David A's New 2x3 Bench Top CNC

[davida1234]

Assembling the X-Carriage:

Install one side plate to the lower plate using the standard 8MM screws for the pillow blocks:


And then the other side plate:


And finish the frame with the lower plate:


Side view:


And for demonstration, the X-brace on the back:




You are welcome to utilize any parts of the design for your personal use.
Please contact me for commercial applications.

[davida1234]

With the X-Carriage assembled, the Z-Slide can be inserted:


Back views:






You are welcome to utilize any parts of the design for your personal use.
Please contact me for commercial applications.

[wmgeorge]

Hi wmgeorge, do you mean the machine frame's side rails or the x-carriage side plates?

The spindle is the standard Chinese 80MM 2.2kW spindle.

Your side rails with the linear rails on for the Y. They are very high off the frame and not that wide. Most machines have 3 or 4 inch wide rails and are much lower as this one. http://www.cncrouterparts.com/images...4_Base_800.jpg

My Saturn 2 from FLA has 3 inch square steel welded.

Or this one from Camaster https://www.camaster.com/wp-content/.../Stinger-I.jpg

[davida1234]

Thanks for the input. The Saturn is one of my all time favorite designs and, admittedly, was a starting point for my design. I did the side rails with 3030s first and still have them. But the machine being a test mule, also built the thinner ones with 1530s, thinking that the 3030 looked so massive. Want to explore if the thinner frame will support the side loads. If I get any flexing or twisting, I will revert to the 3030 frames.

[wmgeorge]

I would go back to the 30x30 now because once you get it running it will be so much fun you will not want to redo then, I have cut and routed some 1/2 and 3/4 MDF and besides being dirty its tough but it carves so nice. I have done 2 inch thick walnut live edge slabs and it takes all the Hp I have to get it turned into a nice planed finish. I have a decent dust collector and would not cut without it with the MDF.

The rest of the machine looks very nice!

[davida1234]

Just trying it out (with no oil yet in the ball bushings):

[davida1234]

wmgeorge, thank you for your encouragement. The machine is already 3/4 built and I built it for testing. The thin side walls are built with a shear panel inside which is permanently attached with ss anchors and FRP in the channels. I want to particularly test how they will perform as it will reduce the width by 3".

I will need all the help I can get from you and everybody else with the electrical and setup because that's where I am pretty clueless.

[davida1234]

With the X-Axis and Z-Slide finished, it's time to put that assembly on the gantry!

Just move the setup over the gantry linear rails:


Attach loosely onto the top rail blocks:


Install the proximity sensor. There is provision for another sensor if needed:


Attach the lower plate to bottom rail blocks as well.

X-Carriage and Z-Slide is on the gantry!

[davida1234]

With the main assemblies of the machine mostly finished, time to move onto the details.

First, the weight of the Z-Slide will be balanced with springs to provide an equilibrium.

I use four small springs. Unfortunately, I could not source SS springs with the required properties:


Slip two of them onto the 3/16 spring pin and drop in place:




That's how it looks like from the side:

[davida1234]

Next, bend a small hook at one end of a 12ga wire and push it up from the bottom:


Catch the loop of the inside spring:


Pull down the spring and place it onto the inside position of the spindle mount bar:

[davida1234]

Pull down the same way the second spring:


And place it on the outside position of the bar:


Repeat the same on the other side for the remaining two springs.

The four springs balance the weight of the Z-Slide and the spindle nicely at about half way of the Z travel.
If equipment weight changes, there are simple spacers that can be placed under the top pin:

[wmgeorge]

So you not only lifting the weight of the spindle, but that massive mount for it and the those heavy steel round bars. A lot of extra weight compared to others of the same size.

[davida1234]

Good point wmgeorge. The complete setup with everything including spindle, weighs about 25 pounds.

I don't know how that would compare to a conventional, fairly heavy duty Z-slide, with the linear rail part,
the spindle mount, the extension plate which usually is necessary, screws/bolts, spindle, etc.


Also, please note that the mount provides a full 4" of spindle clamp height for a firm hold of the spindle
body which very few mounts would provide, I would think.

[davida1234]

Another point I would like to make is the leverage on the Z-Slide.

From what I saw on conventional Z-slides, the spacing of bearing points of the
Z-axis are usually fairly close to each other to provide for max. vertical movement,
thus creating a large cantilever of the Z-slide.

On this layout, the bearing points are much farther apart, with the spacing
of bearing points being larger than the cantilever distance (B) even at the
bottom of travel:


The point I am trying to make is that this is a test mule where this new layout
has nothing proved yet. Right now, the shafts are 30MM. Once I get to the
cutting phase, maybe it turns out that the shafts are over sized, maybe 25MM
or even 20MM would be sufficient which would reduce the weight even further.

[wmgeorge]

I do a lot of 2.5 D work and V Carving. I also cut MDF board so I need speed on the Z for one yet heavy duty for the other. I have a NEMA 34 motor driving the Ball screw and running on linear rails. My Z is maybe 10-15 Lbs. I have the speed for the carving, and durability for the MDF.

[davida1234]

That's great info, thank you. The servo I have is a lower power Teknic.

[wmgeorge]

On your drawing above you show both A & B having the same direction of force. Actually when cutting or engraving but not so much, a twisting action force is present, on the Z carriage which is transferred to the gantry as well. Perhaps thats the reason most builders are using the flat linear rail and bearings?

[davida1234]

wmgeorge, of course you are correct and have a keen eye. The upper blue arrow is actually the other way and the lower blue arrow is almost the fulcrum. This was more to show the spacing of the two bearing points (A) relative to the distance (B) of the cutting force and the two blue arrows opposing the cutting force looked more descriptive to me.

I have to be more careful next time I paste a quick sketch!

[mactec54]

wmgeorge, of course you are correct and have a keen eye. The upper blue arrow is actually the other way and the lower blue arrow is almost the fulcrum. This was more to show the spacing of the two bearing points (A) relative to the distance (B) of the cutting force and the two blue arrows opposing the cutting force looked more descriptive to me.

I have to be more careful next time I paste a quick sketch!

You are on the right track the design is good I have a similar but quite different design same idea and principle just waiting for a patent on the design before I show it here

[davida1234]

Thank you for the encouragement mactec54. This prototype was planned to have a
slightly different approach to some of the conditions on a conventional CNC.