Cut dimensions and drawings are not matching

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dannymcic
Posts: 6
Joined: Thu Jan 26, 2012 12:56 pm
Model of CNC Machine: Cnc router

Cut dimensions and drawings are not matching

Post by dannymcic »

Im trying to make simple pocketing between square drawings , and saving it in g code mm . When I preform the cut , I'm getting a huge difference in size upto 20 mm smaller . How can I adjust the axis or router or find the problem if it's the post processor or axis. I'm new to cc routing and bought a Cnc gantry kit with a g code hand held processor . I tried small size and large size cuts and all seem not to match the drawing sizes .

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Adrian
Vectric Archimage
Posts: 10245
Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: Cut dimensions and drawings are not matching

Post by Adrian »

Do you know what control software are you using to drive the machine?

The best starting point is to use the control software to tell the machine to move, say 50mm, in one direction and then measure to see if it actually went 50mm.

There will be settings you can adjust in the control software to get the relationship between the steps of the motors, leadscrews etc set correctly.

Don't worry about the Vectric software or Post Processors until you've got that side of things working correctly otherwise you're going to have too many variables.

dannymcic
Posts: 6
Joined: Thu Jan 26, 2012 12:56 pm
Model of CNC Machine: Cnc router

Re: Cut dimensions and drawings are not matching

Post by dannymcic »

I don't use the machine software since it doesn't run on windws 7 . I just save the file and save it on a flash disk and run it directly from the handheld controller . I opened the machine software once but there is nothing I can adjust or modify , it just runs the drawing but its not connected to the machine.

dannymcic
Posts: 6
Joined: Thu Jan 26, 2012 12:56 pm
Model of CNC Machine: Cnc router

Re: Cut dimensions and drawings are not matching

Post by dannymcic »

One more thing i would like to know , when I'm making a pocket , let's say using a 16 mm dia bit , if I start from 0 ,0 x,y , and run the file , the starting point will leave 8 mm from each axis which I figured is radius of the bit , is there a way to make the machine remove that and add it to the pocket? I'm using 0 mm pocket allowance

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Adrian
Vectric Archimage
Posts: 10245
Joined: Thu Nov 23, 2006 2:19 pm
Model of CNC Machine: ShopBot PRS Alpha 96x48
Location: Surrey, UK

Re: Cut dimensions and drawings are not matching

Post by Adrian »

Sorry I don't really know how to help anymore with the dimension problem. Without knowing that the machine is correctly configured it's difficult to see how to verify what's causing the problems.

Hopefully someone with direct experience of your type of setup will jump in.

dannymcic
Posts: 6
Joined: Thu Jan 26, 2012 12:56 pm
Model of CNC Machine: Cnc router

Re: Cut dimensions and drawings are not matching

Post by dannymcic »

Just to understand better my positioning , is 0 ,0 axis usually set outside the corner of the work piece or right ontop of the corner ?

kilrabit
Vectric Wizard
Posts: 487
Joined: Thu Feb 26, 2009 4:04 am
Location: Uvalde Texas

Re: Cut dimensions and drawings are not matching

Post by kilrabit »

I use 0,0 xy on the corner, and that is the center of the bit. If I have a .25 bit, when beginning the cut, the center moves over by .125, or half the width of the bit, and the outer edge of the cut will follow the edge of the chosen vector.




Roy

angelinamartin

Re: Cut dimensions and drawings are not matching

Post by angelinamartin »

CNC cutting machines try to make their instructions as clear and understandable as possible, chances are that you will at one time or another need to call for technical support. Make sure you don't have to pay for it, unlimited free telephone technical support for as long as they own the machine. First see the machine is properly installed as per the instructions guide or contact the technical support team. To give best results for the customers in sign making the machine used should be properly installed and follow the manual guide.

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zeeway
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Model of CNC Machine: Self-built
Location: SC, USA

Re: Cut dimensions and drawings are not matching

Post by zeeway »

dannymcic wrote:One more thing i would like to know , when I'm making a pocket , let's say using a 16 mm dia bit , if I start from 0 ,0 x,y , and run the file , the starting point will leave 8 mm from each axis which I figured is radius of the bit , is there a way to make the machine remove that and add it to the pocket? I'm using 0 mm pocket allowance
First make sure your machine is adjusted to move 100 mm (or whatever) when the code calls for such a move. You will have to consult your machine instructions or the manufacturer for detailed ways to accomplish this.

In running a pocket, the software will generate g code that directs the center of the tool to a path that is half of the diameter that was stated for that tool in the database...away from the pocket vectors. If the tool is described as 16mm, and no allowance set, the tool center will follow a path that is 8mm away from the pocket vector. If the tool is truly 15 mm (instead of the 16 mm stated in the database), for example, the toolpath will still be 8 mm away from theoretical pocket vector, and the pocket will be machined by 1mm small per wall, or 2 mm across. You can narrow this down by measuring your tool diameter; or by cutting a simple groove in you material and measuring the width. The actual material you are using will also affect the size of the cut.

Now having said all that, if you want the pocket larger, you will have to go back to VCarve Pro or whatever software you have, and make the pocket bigger on the design...or if the tool diameter measures as something different than that described in the tool data base, you would correct that. And in both cases, regenerate the toolpath.

Angie

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