OK, so I don't know where to start. I guess I'll start with the design so you'll know where I'm heading.
Our 1.5 car garage shop is used for many different purposes; from metal and woodworking, to use as a greenhouse for plants in the winter, to serving as a chemistry and nuclear physics lab. So I want to keep the footprint of the mill as small as possible while not limiting its capabilities too much. I also want to make it as self contained as possible and to have all the sensitive components such a limit switches, couplings, gas struts ect. tucked away so they will not collect wood dust and grime.
I based much of my design off the excellent conversions documented here by the likes of gd.marsh and 91TSiGuy. Thank you all for the inspiration! I would especially like to thank 91TSiGuy for providing me with some of his CAD models to get me started.
Below (hopefully) is a screenshot of the overal CAD model so far. I have not modeled the head since I am not making any modifications to it, yet.
The control panel uses an elo InteliTouch screen I got on ebay and will have physical knobs for the most common controls, such as FO, RO, Joging and program Start and Feed Hold. Eventually spindle controls will be added, but are not in the plans at the moment. All the wires will pass thru the control panel swing arm and into the column, from whence they will go down into the stand were the electronics will be located.
All the motors are direct drive and tucked in close to the machine to save room.
Here is bottom view showing the mounting of the ballscrew bearing blocks and the motor couplings. It is a tight fit but results in a very clean and simple conversion. I will not be able to over travel as much as with the other designs where the bearing blocks and couplings are outside the castings, but that is not my goal and I still have more travel then stock. I have access to bigger machines if I need more travel.
I know I will need some type of counterbalance on the head to keep it from falling when power is cut to the axis motor, but i would like to avoid having gas struts or a counterweight on the outside of the machine as is the typical solution. Fortunately the column is just tall enough to allow placing two gas struts inside it, see below.
My head weighs right at 200#, well, you know what I mean .
I did some quick calculations using the gas laws and found that two of the 100# gas struts sold by McMaster produce about 180lbf while extending at free length (full extension) and require 301lbf for compression at solid length (full compression). This results in an average force of about 241lbf. I was hoping for something closer to 200lbf but without custom struts that is unlikely to happen so two 100lbf struts it is! I also figure most downward moves are at feed and most upward moves are rapids, and since the motor has more torque at feed speeds everything balances out nicely.
Here is an ISO view of how the struts act on the ballscrew mount. The studs on the end of the struts are just a slip fit in the holes, but they won't go anywhere since they will always be in compression, unless I rapid faster then the struts can keep up with, which I doubt!
I have to run, more later tonight, hopefully.
I like constructive criticism, so if you think something will not work let me know!
Thanks for looking!
Kurt