What size machine to build?

[CNCMP]

I am designing a CNC router and I need to decide what size to make it. X and Z axis is easy but how long is an issue. In theory it should be possible to machine a long work piece in two stages, sliding it along the table and re aligning between stages. Is this a practical procedure?

CNCMP

[kdoney]

I would suggest you build the smallest machine that will do the job you need it to do. If this is your first machine, you will learn enough to save money and build a better "next machine". Just do not skimp on those parts (electronic and electrical) that you can use again later. Try to buy standard parts so if you need to sell them, you can.

It is difficult to find the source of errors in a machine. The smaller the machine, the easier it becomes. You will have errors, just like everyone else. In the beginning, keep it simple and I suggest you concentrate on just finishing the machine. Improve it later. You will find out a lot by fixing the errors.

[chuckknigh]

What is the largest item you are likely to cut? Notice I didn't say theoretically possible...just likely.

In my case, I like clocks, and clock gears are rarely more than 6" in diameter. So, despite the fact that I enjoy woodworking and could make a machine capable of taking a 4x8 sheet of plywood for the purpose of making big parts, my ideal starter machine would have somewhere around a 6"x6" working envelope. Maybe just a little bigger...

Small, simple, easy to keep it stiff... KISS is a good principle, for a reason...seriously, guy...KISS! It'll increase your chance of actually finishing the project, too.

-- Chuck Knight

[CNCMP]

Hi Chuck

I am sure this is good advice. If there is a complicated way of doing things this is what I normally choose, to my regret!. But I usually do finish.

Murray

[buscht]

Murray, it is possible to work a long piece in multiple steps. A machine like the HobbyCNC machine is perfect for doing this. A stationary table, and the gantry moves.

The trick is in how good your reposition and alignment mechanisms are.

Good luck

[chuckknigh]

Well, the reason I mentioned a "starter machine" is that almost EVERYONE on this board has wanted to redesign and rebuild their machine. Usually it's done as a second machine...sometimes it's done DURING construction of the first one.

Nevertheless, there WILL be things you want to change, as you get hands-on experience building your first machine.

Keep the first one small, and you'll probably get better results. AND, you can use it to machine parts for your second machine!

-- Chuck Knight

[sixpence]

Good advice has been given and I am eternally grateful that I followed it. Just finished my starter machine. I will be cannibalising it for my new and improved design. It is much cheaper to start small even the mistakes I made on it proved to be costly and not to mention time consuming to rectify. I amazed myself as to the amount of errors possible!