[Thorn3]

Hello all,

I am presently designing an SX3, table top mill conversion. This project will be in the planning stage until all needed components are first fully researched. I am sure anyone on a budget will fully understand that.

Right now, I am researching axis drive motors and a new spindle drive motor. My goal is to use quality servos that don't cost an arm and a leg. I came across the company Teknic and investigated their site. I am impressed with their line of servo motors, meant to replace stepper motors and associated controllers. The price is within my budget and is comparable to a quality stepper setup.

All of the new Teknic products offer extensive documentation, and is well written for a hobbyist building a CNC conversion. Each motor has its own, built in controller, that accepts direction and step signals, as well as output for position sensing. According to documentation, these motors are intended for uses that include CNC machines. They will sell any number of product to anyone, not just OEM. This opens them to the hobby market as an affordable, quality solution. Here is a motor that I have been thinking about:

https://www.teknic.com/model-info/CPM-SDSK-2321S-RLN/

[Thorn3]

The manual for the Teknic motor has been read to familiarize with content, then read again to better understand it. Documentation is quite extensive and covers everything in easy to follow steps, with simple and to the point instruction. These motors can be programmed via a USB cable and come with the software to do it. Nothing complicated really. Although the manual is extensive, it is only so, due to the number of ways such motors can be set up. The motors are programmed before use, to define their operating mode and associated parameters. The setup is saved in a file, inside the motor. This would be great for hobbyists, as it allows people in the know, to set up a motor, then pass the file on to other hobbyists who may not know how to do it. Although, with such clear instruction in the manual, I think anyone can do it. In my case, it would be set up in a 'step and direction' mode, as a direct replacement for stepper motors. I do believe that with a product line like this available to hobbyists, steppers will become a thing of the past. I am going to go ahead and incorporate these motors into my design. Teknic also sells power supplies at a reasonable cost, specifically designed for these motors, creating a more simple, plug and play setup.

[Thorn3]

The table that comes with the SX3 is pretty short for my needs. Found a longer table for it here:

Super X3L Long Table Kit 3845 - LittleMachineShop.com

This table comes with a lead screw. I won't need it ultimately, but while machining parts for the conversion, it will come in handy.

[Thorn3]

Lots of options for ball screws and nuts. Prices range from cheap, to hang your head and cry. I checked out the Chinese options and could not bring myself to plan on using them. Sure, the price is good, about half that of the next option up... but cheap and mysterious isn't what I am looking for. I want to know how the screws are made. What materials, what heat treatment and coatings? If you don't know that, you really don't know what you are getting.

I opted for ball screws from Thomson. The type I will use, 'Precision Rolled', have a typical backlash of .004". When using two nuts in an anti-backlash setup, this is no longer a real problem. Thomson also offers 'Precision Plus Ground' and anti-backlash nuts to go with them... but at a much higher cost. Two nuts will do just fine, for much less money. For all three sections of screw, the cost is $140 (one 1', and two 3'. For all six nuts, the cost is about $187. I will machine the ends as I need them on my lathe.

http://www.thomsonlinear.com/website...nch_series.php

[Thorn3]

The head of the SX3 is a bit quirky for CNC use. The quill has to go. With a Z axis drive.. who needs the quill? After removing it, appropriately cut covers will be screwed over the holes.

The spindle will have to go too. Hobby level spline shafts tend to be sloppy and can induce tool chatter. I will machine a new spindle on the lathe, that eliminates the spline shaft and mounts directly into the motor pulley.

Since I plan to replace the spindle motor with a higher torque, higher speed motor, the control panel on the head can go too. RPM and on/off will be controlled via the computer. The resulting holes will not be covered... instead, the entire faceplate will be removed and replaced with a steel plate.

[Thorn3]

I am not entirely confident in the Z axis column. I have noted minor flex in it. A steel tube mounted behind the column should help stabilize it. It will be spaced out from the column just enough to allow head movement. The top of the tube will bridge to the top of the column via a steel plate. The bottom of the tube will mount to the main base, via steel brackets machined for the task. The tube can then be filled with concrete.