Need Help!- 2'x8' or 4'x8' as a first, cheap build

[CarlofET]

Hey everybody -

I've spent the bulk of the day reading around the forums, but I still haven't found the answer to my question.

I'd like to build a CNC router with the ability to handle 8' long pieces of material. I would preferably start with 2' wide for space concerns and upgrade to 4' or a new table later.

However, I need to keep the price as low as possible, and so far the only solutions to the long tables I have seen are a bit expensive. The machine does not have to be anything special -- tolerances of .05" would probably be more than we need, and we won't be cutting anything hard. I can't see doing anything other than wood or HDPE.

Anybody know of some popular designs that would work to get us going? Something cheap and basic but usable up to 8' long?

[hemsworthlad]

Hi,

What you want shouldn't be too hard to design or build.
A steel frame with a 8020 gantry for lightness would probaly give you the best price to strength ratio.

If you go look at my build http://www.cnczone.com/forums/showth...t=92404&page=4 a some thing like this could be easily modified to suit.
You dont need the moving bed etc and if you keep it 2' wide you could get away with 1 central screw. but to be honest i would just build the size you would ideally like straight of the bat, it will work out a lot cheaper in the long run.
I would use rack & pinion if going wider than 2', infact i would probably use it at 2' with a 8' bed.
The use of steel for the frame makes it very strong and it's Cheap compared to using all 8020, you could use it for the gantry but then it makes a heavy gantry which needs larger motors/drivers etc which cost more $.

There are various ways to do the linear side of it, by that i mean bearing/carriages for movement. There's the expensive but IMO the best for long term hassle free use right down to skate board bearings and angle iron.?

Arran at cncrouterparts.com does a great carriage system that is cheap and would suit a project like this perfect, he also does a nice R&P system that attach's to them, plus motors etc well worth a look.

Keep looking and you will eventually come to design that you like or a combination of a few that you can use to make your unique machine to suit exactly what you want it to do, it's not difficult if done in the correct manner straight of the bat.

Best Advice i could give is ASK LOTS OF Q's and DONT RUSH IN . . Look and look and look again before you buy anything and dont buy anything untill your fully sure you understand how it works and more importantly it will do the job with a bit to spare.

Hope this helps.
Dean.

Edit: When you say CHEAP what do you consider cheap.? how much do you have in mind.?

[ger21]

You can modify Joe's 4x4 Hybrid to a 2x8 size.

[CarveOne]

Keep in mind that to get 2' by 8' of actual cutting area the X and Y travels will need to be longer than that by at least the width of the carriages plus some extra inches for home and limit switch margins. Probably something about 3' x 9' if it is a moving gantry. The router placement might not let the bit go to the edge of a 2' x 8' piece of material even with 9' rails.

CarveOne

[CarlofET]

Thanks for the replies so far.

I should probably supply a few more details for what we are looking to get this machine for.

Myself and two other guys are working on a project that requires profiles cut out of HDPE. Currently we trace the shapes onto the raw material with templates we have, then cut them out roughly with a band saw and then use sanders to sand down to the drawn-on lines. I'd like to have a CNC to speed up the process and make it more uniform/precise and to make it easier to change the patterns.

We have a pretty well-equipped woodshop and a fair amount of building material on hand, and I would like to make use of that as much as possible. Further, the other two guys involved are carpenters (I'm a mechanical engineer) and they will be much more comfortable using those materials as much as possible. We're in very early stages of this project so justifying the investment of a CNC isn't the easiest when one can always reply that what we're doing now works fine and we're not overworked, but I am quite sure we'll go this direction eventually and I would prefer to do it as early as possible.

The material we work with is about 18" wide and as long as we want it. I figured 8' would be nice to avoid multiple changes of the material, but 6' cutting area would probably be sufficient. It all really depends on how time-consuming it is to switch out a new piece of stock. If it's fast and easy enough to do, even a 4' cutting area could work.

I would like to be able to cut a full 4x8 sheet someday though I don't really see this project ever needing that. The Widest I can ever see us using is 24" and the longer the pieces the less often we have to switch out the stock. Our largest single pieces are 3' long so that is a requirement. I'd like to be able to cut two lengths in one button-pressing, so that's where the 6' comes from.

Originally Posted by ger21 You can modify Joe's 4x4 Hybrid to a 2x8 size.

