[Phife]

Our maintenance person will probably do the welding. I'm afraid it might break the budget if we had to have it outsourced.

By the way, here is what I have so far. I still need to do some tweaking but if you have any comments please feel free. It's getting late hear, so I will work on it some more tomorrow.

You will need to have a flat surface to mount your rails on, you will not have a flat enough surface from the square tube, especially after welding. you may want to look into that. Your Y axis should be ok if you get some nice flat plate, the X will probably be off a bit. Maybe you could shim up the low spots.

Also, I would probably add an additional leg in the center of the long span. You dont want that to sag, although its probably strong enough.

And I'd still try to redesign the Y/Z carriage, I dont like how the Z hangs out like that, have you looked into moving the Y rails to the backside and building a box around the Y beams? or even mounting your Y rails on the top and bottom of the Y beams. Either one could bring that spindle in closer. just my opinion.

Looks great though, it should turn out pretty solid.

[HereinCS]

Is square tubing not flat? What would you use?

[Phife]

Nope, usually close, but it will have variations, its not even 100% most of the time, at least in my experience.

If it was me, I would weld on an additional 1/2"-1" steel bar onto the side of the square tube that I want to mount my rails to, then have it machined flat.

But you can get away with alot if you pay around with filling gaps with epoxy, and shiming spots, it all just depends on how much time and money you want to spend getting the accuracy you wish to achieve.

Have a look at madvac's cnc for some great info on joining steel tube and epoxy filling. http://oneoceankayaks.com/madvac/machine_frame.htm

[CtrlZ]

@Phife, Thanks for the tips. One of the things I planned on doing is redesigning the uprights to bring the spindle closer to center. The table is long enough now so there is enough travel, but the spindle cantilevers out too far so it doesn't quiet reach the edge of the plywood at the opposite end.

For the surface of the square tubing where the X rails mount I was planning on probably just grinding a narrow strip along the surface of the square tube itself. Is that a bad idea? I don't mind the idea of shimming, it doesn't have to be super accurate since we are dealing with woodworking tolerances. I guess in my opinion at this point, there are enough options with your suggestions that I can decide later what to do.

[eloid]

few issues I improved on long on x axis short up the gantry z brace as seen in my crude red line draw this will short lenth of table ( you may want a middle leg) also I advance you bear mount to be under the vertical gantry support as see my the green arrows ...advancing the bearring will counter some of the rotation forces created from the spindle, but still allowing for a wider stance on the gantry support ,direct down on the bearings but reducing table length also.

also your gantry top support may clash with the rack on your x axis must be lower this maked for simpler design, but you need a way to support the motor
and gear box to mesh into you r/p

[CtrlZ]

I have one question before I redesign the gantry. Is it ok to use direct drive for the R/P? I've seen it done before but I'm not sure if it's a good idea or not. If I used direct drive with the ball screws I was going to use spider couplings to dampen the vibration, but I don't know how to accomplish that if I go direct drive with the R/P.

Thanks

[advt001]

I can understand if you start to feel a little frustrated with the design issues.I do thank you though because I am learning with you.When you first posted your design I thought it looked good but little do I know. I spend a lot of free time here learning about building machines and one day will build one myself

Thanks again,
Scott

[eloid]

I have one question before I redesign the gantry. Is it ok to use direct drive for the R/P? I've seen it done before but I'm not sure if it's a good idea or not. If I used direct drive with the ball screws I was going to use spider couplings to dampen the vibration, but I don't know how to accomplish that if I go direct drive with the R/P.

Thanks

if your machine is lite duty yes, but i would not recommend it, your gantry is not lite its wide in width and you need torque to push that long z axis and spindle about.. you would need some big ass motors but they have no torque hence the requirment of the gear reduction...

Attached are some idea i have see over time for future build for the x axis r/p also
a idea for your gantry support what nice about the idea the motor are out of the way .... they dont stick out and become a safty hazard if the machine running.

[CtrlZ]

I can understand if you start to feel a little frustrated with the design issues.I do thank you though because I am learning with you.When you first posted your design I thought it looked good but little do I know. I spend a lot of free time here learning about building machines and one day will build one myself

Thanks again,
Scott

Thanks for the comment Scott!

I'm not frustrated at all. I appreciate all the help I'm getting here and I know all of this will be worth it in the end. Now if I was to just start building and end up with something that didn't perform very well, or had serious limitations, that would be frustrating. Don't get me wrong, I would love to get on with the building of the machine, but even though this is my first CNC machine, I'm familiar with the design process in general so I expected to put some time into this.

