My NEW Mini CNC Router Design!

[widgitmaster]

This is my 2nd attempt at designing a tight & strong mini Router! The first one used unsupported round rails, and they were way too springy to do anything accurate! So I crunched up a drawing in CAD to incorporate a design which uses supported Thompson rails!

Here is the current design, and the few parts which I have finished so far!

[widgitmaster]

For starters, I made the y-axis support plate, it was machined from solid and has two tracks with .1875 Radius machined in the centers to support the rails.

Each rail has five #6-32 SS SHCS holding the rails in position. The rails were reilled and counterbored using Carbide 4-flute ball end mills, and a flat bottom carbide endmill for the c-bore.

The 1st problem I had was the warpage in the rails when I drilled the holes, they curled up instantly! The problem was solved by drilling the c-bore first, as the larger end mill went through the case hardened skin of the rails easier. Then I drilled the small hole with the ball end mill. The rail was over heating as the ball endmill went through both case hardened skins!

After a little straightening on the surface plate with an indicator and v-blocks, the rails are now ready!

[widgitmaster]

The next part is the y-axis slide block, it will have to be bored to accept two bronze plugs! This block was fun to build, it was interresting to see if I could bore two holes accurate enough to align with the two rails! After the holes were bored, I turned up some bronze plugs in my lathe, and made them .0005 larger than the bores. Then I placed the bloc in boiling water on the stove, while the plugs were in my freezer! After ten minutes, the plugs fell in the block with a slight press.

Then I put the block in the mill and bored the bronze as close to the rail diameter as possible without having them bind while sliding!

The next part of the puzzle was trying to figure out an easy way to add a delrin acme nut to the y-axis slide block! This was bugging me for days, and I had an idea but I kept rejecting it! The idea was to bore a large round intersecting hole through the block, plug it with a chunck of round delrin, then cross drill it and tap it 1/2-10 acme!

Eventually I accepted this idea, but at first all I could think of was the large bore hole in the block, what would I do if it didn't work!
Well, it did work, and the big bore filled with Delrin has lightened the y-axis slide block too!

[widgitmaster]

Next I need to make the supports on the y-axis slide block to hold the z-axis rails! These are 1/4" diameter Thompson rails, and have the same case hardened surfaces!

The tracks were easily machined, and the .1250 Radius was added to center the z-axis rails.

The next thing is to drill and c-bore the small rails to fit five #2-56 SS SHCS!
The procedure was the same, I drilled the c-bores using a carbide endmill, and then drilled the holes using carbide 4-flute ball endmills 3/32" diam.

These rails did not distort as severely as the larger ones, and were quickly straightened!

[pminmo]

wow, looks absolutely great. when you say mini how small? didn't see any dimensions on the drawing.

[widgitmaster]

The next item is the z-axis slide block, it has three 1/8 t-slots to be used for mounting of the spindle! The procedure for making and installing the bronze bushings is the same, and the whole slide block was accomplished in 4-hours!

The z-axis slide is much smaller, so I decided to use a piece of 3/8-10 acme for the lead screw! The delrin nut will be similar, when I decide how its going to be done!

While I made these parts, I made enough for two complete units! These slide units are so precice, there is zero endplay, and zero backlash! They slide frreely enough for an 80 oz/in stepper to move them back and forth!

Eric

[widgitmaster]

Originally Posted by pminmo wow, looks absolutely great. when you say mini how small? didn't see any dimensions on the drawing.

Thanks Pminmo!

The y-axis moves 4.500" and the z-axis moves 2.000"
The x-axis will move around 6.000"

Eric

[widgitmaster]

Next I made some y-axis side plates with the bearings pressed in for the leadscrew. Also has 4 holes for mounting the nema23 stepper!

[widgitmaster]

The x-axis is still using unsupported round rails, because the 1/2 Dia. at 12" length is fairly ridgid!

The x-axis slide block has been completely redone, it now has four SUPER-8 ball bushings!

[widgitmaster]

In order to make the x-axis slide block, I had to order some 7/8" internal spring rings, a special carbide .040 internal grooving tool, and 4- ball bushings for the 1/2" dia thompson shafts.

after I had squared up the block, I bored two 7/8 dia through holes for the ball bushings, then I used the fancy internal grooving tool in my boring head, and turned the spindle by hand! It was easier to cut a .025" deep groove by adjusting the boring head .005 after every revolution! The grooves were cut in a suprisingly short time!

Then I had to make spacers to go between the ball bushings, and everything went together really nicely!

Now I have a smooth sliding x-axis with zero endplay!

[widgitmaster]

I used the same concept for the delrin nut, by simply boring a 2" diameter hole in the center of the slide block, and pressing a solid plug of Delrin in the hole! Then I drilled the cross hole and tapped it 1/2-10 acme!

The leadscrew was turned to the exact distance between bearings, so there is no need to preload, and zero endplay!

[FPV_GTp]

very nice work , will defantly keep a eye on this thread

cheers