Good afternoon,
I am working with a Japanese blueprint that has datum targets called out but no datums that I can see. They are wanting me to hold Profile of a Surface and Profile of a Line on a few of the dimensions. I am a little confused to say the least. If someone is willing to help me on this, I can privately send a copy of the print in question.
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They seem to be controlling the “plane” the datum creates using that “line”
Basically the true form of the plane to the “perfect theoretical” not its “flatness”
the reason for no datum call out is probably because the form that you are needing to hold is not a mating contour.
Think of a profile call out like using the “offset” function when sketching. Just the entire plane can be offset.
Therefore the tolerance is automatically bi-lateral so the profile can move in between that set amount.
hope that makes sense.
Cheers!
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I take back the bi-lateral, I can be an uni-lateral tolerance also depends on how the leader line looks.
if it drawn to another line off the part then that indicates the direction that the form is allowed to move.
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Thank you! The whole thing is confusing to me. I have attached a copy of the print.
R01XF71867-X7V02-1-1-01XFSS0550 71868-02090-ballooned.pdf (580 KB)
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I have attached the print. The whole thing is confusing. The way everything is called out is confusing. If you can help me get clear on this, I would greatly appreciate you.
R01XF71867-X7V02-1-1-01XFSS0550 71868-02090-ballooned.pdf (580 KB)
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I searched for about 10 minutes and could not locate Datum B. So if I am reading this engineering drawing correctly, it is specifications for a finished injection molded part made out of PP or PE. I assume you must be considering to build the mold. It has callouts for gate locations, types of Rawal finishes (they may not call them Rawal anymore) and other gate, rib and other plastic specifications. Of course the mold would have to be designed for the shrink factor, consider any large web thicknesses, etc. Worked with Poulan Saw and they consigned us to make the mold for a weed eater shroud. It was about 20" long and then plastic part. They had datums to specify flatness of plastic part in relationship to connection at the end of shaft. They were rejecting their plastic parts because they were not holding part to spec. They wanted us to redo the mold, although our mold was flat within .0005 at those datum targets. The injection process was warping the part and they wanted us to modify the mold… lol… I tried to explain to the engineers for a week that they did not want us to change the mold based on their last production run. Finally, got a plastic engineer to explain it to them internally. You want to please the customer, but sometimes the customer does not understand the consequences they are requesting.
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Thank you!! Actually, I am writing a CMM program to inspect the part. It is a molded part. They called out prifles against ABC but without B, I cant align the part. That’s where I am having the trouble.
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That part is long and slender, will be difficult to meet tolerance after it has been sitting around unconstrained. We had to recommend to customer to build a fixture to mount and secure the part to and then measure it. The datum could be fixtured and checked, then the part could be fastened, clamped to the fixture surface. I hated to CMM plastic parts.
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Humm. Looking at the print, one of the targets is on one of the tabs on the left of the print. I guess for the purpose of inspection, I can call one of the tabs Datum B so that I can get some kind of alignment for the part. What do you think? Thanks for your help!!!
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If I had to guess, Datum B would be the 7 ±/.01 slotted hole at note 38 & 39 based on the B1 and positioning frame at note 37. There is a A<->B reference at L6 of the drawing that provides some alignment
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I thought about that too. So the way I see it is A is to the left side which is marked, B is the slotted hole and C being the tab above the slotted hole. Is that what you’re seeing too?
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Is it die and mold? If so they are calling cavity center.
@StephenHadwin I want you to know your being a fantastic helper 
Your super Dee duper
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I want to thank everyone that responded to my question. What I did, after much studying of the print, was took the three datum targets (A1, A2 and A3) and created a plane to level to. The other datums where in fact the inside surfaces of the Y and X. For the alignment, I created a bestfit alignment using points taken from each of the datums.
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