Description
I am currently working on a large (~300mm) CNC servo powered rotary table. This newly designed table will facilliate completion of a wide range of other projects as well as offer a more reasonably priced higher capacity rotary table to other machinists.
The problem
Having access to greater than 3 axis motion is almost a necessity for many of the the projects I have been working on. However, large CNC rotary tables can easily cost in excess of $5000. As software and CNC equipment prices have come down over the years we are lucky to have access to a wider variety of machining options. Unfortunately there are still many things that can be quite expensive for many shops. In these cases, we are motivated to come up with effective lower priced solutions.
There have been many attempts to create low priced CNC rotary tables. Most are made from inexpensive and easily machined materials typically found in home or small shops along with surplus motors and bearings. They are rarely suitable for high accuracy work, are usually very small and most are not designed to last long. There are more professional designs with large sizes and high accuracy readily available, however the price is again a major concern. I am seeking to strike a balance between low cost and high accuracy and durability.
My Approach
My solution is bring together features of higher priced CNC Rotary tables but to do all the design, part sourcing and part manufacturing myself to eliminate the middle man. The features I am incorperating into the design are...
- Accurate and rigid cross roller bearing
- Harmonic drive gear for zero backlash and high torque
- Powerful servo motor for smooth operation, high torque and high resolution
- High strength aluminum cast body for easier handling while maintaining a rigid structure
I will be finalizing the body casting design shortly with the hope that casting in aluminum will make the final product easier to handle due to the reduced weight while still providing the rigidity and reduced pirce I was hoping for. The core internal components have been sourced from reliable vendors for a very economical price. I am currently on track to complete the CNC rotary table for a small fraction of what it would cost to purchase a similar model from an existing vendor.
The over all design is very simple with few moving parts. I will be hobbing my own timing pulleys as well as producing reliable molds for accurate and reliable reproduction of the initial prototype model. Eventual out sourcing of the simpler components will keep the lead time short and the price down.
Summary and further work
Even though the project will still have some costs associated with it, the final price will be very reasonable. Prices well into the many thousands of dollars for a Rotary table like this from other machine tool vendors puts it well out of reach for myself and any many others.
Having a CNC Rotary table in the 300mm size range will certainly help with the completion of many of my other projects. I am also looking forward to eventually expanding the capability by embedding the final design into a full size trunion table that will fit on my MD001-CNC machine.
