Hello. I've been looking at and admiring the builds I see here. I have been looking at building a router table so that I can build new cabinets for my kitchen and bathroom. Two things that would make it more user friendly would be a precision router lift and a precision fence. All of the homemade router lifts I have seen are made from wood which is OK but can cause issues. The router lifts that are available for sale range from $200-$400. They can be precise but wouldn't be able to quickly return to a known bit height after changing bits. So I'd like to design a CNC router lift using V-slot rail. That way when I change bits I can use a piece of copper coated circuit board to return to a known point using conductivity. This is a design I came up with. It is simplified, lacking the drive system and connectors. But should give you some idea of what I would like to accomplish. The router motor is fairly heavy, about 18 pounds. That's just a 2 1/4 HP router. Something over 3 HP would be better yet. So I am thinking about using galvanized aircraft cable to run from the top of the carriage, through a pulley inset into the top of the V-rail, and a counter weight running down the outside. I would do one assembly on each side. That way I can cancel out the weight of the router so the stepper motor doesn't have to work too hard. How much holding power does a stepper motor have? I was thinking about using a Nema 23 with an acme thread to drive it. Is the holding power of it going to be enough to keep the router from moving during operation. The other part of the project is the fence. It can be as simple as a piece of wood clamped to the table. But I would like something with precision and repeatability. Incra makes a fence that fits the bill but it costs $459 bucks. http://www.amazon.com/Incra-LS17WFNCSYS-17-Inch-System-Presses/dp/B0007UQ2CI Plus a CNC system would have added benefits like being able to change positions with the touch of the button when make multiple passes. Normally you would set the fence to one position and run all of your pieces through. The adjust the fence and run them through again and repeat. With CNC I could run all of the passes on one piece and then move to the next piece. So it should save a bit of time. Anyway, here is the basic idea I have rolling around. Two pieces of 20x80 with the bottom piece fixed to the table. A NEMA 23 is mounted to the bottom piece and drives an acme thread rod through the top one. The fence is attached to the top piece. I drew up the front wheels attached to the bottom piece and the back wheels attached to the top piece. That way they would always be as far apart as possible. I'm not sure if that is the best way to go about it or not. I also drew up an idea for making the fence more rigid using 20x20 to triangulate the fence to the 20x80 that it attaches to. And if that doesn't work out I could also add 20x20 to the sides of the table and have wheels attached to the sides of the fence that ride on it. Or I could do both. Anyway, I'd love to hear any suggestions that you may have for this project. This will be my first time working with V-track and stepper motors. So I'm pretty green. But I've played with CNC mills, done some manual G and M coding, and have a technical background. I've got an order in for some v-rail, wheels and misc parts. But they were out of the 20x80 and 20x20 when I ordered. So I've got some stuff to play with in the mean time. ETA - Here is how they relate to each other.
There are a couple of other things I could add to this. A sliding table attached to the front of the router table would be easy to make with the V-track and wheels. This would be very nice for coping the ends of pieces. Festool does this and gets $1625 for their system. http://festools-online.com/p00111-f...t8t1l_gtYVRQrSvTMxQTnO1oxxPOPKxoVQaAmgj8P8HAQ Even neater would be two CNC carriages mounted to the fence. They could be used to clamp a piece of wood (or even aluminum) and could move it back and forth along the fence for a third axis. The belt drive looks promising for that. I could make some very complex parts then. I would need to build it in a way that they could move out of the way of the fence for other operations though. I uploaded the sketchup file if anyone is interested
The lift looks fine. If you are worried about holding power, use a lower pitch thread on the lead screws. As for the fence, you haven't accounted for the bit being largely recessed behind the face of the fence or for providing proper support along the edge at the outfeed side should the bit shave off some of the edge. I would suggest splitting the fence you have shown into two parts, both with back adjustment like you have shown such that both sides of the fence can be adjusted individually. I would also suggest leaving about a 3" gap between the ends of the two fence sections to allow for the largest possible bit you may ever mount and then mounting a set of full height sliders on the face of the fence that you can adjust inward to close the gap around whatever size bit you have installed. It would probably be best these sliders are wood as eventually a bit is going to chew the bottom corners off. Don't forget attachment points for featherboards. The end wheels you have shown on the fence are not really necessary and probably not workable based on no decent way to recess them without the tracks filling with saw dust and binding up the wheels. As far as moving the work through the bit, I really doubt you can do any better than a standard miter sled running in a 3/4" slot. You can probably make something up out of the V-slot but I doubt it will be anywhere near as versatile and usable as a standard miter sled.
I was looking at using 3/8-12 acme threaded rod. I can get it locally. I found 1/4 -3/8 couplings for cheap on eBay. I haven't done the cut in the fence for bit clearance yet. I plan on using one piece of 20x80 with two sliding sacrificial boards that can be pushed into the bit to create zero clearance on the indeed side. If I cut them 60mm wide I will still have access to the top track to attach feather boards. I will also need a tall fence for running panels vertically. In that operation the only feather boards would be attached to the table. For coping I prefer a coping sled that doesn't use the miter slot. I like ones that clamp to the top of the work. It allows you to use it vertically on the tall fence if need be. I'll do more modeling when I receive my rails and stuff.
Acme screws are self locking up to the point where the load is heavy enough to nudge past static friction. Increasing pitch as Rick suggested effectively increases the surface area contact between nut and screw and changes the contact angle. Upping the size of the screw may help as well as nut material. There are quite a few variables to consider. Adding, the more self locking the less efficient. Below is a link to a calculator that'll help determine if you have a self locking setup and what torque is required to lift and lower a load. Leadscrew Torque Calculations for Acme Thread Joe
Aloxite, you have gotten my attention with this. I have a small woodworking shop and want a larger router table but like you said, what you can buy is nice but pricey. I have thought about something similar but not motor driven with a table of my own dimensions and availability for attachments. I will be watching this and maybe I can input something, but so far it looks like you have got it on the right track.
You wont need the support for the fence, since it just has to be a certain dimension from your cutter. If its "angled" it wont effect the cut.
