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Snap To Grid - No Way!

Roger BFS

OK - The "Snap To Grid" option simply doesn't work (for what I need) under 16.6 SP5.  I obviously expect too much, but after several hours of clicking and reading the help docs, I can only conclude its broke. (please excuse the rant).

I'm trying to clean up a bunch items imported from dxf that ended up at weird off-grid coordinates, although basically close. The elements of concern just include mechanical features like circles, squares and panel outlines.  I've successfully imported it to a brd file, but not surprisingly the coordinates are all screwed up from accuracy round-offs or whatever.  Things were imported into the non-etch subclass "board_geometry/assembly_detail" for intended use as placement reference.

The problem arises in trying to clean it up a bit using the move > snap-to-grid command option.  I have not been able to find a mouse click sequence that works (usefully) to get the drawing elements to align to my Allegro grid (non-etch), which is currently set to 1-mil.  After several hours of playing around, I've managed to achieve alignment of a few elements, but not by using the "Snap To Grid" command option.

Any of the experts here have any insights into how Cadence intended this option to work?  Is this a new UI productivity feature of 16.6 or do I just need to re-training?  Also, discovering some help documentation (latest version installed) on "nudging" items a small amount, the "Shift-Click, Shift-Arrow" key method described doesn't work either.  The folks writing the help files must be a few revs behind.

One issue might be with my imported circles that are interpreted by Allegro as single-line arcs (segments) with the same start/end point, and a center coordinate identified in the "show element" report.  However there is "no origin" or "vertices" identifyable when tring to use the Move command, which is basically making the snap-to-grid option useless.

Productivity increasing again - - Thanks!

  • Roger,

    I will tell you what I do, but it may not be the answer you desire.  For me this has turned out to be the quickest way to having the outline and holes on the grid.

    I work in mils so that is how I am expressing grids and dimensions.

    I bring the DXF in on a Board Geometry layer I don't use.  I then draw the outline on the Board Geometry/Outline layer with my grid set to 5 and 5, following the DXF as closely as possible but placing the lines on the grid.  For the mounting holes I create a "cross-hair-with-circle" on the Place_Grid_Top layer and then copy the cross hairs to the center of each indicated hole. With a grid of 5 and 5 the max error between the DXF and your design will be 2.5 and 2.5. If there are notches that will have to have an internal radius I draw the line at 90 degree intersections. I then use the Manufacture-->Dimension/Draft-->Fillet command to create the radius I need (usually 62 to match the IPC recommendation for a minimum radius.

    Budd 

  • With an imported DXF file try Shape - Compose Shape - Set the layer in the Options menu and then window select the board. This creates a shape of your board outline which groups all the segments together. Once they are grouped the RMB - Snap Pick to should pick up on the circles, segment vertex etc. 16.6 has three more options for Rectangles which should also help you on your way. If this still fails contact Cadence support or the VAR and give them examples so if required the tools can be enhanced / corrected.

  • Thanks everyone for the helpful suggests.  Meanwhile, I have fixed my immediate problems using brute force Edit>Move>select>"ix nn iy nn" command sequence to nudge things by an amount (predetermined by Show Element) required to get items on my grid.

    I've also spent the past couple days conversing with my VAR tech support and have requested a bug fix/enhancement of the "snap-to-grid" option as applicable to line segments.  Although I'm not sure certain that I convinced them it needs fixing. It seemed perfectly acceptable to them that "snap-to-grid" means "any grid" not necessariy the "closest grid".

    However, they did reveal a click sequence to me that would have accomplished the feat, but had not occurred to me. 

    FYI - Using the pre-select command mode, hover over a circle (line segment), RMB select Line>Move.  At that point the circle's center snaps to your cursor location (provided you have "Body Center" command option selected).   Since that was far away for where I wanted it to be, I was previously exiting at that point.  However, if you don't use the mouse to place it and instead use keyboard Shift>Arrow keys, the circle will then snap back to where it "was" and place itself at the nearest grid point depending on which arrow key you use.

    Obvious!  But don't use the RMB "Snap-to-Grid" selection.  That will immediately place the circle's center on a grid-point near wherever you cursor is, somewhere along the perimeter of the circle where you selected it pehaps.

    Thanks again!

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