[CtrlZ]

if your machine is lite duty yes, but i would not recommend it, your gantry is not lite its wide in width and you need torque to push that long z axis and spindle about.. you would need some big ass motors but they have no torque hence the requirment of the gear reduction...

Thanks eloid, I have timing gears and belts with the motors I will be using so I can probably just use those. I will get the specs from the motors and gear ratios next time I'm at the shop. I won't be there tomorrow, so probably the day after, but I think I can proceed with the gantry design now. I can retro fit the motors later.

Thanks

[CtrlZ]

Well, here's where I'm at so far.

I made the changes to the gantry. Now I have the travel from one edge of the plywood to the other, and the X bearings have a little more separation. I like how everything works, but one thing that I don't like are the nasty pinch points created at the limits of the Y axis, at the ends of the gantry, so I think I'll have to make some more changes to the ends of the gantry. Any ideas?

[eloid]

made some notes on the pictures.... hope it helps

[CtrlZ]

Thanks eloid, I like it! I added one additional brace at the bottom.

[eloid]

Thanks eloid, I like it! I added one additional brace at the bottom.

question? will the table be all weld or made to taken apart if you ever need to install or relocate it?
The gantry look good , its Fabrication will be simpler also.

you could make the the plate steel brace on the front of the gantry "taller" and weld it more to the side so it clear your x axis rails?

[CtrlZ]

Thanks eloid, I don't think we need to be able to take the table apart. In the unlikely event we ever move, the router table will be one of the easier machines to move. We could just pick it up from the end with our fork extensions.

you could make the the plate steel brace on the front of the gantry "taller" and weld it more to the side so it clear your x axis rails?

I was thinking this too, but I think it will be good to not have anything in the way if we need to replace the bearings on the bottom rail.

I brought home some servos and components today so I can start working on the drive. I will post some specs later.

[eloid]

Thanks eloid, I don't think we need to be able to take the table apart. In the unlikely event we ever move, the router table will be one of the easier machines to move. We could just pick it up from the end with our fork extensions.



I was thinking this too, but I think it will be good to not have anything in the way if we need to replace the bearings on the bottom rail.

Orginally that what why i suggest it being low pofile knee brace... you could have a side bolt on plate or brace add later if required? the design is very flexiable

I brought home some servos and components today so I can start working on the drive. I will post some specs later.

[CtrlZ]

Ah, I see. Thanks for the tip eloid...and all the help so far.

OK, here's where I show how little I know. Here are the specs on the servos I have and where I plan to use them. I assume they are big enough, have enough torque, or whatever because of the huge wood carving machine we salvaged them from, but other than that, I'm clueless.

I appreciate any advice and I apologize if I didn't give enough info.

[eloid]

Ah, I see. Thanks for the tip eloid...and all the help so far.

OK, here's where I show how little I know. Here are the specs on the servos I have and where I plan to use them. I assume they are big enough, have enough torque, or whatever because of the huge wood carving machine we salvaged them from, but other than that, I'm clueless.

I appreciate any advice and I apologize if I didn't give enough info.

i would use the 7:1 on the x axis long axis and 5:1 on the y

Your x axis is long, idealy you want fast rapids there ie on homing your machine and changing your sheet stock , changes overs etc

your y axis shorter axis shorter so you will not see huge rapids there ( time you get to speed you have slam on brakes to slow down before you hit you limits) z axis could be direct drive with muilt start ball screw?

[CtrlZ]

That makes sense eloid, but I have a couple questions. Bear with my ignorance.

The motors with the 5.5 ratio are much larger motors so that's why I first thought to use them for the X axis. Would I be able to use them for the X and the others for the Y and Z and change the ratios with the timing pulleys?

Also, do I need more rpm for the Z axis since I'm using ball screw for the drive?

[eloid]

That makes sense eloid, but I have a couple questions. Bear with my ignorance.

The motors with the 5.5 ratio are much larger motors so that's why I first thought to use them for the X axis. Would I be able to use them for the X and the others for the Y and Z and change the ratios with the timing pulleys?

just swap out motor if there the same motor fram size or make a adapter plate if you have to... if different size?

Also, do I need more rpm for the Z axis since I'm using ball screw for the drive?

most cases your plug rate will low, not sure what your cutting
5-50 ipm is typical