I do like his design and will be keeping it in mind as I come up with something. I'm concerned though that our uses would require upgrading to R&P and that might put the project in a price range that won't work for us.

Originally Posted by hemsworthlad Hi, What you want shouldn't be too hard to design or build. A steel frame with a 8020 gantry for lightness would probaly give you the best price to strength ratio.

I would love to use 80/20 as much as possible, and might very well end up doing that, but I'm going to have a hard time convincing them that we should use anything but wood (or MDF) for any component . . .

Originally Posted by hemsworthlad There are various ways to do the linear side of it, by that i mean bearing/carriages for movement. There's the expensive but IMO the best for long term hassle free use right down to skate board bearings and angle iron.?

That's what I'm leaning toward as well. I really like the v-groove bearings, but again, I might have to wait until version 2 to make a system like that. The skate bearing / angle iron seems to be a fairly good way to start and looks pretty cheap.

Originally Posted by hemsworthlad Arran at cncrouterparts.com does a great carriage system that is cheap and would suit a project like this perfect, he also does a nice R&P system that attach's to them, plus motors etc well worth a look.

I did check out cncrouterparts.com and it looks great. I'll probably at least get some of his mounting brackets to start with that I'll be able to use later on. I really want to use his R&P system too, but again, it'll probably be for version 2.

Originally Posted by hemsworthlad Edit: When you say CHEAP what do you consider cheap.? how much do you have in mind.?

I mean CHEAP. ;-)

But really, if I could get away with spending under $1000 (and using what we already have in materials) I think I could fairly easily swing it. Once we have the system up and running and proving to everyone how much time and work it can save us, it'll be easier to swing for the more expensive upgrades for the second machine. I know that's a pretty low price for what we'd like to do, but there are three of us with a fair amount of time on our hands and I figure we should be able to figure something out.

Originally Posted by CarveOne Keep in mind that to get 2' by 8' of actual cutting area the X and Y travels will need to be longer than that by at least the width of the carriages plus some extra inches for home and limit switch margins. Probably something about 3' x 9' if it is a moving gantry. The router placement might not let the bit go to the edge of a 2' x 8' piece of material even with 9' rails. CarveOne

Yeah, I'm thinking a cutting area of 2x6 could be accomplished with a 3x8 or so machine, and that would be sufficient for us for now. I'm considering dropping it to 2x3 cutting area to really help with the ease and cost and to be a better intro machine.

[hemsworthlad]

So what you need is skate bearings/angle/tube for linear motion and timing belts for drive coupled with a wood for a frame for the base.
This will be the cheapest way to do it and will satisfy your partners thirst for wood.!!
It will easily cut what your wanting to do esp if most of your work is going to be 2D profiling and drilling.

Go have a look at this machine it dont get much simpler or cheaper

YouTube- Homebuilt CNC

YouTube- Homebuilt CNC

[CarlofET]

So you think I should use one long timing belt? Or are you saying I should do the timing belt to drive a R&P system?

Thanks for the video - it's very encouraging.

[hemsworthlad]

Originally Posted by CarlofET So you think I should use one long timing belt? Or are you saying I should do the timing belt to drive a R&P system? Thanks for the video - it's very encouraging.

No i was meaning just use timing belts, it's about the best cheapist way to do long run's. The R&P is the best for sure just not cheap.
Timing belts are a good alternative and cheap to replace, easy to find and not overly complicated.
They can be a bit fiddly and require a little setting up but when setup right work good and are quit accurate.
On a 2' wide bed you could use a shaft at 1 end to cross over and turn belts on both side's of gantry using just 1 motor to save cost's this will also help eliminate racking.
The bearing pillow blocks and shafting required are easily available at any bearing company and not expensive, I just bought some a few weeks ago to suit 3/4" shafting and they cost me $6 each.
Or just do like this this person as done, this shows a little more detail.
Also checkout his other vid of it cutting, not the fastest cutting but i dont think thats because the machine cant do it's just he chooses not too.?

YouTube- Homemade CNC Router

YouTube- Homemade CNC Router

And here's another slightly stronger built and working at a decent speed and showing just how accurate a belt driven system can be.
(checkout the second part as well.)

YouTube- My Solsylva Belt Drive CNC Router Part 1

YouTube- My Solsylva Belt Drive CNC Router Part 1