First Build 5 x 12 Steel Frame CNC router

[Scott Damman]

First I would like to say the information here is amazing and has greatly helped my design and learning for this CNC router build.

Objectives,

5 foot by at least 10 ft of machining area
Z height high enough for paddleboard foam blanks ~ need roughly 12 inches under the tool
ability to machine wood, aluminum, foam
good accuracy/precision (still trying to figure out where I want/need to be)
Vacuum hold down


Parts I already have
Linear rails - INA 25mm 4 row linear rails - I have enough to do all axis's and enough bearings
Y axis ballscrew - 10mm/rev rolled ballscrew
1850 oz/in stepper motors - 2 for X (long axis) and 1 for Y
2 4hp regenerative vacuum blowers
Colombo 10hp spindle with ISO30 ATC

I will start out where I am now and then go into some questions I have.

The gantry legs mock-up 4 x6 x 1/4wall box tubing, 1/2 inch plate for the feet.






Gantry partially welded up, Gantry is built from 4in x 6in x 1/4in wall box tubing and will get blocking in between the 2 tubing with some vertical bracing on the back. I machined the ends of the gantry before welding them up so I can put an e-stop on each end. The ballscrew is laying ontop of the gantry and will live between the 2 box tubing when complete.



Here is the plan for the Z axis, made from 3in x 6in x 1/4wall box as a starting point. I plan to make an A axis and have mounted the motor up and off to the side. Although this could still get in the way. Should I put the motor for the A axis above the spindle motor? This will make the HTD belt 20 inches center to center. If I did that would I be looking for trouble as far as belt stretch is concerned?




Heres what I was thinking for A axis


A few questions,
Gantry and Z axis is going to be ~550lbs (~250kg), am I shooting myself in the foot using steppers for this weight? I would like to get decent speed out of the thing without the risk of missing steps. When I purchased the steppers I was trying to balance cost but now im worried I will have trouble with it when im done.

What pitch should I shoot for on the Z axis screw? I was planning on using the stepper motor with a ~4:1 reduction. Total travel as it stands right now will be 16 inches. Weight of Z with Spindle will be around 100lbs should I add spring assist to this? or air springs etc?

Next steps for me,

I am working on mounting the rails on the Y Axis and getting prepped for pouring epoxy as soon as the temp rises a bit. Here is the plan for the pour and looking for any insight.

Lay gantry on its back
Level with starrett precision level as close as I can in both planes
pour epoxy for Y axis linear slides
at the same time pour the mount pads for the Y Axis ballscrew, in my mind this gets the ballscrew on the same plane (albeit at a different height) as the linear rails
Paint Gantry
Mount the lower linear rail for the Y Axis
Flip gantry upside down
Use precision level on the linear rail and set rail level and also use a precision square and the level to level in the other plane
Pour expoxy on gantry feet (my thinking here is that I can then get the gantry feet 90 deg to the Y axis linear rails and also on the same plane as the linear rails) I would assume there may be some slight shimming still but the epoxy will be close.


Thanks
Scott

[Scott Damman]

Some updates on the gantry

All of the bracing clamped in place ready for spot welding. The ballscrew is in place to set the distance between mounts.




Here is one of ballscrew mounts




this is the end of the gantry showing the space for the estop


This is one of the longer braces that connect to the ballscrew mount block




Here is the backside with all the bracing welded up


And the front side, notice I drilled some 1/2 in holes on the wrong side. My linear rails are threaded from the backside so I have to through drill from the back. The good news is I am welding on 3/8 plate (I drilled the holes to the correct spacing on the mill first and used the 3/8 plates as templates) on the front side where the linear rails are going to mount.

[sinnsvak]

Very impressed, with a lot of things. Very excited about your A-axis, sometimes one should just go to ahead and build it instead of pondering if it will work or not :D I have not attempted to build it yet, as I dont even have an idea of how I would use it. I really have no clue how one would incorporate 4 axis programming.

I would probably fit the widest possible belt there, if I were to use belt, you want the spindle to be rigid enough. What kind of bearings, if that is how you are pivoting the A-axis? Got any detailed view of it?

Nice work so far.

[Scott Damman]

What kind of bearings, if that is how you are pivoting the A-axis? Got any detailed view of it?

Nice work so far.

Thanks for the comments

Heres a view of the bottom of the Z axis and a section cut into it.




**sorry the drawings are upside down**


Here is the box tubing removed

The bearings are roller bearings that I can get from McMaster Carr easily. 1 1/4 diameter shaft. Bearings are designed to be held into aluminum housings bolted into the 3 x6 steel tubing. The shaft is a 6 inch threaded on both ends. Again something I can just order from McMaster. The bolts into the shaft allow me to put preload into the bearings. I was thinking of bolting the pulley hub (pulley is not pictured) to the spindle mount.

Open to thoughts on this design. I think it will work....

[Scott Damman]

A couple more updates sorry for the bad pictures
Drilled backside holes out to 1/2 inch to allow bolt and ratchet to be put through from the back. Im thinking I will just order a bunch of plastic plugs to put into these holes once I am done.



I threw a couple bolts into one of the linear rails just to see how things were coming together.



So far I am pretty happy with how the build is coming together. Time will tell if I have some precision/accuracy when im done...

Here is a ~bad video of me test running the used colombo 10hp ATC spindle that I got. Running it at ~18,000rpm after running at ~8,000rpm for 10 mins to get the grease moving in the bearings.

[Boyan Silyavski]

Very ambitious for a first build.

Some thoughts:

-the gantry legs dont seem adequate for the rest of the parts you will use on your machine

-the A may work for foam but i dont see it serious for anything more than wood

-the stepper motors , ok- the huge stepper motors, what drives will power them? 230VAC?

-that bracing may be was totally unnecessary. I dont see how that will strengthen anything. It could even make things worse, strengthening one point too much and not allowing the forces to spread uniformly and creating pressure points. So later all rings.


What will you be using this machine for? Remember- the weakest point is the criteria for how strong your machine would be. Again-the gantry legs.


PS:
That gantry legs will greatly benefit from bolting or welding on them 10mm steel plates in both directions, 2 per leg in total