Need Help!- New trying to build

[Happy Feet]

Hi guys,

I am Pavlos from Greece and first of all I would like to congratulate the people of this community. You are a great help.


The reason I am posting is that I need some help for planning and building my first CNC router.

I am new to this section but i really like and watch the progress of this machine from when i start to work as an interior designer some years ago.

The need for building my first cnc is for use it in my work for produce things by my own. The price for buying one is extremely high for me (i think building my own would save me some money).

So i need a machine which could work enough materials including metals ( non ferrous at least ) wood of course Plexiglas and even harder ones like ceramic, cement and plaster cubes.

I am not interesting in repeatability ( nothing would be produced the same more that 5 times, and this would be once in six months).


I know that you already thinking that i am asking too much but getting the half of what i am asking would be a dream to me.


I also need it to have something about 8” z travel and the ability to add another axis on the router and one on the table ( as you can see I want a 5 axis router )

Anyways at his point after a lot of reading the time for the cad has came.

But i am having some basic questions for beginning with my plans.

Lets start.

I need a machine that would be larger than 4' x 8'. My way of moving the Y axis ( 8') was a leadscrew or a ballscrew. I know that in this solution you should made a partial supported table with legs only on the corners.

So my first concern is the table material. Is there any way of making a table from structural aluminum or metal one, ( without welds only screws) without support except, the four corners ?


Is the rack and pinions solution so much worst from the leadscrews and ballscrews?


If it isnt, I 'll choose this one as there is a profit on the cost too.


I wont ask any other questions at that time . But I 'll keep updating this post with questions, and I have a plenty of them.


Thanks in advance guys,
Pavlos


PS . Forgot to mention the budget. I intend on spending 7000$-9000$ to complete it ( including software)

[stevespo]

Pavlos, good luck with your project. I cannot give any technical advice regarding such a large machine. My own DIY build was a benchtop model in aluminum.

What I can say is that a machine like you're describing is a big undertaking. It will take a lot of time and much more money than you initially think. Once it's up and running you will probably discover that you undersized the motors, or need new electronics, or should have done something else differently.

You can't expect to get everything right the first time. If you get 50% of it right, it's probably a success - but you may feel the need to keep tinkering and improving, and that is more money and time you're not spending generating income.

I don't want to discourage you. I have two or three other machines in my head that I would love to build someday. These CNC machines are a great project. You will learn so much, and have a knowledge of your machine that you'll never get from a commercial unit. But the commercial units also come with support, diagnostics, documentation, etc. If you truly want to use this for your business, you may find that it makes sense to invest a little more money now and save yourself a LOT of time and frustration later.

I don't know what your CAD/CAM/CNC background is. If this is all new to you, you might consider building one of the proven benchtop designs first. Learn to use the software, learn about the electronics and motors, about the different options for linear motion and spindles. Then you can tackle the big, 5 axis you machine you dream about. Also, don't forget the software to run such a machine will be tremendously expensive. It alone could cost several thousand dollars.

Good luck, please keep this thread updated with your progress. There are so many great builds on this site. Anything you can dream of can be built, but as you're aware, it is a big undertaking.

Steve

[selbuss]

Hi pavlos
try MachMate, this machine i think you like
http://www.mechmate.com/forums/index.php

[Happy Feet]

First of all thanks for ur replies.

Originally Posted by selbuss Hi pavlos try MachMate, this machine i think you like http://www.mechmate.com/forums/index.php

Yes i did look the mechmate wich is a perfect macine BUT there are two thinks that i dont like on that cnc.

The first is that it has a small clearance ( gantry-bed i mean) and the second one is that i cant fix another axis on the gantry and to the router.

@ stevespo

I would really like to buy one commercial machine. And this is what i have planned . But i think they are expensive ( or to say it right i cant afford any of them ).

I did saw some people though to produce work with DIY CNCs.

So let me ask something again. Do the racks and pinions are so much worst from the leadscrews ?

[LeeWay]

They aren't worse than some lead screws with regard to accuracy. I don't think they can provide the accuracy of a ground ball screw and maybe not even a double ball nut rolled screw. They can however function pretty well on a large machine if minute accuracy isn't needed. This is why many choose the rack and pinion for doing plasma cutting. It is more affordable and easier to maintain than a screw in this case. Plasma creates a lot of nasty dust and would be very bad inside a ball nut.
The design of the pinion system is pretty crucial to the accuracy as well i think. Some good designs here in the plasma forum.

You could do two axes in R&P and make the Z axis more accurate with a ball screw. Just a bunch of ways to do these machines depending on budget and end use.
Take a look aound at some of the builds on here. Some really great ideas implemented with nice results.

[Happy Feet]

o guys you are so helpful .


I am like a little kid in this one . I won't stop asking if you won't stop answering.

the middle and small axis would be a ballscrew ( that's what i want at least...!)
My problem in this point is the table. I cant support a table with moving gantry, at big dimensions, in the bottom middle with only one ballscrew .as the most cnc used too.
The only way is to support with legs in the middle and put leadscrews or pinions on the two sides of the big axis ( lets say X ) with two steppers or servos .

If i go with the ballscrews on the both sides it will cost a lot, as i have on my current plan 2200mm (86" 1/2 . did i write that correctly?) of X axis.
So i intend of putting either leadscrews or pinions or timing belt and later upgrade it to ballscrews. What is your opinion on that . Leadscrews or something else for the first X axis solution .

I think i know what you ve tell me . This is what i am afraid in pinions. You are forced to slow speeds to have high accurasy. But is this happening with leadscrews too ?

Believe me guys i have spent a lot of time to net trying to learn, the last two months so i have seen a lot of designs.

I saw somewhere in the DIY sections a metal frame with screws and not weld which i like most of all ( not big 4x8 i think). But i cant find it again

[stevespo]

Pavlos, what type of work are you going to be doing? What materials are you cutting and what type of positional accuracy do you need?

A well designed rack and pinion system should be able to handle all your needs. My friend's ShopBot 48x48 has a stated positional accuracy of .002". This is able to do very complex inlay for guitars using endmills as small as .015". This is a stepper (with encoder) driven rack and pinion system on the X and Y with (I believe) a screw for the Z.

Why not take the MechMate design and just extend the uprights for more clearance? You can at least take the proven elements of the design and improve it for your own needs.

Steve

[selbuss]

hi Pavlos
If you look trou the MM forum you will see that you can build your machine like you want and also make your own ideas and use leadsrew, but i think it`s better with the rack and piniong on big machines thats why i want to try building the MM