[Coco] [coco] coco CNC
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
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
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
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
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
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
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