![\"Aero3\"](\"https:\/\/blog-assets.solidworks.com\/uploads\/sites\/2\/2016\/03\/Aero3.jpg\")
<\/p>\nMissing critical dimensions and tolerances is one of the major complaints against MBD in production, especially among suppliers. Some machine shops dismiss\u00a0MBD as \u201cirresponsible laziness\u201d because their clients provided only 3D models with no 2D drawings, 3D dimensions or tolerances in the hope that machinists can measure models in SOLIDWORKS or 3D PDF directly.<\/p>\n
However in reality, shop floors often times still need explicit critical dimensions and tolerances to machine and inspect, so some even end up creating 2D drawings themselves based on 3D models or 3D PDFs just to add and present necessary manufacturing information.\u00a0 Consequently, machine shops not only didn\u2019t see any MBD benefits, they even felt disserved: \u201cMaybe our clients saved some time because they didn\u2019t have to generate 2D drawings, but the workload was simply thrown over the wall to us.\u201d<\/p>\n
Worse still, when\u00a0the self-generated 2D drawings by suppliers mismatch 3D design intentions by clients, the finger-pointing games start: \u201cYou didn\u2019t measure the model!\u201d \u201cYou didn\u2019t specify dimensions and tolerances!\u201d It\u2019s not uncommon to even go to court. But the truth is, whether we like it or not, machine shops’ business interests favor design interpretations that can simplify manufacturing, which may not be in the best interest of overall product function or quality. Therefore, to avoid conflicts of interests, it\u2019s really vital to set the game rules straight. Calling out product and manufacturing information (PMI) explicitly is one of the key measures here. Let\u2019s drill down further piece by piece to its detailed benefits and problems avoided.<\/p>\n
<\/p>\n
1.\u00a0\u00a0\u00a0 It is the design team who knows best about product use cases, design intention, important features, and technical requirements, therefore, they should be the authority to convey these without any ambiguity. If these important callouts are missing and left free to other\u2019s interpretations, then misunderstandings and even conflicts\u00a0are prone to happen. Plus, it\u2019s in production or suppliers\u2019 best interest to interpret requirements in favor of manufacturing, but not necessarily the ultimate product quality.<\/p>\n
2.\u00a0\u00a0\u00a0 Calling out PMI at Design is an opportunity not just to communicate, but also to review, check, and improve design and manufacturability. Skipping this step means missing this opportunity.<\/p>\n
3.\u00a0\u00a0\u00a0 There could a be substantial amount of manufacturing information, even just critical ones, in a design. If downstream staffs always have to manually measure to get key ones each and every time, it not only takes time and effort, but also is easy to miss design requirements and manufacturing errors, because key information is hidden in the model. The consequences are jeopardized qualities, prolonged cycles, and increased costs. For example, suppliers would definitely bump up their quotes to compensate this operational overhead. On the other hand, key callouts not only ease the reading of each and every requirement, but also present a complete check list as a visual reminder.<\/p>\n
4.\u00a0 Model geometries provide dimensions, but not necessarily tolerances. The lack of tolerances obviously is prone to misreading. The best case is shop floors can follow undocumented conventions to machine and inspect. Even so, real tolerance requirements are nowhere to confirm: maybe general tolerances are fine or maybe tighter requirements get simply ignored leading to rework or scrap. The worst case is even general tolerances are unknown, leaving shop floor clueless or complete freedom. Another possibility is design team defines both dimensions and tolerances in sketches or features. If so, we might as well just expose these callouts in 3D to avoid recreation and manual repeated look-ups.<\/p>\n
Let\u2019s take a break here before this blog gets too long. Next, Part 2 of this same topic will discuss additional benefits besides these above four, also the PMI schemas and use cases recommended in Military-Standard-31000A. To learn more about SOLIDWORKS MBD, please visit its product page<\/a><\/strong>.\u00a0Also welcome to discuss with me at Twitter (@OboeWu)<\/a><\/strong> or LinkedIn (OboeWu).<\/a><\/strong><\/p>\n <\/p>\n","protected":false},"excerpt":{"rendered":" Missing critical dimensions and tolerances is one of the major complaints against MBD in production, especially among suppliers. Some machine shops dismiss\u00a0MBD as \u201cirresponsible laziness\u201d because their clients provided only 3D models with no 2D drawings, 3D dimensions or tolerances<\/p>\n... Continued<\/a>","protected":false},"author":78,"featured_media":28811,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[18],"tags":[173,1620],"class_list":["post-28765","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-solidworks","tag-drawings","tag-mbd"],"acf":[],"_links":{"self":[{"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/posts\/28765","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/users\/78"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/comments?post=28765"}],"version-history":[{"count":0,"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/posts\/28765\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/media\/28811"}],"wp:attachment":[{"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/media?parent=28765"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/categories?post=28765"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.solidworks.com\/solidworksblog\/wp-json\/wp\/v2\/tags?post=28765"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}