[Sil_x]

I decided to build up a 4th axis for my table router. I have a new R8 spindle from an x2 machine laying around and I have always wanted to try the epoxy granite idea

Step 1: build mold box
I have plenty of solid surface counter top laying around. It has a pretty good finish and releases from epoxy decently with wax mold release.

Step 2: Prepare the spindle.
I am going to use 3 bearings, 2 are going to float in the epoxy and one in inside a aluminum shell for support. I did this because it was what I had available at the time. I would have preferred to press all of the bearings in an aluminum shell but at least this will show how good epoxy granite supports a bearing. I used foil tape to prevent the epoxy from getting into the bearings. The pictures show the fronts of the bearings open but I sealed them with foil tape also

[Sil_x]

Step 3: assemble the mold
Pretty simple, I drilled and tapped my cutouts. Before assembling it is a good time to wax and apply mold release. As an after thought I added bolts for mounting the axis when it is complete

Step 4:Seal everything
In case there were any leaks I used modeling clay and sealed up around everything including around the bolts and on the ends around the spindle.

[Sil_x]

Step 5: Mix epoxy and aggregate
I needed about 64 ounces to fill my mold. Here is what I used
1/2 inch pea gravel: 48 oz
80 grit glass blasting medium:16 oz
Grog Mulcoa 20 mesh(ground up recycled ceramic media): 16 oz
Ultra blue dry tempura paint for color: ~1 oz
2 part epoxy : ~17 ounces

Slowly pore dry into liquid and mix until uniform. If you have the equipment, its a good time to de-air and vacuum the mix.

Step 6: poor and vibrate.
Always fill from the lowest spot and then shake or tap or vibrate until your arms turn to rubber and then keep going. My mix was very thick so I added a top coat of epoxy and glass bead for leveling purpose. I was 115 in my garage today so in 6 hours the epoxy was fully cured.

Step 7: De-mold
If you waxed enough and used mold release this shouldn't be a problem. I should have used more on the 3/8 -6 long bolts I uses so they were definitely difficult to remove. Clean up any holes or deformations.

[Sil_x]

A real quick test of the spindle with a Kollmorgen servo disc gear motor attached, I am not completely sold on the gear motor since there is a tiny amount of backlash

[ame=http://www.youtube.com/watch?v=d6uISGio5Xc]4th axis cnc test - YouTube[/ame]

I still need to build the mounting bracket and mount it to my router but that's all for now.

[Drools]

subscribed

[Sil_x]

I started working on the tail stock today.

I lathed out a mt2 quill out of alloy steel and I decided to use an scrap aluminum rectangle tubing to contain the tail stock. My process was pretty much the same except for my quantities of grog and glass were way high and my epoxy was pretty much needed to be trowed in. It will be interesting to see how well it performs.

[Sil_x]

Here is the finished tail stock. The quill extents and contracts by turning the bolt on the end. Any questions, comments, improvements?

[RomanLini]

I'll comment!

It's very clever of you using an easily worked metal form, especially one that gives nice straight 90 degree sides, then just filling it with EG.

And I like your cobalt blue colour!

[slowlearner]

Who is your supplier for the epoxy?

[Sil_x]

I am using the US composite thin epoxy, medium set speed. I read somewhere that it wasn't the greatest for EG but I haven't seen anything to complain about yet.

[Sil_x]

I have the axis mounted to my machine on the B axis. I am using 80/20 rails to allow me to adjust the tail stock position. There are a few more things I need to adjust like my motor mounting, a good method for workpiece holding, and basic tramming.

Here is a vid of me goofing off with an oak log.
[ame=http://www.youtube.com/watch?v=yImY2eFdybc&fmt=22]4 Axis Test oak log - YouTube[/ame]

[Sil_x]

I decided that the backlash on the servo gear motor was unacceptable to I decided to build a worm gearbox. I started out hobbing a pvc gear blank with a tap I made. Next I casted it in urethane rubber to make a mold. After that I made a aluminum hub and casted a mix of urethane castable plastic and a 10% urethane rubber to make a semi-rigid worm gear. I used a piece of 3/4-6 acme screw to make the worm and lathed it to fit bearings. Using 1x2 inch aluminum bar, I cut and bore holes for the bearings.

[Sil_x]

To build the base of the worm gear box i used 1/4 inch aluminum plate and cut, drilled, and tapped everything. I am using the a set screw at the end of the acme screw to manage backlash and to provide the clamping force retaining the bearings. After a few test fits I was able to get everything mounted properly. I used the same 1x2 aluminum bar to make a motor mount for the servo motor.

So far I can not detect any backlash on this setup and I am not worried about the semi-rigid plastic failing. I have been using this same plastic combination as the pinions for my leadscrew/rack-n-pinion linear motion on my x axis for the last 6 months. (http://www.cnczone.com/forums/linear...screw_r_p.html)

[Walky]

Nice! This thread just keeps getting better. That last picture is amazing.

[Sil_x]

I just did the math for the resolution on this axis:

The worm gear has 75 teeth so

75 /360 = 4.8 deg/worm revolution

Motor has 4000 pulses per revolution

4000ppr / 4.8 deg/worm revolution = 833.3333 pulses/ deg

360 deg/worm revolution * 833.3333 pulses/deg = 300000 pulses/ worm revolution or 0.0012 resolution

I Like

[Drools]

great work. I have been wanting a rotary axis for some time. I don't suppose you have a build log? I have seen a little of the hobbing process when I researched the RepRap, it looks like the gears might be made on a RepRap if the tolerances could be kept in check.

[Sil_x]

Drools: Sorry no build blog, everything I have is posted on Cnczone. Using the reprap or other FDM technology would be a good way to make the worm gear, although if I had one I would use it to make the blank, then mold over that and cast worm gear with stronger material.

I'm working on making something with this 4th axis so I will post a video when I am done.

[slowlearner]

This is what I call thinking outside the box . Great job!

[Sil_x]

Nothing using the 4th axis yet but here is a time lapse of testing the 4th axis for rigidity on a 3d cut
[ame=http://www.youtube.com/watch?v=sHLzTwcpvvc]CNC 3d cut time lapse - YouTube[/ame]

[brihoo2k]

Very nice. I like how you casted your own gear. May I ask what sort of projects you plan to do with it?