Installing the Little CNC Z-Axis

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The new axis is complete, installed and tested - yeah!

Where did I leave off, oh yeah, the spindle mount and linear bearings where built. Next step was to add the actuator to the assembly.

CNC z-axis installation
Using some lighter weight angle aluminum (3/4"x3/4"x1/16"), I constructed risers. A plate across the top holds the bearing through which a threaded rod with a locking nut rests. The stepper is reused from the big CNC in the man-cave (currently awaiting a much needed upgrade). It is a 5V 1A 35oz stepper - adequate, but barely. A spider coupler joins the threaded rod to the stepper, which is held above the bearing plate by 4 threaded rods and a collection of nuts (one more if you include me).

Barely visible near the middle of the bottom cross brace is a screw that extends into the assembly. One of (many) holes nearby complements that screw - together they will push and pull the bottom of the assembly out to provide an adjustment to help square the bit to the table.

CNC z-axis installation

Attaching the threaded rod to the spindle holder was a matter of crimping some of the light gauge aluminum around a 1/4" union and fastening the aluminum to the top of the holder. The better aligned this is with the stepper the faster things can move without binding. I left a fair bit of play in the spider coupler / weight bearing at the top that I am getting a respectable travel rate.

CNC z-axis installation

The whole thing weighs more than the previous design. 2.3 kgs is without the spindle. With the spindle it weighs 2.8kgs, which is about a full kg more than the current assembly.

CNC z-axis installation

And here it is installed! Some tweaking and adjusting, but so far it is very square to the table. Total travel is almost 4". Feedrate is 9-10ipm (which is slow, but compared to the 3-4.5 that I was getting on the previous model, much better!). I have gained a couple inches on the X axis due to the back of the assembly NOT interfering with the gantry, so that's good. However, I have lost a couple inches on the Y axis because the Z-axis assembly sticks out further - that is not so good.

Whipping around at 100ipm there is a lot of bouncing / shaking. The whole machine needs a lot of stiffening - so for now, I'll run a lot slower.

I did run into an interesting problem - I put a brand new, long cutting tool and did a small test run. The collet slipped and let go of the tool, causing some deep gauging in the table. I have since read up on why it is important to clean the oil off the cutters before using them....

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