Author Topic: How to set scale of CAD in micrometer  (Read 6544 times)

Hari

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How to set scale of CAD in micrometer
« on: August 31, 2011, 09:31:05 AM »
Dear Friends,

I am new to design CAD. It would be great, If some one can help me how to set dimensions/units in micrometer or nanometer in CAD, as I am not able to see these scales. I am pretty much sure there will be a way for it as I used a CAD from someone else, and its default measuring unit was micrometer.

With thanks.

Hari
« Last Edit: August 31, 2011, 09:36:40 AM by Hari »

JJG

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Re: How to set scale of CAD in micrometer
« Reply #1 on: August 31, 2011, 10:05:02 AM »
Dear Hari,

I think this issue is not in the correct category: it would have been better in "Looking for Help?"

Nevertheless, the unity of design is defined in "Option / Unit of Measurment", but I do not think it is possible to choose micrometer or nanometer, as you request.
In this case, choose simply "no units", and then the drawing will be drawn to the unit you have in mind ... !

To define the settings for Unit, see please the picture below.

Hari

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Re: How to set scale of CAD in micrometer
« Reply #2 on: August 31, 2011, 10:55:01 AM »
Dear JJG,

I am sorry, for not posting issue in right category.

But still I have a doubt in my mind. Suppose if I define my CAD as a dimension less then during lithography writing, how can I  write it in a given area/dimension ?

With thanks.

Hari


Dr PR

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Re: How to set scale of CAD in micrometer
« Reply #3 on: August 31, 2011, 11:25:34 AM »
Hari,

To expand upon what JJG posted, the default mode of DesignCAD is "unitless." If you draw a line with a length of "10," it is 10 of whatever you want. As long as you remember to always draw with the same units in mind you will have no problem.

For example, I am working on a unitless ship model drawing, and my base unit is the inch (the original blueprints were drawn in inches). So the whole ship is 7320 units long. Although drawing units have not been defined I know they are inches. In fact, I have drawn a scale in the 2D drawings that defines the length of the scale bar in inches.

Everything works OK in unitless drawings. If I wanted to I could assume the drawing units were microns, so the full length would be 7320 microns. Or nanometers, furlongs, parsecs - it doesn't matter.

****

However, if I need to send a 3D drawing to a milling machine or stereolith printer I must define the units in the drawing. For example, I might want the machine to create a part in millimeters and not feet. To do this:

1. If you do not know what drawing units a drawing has, pick some part of your drawing that has a definite known dimension. For example, you might have a sketch that was drawn over a scanned image, and the drawing units are actually just pixels with no real world dimensions. Pick two points that should be a known dimension apart and use the "Dimension/Units" function to define the distance between these points. If the drawing has dimensions in it, use these to set the Units.

Now the basic dimension units in your drawing are correct.

2. To define the actual drawing units open the "Options/Units of Measurement" function.

Be sure the "Rescale to new units" option is not checked.

Now use the pull-down list in the "Units for Current Drawing" box to select the drawing units for the drawing.

The numerical values (lengths, volumes, etc.) in the drawing will not be changed, but the units will be assigned to whatever you select from the list. It looks like millimeters is the smallest unit available.

For example, if you select "millimeters" from the list all formerly undimensioned objects 10 units long will become 10 millimeters long. Of course this is 10,000 micrometers. If you have an object in the drawing that is 100 micrometers long, it will then dimension "0.1 mm."

3. If you find that the dimensions are still incorrect after assigning units to the drawing, you can always follow the procedure listed in step 1 above to force the dimensions to be whatever you want. For example, if you know an object is supposed to be 10 micrometers wide, but it dimensions to something else, use the "Units" function to assign the width to be 0.01 mm.

4. You can force dimensions to be in some unit other than the base drawing unit. For example, if you find all of the leading zeros to be inconvenient with the millimeter base unit, you can use the "Units Multiplier" in the dimension dialog.

For example, if you assign a multiplier of 1000 and dimension an object 0.01 mm long, the dimension will read "10.000." In other words, it now reads in micrometers.

Furthermore, you can assign a suffix to the dimension. This is any text you might want to follow dimension numbers. So if I enter a suffix of "um" the dimension will read "10.000 um."

Now I have drawings with dimensions in micrometers, and if I send them to a fabrication machine the parts will be dimensioned correctly in millimeters so they will come out the correct size.

Did this help?

Phil
DesignCAD user since 1987

Hari

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Re: How to set scale of CAD in micrometer
« Reply #4 on: September 01, 2011, 01:57:42 AM »
Dear Dr. P R,

Thanks for your help. Now things are more clear to me.

Only problem is that somehow Units multiplier and suffix are not working in my CAD. Though I have saved it after changing it into the Option/Dimensions settings.

Thanks.

Hari

Rob S

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Re: How to set scale of CAD in micrometer
« Reply #5 on: September 01, 2011, 07:27:34 AM »
What version of Designcad do you have?  Units multiplier has been around since at least V17.

You can set these for an existing selected dimension - as long as it is drawn as a dimension, and not as text - by using the second tab of the info box (or near the bottom in V17)

In recent versions if you pick a predefined unit for the dimension, such as feet dimensions in a metric drawing, then the "multiplier" field is set automatically, and greyed out to provide the correct conversion.

So you need to select a unitless dimension format without a predefined unit
User since Pro-design

Hari

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Re: How to set scale of CAD in micrometer
« Reply #6 on: September 02, 2011, 03:16:32 AM »
I am using 3D max V21.

Just one more quarry -- How to convert dcd/dc2 to GDS file format.
« Last Edit: September 02, 2011, 03:26:01 AM by Hari »

DrollTroll

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Re: How to set scale of CAD in micrometer
« Reply #7 on: September 02, 2011, 12:41:05 PM »
GDS is a Cadence file? No idea. Probably you'll have to export as dwg, then see if you can import that into the target software.
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Bob P

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Re: How to set scale of CAD in micrometer
« Reply #8 on: September 02, 2011, 03:02:21 PM »
I think that GDS (II) is a circuit board standard.  I've fiddled with free converters with little success.

JJG

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Re: How to set scale of CAD in micrometer
« Reply #9 on: September 03, 2011, 10:43:30 AM »
for more information about .GDS files (which are an equivalent to "Gerber" format-files), look at this :
http://www.fileinfo.com/extension/gds

Dr PR

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Re: How to set scale of CAD in micrometer
« Reply #10 on: September 03, 2011, 11:38:34 AM »
GDS is an IC design file type. Your best bet is to export from DesignCAD in DWG or DXF format and look for a translator to convert from DXF/DWG to GDS. Use DWG if possible - it makes a smaller file size and it is a much better defined file format (less chance of mistranslation).

Now I understand why you want to work in micrometers.

Phil
DesignCAD user since 1987