Scaling Issues from Sprint-Layout to Cut2D

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Micronaut
Posts: 2
Joined: Thu Jul 01, 2021 2:16 pm
Model of CNC Machine: Wegstr CNC

Scaling Issues from Sprint-Layout to Cut2D

Post by Micronaut »

Hi,

I am under some pressure to mill out a circuit board using the Wegstr CNC machine.

My work flow has been as follows:

Circuit designed with Sprint-Layout 6.0. Board measures 80 x 40mm.
(Leg spacings measured and pads placed those dimensions apart)
Untitled0.jpg
Circuit and drill holes exported [File/Export/Isolation Milling]
There are two options for scale (Scale: 1 HPGL - unit = 0,0254mm (1 mil), 1 HPGL - unit = 0,025mm (1/40 mil)) What do these mean?
Untitled3.jpg
Exported PLT file is converted to PDF using coolutils.com/online/PLT-to-PDF

PDF opened in Cut2D Desktop.
This warning message is shown
Untitled1.jpg
Board dimensions are entered
Untitled2.jpg
Now when I make a measurement in Cut 2D it reads 4.09mm
Untitled4.jpg
as opposed to 4.92mm in Sprint-Layout
Untitled6.jpg
When the drill file is exported seperately from Sprint-Layout, its scale is different to the tracks. It is really frustrating. Please can somebody help me to resolve this issue with the scaling?

Thanks!
Karl

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adze_cnc
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Model of CNC Machine: AXYZ 4008
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Re: Scaling Issues from Sprint-Layout to Cut2D

Post by adze_cnc »

In the following, remember that 25.4mm is the equivalent of 1 inch.

Historically, PLT files were created using 1016 units per inch. So, if we take 25.4mm and divide that by 1016 we get 0.025.

Presumably somewhere along the way someone decided that 1016 units per inch was too cumbersome and decided 1000 units per inch was better. So, if we take 25.4 and divide that by 1000 we get 0.0254.

This should explain the two scaling factors in the Sprint-Layout export dialog.

When you convert the PLT file to PDF the underlying units are still 1000 or 1016 (depending on that scale to chose). Because of that your 80mm wide job is either 3150 or 3200 units wide in the PLT depending on which scale you chose. Cut2D interprets those 3150 or 3200 units as mm so you get the exceeds 625mm error.

Having the "Scale design with job size" is the way to convert that 3150 or 3200 units to 80mm.

Which scale did you choose (1 HPGL - unit = 0,0254mm or 1 HPGL - unit = 0,025mm)? You might try the other option to see if all this unit conversion can be made to work.

Micronaut
Posts: 2
Joined: Thu Jul 01, 2021 2:16 pm
Model of CNC Machine: Wegstr CNC

Re: Scaling Issues from Sprint-Layout to Cut2D

Post by Micronaut »

Hi adze_cnc,

Thanks for your good detailed response.

I have finally found a work around.

I measured the distance between pad centers in x and y directions in Sprint. Then upon importing the PDF into Cut2D without rescaling, I measured the equivalent distances for the same pads for the x and y directions. Dividing Cut2D by Sprint Layout gives the scaling factor by which the I should reduce the drawing by. Works great now!

When importing the drill holes subsequently, I must manually resize these so that the sit on the pad centers.

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Adrian
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Model of CNC Machine: ShopBot PRS Alpha 96x48
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Re: Scaling Issues from Sprint-Layout to Cut2D

Post by Adrian »

Not sure if it helps or not but bear in mind that the drilling toolpath doesn't need circles. It will drill in the centre of any shape vector so if it was a square it would drill in the same place as if you added a circle.

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