My first build possibly.

[tsknutsen]

OK here goes, i'm in the process of drawing up what possibly will be my first cnc machine. And i'm curious what some more experienced guy's think about it.

As my rc club has a phlatprinter cnc machine, i will most likely use that to cut out "stensils" which im going to glue over on mdf and then cut out with a bandsaw and the likes.

The building material will be 12mm MDF

I've made a sketchup drawing of the machine if anyone is interested in taking a look. Keep in mind its not completely finished http://dl.dropbox.com/u/44376466/flatbedcnc.skp


I'ts going to be fairly big somewhere around 170x120cm, with the x-axis going along the 170cm part y along 120cm part (not accurate numbers btw)

I'm aiming for the x-axis having just below 130cm travel, the y just below 100cm and the z around 10cm travel.

Along all the axis i will use 16mm linear bearing blocks which is open in the bottom (i found some cheap ones of ebay), these i will fasten to 16mm axle iron rod which im going to weld onto two 25x25mm angled steel each, hopefully not messing up when welding and getting it nice and straight.

I will use some 425ozin stepper motors i found at hobbycnc which where kinda cheap. I'm thinking two steppers on x-axis and one each on the y- and z-axis.

The x- and y-axis will be belt driven while im waiting for some data on a ballscrew-set i found at ebay.

As for the drivers im probably going to use some i've found of Keling cnc though im not sure which kind, I see they have some digital one's and i'm not really sure which im going to take.. Also i've sortof imagined i could run both steppers for the x-axis of one driver; can i do that with a digital one? Or is it all in all not reccomended to do?

Im sortof mind set on using a cnc usb controller from planet-cnc.com, as that seems like a simple sollution. If nothing else; easier, cheaper and better is reccomended.

As for the spindle, im probably going to start with using a rotozip or something.

Also im trying to keep the cost as low as possible.

What i am mostly curious about if you are looking at my sketchup drawing of it, is what can i cut with it.. What i'm going to cut with it is mostly foam, but i'm hoping to atleast be able to cut some thin plastic and maybe engrave some wood, would this be possible?


All answers appreciated with gratitude.

Regards,

-Tsknutsen

[RomanLini]

You might want to post in the "DIY-CNC Router Table Machines" section of the "Woodworking Machines" forum. That is where most of the router type machines are and your machine looks very similar to the ones there.

You will probably get more interest and more help in that section of the forum.

[Al_The_Man]

Moved.

[PaulRowntree]

Hi Tsknutsen
Some observations from the drawing and your text
- my guess is that you will not be satisfied with welding up the rails unless you are a consummate expert welder. Even commercial rails are usually bolted up to prevent warping etc. If you are going low cost you should check out the Joe's 2006 type of machine, with gas pipe rails that are secured, not welded.
- 12 mm MDF is really, really light and will flex horribly. Foam is easy to cut, but wood isn't, and even if the cutting forces are low, the forces caused by moving your gantry will be large for reasonable speeds and accelerations (F=ma).
- if I understand the drawing correctly, the rails are on the inside of the cutting envelop, with the vertical walls to their outside. This will accumulate lots of cutting debris (dust and worse) which will degrade your motion quite quickly.
- I see the X motors, but not the way they cause motion. Belts? Chains?
- the table itself is not constrained to be flat, and will distort heavily in use. Even moving it on its support will cause it to deform. Explore a torsion box. Again, Joe's 2006 could provide some ideas.
- have you considered how you are going to hold down your work pieces during the cutting?
Cheers!

[tsknutsen]

Thanks PaulRowntree, i will check Joe's 2006 out, and probably come up with a whole other design..

I initially designed it for belt use on the x and y axis, but after some suggestions on another forum im going to go with ballscrews instead, as that is more stable..

Also i might make it out of metal rather than mdf, to make it more sturdy.

But first ill check the build you referred to and get some more inspiration..


Thanks

[PaulRowntree]

Glad to help a fellow traveller navigate the waters. To be clear, Joes 2006 is a widely used model, with its own web site
The Original Joe's 06'

The plans are free, and there are many builds of this design and its derivatives. It takes some very careful cutting (nice to have access to a CNC at this point!). I believe the plans are available here on the 'Zone, buried in the following thread that provides support

Joes CNC Model 2006 R-1 - CNCzone.com-The Largest Machinist Community on the net!

There is a larger design called the 4x4 hybrid, documented on Joe's site that may be interesting as well : it used less MDF, more simple metal framing. $100 to get plans and access to their forum.
Cheers!

PS : I love the way your sketchup image makes it look like a pen-and-paper drawing, with ink blots at the corners.