Hello - first post here, but I've been lurking for awhile. I am venturing into a CNC router build, primarily for cutting larger shapes out of 4x8 sheet goods (3/4" plywood, MDF, foam core material for composites laminations, etc). Even though going 4x8 for my first build seems to really be jumping in headfirst, my uses for the machine would be significantly limited without being able to cut in that size format, to the point where I have a hard time justifying it at all. Anyways, I started out by gearing up to build the "Plastic Monstrosity" unit (seen here: Plastic Monstrosity) as I've become pretty comfortable with 3d printing and I'm always looking for an excuse to break out the NylonX and make some nice looking prints with it. It seems like, for the money, a very practical design and getting to print a lot of the components seemed like it could be fun. In fact, I started printing some of the smaller components for it today. Well, while those parts printed, my thoughts on my direction with this project snowballed, which is fine. I ended up deciding rather than printing the parts for the X and Z, I would just buy the 1500mm C-Beam Tension XL bundle for the X and the 250mm C-Beam Linear Actuator bundle for the Z. At that point, essentially the only parts I'd be using from the "Plastic Monstrosity" build would be the gantry pieces that connect to the 2" EMT conduit and the very simple system utilized for the belt drive along the Y. I ordered the 1500mm and 250mm units today from openbuilds to get things moving. Then I decided rather than build a table for it from 3/4" plywood as I planned, I became very attracted to the idea of using Openbuilds V-slot bench system. I can get it in black, it will just look like a much more polished unit than if I built the bench out of plywood, not to mention easier to break down on the very off chance that I ever had to do that. It just looks great, I can imagine feeling a lot more satisfaction walking in the room and seeing that everyday. Once I found out from customer service that I can order linear rail in lengths up to 3000mm, and I saw the nice belt tensioning system on the 1515, I started thinking at this point why don't I bring this to the next step and save the 40+ hour print time of printing each of those gantry pieces to utilize the EMT for my Y rails and just order C-Beam in a length above 8' and somehow integrate it into the v-slot table and just forget all about the 2" EMT and 3d printing anything at all. This all brings me to my question for the forum. I'm really just looking for input on this concept and if my thinking is correct that the direction I'm headed might be simpler than messing around with 3d printing gantry pieces and worrying about how true EMT conduit is.. I'm just seeking some guidance on if I'm headed down the right road with this or not.. Dynamic and situational question, I know.. I understand I'm facing some deflection with this thing at this scale.. How concerned I should or should not be based on my uses is another conversation I suppose. My work surface doesn't need to be the full 2500mm wide. Ideally I want to get just about 50" X 98" as some of the higher end MDF's and plywoods I use come an inch or so oversized. Thanks in advance for any and all input on this as I move forward. This is a great resource you have all assembled here.
It's hard to visualize what you are asking without some design schematics.. you should post those if you have them.. if you don't, you should make some because you cannot really get a decent build without some sort of preplanned design.
Another build you might take a look at would be Prototype Rack-n-Pinion 4'x8' | OpenBuilds. While the rack and pinion may be beyond your scope it does show good table integration. A similar approach could be done with the OpenBuilds Modular Table Series - OpenBuilds Part Store but the stock tables will require significant customization. As for power transmission, for an 8' table with belts you will probably want to go with 12mm to 15mm wide belts for the Y-axis to reduce problems with stretch.
Once I read your comment it felt so obvious that I should have had a drawing ready to go along with the post. As I’m sure you would guess, as I drew the machine a lot changed while I figured out what fits and what doesn’t.. Pretty much a table built from the 6020 v-slot, sistering a 8020 v slot rail to the bench on either side for the Y axis, and utilizing the NEMA 23 belt and pinion actuator assembly for the Y. The additional height of the 8020 will be left proud of the 6020 rails they are attached to. From there you will see I pretty closely mirrored the 1515 gantry assembly. Looking at it, it feels like overkill and almost like it would add weight that is unnecessary for my application. Part of me is debating cutting that Z axis actuator (250 mm out of the box) down to only what I really need to save some weight and going with the single C beam gantry. The only concerning part of the design to me is where all the weight of the double gantry attaches to the plates on the Y with the belt and pinion.. it just doesn’t feel right. Some of the brackets and caps you see I plan on 3D printing from NylonX, for now at least. There are some missing pieces here as I could only find some of the newer parts in SketchUp file format, I could not for the life of me figure out how to convert to a step file. The table corner brackets, the 1500mm c beam tension assembly, etc.. I just used a normal c beam assembly, changed the plates and extruded it out to 1500 mm. I also didn’t bring this to the point of every nut and bolt. Just trying to get a high level direction of where I’m going. Open to input and suggestions - thanks!
