Hi

Inspired by the many much more talented members of this forum I'd thought that I'd share our build progress. First I've got to thank a couple of people that got me over the paralysis of the comfuser and electronics side of the build. So special thanks to massajamesb and darrencnc to get to this point. And I'll say this build was inspired by yohudi and cncfoams build logs.

Background info...I'm a pretty accomplished woodbutcher, millwork and cabinetmaker with a fully equiped woodshop. I've got a mill and a southbend lathe as well, although I'm not as good in metals as I do in wood. Obviously everyone wants a 4x8 for lets say 2k, why not dream right. Well, I've been accumulating (ie. ebaying for about 6-8mo.) and that buget wasnt realistic, ha. So after getting parts and redesigning etc I settled on a compromise of sorts. Keep reading...anyway if one had an unlimited budget then you woundn't build it yourself and it seems everything is a compromise of sort. Speed, accuracy, and dollars...although three are a compromise of sorts.

So, even though I've got a couple of thk 25mm rails and ball screw to give a 5x5 table, I scaled back the design. The dimension were dictated by the linear rails that were ebay find. So for a x-axis with 49" rail the cutting area will be alittle less than 40 and the y-axis if running on 39" rail and will give 29" . So in effect this is only a 2x3 with 8-10" of z..thats ok...the project started over budget anyway. The gantry will be the long axis and will be drive with slaved steppers, to test for strength when/if a larger machine is built. The rails are 15mmthk rails and the z is a thk linear actuator. I compromised and chose 1/2" 8-2start acme drives screw with dumpster antibacklash nuts, based on reading for months now this should be fine as far as speed and accuracy and its a really easy upgrade to nooks should that be necessary, but I figured that 300 saving should go towards electronics. I bought the keling 4-495 steppers with the 4030 kit, after disscussions with a few people the power supply will be upgraded but I haven't done much with the kit yet--hopefully this week will get alittle time to setup mach and do a motor test.

With the help of my brother (M.E. and resident cad driver) we settled on a design, I'll post it as soon as I figure that part out. Did I mention that I was computer and electronics challenged. About 300lbs of 80/20 ordered and another 40lbs of ally block stock also ordered. I cleaned out another ebayer's supply of double tee nuts and brackets. The extrusion stock was a good deal, they obviously make their money on the mounting plates....ooouch! 12 double tee-nuts for 9buck, doesn't seem like alot until you need 300 of them. Like I said we're already over budget, oh well, spend it while you got it. I'll digress here, my dad runs a stamping and fab outfit...we did alittle brainstorming and with some simple tooling we thought about making a run of 10-20K double tee nuts up and putting them up for sale for a round 0.50 with a price break in quantity. But gotta get the router running first. Other lessen, order any cap screws in quantities from enco or other online vender vs using a local store. With free shipping you get 3-4 boxes vs the price of one at the box stores.

This last weekend we fabed the table and made the rail mounting brackets and gantry mounting brackets. The nonferrous metal blade in my chopsaw cut thru the extrusion and left a polished finish, highly recommend the $50freud from amazon, cuts were pretty accurate in all but the 3030 material and that cut left a low corner on one side that I think was caused by the miminal set in the teeth. We only got one side of the gantry trucks, mounting blocks and uprights though before we called it a day and pics will follow next week. All I can say is smooth sliding...like butter. Pics are still in my camera at the shop so stayed tuned.

Brian

Cool deal! I think 8020 is the way to go for these machines (obviously I'm biased, since mine is made out of it). It's easy to get it relatively straight and square, and adjusting yhe drive axes is a breeze with the T-slots.

I'd be down for some inexpensive double T-nuts (and connecting plates!) if you start selling them. Let's see some pictures of your build!

Ahren
www.cncrouterparts.com

Yea,
Welding steel wasn't an option and the frame with >450lbs is rock solid. Not sure that even an really overbuilt wood table is that stiff. Plus I'll have a place to store short cutoffs and that weight should keep the table from moving on the floor.

BG

Brian, You can buy and make you own t-slots from the blanks that they sell on 80/20's website. They come in 12" sections which is kinda short. I didnt even cut them I just drilled the holes where I needed them to attach my rail. I believe they cost 2.50 a piece plus shipping. You can also use lag bolts to attach things to 80/20. the sqaure part of the bolt fits into the rail nicely and it will stop them from twisting while tightening the bolts.

The solid undrilled pcs are $5/ft from the 80/20garage sale and I got 14' to mount the rails and the rail mounting plate to the 80/20. Yea, I have some cold rolled 1/8 but it was too wide and I figure I'd spend all weekend cutting and grinding just to make the tee nuts and I'd rather spend my time building the other assemblies. While I consider my time free for this project you'd have to complete this is about 3 hours @20/hr to break even. We cut them down and drilled at 4"OC and tapped them for countersunk 1/4-20 screws. The rail mounting plate is 0.5" x 1.5" and is also drilled and tapped for the m3 screw 60mm OC to mount the rails. The THK hsr 15 rails aren't much wider than the t-slot and I thought that the flange would be too weak to support everything hence the mounting plate. The rails have hardly any adjustment (ie no slop) so I may have to overbore the 1/4-20 through holes to allow for some lateral adjustment, I've only mounted one and the gantry isn't tied together yet so I don't know how parallel the rails are at this point. That's the $20 question to be answered this weekend.

Quick note on the rails, I did alittle research before mounting on the rails and bearings. Everyone seems to think that the 25mm rails (higher ebay prices)are the ones to get and after I got the 15mm rails I thought the same thing. They look tiny compared to 25mm rails A quick check shows that these will support 750lbs side mounted and 1500lbs top mounted per bearing. Now thats a force not just total weight, my brothers the ME so in his opinion these should be overkill for a wood router. The cutting forces are relatively small compared to machining metal.

Regnar, thanks for the heads up on the lags, didn't think about that.

"Everyone seems to think that the 25mm rails (higher ebay prices)are the ones to get and after I got the 15mm rails I thought the same thing"

I ended up doing 15mm rails and got 4 31.5" rails with 8 blocks for $120 and two 13.5 rails and 4 blocks for $25 so all in all 145.00 plus shipping for linear rails. If I figure in all the skate bearings and time, angle pieces there really isnt much of a savings in the end. I am still collecting parts for the new build. I have a 3/4 by 6"x48" and a 1.5x1.5x18" piece in the mail. I should start building the new machine soon. So maybe we can share a few ideals.

Don't just look at the load ratings for the bearings. This is unlikely to be the limiting factor -- you could park a car on top of some of these bearings. The moment ratings are the real killers. A long, cantilevered Z or a tall gantry can cause trouble, so make sure to check out the moment loads before going too far with your design.

Ahren, I wont lie to you I had to look up what you where talking about. Now I can see where this would be a great concern if you only used one bearing. But some of the motions would be almost impossible to achieve if you make a rigid square machine. If and what most people do is mount 4 blocks to a solid piece. By doing this you have limited your directional axis to 6 directions 2 of which are the direction of the rail. The other 4 are your loading directions.

I would also like to point out that this is initial load ratings. Once the bearings are rolling with a load the numbers no longer in effect. So it takes 82lbs for INA 25mm and 12lbs for a 15mm to receive 1/10000 permanent deformation in a ball ball bearing. With either weight I don't think you would want to put 12lbs instant of pressure on the router bit.

Now with ramping, acceleration, spindle speed and a solid machine with all 4 bolts attached to each bearing I don't see where those MX MY MZ numbers would come into effect.

I by far do not know it all hell I just read it 20 minutes ago so if you could give a few sites or examples of where these number would come into play please send us in the right direction.