Datum targets on edges? 1

[TheTick]

I am using a datum target symbol to designate a point on an edge, with an "X" for the area. I noticed that the target can "latch on" to a sketched line, but it will not latch on to a model edge. Also, the target point will not "Double latch" onto two lines to stick to an intersection.

Does anyone have advice on how to control positions of datum targets in a drawing?

All this machinery making modern music can still be open hearted.

 

[jimden]

Hmm

Was lookin at that, seems to stick to a face well,
goes funny on a plane even



The illulsion of integrity

 

[jimden]

Tick

Datum Target (not symbol) seems to stick to a point
in an open sketch with all filters turned off
bizzarr


How nice to believe in the freedom of Solidworks

 

[jimden]

Oh

Insert it then reselect the end and drag it over to the point

 

[TheTick]

Seems you can attach and detach from a point. At least this gives me the control I want (constrain the target to the intersection of an edge and a centerline).

I also noticed that once the target "grabs" an edge, line, or face, it will not let go and allow me to reattach to something else. The remedy for this is to click-drag-copy the symbol, delete the old symbol, and attach the new one to where I need it. Not too bad a workaround.

All this machinery making modern music can still be open hearted.

 

[automationbabe]

TheTick -

I have found that SW follows the ANSI/ASME rules for GD&T very well. Learned the hard way that if SW won't let you do it, it's probably not being applied correctly. Makes me look at my book to see how I should be doing things.

According to GEO-METRICS III by Lowell W. Foster, and the samples I've seen in there, targets define separate points on a plane which may explain not being able to "double-latch" and share the same name.

Hope that helps. Really good book too. Highly recommend it.

D~

 

[JNR]

Ahh... The Tick took the words out of my mouth... er, or off my finger tips or whatever ya do in computer chat.

SolidWorks has done a remarkable job of keeping you to the standards. GDT is a difficult subject to apply correctly. (Everyone should go to a class in my opinion.)

BTW: Mr Foster is on the GDT committee, so he definitley knows what he is talking about.

 

[TheTick]

Been to class. Got the book.

Actually, if you could see what I was doing, you would be able to tell that it is not "out of line".

I need to use two points of a sheet metal edge to use as a secondary datum. The locations that I wish to use are at the intersection of that edge and the centerlines of nearby slots, which are already dimensioned with basic dimension. I was just looking for a way to set up the target so that if the geometry (and resulting centerline and intersection) change, the target location changes with it. Lots of words, but one picture is likely to generate an "Ah, yes" response. Anyone interested?

 

[JNR]

Well... you are not going to want to hear this.

Paul Wanner taught us and he is also on the commitee. I confirmed with one of my co-workers who did the advanced class to get certified.

Datum targets must be on a feature. They can not be in fresh air. GDT is designed such that a part can be fixtured and/or measured to the datums. The ACTUAL datums are wherever the ACTUAL feature is on the part. (Even the axis of a cylinder is defined from the surface of the cylinder). For datum targets you have to have something that could be set against a tooling button or ball (One reason why they have a diameter). I believe that if you think about it, you can't know where the points are, since there is no surface to intersect with (it's in the machinist's scrap bin), thus you can't measure or fixture to it. You can't just measure the surounding surface and call it good either according to GDT rules.

Maybe you could use the whole surface as a datum and then two hole axis datums, then effectively use the intersections of these to dimension from, which sounds like what you are really looking for. But inspection could be interesting. Hole axes are harder than you think to inspect correctly per GDT.

The problem with GDT (and its strength) is in interpretation. If you don't get the definition correct per standard, you can't argue when the parts come in wrong.

Good Luck with this one - sounds like some of the ugly stuff you have to do!

 

[TheTick]

The target is ON an edge-face. It is not at a "virtual" location in space.

I will post a PDF image tomorrow (6/10/03) and put a link here.

 

[TheTick]

Got some links to images so as to save words.

The square slots engage snaps. The datum targets would coincide with the centerline in the ideal state. The (driven) basic dimensions show where the check fixture pins would contact. Should the slot positions ever change, the fixture would be updated, as well. I want the target to follow the point where the centeline CROSSES the edge when geometry changes.

image of drawing view-- note: not fully detailed as yet

http://www.liquidschwarz.com/CAD/SnapSlots.pdf

scanned image from GDT reference (sorry, it's a big bitmap 1.1MB)

http://www.liquidschwarz.com/CAD/DatumTarget01.bmp

I've found how to do this. Jimden nailed it when he noted that targets can be attached to points. The point can then be constrained to the intersection.

All this machinery making modern music can still be open hearted.

 

[TheTick]

Jeepers, Marty, and JoBeth!

The link is behaving poorly, due to my discount Tripod website. Cut-and-paste the link to the address bar of your browser and it ought to work. If it doesn't, do let me know.

image of drawing view-- note: not fully detailed as yet

http://www.liquidschwarz.com/CAD/SnapSlots.pdf

scanned image from GDT reference (sorry, it's a big bitmap 1.1MB)

http://www.liquidschwarz.com/CAD/DatumTarget01.

 

[SBaugh]

The first one worked if you copied it, but the second one doesn't. I have tried coping it (With and without the . at the end) also tried clicking on it. With no result other than "Sorry, but the page or the file that you're looking for is not here."

Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help

 

[TheTick]

a la Rocky from "Rocky and Bullwinkle"

This time for sure!

http://www.LiquidSchwarz.com/CAD/datumtargets.htm

 

[SBaugh]

Your going to for saying this.

When I click on the DatumTarget01.bmp link nothing shows up just a blank white screen.

Heck I would post it for you, but my site is down at this moment . Going to be up soon though.

Best Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help

 

[TheTick]

for the bitmap you'll need to right-click the link and "Save target as..."

 

[JNR]

Hmmm..... I cut-n-pasted BOTH links to IE and they opened fine - one in Adobe Acrobat and the other opened an MSPaint window.

I see what you mean and what you are trying to do - misunderstood and thought the hole axes were parallel to the screen not perpendicular to it. You can rest your hammer now....

Yeah, I agree the only way is use points. We have done something similar in a way in the past. For doing datum targets on a surface, we did circle/split lines with the target diameter. Dims or relationships in the circle sketch kept the position relationships for us as things changed in the design. The target was made concentric to the circular split-line. (Also by the way gave a neat indicator in the part file to show where the dataums were located.)

Here's the rub - in SW2003 (and I have not pulled one of these old files up and checked if it affects them). SW2003 likes to count curved edges as SPLINES in a lot of cases now. It knows they are geometrically circles, but in SOME commands it now thinks they are splines and refuses to cooperate like it used to. Anyone seen this is and/or found a way round it?

3/4 of all the Spam produced goes to Hawaii - shame that's not true of SPAM also.......