Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: KRAM242 on January 16, 2007, 11:47:42 AM

Hello, I have an issue where If I create a tool path in Artcam, and then open it in Mach3 the scale is off. For an example if ithe part is suppose to be 10" it comes up WAY smaller and I have to scale it up.
I have been messing with it and found that if I scale up all the axis in Mach to 13% its close to the original, but not right still.
Any ideas about what Im doing wrong would be a great help. Maybe I did not set up Mach right? Im new to all this.
Thank You,
Mark

Hey Mark,
Have you verified that you steps per are right in motor tuning?
Hey,
Checking your backlash should be no problem if you have an indicator. Put the indicator on something solid. Jog your axis until you move the indicator to a reading of about half of its travel. Write down the reading on the indicator. Jog the axis in the other direction by a set amount, say .010" and see how much difference the indicator shows. If the indicator says you moved .005 and Mach says it has moved .010 then you have .005" backlash. With that being said, you really need to know the pitch of your ballscrew first. I would say your steps per will be 10,000. You can check this with your indicator also. Set up as before., only this time run the axis in until it just starts to move the needle on the indicator. Write down your reading. Going in the same direction give the axis a move with Mach. If Mach thinks it moved it .010" and your indicator says it moved .010", your steps per are right. ;D
Brett

Thank you Brett,
The machine I'm using is my first and its homemade, using allthread from Lowe's so I'm really not sure what the pitch is, also it is a proof of concept machine just to get my feet wet in learning the software. I must say that its working way better then I could have ever hoped. The only problem that I'm having so far is this scaling factor. Thanks again for all the info I do have a question though "Checking your backlash should be no problem if you have an indicator"
May sound stupid but I won't know until I ask What is an indicator?
Mark

Hey, I didn't know what one was when I was born either. Somebody had to tell me. I was referring to a dial indicator. Here is a link.
http://catalogs.shoplocal.com/jlindustrial/index.aspx?storeid=1038424&circularid=7228&jlpass=1278&loggedin=false&itemcount=0&jsessionid=ymq5bx1yd2tqplaubiwsfevmcqfcyiv0&pagenumber=1300
These are cheap. Not the best, but cheap.
What kind of threaded rod did you get? 1/220, 3/816,etc.? The last two digits in the previous numbers indicate the thread pitch. 1/220 says it is 1/2" in diam. and 20 TPI (threads per inch). 1"divided by 20 = .050" travel per round.
Brett

lol. Thats true :)
Well I have 3/8" threaded rod so I think that is the 16 so I suppose that would be .0625 travel per round?
Thank you so much for that help and the links.
Mark

Your welcome. Let us know if you have any more trouble. Here is a little more info that might help. It is an old one that I copied and pasted.
Here is how you do the math. I will give you mine as an example. What we need to know is, How many pulses from Mach will it take to move the machine 1 of your units? (inch,mm) Mine is in inches. 1 inch = 10,000 pulses on mine. This is how I came up with the number.
My steppers have 200 pulses per revolution. ( 360 degrees divided by 1.8 degrees = 200 )
Micro stepping = 10. So 200 X 10=2,000
Motor to screw gearing is 11. So 2,000 X 1=2,000
Screw lead is .200 of an inch. My screw will have to turn 5 rounds to move the nut 1". 1.0 divided by 0.200=5. So 2,000 X 5=10,000.
Do the math first. Then we can move on. Once we are certain of all of this, dialing it in should be easy.
Brett

OR you could use the "Calc Steps Per Unit" onthe settings page :) it should get you started...