We run a small shop that makes a product consisting mostly of 6061 aluminum square and rectangular tubing up to 41" long and 2" across. The wall thickness of the material we drill is no more than 1/4". We currently make all our parts using jigs and a drill press, but would like to automate it. I'm considering using a CNC router to speed up and automate the task. We might occassionally use the machine to do some routing, too. A machine built similar to the OX appeals to me because of its cost and its ability to be modded. But I'm concerned about it's precision and long-term accuracy. (The parts we make bolt together, so all the holes have to line up properly.) I've been thinking of making a ~750mm x ~1500 mm OX with the following modifications: 1) Replace the X-axis belts and Z-axis Acme screw with ball screws. 2) Replace the two Y-axis belt drives with a single center drive ball screw. 3) Fasten the two Y-axis rails together with crossmembers spaced about 300 mm apart instead of only joining them on the ends to increase the rigidity of the frame. 4) Replace the standard 5mm guide bearings with ones having a larger ID, specifically some RM2ZZ 3/8" (= 9.5mm) ID bearings. An example is here: RM2ZZ 3/8" V-Groove Guide Shielded Ball Bearings W2 W2ZZ NW2 0.375 inch CNC . I can make new eccentrics using our lathe. 5) Replace the router head with a lower-speed spindle more appropriate for drilling. Any thoughts or recommendations about this? Thanks in advance, -Jim
Hi, my thoughts: Ball screws not automatically meaning better accuracy. Most of the time they are desireable when doing 2,5 d where fast speeds needet for finishing... opposed to trapezodial screws the ball screws have a better efficiency and thus heat up less and the steppers do not need to work as hard. But remember that is when finishing. They do all have a tiny bit of backlash and there is nothing you can do about that. My last cnc used trapezodial screws ( i think that is what you guys call acme - i am from germany..) and did cut aluminum just fine. The holding block can be tightended when needet (hardly ever) and so the screw can be almost free of backlash (depending on construction of block). As for drilling: using a slow kind of router automatically transferes into more torque needet and thus the frame has to withstand those forces... Whynot turn the drilling operation into one of milling using smaller bits .. better suited to the frames stability. I mill my holes all the time.. not need for toolchange Of course the mill has to be tuned in so round will turn out round and not egg shaped... Also to my opinion a faster spinde will give you more possibilities for other milling tasks. Bigger dia bearings is always good. With x being spaced750 appart you are right at the end of what most people recomend for a central/single screw.. The wider you go the more you have to worry about turning the mill into a parallelogram when milling.. make sure your frame and gantry beeing stiff enough.. not sure about 3) crossmembers for spacing them appart? or a crossmember every 30 cm? as always .. just my thinking greets flo
You might take a look at this concept. You'll just need to add length. You'll probably want to size up the side plates to 1/4". As far as X-axis width, if you plan to do a center drive you'll want to keep it as narrow as possible unless you plan to do a parallel wiring scheme to keep it square. As far as item #4), steel wheels are an absolute no-go. They will grind through the aluminum rails in no time. If you can manufacture your own eccentrics, consider an 8mm axle. 8x16x5 bearings that will fit the stock Solid V-wheels or X-treme Solid V-wheels are readily available. You will also need to work up some 8mm(ID) x 1mm shims to fit between the bearings. The main issue here however is the extent you plan to use this machine. These parts are designed for hobby grade systems and if you plan to have this machine in hardcore use you would probably be better off to consider purchasing a more commercially oriented machine.
pls help ! any one knows where can I got v-slot and etc from Germany ? I got this web link from France <http://vslot-europe.com/> but looks no one there...
