[Coco] [coco] coco CNC

George Ramsower georgeramsower at gmail.com
Fri Feb 15 01:27:51 EST 2008

 This is a long post.. a Micro Novel...

 Just in case anyone wanted to know.....

 Calibrating a lead screw is not difficult.

We'll start with the stepping motor.

If a stepper does 1.8 degrees per step, this comes to 200 steps per 
If it's connected to a lead screw that has a pitch of 32 TPI (tuns per inch)
You multiply 200 times 32 and you get 6,400 Steps Per Inch.
 It is possible to "Half Step" these things so you could get 12,800 steps 
per inch.

 Screws are NEVER what they are supposed to be.

 So, once I install a lead screw, I connect a dial indicator to the driven 
slide and run a program to step it according to the theoretical 
 If I tell it to go one inch and it goes 1.004 inches, then I take the steps 
I used to get it there and the resulting distance it traveled and do the 
following math:

Inches travelled/steps used = steps/inch

 Easy. Some fine tuning will be necessary. So I then go four inches and 
measure again. I also test in one inch increments to see if the screw is 
actually linear. I can then average it out to get a satisfactory result.

 This last screw I used on the X axis I just installed amazes me. I can't 
find a fault in it throughout the entire six inch travel. It maintained 
tolerance within .001 anywhere I placed it. I wish I could remember where I 
got it.

 This CNC Coco machine surpasses my expectations in: Accuracy and ease of 
 Basic 09 makes this possible.

 Of course, the milling machine is important also.

 If anyone thinks they can't figure out how to do something such as this, I 
have to tell you this....

 You don't have to be a genius to figure something out. You only have to 
study it long enough and you WILL figure it out. I have no idea how many 
days I've pondered problems on this project until finally I have developed 
an idea that might work... sometimes it doesn't. So I ponder some more, or 
see what I did wrong. I've tossed plenty of ideas and failed parts. It 
wasn't/isn't easy and it is still difficult. But it's fun, nonetheless.

 I've experimented with different ideas such as ball bearing drawer slides 
and others. They all failed my tests. Trial and error and finally I found 
something that works.

 It's not majic or anything else other than just simply patience and 

 Edison experimented for several years before he came up with a reliable 
light bulb. I've been doing the same thing with this machine and it isn't 
done, yet.
 I won't give up until I actually make a good part for a steam engine. Then 
I may consider a more powerful computer and $$$$ to make this machine work 
 Faster is all it will do. Accuracy will not improve. So it's sort of like 

 If all I need is ONE part, the coco will do nicely.
 If I need a lot of parts, then speed will be important.... maybe. Depends 
on how many parts and the time alloted.

 Sure, I've been going on and on but, I've got to tell you that we can do 
anything our dreams can come up with. This is MY dream and I believe it will 
come to fruition.
 It's so close now, I can taste it and I'm excited about it.

 I'm anxious to see the first part come out of this thing, but there is one 
little problem...

 Once I get this part done, I then need to meke the rotary table. This is 
the part that makes it possible to make a gear/sprocket.
 So, it ain't done, yet... not even!


 If anyone want drawings on this project, there are drawings on the bearing 
blocks. Everything! else is done by the  "Seat Of The Pants" ..... Cut and 

 Sorry.'bout that.


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