converting the dimensions of drawing from inches to mm for cnc laser cutting machine.

[abhishek]

dear seniors,

 

i have a few .dxf files which i want to get cnc laser cut. I had gone to a local cnc shop and showed them the files. They said the dimensions are all in inches and that they required the dimensions to be in mm. So they have asked me to get the files converted in mm.

 

As this is my first time running autocad, I would like some help. I have understood a little from a few of the threads which contain things like converting from inches to mm etc. but the problem is that they have not showed a step by step procedure for it.

 

All I could gather from the other threads is as follows (I don't know if its correct):

 

if i have my drawing in inches and want to convert all the dimensions into mm , then i would want to scale the whole drawing up by a factor of 25.4, because 1"= 25.4mm.

 

so for doing this :

 

1>I type "dimstyle" in the command box/space.

2>a window opens titled "dimension style manager"

3>I press the modify button on the right

4>another window opens in which i goto a tab called "primary units"

5>in the "primary units" tab I goto " measurement scale" and type 25.4

6>click ok

7>in the command box i type "units"

8> and select the INSERTION SCALE to be "millimeters"

 

 

please tell me Seniors...if this procedure would be correct and that the cnc machine would cut the parts as per the drawings.

 

hope to hear from someone soon.

[Pablo Ferral]

I'm afraid that you've missed an important concept. This change will only effect your dimension style - not the geometry. Unfortunately Autocad doesn't use real world units. 1 unit = 1 Unit. 1 Unit can be used to represent anything you want; Inches, mm, Rods, Cubits, Parsecs, Bananas - you get the drift.

 

In this case you have chosen that 1 Unit should equal 1 Inch. If the laser cutters cut to this file everything will be 25.4 times to small. ie for a value that you have chose to represent 29 Inches, the Laser guys will assume it to mean 29mm. The answer is simple; all the geometry in the file needs to be scaled by 25.4mm.

 

Type 'SCALE' at the command line.

Select all the geometry that needs scaling

Pick a base point

Enter a value (25.4)

 

You may want to save a copy of your original file before you do this! This will probably make a mess of your Dimensions, Text and layouts. I suggest that you delete all of this stuff out of your 'Laser' .dxf File, perhaps just add in enough notes and dimensions to make sure that everything can be coordinated with your original file. For extra comfort you could give them a paper copy of your drawing for reference.

 

This is something the Laser Guys could have done for you. They are probably reserved about editing your files in case something doesn't fit and they get the blame.

 

Have a read over these tutorials:

http://www.we-r-here.com/cad/tutorials/level_1/1-1.htm

[BIGAL]

I very much doubt the laser cutter program reads the dimensions it just cuts a 1:1 copy of the shapes you have drawn so your shape must be 100% correct the laser cutters will work down to real small tolerances. As per pablo not sure why they didn,t do the scaling not much CNC is hand written any more.

[abhishek]

Type 'SCALE' at the command line.

Select all the geometry that needs scaling

Pick a base point

Enter a value (25.4)

 

Thank you for your reply Pablo.

 

I have done what you asked me to do, i.e using the 'scale' command.

After I enter the value 25.4 . The drawing becomes too large, I had read this in some thread, that after scaling to a particular value you would have to use the 'z' command followed by the 'e' command.

May I ask what are these for?

 

And also after using the above commands my dimensions become so small that I've to zoom quite a bit to read them.

Is this fine, I mean is my drawing still according to the same dimensions but just converted in mm?

or has it become too large?

[abhishek]

I very much doubt the laser cutter program reads the dimensions it just cuts a 1:1 copy of the shapes you have drawn so your shape must be 100% correct the laser cutters will work down to real small tolerances. As per pablo not sure why they didn,t do the scaling not much CNC is hand written any more.

Thanks Bigal,

but the cnc shop guys said that all the dimensions mentioned in inches will be read in mm by the machine.

[daft vader]

Scaling to a particular value you would have to use the 'z' command followed by the 'e' command.

 

means you are selecting Z = (Zoom) then press enter, then e (=extents) then press enter , and then you will see the whole drawing

[abhishek]

Scaling to a particular value you would have to use the 'z' command followed by the 'e' command.

 

means you are selecting Z = (Zoom) then press enter, then e (=extents) then press enter , and then you will see the whole drawing

 

okay, but what happens to the written dimensions.... why do they become so small?

I will upload a picture, that would explain my problem.

See in the first picture all the dimensions are in inches which I have to scale up by 25.4. After scaling up and using the 'z' & 'e' commands the drawing become like picture 2.

 

now looking at the portion marked in red, you will see that the written dimensions become so small that they can only be read when the drawing is zoomed as in picture 3.

 

The doubt that I have in mind is that, is my drawing scaled up correctly ?

and if so why are the dimensions appearing to be diminished?

 

 

 

 

 

 

[designerstuart]

after scaling, select a dimension, right-click and 'select similar'. now you have all the dims selected. open the properties palette (command CH) and increase the text height to something more appropriate..... maybe 25x the original size will work.

[abhishek]

thanks a lot designerstuart......but is it scaled up correctly?

[Cat]

Set your dimscale to 25.4 and then update your dimensions. Your dimensions should look the same as they did before you scaled your drawing objects.

[Pablo Ferral]

That's right, the dimensions have been scaled by 25.4 as well. You will need to adjust the size of the Annotations to suit.

 

I don't wish to be negative but you really ought to read some of the tutorials from that Link that I posted. You have some fundamental concepts to learn. It really is a good site...

[asjriyas]

This need to be scale = 1/25.4 (inches / Millimeters)

Then your scale factor will be 0.039:)