First, let me express my gratitude for the work of all the contributors involved in creating Kicad.
Six weeks ago I started learning Kicad, my first encounter with a full blown PCB tool. As a hobbyist I’ve previously made a few boards using ExpressPCB, which is not a good long term solution. I considered Eagle, but the news that they’ve been bought by AutoDesk put me right off that idea. Fortunately there is Kicad!
My pcb is a power supply board for a tube amp. It provides voltages for the output tube screen grid, the plate for the driver, and a voltage for heater elevation.
I sent it out last week and then began configuring 3D footprint parameters. As others have, I encountered the problem of the device being the wrong size and offset from the holes. So, I installed MeshLab, imported the .wrl, exported it from MeshLab, and diff’d it with the original. This revealed that the .wrl MeshLab output has a section for scaling and translation at the top of the file. I then edited the file in WordPad to scale down by a factor of .39 and shift by 1. This is faster, and in my view better, than doing this directly by editing footprint 3D parameters.
As for my board, I think it may need another rev. Carefully following the dimensions in the data sheet, I made my own footprint for the LR8 TO-252 package, U1,2,3. Then when I added the 3D model I see that it EXACTLY covers the pads! I have a feeling I may have trouble soldering this by hand.
Never trust the dimensions of a VRML file. It is better to use STEP files; then at least you can make measurements in FreeCAD and see if the dimensions are correct. Assume that the TO-252 models are wrong and use the manufacturer’s recommended footprint to check your work. If you are using a soldering iron (not so easy with such a large heat tab) you can make the pads slightly larger. If you are doing hot air soldering then the pads are often barely larger than the leads; there is just enough space for a good toe and heel connection to the lead and often not even any space to the side of the leads.
If you search the forum for ‘stepup’ you will find more information of a tool which can help you. If you use the nightly builds rather than the stable, you can use STEP models directly.
IF, and ONLY IF, everything in the 3D parts are good, then the 3D viewer is a good source of information.
HOWEVER, the native 3D viewer is fairly new in KiCad.
In my opinion, your best chance of getting a quality board back from your chosen PCB manufacture is to create Gerber Files, to their specification, for you to thoroughly review for errors.
Thank you and Sprig for your advice and admonitions about dimensions.
I was intending to use STEPUP but took a shortcut with the MeshLab output, in part from weariness after having to learn FreeCAD to model the turrets. Btw, in the case of the TO-220, which showed up as too large in 3D, I did load the Meshlab file into FreeCAD to measure the pin spacing. To my surprise it was correct.
Anyway now, especially in light of these replies I will certainly step up to STEPUP.
OK. I’ve upgraded to the latest nightly KiCad build of 8 May. I’m running FreeCAD Ver 0.16. I configured the kicad-StepUp-tools.FCMacro in FreeCAD. I made a new turret in FreeCAD and then created the .wrl with StepUp and voila!
If you want to create your own 3d models and export not only the wrl but also the step file, you should use either freecad 0.15 or a 0.17 recent development build.
0.16 and older 0.17 have a bug in the step export. https://forum.freecadweb.org/viewtopic.php?t=20455
please consider that recently kicad 3D library has increased a lot with accurate mechanical models, already within their wrl counterparts and aligned to their corresponding footprints thanks to the MCAD team
just have a look at here
you can follow this thread to see recently additions
Just finished changing the pads for the DPAK chips to make space for
solder. The tool is easy to use, ensures accuracy, and can viewed from any
angle. Yes, I really appreciate this.
Btw, the DPAK was not offset in the X direction. When I first drew the
pads I did not have the blue lines in the Footprint Editor centered.
