[Coco] leading to that CNC Coco machine

George Ramsower georgeramsower at gmail.com
Thu Feb 7 07:42:36 EST 2008

Correct. However, I won't be doing complicated work with this setup. What 
really slows down the coco is doing arcs and circles. There won't be much of 
that done so this may not even be an issue. If I were to draw a 2 inch 
circle at the most precision the steppers can do, would take about 80000 
steps to simply draw a circle.If I precalculate this circle in another 
process and save the results to a file, the file might even be larger that 
what I can fit on a floppy.  The coco can muster up about 800 steps per 
second with the only math being addition or subtraction to make a straight 
line. Using SIN to create a circle slows it down to about five steps per 
second.  I expect if I have to carve a circle larger than about a half inch 
on something, I'll find a way to fixture the part in my lathe.  Keep in mind 
that the 800 steps/second is just a straight line on a single plane. If I 
were to do a diagonal line of 45 degrees, then X and Y steppers would each 
be doing about 400 steps/second and the match to this would even slow things 
down more.

 My original intention for this mill is to make small gears and sprockets 
using a rotary table and other tiny parts for my steam engine stuff.  I 
expect I'll make a couple of parts and then abandon the idea of using a coco 
and spend some money to put a PC and stepper drivers on it. Mainly, I just 
want see if I can make a part using a coco to do all the work. The only 
parts outside the coco to drive the steppers are power transistors and home 
switches. Everything is done with coco, including the sequence of stepping 
the motors. So the coco is pretty busy just stepping the motors.
 Right now, I have to get the permanent lead screw, nut and mount the 
stepper to the X axis table. I have a temporary screw on it now so I can 
machine the slide to accept the new screw. I have most the groove cut out 
now, I have to make it a little deeper and make a pocket in it for the lead 
nut assembly. Once the lead screw is done, I can mount the working table 
onto it and get started. The working table is 6 X 6 X 1/4 inches. Small 
indeed. A micro mill is usually a bit larger than this so I suppose this one 
is could be called a nano mill ;-)

----- Original Message ----- 
From: "Charlie"
> So, what you are describing below, the coco would basically pre-render the 
> program and then feed it to the machine
> with all the math done already?
> "George Ramsower"
>> The coco takes WAY too much time to do the math while in operation on the 
>> mill. So I intend to build a file generated from the desired  plans to be 
>> loaded and used by a smaller program to make the machine do what the file 
>> indicates... much like the original paper tape NC  machines did. It would 
>> be my own code, since mine would be a lot simpler. I don't need to do 
>> "rapid moves", control feed rates and things like that. It's too slow 
>> already and all I need to do is just tell it where to go.
>> I haven't actually tried this theory yet. I'm still working on completing 
>> the mechanical part of the mill. Right now, I'm finishing the X axis lead 
>> screw assembly which is making my brain ache. Only photos can explain 
>> this and I'll get that onto my site as I feel the propensity to do so or, 
>> if people start hounding me for the details.
>> http://coco.thetinbox.com

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