Enco CNC Conversion
|Enco mill CNC Conversion|
|Start Date: 01/14/2016|
This is a project to convert the current fully manual Enco mil/drill to a CNC machine.
After some investigation I think this will have to moved over to the back burner while the PTDR and other projects get priority.
What needs to be done
- Research what we have (motors, controllers, etc.) and what we need.
- Will probably need to replace the leadscrews on the X and Y tables. Will have to design a bracket to connect the ballscrew to the table.
- Will have to create brackets to mount the motors.
- Will have to install pulleys on the leadscrews.
- Investigate how to incorporate the existing scales that talk to the DRO.
- Looks like it would be easier (and cheaper) to just get a machine that is meant to be a CNC instead of fighting with a design that was meant for manual operation. :)
What has been done
Mapped out the error on all the axes (yes that is the plural of axis - I looked it up 😀) Looks like all the axes are a bit short. They feed about .002" less for every .5" requested (five turns of the screw). In certain spots the short feed almost .008".
The backlash of the X axis is about .020" at the ends and .032" in the center. So that means to reverse the direction of the table you would have to turn the screw about 72° to 115° before the table began to move in the other direction. This can be very problematic for a CNC machine. In manual machining, you are usually continually pushing or pulling in one direction for an operation. In contrast, a CNC operation could involve many direction changes for the tool.
The Y axis had about .020" backlash across the travel (about 72°).
The Z axis only had about .004" backlash. Probably because the return spring pulls out the backlash. Many CNC conversions put a ballscrew on the spindle because of the slop in the spindle screw drive. Some people just preload the heck out of the existing system by the return spring and get pretty good results.
Currently on the ToDo List
- Find out what other people have done on the interwebs
Design & Planning
Link to a company that makes a conversion kit (many thousands of $) http://www.flashcutcnc.com/retrofit-solutions/benchtop-kits
Found an excellent CNC site that walks you through the steps for building a CNC machine: http://www.cnccookbook.com/CCDIYCNC.htm