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Author Topic: I am sure this has been asked but i need a bit of guidance please  (Read 4602 times)

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Hi All and thanks for reading this posting.
i am new to the cnc world and have just completed the build of my CNC machine.
I am currently running the demo version of mach3 until i get the machine working correctly.

All the axis work and it seems to run well except for i havnt got to the stage of calibrating the motors so that the file i run from mach 3 cuts or machines an accurate part.

I have created a couple of test files..... 100mm circle and square to see how far out i am.... ehhhhmmmm miles off.... about 40mm at the moment so small mainly in the y axis.

So you guessed it here comes the question.... what is the best process to set up the stepper motors and machine so that what i design is what is cut.

I am sure that this has been asked countless times before but searching the internet comes up with umpteen different ideas, i am looking for an explanation of what the process is and the best way to achieve accurate results and the best way to test the changes.

The other question i have is how do you set up a probe with a plate so that i can zero the z axis, i have plenty of spare inputs into the controller and i understand the principle of how to set this up  but again find lots of conflicting information on how to best achieve this.

I am really looking forward to getting my machine up and running accurately but want to do it properly so that i understand what i am doing and hopefully in the future will be able to help someone else out that is running into
problems.

Thanks for your time and i look forward to any help or advice that can be offered, i am based near hastings in the uk

I have attached a photo of the machine i have build just in case anyone was interested, its taken quite a long time to get to this stage !!!!

Offline Chaoticone

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Re: I am sure this has been asked but i need a bit of guidance please
« Reply #1 on: February 04, 2013, 10:36:36 AM »
Hey, the machine looks great!  I have attached several links.  These simply cover the meat and potatoes of what your looking for I think.  Not a lot of extra in them and will get you sorted in no time.  I listed them in order of how I would attack it.  The first explains the math needed to figure steps per unit.  Second is a spread sheet to help.  The third explains backlash and how to test it.  The 4th covers the right hand rule.  Fifth should help with the probe but I'm going to edit it a bit right now.  Please don't reply in those threads.  If you have any more questions reply here.  We try to keep those clean so others can find just the relevant info.

http://www.machsupport.com/forum/index.php/topic,12512.0.html#new

http://www.machsupport.com/forum/index.php/topic,16315.msg110286.html#msg110286

http://www.machsupport.com/forum/index.php/topic,12513.0.html#new

http://www.machsupport.com/forum/index.php/topic,10308.msg63702.html#msg63702

http://www.machsupport.com/forum/index.php/topic,10088.msg62024.html#msg62024

Thanks,
Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: I am sure this has been asked but i need a bit of guidance please
« Reply #2 on: February 04, 2013, 01:42:00 PM »
thanks for the info Brett, i will get on with it tomorrow but this looks great.
regards

Gary
Re: I am sure this has been asked but i need a bit of guidance please
« Reply #3 on: May 21, 2013, 11:23:54 AM »
Brett, great articles and documents. I'm new as well and switching a machine from NCStudio to Mach3 and had a question about your Excel doc for speeds etc. If I change the pulse in the Metric section shouldn't it change all the calculations? Only the section I change it in changes and doesn't get reflected in any of the other columns/sections.

Offline Chaoticone

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Re: I am sure this has been asked but i need a bit of guidance please
« Reply #4 on: May 21, 2013, 12:40:49 PM »
I will have to look at it and see.  Our good moderator Rich made the spread sheet.  When doing the math to figure out your steps per you are only measuring units........ doesn't matter if it is an inch or mm.  What does matter is that if you have it set to native units of inch or MM, the steps per will be entered to what ever number you need for the table to move 1 inch or mm respectively.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: I am sure this has been asked but i need a bit of guidance please
« Reply #5 on: May 21, 2013, 07:14:22 PM »
Thanks Brett. It's been fun trying to get the specs I need for these steppers. The Chinese sale rep knew NCStudio but is clueless on Mach3 setup and all he could tell me was my X & Y use 96.01536 and Z is 160. I finally found the X & Y motors online and found they have a 1.8 pitch but that's it.  Haven't removed the wiring to be able to take the Z axis cover off and look at that motor yet. So tuning has been trial and error at best as a newb http://www.goodluckbuy.com/86bygh450b-06d-stepper-motor-hi-torque-60-kg-cm.html

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Re: I am sure this has been asked but i need a bit of guidance please
« Reply #6 on: May 21, 2013, 10:33:50 PM »
Those numbers the guy gave you, is that suppose to be your steps per unit and if so, in what units?  mms to be sure?

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: I am sure this has been asked but i need a bit of guidance please
« Reply #7 on: May 21, 2013, 10:37:04 PM »
Definitely mm and it must be steps per cause it'a gotten me pretty close but seems to be losing a fraction of a step when I move it around telling it to go to X200 Y300 it will be X199.845 and Y 299.983 for example.

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Re: I am sure this has been asked but i need a bit of guidance please
« Reply #8 on: May 22, 2013, 08:03:18 AM »
You may not be accounting for backlash in your test or you could be skipping steps because you have the accel or velocity higher than the motors can move the machine.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!