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This is my 2nd CNC Machine a smaller desktop version my ongoing project. Now I am gathering some parts to be used such as linear rails, motors, parts of inkjet printers that I can use, etc.
It will somehow look like this when finished.
I will post all my worklogs here. As a newbie I learned a lot here so I completed my 1st successful CNC machine with a working area of 20"x40" inch. Will try to post my work logs about my 1st CNC Machine soon
build my spindle holder for the Z axis
finished my 2nd Desktop CNC using belt and chain to drive my X and Y Axis, for Z axis using threaded rod 20TPI 1/4 diameter
Somethings wrong during my testing using mach3. when I move X Y and Z axis to 1 inch, it moves perfectly to 1 inch. But how come when I draw a circle it is not circular shape? Im using 3 kinds of stepper motors.
backlash on the left to right axis in the first pic.
Gerry
Mach3 2010 Screenset
http://home.comcast.net/~cncwoodworker/2010.html
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
My guess is that the looseness of your chains is contributing to your backlash. You need to have the chains as tight as possible to remove that backlash and your design may not be strong enough to allow you to really tighten up the chains.
Alan
Thank you ger21 and acondit, will try to put rubber tension to stretch the chains if its possible to make it circular shape
l able to remove the backlash of my machine as I am using chain gear and timing belt pulley for my X and Y axis. I put rubber tension to stretch my bicycle gear and chain. It moves perfectly when I move it to 1 inch, but how come if I move it to 2 inches up to 10inches the measurements doesnt match up for both X and Y axis? Z axis I dont have any problem as im using 20tpi threaded rod and I know the computation to get the steps per inch, but Still im having some problems drawing a perfect circle, its irregular in shape with no backlash. Why is that? Im using 3 different kinds and sizes of stepper motors. Is there a computation to get the steps per inch in Mach3 using gears and pulleys by measuring the diameter of the gear and pulley im using?
It looks to me in the picture like your chain is still sagging on the bottom. It needs to be stretched so there is virtually no sag. This requires a lot of tension and hence a very strong frame.Originally Posted by guy2b1
There are formulas to get you close, but I suspect your best bet is to keep adjusting the step setting in Mach and measuring the result and comparing the result with the commanded move, then adjusting again to get closer.
Always approach your measurements from the same direction, move past your starting point by some amount (say 1/2" or 1cm), reverse directions and move to your starting point (thus taking up any slack), then command a move in the same direction as you approached your starting point and measure the actual move against the commanded move.
Alan
I understand I really need to stretch the chains for my X axis using rubber tensioning and I tested it its no longer jumping for rapid movements, but how about my Y axis? Im using my Y axis from old damaged canon s400 printer head using motor head mount slides pulleys and belts, this definitely does not have any backlash problem from a printer but how come am I having the same problem when I move to 1 inch its perfectly moves to 1 inch but when I move it to 2 inches or more it does not measure correctly, what should I do?
I slightly improved drawing my circle say 60% from my first attempt, but now its about 85% almost perfect to draw a circlular shape.
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