Hey guys I'm new to this CNC thing. I have been reading through the forums and checking out all the sweet builds. I have a question regarding size? My minimum would be 2x4. Was thinking of maybe going 4x4 or 4x8. I wanna use it for all kinds of projects from signs to building guitar parts. I also like to build furniture so i woiuld probably use it to do some custom designs on doors and things like that. Is it worth going up to 4x4 or even a 4x8? I'm not to worried about cost cause i'm gonna take my time building it. I only wanna build one cnc and don't wanna undersize it. Also I'm gonna need a set of ox plates. Do they vary in size if you go bigger or can i ask someone to cut them for me? Was thinkin I would contact Chris. Seems like everyone really likes his plates! Thanks guys. Alot of great info on this site and it has me pumped to start this project!!! Travis
Ah. The ultimate question. How big?? Firstly. You could make it as big as you want, but, the cost is going to be structural flexing, and therefore variation in repeat cutting. However, this can be overcome by proportionally increasing the strength and overall weight of the machine. You will need to take in to consideration such things as the motors, and drivers, you will need to move heavier weight etc. Secondly, the type of drive mechanism, ie, belts for lighter machines, and rack and pinion, or lead screws, for heavy duty work. It is great you have been bitten by the CNC bug, like the rest of us, and that you can see the many, many, possibilities that these machines can be put to. However, don't jump in just yet. Do read more of the Forum chat. All the answers are there, somewhere, even to the questions you don't know to ask about yet. Take your time, and consider all the variations available. Please feel free to ask for any info at any time. There are many experienced builders here who are more than willing to help you out. Cheers Gray
Travis, I would suggest you start with a smaller machine first. You will need at least a 3'x5' table top to yield a useable 2'x4' cutting area. I started with a 4'x8' machine but found 99% of my work was in the 2x4 range. And like Gray said, its difficult to get a rigid home build in a large format. Last spring, I build a smaller 3x4 CNC incorporating many unforeseen improvements I wished the 4x8 had. It has a vacuum table and is now the go to machine for almost all my work. Very rigid and very accurate. X & Y axis are repeatable to around 0.002+/- and Z is 100% repeatable to 0.000. I can only measure to 0.000 so if its off, it's beyond this range. I cut full 4x8 sheets quite easily. Use roller stands and slide the 4' width in until it hits the pegs, suck it down and cut away. All my projects include a 'cutoff' routine to separate the 2x4 section from the rest of the sheet. Remove the section, cleanup any residue, slide the remaining 4x6 sheet in to the stops and cut again. Most projects will fit in a 2x4 machine. Just requires a little creative thinking on the design side. This spring, I will be upgrading the 4x8 machine to incorporate improvement ideas now installed on the smaller machine. If it wasn't for the 8' A axis, I would probably do away with the larger machine. I like having an 8' lathe for turning picture/mirror frames, making spindles and any other project that is best made by a lathe. Taking your time to build something is the same as not building it at all. Start small and learn. The most expensive items like electronics, motors, computer, software, etc will easily migrate from a small machine to a larger one. If you have any questions, I will try to answer them. CNCzone.com is the go to site for all things CNC. That's my 2 cts worth. Dave
If you want big you might look at joe's cnc. this is a variant of it. openbuilds ox is great just isn't the best choice if you want big.... Bob
Thanks guys! I have been reading a lot of info. I am gonna go ahead and buy all 1500mm extrusion and go 4x4. I was thinking an 8' table would be overkill for my needs. I was reading about a 4x4 build and he was gonna try a triple layered extrusion for the gantry. I like that idea with the 4' width. I guess a 3' width would probably work as well. Do you think I would have more problems with the strength going bigger? I think you are correct Dave. 99% of my projects would fit on one of these size tables. Thanks again for all the replies!
The build I've been looking at is the one Guiliano M was gonna do. That looks very similar to what I was looking at doing. Im currently making a list of all the projects I want to use the cnc for. Don't have any so far that wouldn't fit on a 3x4. Or I would just buy 2 1500 length and leave them uncut. That would be a 3x5 as Dave suggests. Thanks! Travis
1500mm may not give you a full 4x4. Don't forget the gantry rides on trucks of some form and these trucks have length. With a truck length of 12", the last 6" of the table will not be used. And with the router mounted 3-5" in front of the gantry, in all likelihood the back 10-12" may not be accessible. Same with the Y axis. The carrier rides on rails of some form and it has a width. 8" wide is not unrealistic and the cutter sits in the center. So the cutting will stop at least 4" from the edge in Y. These are design factors. Longer trucks and wider Z carriers allow for more rigid design which requires a larger table. Don't be surprised if the actual cutting area becomes 47 1/2" x 35 1/2". Dave
I have a 1500 x 1500 ox, and unfortunately i purchased it before robocutters bought out this one: https://www.robocutters.co.uk/proddetail.asp?prod=RoboCutterX4CNCKit which has double profiles all round. so mine having only single profiles, has masses of flex. im now having to add modifications in a bid to strengthen it. one major issue i found with the flex is that conventional and climb milling will put different amounts of stress into the frame, and i would get a difference in depth of cut between the two. and the only way to get results was with a horrendously slow feedrate so as any backlash didn't make the machine wobble and over run.. which in most cases means your running the spindle to fast. though robocutters may have improved on this with the model in the link above.. if i were to build another ox, the most id go is 1000 x 1000 with this system. I am slowly improving on mine with the modifications.. but its a long way from being as rigid as it needs to be. have been very tempted to take a chop saw to it and make it smaller in all honesty.
That robocutter isn't a great design. It should at least be able to cut its own improvements though. I think the OX clearly benefits from it's double extrusion gantry the most when they are bolted together. But...yeah. Flex should be noticeable with a single thin extrusion gantry like that. Probably best to do multiple rough cuts for a rough profile then a really light finish cut on the part profile with that design.
here's a link to one of the mods im having to do: http://www.openbuilds.com/threads/frame-mod-1500x1500-ox-max-plates-needed.1025/ fingers crossed it works
Hi, I'm building a 4x8 CNC using the OX CNC method with C-beam and 20x40 for the s.board using an 8mm lead screw for gantry and my dilemma is what o use for the Y-axis, I bought a 3GT (GT@-3M) timing belt and pully. Is that good for this kind of build? Thanks for any help you can give me, Joe
I have a belt driven Ox HD, C-beam Z axis (big improvement over 2040) and dual 2080 X and use gt3 with dual belt setup,16 tooth pullies. Basically dual belt makes it almost a rack and pinion because the lower belt is glued to the rail. I used CA glue like type used for gluing RC truck tires and this has held up for years now. You need about a 0.5mm spacer to lift the lower belt that is glued, I used 5x0.5mm carbon fiber strips (not expensive and consistent thickness something like these and this ca glue) Some people have used 3m VHB double sided tape but not sure it lasts years. Good luck Gary
