[denzil]

Hello everyone,

I am very new to this cnc stuff but the bug has bitten and i want one. Just hope the missus doesn't kill me when we are struggling to pay next months mortgage (chair).

First of all can i take this opportunity to thank SPALM for his helpful feedback via PM. http://www.cnczone.com/forums/showthread.php?t=15270

I am looking to build my first router and am thinking of using vgroove wheels for all three axis. I am thinking of using angle iron runners for the x and y and guide rail for the z. The z axis will have 4 wheels (2 each side). For the x and y i am thinking of using 3 wheels as per attached sketch. Could any of you wise folk out there tell me if this 3 wheel setup will work effectively.

Cheers,

Steve

[wcarrothers]

You should take a look at my thread in this area with my 4x8' router pics. http://www.cnczone.com/forums/showthread.php?t=24582

I'm doing vgrove bearings. Only thing about a 3 wheeled design I could suggest is you should figure where the stagered 3rd wheel (on the bottom) should be in relation to the weight of Z wanting to twist the gantry... (ie you could not have the 3rd wheel directly under either of the other 2 although to far back or forward could cause one of the upper to jump. in my mind) Course weight of the gantry could keep that from happening anyway..


Check out my pics. Also have some ideas of how to hole the bearings and do the adjustments of them..

b.

[denzil]

Thanks b, I hear what you are saying about positioning the third wheel in just the right place. From an adjustment point of view the three wheel triangle seems to make sense but at the same time i can see that 3 wheels can cause too many variables. I will play safe and go for 4 wheels.

I like how you have used box section for your runners.

Steve

[project5k]

one other thing to think about would be how far apart the 2 upper whele are in relation to how far down the bottom wheel is... just as a source of head scratching.. you might wanna look at www.jpcustomcrafts.com/shopmachines.htm its just a little something that i drew up when i was originally planning to go with a 4x8 machine...

my plan was to use small block chevy valve springs to "load" the upper rollers, but if something bad happened, that maby they could flex and not really tear something up.. but i have no idea if they might give too much under a normal load, maby sometime i'll have a chance to build a prototype and try it out...

[wcarrothers]

Proj has a point about the 3 and the torque generated by rotation force (sorta like I was saying).. I went with 4 because it "looked" righter to me with the idea in my head.

My machine is for the most part almost driect out of my head out side of a few thoughts on paper.. Just the way I do things.

Trying to slow my self down so I don' thave to redo to much although the UPS guy also has had his hand in helping with that for this project

b


b.

[project5k]

yea good ole men in brown.. have you seen thier latest debokle??
www.jpcustomcrafts.com/badshipping.htm
its all cool now.. i really have to praise my seller for taking care of me so fast...as soon as i emailed him, he replied, and shipped me replacements.. i actually had 6 motors in my house for about 5 min... the ups dood brought the replacements and picked up the destroied ones all in the same trip...
they sure can put a damper on that "christmas" feeling you get when you see a package on your front porch... my story tells it all...

but anyway, back on topic... i would be afraid that 3 rollers would allow the gantry to cant forard and aft while under a cutting load.. while i can definately see some advantages of having fewer rollers... i would personally prefer the stability insurance of having 4 per side... just my take on it tho.. im sure that theres someone out there that has a machine thats running 3/side, and is just cutting up a storm with no problems...

[denzil]

Thanks for the input guys. I will use 4 per side. Got some bits coming in the post so should be able to get going soon.

[project5k]

keep us posted, and if you can include pictures.. even if thier not good quality, thier better than none

[Normsthename]

Only problem I can see using angle iron is that it is not very hard, and I am sure that it will wear quite rapidly.

Andy

[wcarrothers1]

I agree and gave that some though (about it wearing) but after the iron bearings wear them selves some nice smooth seats I'm going to bet the wear after inital break in if you want to call it that would be minimal.

Becides at least with using the box tube I'm using I could always weld on a layer of angle iron to give a new surface. Figure I could do that at least once before needing to replace the rail if it came down to that. Although I hope that does not happen in my lifetime..

b.

[svenakela]

I'm a bit negative to angle iron, not because of the softness and wear but because it's not straight enough. I'm building a bigger machine at the moment and could only find THK rails for two of the axis at a good price so I decided to make my own rails for the third (it's pretty long...).

So, I made some prototypes from angle iron. The design works very well and can take massive loads, but I found out that they weren't paralell. So now I'm making a new pair from steel plates and will mount them together with screws instead.

So my conclusion is, make sure you get quality angle iron.

[denzil]

My wheels have arrived and my motors will be arriving on Tueday so i will soon have to pull my finger out and get building. My biggest problem now is deciding how big to make this thing. Motors are 200 oz. There will be two motors on the x axis (1 each side) . I would like to go for a size of 3ft x 4ft. Am i being a bit ambitious here ??

Steve

[project5k]

its a big machine to start with, but i started with a 3x3 usable for my first, and so far i'm really happy... just make sure to take your time and make sure that everything is dead straight, level, and plumb, or you'll have nothing but nightmares later on... measure, measure, think, measure, cut, measure, weld, measure, measure, measure! i think that you will be happy going with the twin screws on your x... it will greatly reduce the possibility of gantry racking...