[Ro...] Posted November 25, 2019 Share Posted November 25, 2019 So im remotely helping out the programmer at another facility. Hes having "issues" because he thinks calypso is giving too much bonus. .1TP with MMC on a 1.7mm Radii, with a tolerance of +/-.1mm. So using the standard MMC button were getting total tolerance of around .25mm. I created a formula, doubling the Radii and doubling the tolerances, and was able to recreate the same amount of tol that Calypso was giving, and i told him "this is the correct amount of tolerance, Calypso was not wrong". But he (and I to a lesser amount) think that this is too much tol for comfort. Is it right? Double radii and double the tolerance for modifier calculations? Or, do you double the radii and keep the tolerance the same?jhgmnbjhg.JPG Link to comment Share on other sites More sharing options...
[Ia...] Posted November 25, 2019 Share Posted November 25, 2019 I would double the Radius and size tolerance for it, but leave the TP tolerance the same. With the ø symbol in the control frame, it is already signifying the diameter of the tolerance zone, not the radius. So I think you are correct. The design engineer may not have intended for that much TP tolerance, but that's how it is written (at least to me). Interested to hear other opinions. Link to comment Share on other sites More sharing options...
[Cl...] Posted November 25, 2019 Share Posted November 25, 2019 Because a radius is not a feature of size can a position tolerance be applied to it? Link to comment Share on other sites More sharing options...
[Br...] Posted November 25, 2019 Share Posted November 25, 2019 The problem is that position is ONLY for features of size which this radius is not. It's completely subjective because this has no support within the standard. I think you are doing the best you can do with what you have if you cannot speak with the costumer directly to find a solution to this. Furthermore, the MMC modifier requires a size tolerance (or profile tolerance but this is rarely used.). The radius tolerance is not a size tolerance. It's more of a surface tolerance similar to a profile tolerance in the way that there are inner and outer boundaries that the surface must lie within. Technically, with the MMC modifier there is a surface interpretation to the position tolerance. This would mean that there is an inner boundary based on the virtual condition, that no element of the surface may violate. You can create this (It's a little complicated) in calypso using the profile characteristic and creating a nominal circle feature that is equal to the virtual condition size of the feature. Then you would use a tolerance zone that goes to infinity in one direction. But what you're doing is the axial interpretation, and in that regard-yes- double the radius tolerance because in a complete circle, you have the radius tolerance on both sides(even though we're converting a radius tolerance into a size tolerance which it is not). So think about it. if your tolerance range is R1.60-1.80, then double those numbers to get the diameters- Ø3.2-3.6- that's Ø3.4±0.2. I would say you are perfectly justified in this. If its not what they want, they need to correct the drawing. Link to comment Share on other sites More sharing options...
[Cl...] Posted November 25, 2019 Share Posted November 25, 2019 Profile not position. Link to comment Share on other sites More sharing options...
[Me...] Posted November 25, 2019 Share Posted November 25, 2019 Please sign in to view this quote. That's exactly what I was gonna add. Link to comment Share on other sites More sharing options...
[Ia...] Posted November 25, 2019 Share Posted November 25, 2019 Please sign in to view this quote. How do you determine when a circular element is/isn't a feature of size? Standard defines a regular feature of size as: Not disagreeing with you, just curious. Link to comment Share on other sites More sharing options...
[Br...] Posted November 25, 2019 Share Posted November 25, 2019 It needs to have opposed surfaces in order to contain an Actual Mating Envelope.So with a partial arc, sure you have a circular surface, but it does not have the opposed elements. If you tried to expand an AME within it it would just expand forever. The arc cannot contain the AME and therefore a feature axis cannot be produced. You have problems as well with the idea of rule #1. A radius tolerance as I mentioned before also is not a size tolerance. A size tolerance is subject to Rule #1 (Perfect form at MMC). Even if it had a size tolerance applied to it, It would never violate the boundary of perfect form at MMC because no opposed surfaces can contain it to force a violation of the boundary. On top of that, Rule #1 states that the feature's actual local size must also be within the LMC size. But any feature without opposed elements has no actual local size!!! Hopefully you can see from these issues that a radius is not a FOS. To further back this up, here's a video from Tec Ease explaining the "Caliper Rule" for identifying features of size. https://youtu.be/wNTmeSkgYh4 Link to comment Share on other sites More sharing options...
[An...] Posted November 26, 2019 Share Posted November 26, 2019 Please sign in to view this quote. There is even more tolerance. See attached.Contribution_26_11_2019_a.pdf Link to comment Share on other sites More sharing options...
[Ro...] Posted November 26, 2019 Author Share Posted November 26, 2019 Thanks all. I think what we're going to do is to continue giving them (production) 1/2 bonus tolerance since this is a very simple "ring groove on a shaft" dim to maintain. but if questioned by anybody we will pretend this was an oversight and use the "ooh i didn't notice that" defense. I just wanted to know in the end that Calypso was correct, but i also wanted to know that i was pumping the right info into the generated Diameter feature for Calypso to use. I consider myself to be a very good programmer, but i also consider myself to be almost functionally illiterate when it comes to reading standards and whatnot. it's like the moment my elbows hit the desk, dream weaver starts playing in my head...... Link to comment Share on other sites More sharing options...
[Ia...] Posted November 26, 2019 Share Posted November 26, 2019 Please sign in to view this quote. I have seen a lot of drawings that references the axis of a radius for location. Some coworkers are about to hate me.. Link to comment Share on other sites More sharing options...
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