Project priorities...I need some help.

[Azonic]

Main parts to be built are adapter parts for racing..

I was going to use to to make foam models for wind tunnel testing...

Long term, I would love to make very accurate parts such as cams and things..

However, I know I need to keep tolerances in check...

So what is SO wrong with the idea anyway?
That is the part I do not get...

I draws out, models out, and with effort should build out..
I know it is not the norm... but why is it wrong?

[jstiltner]

Here is a point to consider that you may not have.
Is the size of this machine 2'X2'X2' required because you will be cutting the foam? Do you plan to ever have a block of aluminum in there that big? The reason I asked is the rigidity and accuracy needed for foam is much less than for aluminum or wood. What the real jist of my comment is, could you build a smaller machine for your aluminum work, and the larger one for foam, I doubt that your $1000 will go very far at all toward making this if you intend to cut aluminum on a machine this big. However you could probably make a nice foam cutter for that much.

But then again, you may need to define to yourself what accuracy you need. Just thoughts

[ger21]

What software do you plan on using that can write code for that axis arrangement?

And $1000 will not go far at all. Most guys spend more than that building similarly sized MDF 3 axis machines.

[Azonic]

I can see I am getting alot of help here...

I do not want to try to build a robotic arm to run more than 3 axis..
Just not worth the effort to get that complicated...

$1000 would get the bulk of the motors and controls..
The metal work will cause it to go above that..

Now I have seen several 3 axis units with 2-3' tall gantrys
that seem to wrok well for what people do with them...

I still ask, the question...
And it is a convince me kind of thing..
What is wrong with it? And better yet, help me with any design changes...

Proper triangular bracing, rigid materials, proper alignment, and good equiptment...

Tell you the truth, the first robotic arm 5 axis machine I saw, I thought there was no way that thing can be rigid, but it was, and cut large blocks to fine detail... A multi-joint arm is harder to keep rigid than a gantry??

[ger21]

Originally Posted by Azonic I can see I am getting alot of help here...

Like i said, nobody has built one here. People may be hesitant to offer suggestions, when they have no first hand experience.

Originally Posted by Azonic I still ask, the question... And it is a convince me kind of thing.. What is wrong with it?

Bottom line is that while you think it'll be easy, in reality it'll be much more difficult to build an inexpensive, rigid machine than you think it will.

Your original post asked about spindles. Anything will cut foam. But you want to cut aluminum. What exactly do you want to make from aluminum? Will you be cutting large blocks, and removing a lot of material? Typically that requires lots of flood coolant. And typically slower spindle speeds. However, you can also get router bits for cutting aluminum with router spindles at high speeds. But you have to keep in mind that the faster you go, the higher the forces involved. There are a ton of variables involved, and only you know what you really need. Ideally, you'd want a 2 or 3HP spindle like these.

http://pdscolombo.com/fan_cooled_rs_rv_manual.htm

You can get similar water cooled chinese made spindles on Ebay for $500-$800


As for motors, you need to answer these questions, for starters. How fast do you want to go, screw pitch, gearing, how much weight you're moving, how fast do you want to accelerate....?


And for slides, I'd say nothing less than THK type linear rails and blocks.

[Azonic]

Gerry, very good questions..

And answering them aids me too...

As far as speeds go..
I will not be using this machine to make money, so if it takes it the better part of Thursday night to get the rough cut done on a block.. won't hurt my feelings...

I had thought along the lines of this type of rail and guide... thoughts?


However, the ones you suggest..THK have been part of my consideration for at least the X axis...

I was looking at the liquid cooled spindles, for their size, power, and speed.
Mostly as they are very "small" for their function...

[Azonic]

My original thought was to use angle iron and square tubing to make the X axis rails, then use a series of flat roller bearings to use a guides..
I have seen that method alot. I think however after looking more.
That I will use the rollers above with the angle iron rails. Then I will only have to use a few rollers to prevent lateral movement...

I have also thought that a triangulated vertical for the gantry will be a good idea...

At about a 15 degree angle from the top, down parallel to the X rails, then create a smaller rail system to work in tandum with the X. This will keep the vertical rails of the Z axis from flexing...