[Ja...] Posted August 27, 2020 Share Posted August 27, 2020 Recently I have been encountering parts that use datum targets and it is my first time working with them. I have a part with six datum targets (see attached pic). I want to use those datum targets for alignment and have looked into P6, RPS and 3D best fit alignments with looping with break condition for baseSystem Avalue as <.001. It seems like P6 and RPS 321 alignment wont work in this case. The question is when I select the six points for RPS alignment, I dont understand how the checkboxes function? I selected x and z checkboxes for A1 to A4 , selected z checkbox for B5 and y checkbox for C6 points. But 321 alignment doesnt work and freeform alignment keeps on looping till end. Any input on how should i approach this alignment?tempsnip.png Link to comment Share on other sites More sharing options...
[Me...] Posted August 27, 2020 Share Posted August 27, 2020 Interesting targets. A1-4 define a plane, not a cylinder, yet they're on a cylinder. Not knowing the function and if any of the targets have greater weight than others, I would use a Geometry Best Fit alignment of all 6 points and allow all degrees of freedom to fit under the evaluation constraints. I'd also loop it numerous times since it's trying to fit all the vectors of the points simultaneously. Link to comment Share on other sites More sharing options...
[To...] Posted August 27, 2020 Share Posted August 27, 2020 There's a great video webinar on this topic. https://www.zeiss.com/metrology/events/ ... dings.html# Just register and you''ll have access to the videos. scroll thru until you find the one below.webinars.JPG Link to comment Share on other sites More sharing options...
[Me...] Posted August 27, 2020 Share Posted August 27, 2020 If they're wanting them ordered then you're on the right path. But A1-4 won't create any sort of realistic axis or cylinder since they don't have opposing points on the cylinder. Creating a plane is odd, because they're using points that are not in the same vector. Does this part lay in a valley tangent on the shaft? Link to comment Share on other sites More sharing options...
[Me...] Posted August 27, 2020 Share Posted August 27, 2020 Correction. 3d Best Fit alignment. Looks like you can't loop a Geometry Best Fit. Same principal. Link to comment Share on other sites More sharing options...
[Ja...] Posted August 27, 2020 Author Share Posted August 27, 2020 Please sign in to view this quote. Thank you Tom, I will look into it. Link to comment Share on other sites More sharing options...
[SH...] Posted August 27, 2020 Share Posted August 27, 2020 Please sign in to view this quote. Thanks , it is a icing on the cake.... Link to comment Share on other sites More sharing options...
[An...] Posted August 27, 2020 Share Posted August 27, 2020 Sorry! This is Science Fiction. Link to comment Share on other sites More sharing options...
[Ja...] Posted August 27, 2020 Author Share Posted August 27, 2020 Please sign in to view this quote. I do not know about its further assembly but looking at these targets it seems like they are trying to simulate laying down the part on a fixture with A1-A4 being the touch points on a 90 degree V block. point B5 as a touch point to lock its rotation along axis using pin on the fixture and C6 to lock its translation along the axis using another pin on the fixture Link to comment Share on other sites More sharing options...
[Ja...] Posted August 27, 2020 Author Share Posted August 27, 2020 Please sign in to view this quote. Thank you, I will try using this. Also, should I check best fit on CAD model while using this alignment. What is its purpose? Link to comment Share on other sites More sharing options...
[SH...] Posted August 27, 2020 Share Posted August 27, 2020 Please sign in to view this quote. Yes, I agree with you , I have seen lot of caterpillar drawing like this useful for fixture designers.. I didn't use that datum target for inspection. Link to comment Share on other sites More sharing options...
[Me...] Posted August 27, 2020 Share Posted August 27, 2020 Please sign in to view this quote. Yes, if you have one, it's accurate, and you created your points directly on the model, as opposed to keying in the values. Link to comment Share on other sites More sharing options...
[Ja...] Posted August 27, 2020 Author Share Posted August 27, 2020 Please sign in to view this quote. Getting the points the on the shaft A1-A4 was hard so I created points on the CAD model using "Define points" and then keyed in proper xyz and ijk values for each point. CAD model comparision showed zero deviation for those points. Do you think that will still not work if I use best fit on CAD model options? Link to comment Share on other sites More sharing options...
[Me...] Posted August 27, 2020 Share Posted August 27, 2020 I don't know the exact technical fitting method that the CAD uses, but I believe, like Freeform, that it derives and fits to the actual CAD surface model and is dependent on it. I've had the best results using the CAD model, as long as it's accurate. You can always create 2 alignments and compare results if you have doubts about how it's fitting. Link to comment Share on other sites More sharing options...
[Ma...] Posted August 27, 2020 Share Posted August 27, 2020 If you have CAD model, then it could work. But i would try with point on radius ( or how it is named ) - it gives you a circle from one point by defining radius and angle. Combining A1 and A2 ( symmetry ) will give you 1 point of axis - same for A3 A4. Other points just block rotation and translation of rest. Start system should be used for exact contact points ( +/- 45° ). Like 90°prism. I always use teoretical diameters for this because of machining program. They predict size of part and it's position - then they create a program for machining. Link to comment Share on other sites More sharing options...
[Da...] Posted August 28, 2020 Share Posted August 28, 2020 Please sign in to view this quote. Which of those 2? Please sign in to view this quote. Please sign in to view this quote. Link to comment Share on other sites More sharing options...
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