which is on the moving part (forget what it called) has a top bearin of choice and a bottom one with another stepper and lead screw in between? Then the z axis is relatively simple with just a sliding part and another stepper and led screw with a spindle on it. Have I got all that right? I have a fairly small budget so I think skate bearings would be best with some tube. I can use that on x and y axis can't I or only x? I will be cutting max 5mm steel and 10mm alu and 20mm acrylic but I have no issue with it taking it's time. I have a massive shed nowhere near the house or neighbours so space and noise is somewhat of a non issue. As ling as there is coolant I can pretty much set it up and leave it to cut while I go do whatever I want can't i? Could I do it for under $5k?
Thanks. Also I know a machinist go sells bearings so that would be useful wouldn't it?

[njhussey]

Motas

if you want to machine steel then you are best converting a manual milling machine as the forces that will be involved will At the very least cause resonance and vibrations. A good starting point to look at is joe's2006 cnc. That will show you where to put the leadscrews etc. You will be able to build a good machine for <$5000. I am looking to build mine for <$600 but I am begging, borrowing and raiding out scrap bins!

[Plugger]

Motas,

I have been working on a machine to cut aluminum. Finish quality is important to me. If you check out the link below, you will see how I received feedback from my postings and modified my machine. I ended up making it much stiffer (and heavier!!) than I originally wanted to. I also list major components and design calculation results. I have not built and tested the machine yet, so verify anything you borrow!!

http://www.cnczone.com/forums/showth...435#post803435

Watch out for "racking" with a single ballscrew on the gantry long axis (typically called "Y-axis"). You want .1mm accuracy so, I believe you will need two ballscrews on the Y. Use precision ballscrews with zero backlash and precision linear guides with preload. I believe the less expensive (less accurate) components that you may find around are for woodworking machines.

The estimated cost of my machine is <$8k.

[ger21]

Originally Posted by Plugger Watch out for "racking" with a single ballscrew on the gantry long axis (typically called "Y-axis").

Should be called the X axis, imo. Far more common, especially on larger machines.

[Plugger]

Ooops!
Gerry is probably right when he says the x-axis is more common as the long axis, especially for larger machines. I have only had exposure to ONE large machine and its home happened to be in the back right corner.

So, with that in mind, my machine copies it, using the "right hand rule" for axis selection -- with z up. If you make home the far back right corner, it makes sense. If you switch home to the far back left corner, then x on the long axis makes perfect sense too.

I use the right hand rule because it is a common 3-dimensional coordinate system convention...

Here's a link. I use my thumb as z.
http://www.cncexpo.com/Cartesian.aspx

[Al_The_Man]

It is up to the MTB which axis he uses, but if you follow the cartesian coordinate system it should conform to how the typical job is going to be placed or viewed on the work area.
IOW although the operator may stand at the narrow side, if the work area is laid out as viewed from the long side (X) with the 0,0 at what is now the operators r.h. side.
If the operator views and lays out the work area from the narrow side with 0,0 at his left hand side, it is now X along the narrow side, which is the correct way when viewed relative to cartesian coordinate practice.
I have converted many trace cutting machines that typically are viewed this way by the operator, so when setting up the axis I have used X on the narrow side with the long side Y.
And Z of course, is viewed as looking down through the table.
Al.

[motas]

Thanks for everyones replies. This got lost in my emails and forgoten about till now. What I am thinking now is making a regular mill but based around upgrading to cnc when I have the money to buy sevos and controllers etc. Would this work well? What I am thinking for the design is simply a 2m by 2m piece of mdf sitting on some steel braces as a base and cutting table. Off the side of the steel is a skate bearing on each side holding the over the top bit (forget what it's called, the bit that holds the y or x axis with the spindle hanging down) and in between a bearing and the steel a servo with a lead bearing. Would this be strong enough to slowly cut aluminium and steel? Then the over the top bit has two bearings of a suitable type (know a guy who can suggest it) with the servo and lead bearing in the middle. Off this o sobvioisly the z axis and probably a drill motor. All the controllers etc would be hanging off the side. Until I can afford it replace servo with wheels and controllers etc with me and I have a simple mill ready for cnc.
Would this be good?
Thanks. Your help is much appreciated.