{"id":13037,"date":"2025-07-24T14:29:12","date_gmt":"2025-07-24T14:29:12","guid":{"rendered":"https:\/\/eli-tec.com\/?p=13037"},"modified":"2025-09-12T08:11:12","modified_gmt":"2025-09-12T08:11:12","slug":"how-to-design-parts-for-mjf","status":"publish","type":"post","link":"https:\/\/eli-tec.com\/ar\/how-to-design-parts-for-mjf\/","title":{"rendered":"How To Design Parts For MJF That Perform And Scale"},"content":{"rendered":"<p>If you\u2019re figuring out <strong>how to design parts for MJF<\/strong>, you probably care about three things: reliable, repeatable quality; tolerances that don\u2019t surprise you after post\u2011processing; and unit costs that still make sense when you move from ten prototypes to a few thousand production parts. Multi Jet Fusion is forgiving compared to many processes, but it rewards disciplined CAD. This guide\u2014aimed at U.S. product teams and manufacturers\u2014lays out actionable, shop-proven practices you can apply immediately without drowning in jargon.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Quick refresher on MJF&nbsp;<\/strong><\/h2>\n\n\n\n<p>Before you start changing wall thicknesses and fillets, it helps to remember how MJF actually fuses powder. Agents are jetted where you want polymer to solidify, infrared energy does the melting, and the surrounding powder acts as a built\u2011in support. That freedom comes with responsibilities: thermal mass, powder evacuation, and finishing all nudge your dimensions. Understanding that interplay is what turns passable prints into production-ready parts.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>How To Design Parts for MJF? Starts With Business Targets<\/strong><\/h2>\n\n\n\n<p>Before any geometry decisions, align your team on the business constraints so the engineering choices you make are intentional, not reactive. This short exercise prevents you from over\u2011engineering prototypes or under\u2011engineering bridge\u2011to\u2011tooling runs. Think cost per part, lead time, and which dimensions must be post\u2011machined versus \u201cprint and go.\u201d<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Define cost and schedule realities<\/strong> you must hit (prototype vs. pilot vs. low\u2011volume production).<br><\/li>\n\n\n\n<li><strong>Capture functional requirements<\/strong> like load paths, sealing, UV exposure, and required aesthetics.<br><\/li>\n\n\n\n<li><strong>Lock QA and validation<\/strong> up front (CMM scan, go\/no-go gauges, drilling or reaming bores, dyeing, vapor smoothing).<br><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Core Geometry Rules You Can Trust&nbsp;<\/strong><\/h2>\n\n\n\n<p>Numbers alone don\u2019t guarantee success, but they eliminate the most common failures. The figures below reflect widely adopted practice across major U.S. service bureaus and HP guidance. Deviation is fine if you test it, document it, and keep print orientation consistent across builds.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Walls:<\/strong> keep short, non\u2011structural walls at <strong>\u22650.8\u202fmm<\/strong>; for enclosures, brackets, or load-carrying parts, use <strong>1.2\u20132.0\u202fmm<\/strong>.<br><\/li>\n\n\n\n<li><strong>Embossed\/engraved details:<\/strong> height or depth <strong>\u22650.4\u202fmm<\/strong> with strokes <strong>\u22650.3\u202fmm<\/strong> to stay legible after blasting or dyeing.<br><\/li>\n\n\n\n<li><strong>Living hinges:<\/strong> around <strong>0.3\u202fmm<\/strong> thick and oriented in XY, not Z.<br><\/li>\n\n\n\n<li><strong>Fillets:<\/strong> add <strong>\u22650.8\u202fmm<\/strong> internal and <strong>\u22651.0\u202fmm<\/strong> external to reduce stress concentration and stair\u2011stepping.<br><\/li>\n\n\n\n<li><strong>Lattices:<\/strong> keep cell sizes <strong>\u22651.5\u202fmm<\/strong> to ensure consistent fusion and predictable de\u2011powdering.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Accuracy, Shrinkage, And Realistic Tolerances<\/strong><\/h2>\n\n\n\n<p>Dimensional accuracy is a function of geometry, orientation, local thermal mass, and post\u2011processing. Instead of promising a blanket tolerance to your stakeholders, set a primary rule of thumb and specify exceptions for CTQ features in the drawing.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u0627\u0644\u0627\u0633\u062a\u062e\u062f\u0627\u0645 <strong>\u00b10.2\u202fmm up to 100\u202fmm length<\/strong>, then <strong>\u00b10.2%<\/strong> beyond that, as a conservative baseline for PA12.<\/li>\n\n\n\n<li>Expect <strong>holes to print slightly undersized<\/strong>; leave <strong>+0.1 to +0.2\u202fmm<\/strong> for reaming or drilling.<\/li>\n\n\n\n<li>Model <strong>assembly allowances<\/strong> anywhere you plan to bead blast, dye, vapor smooth, or machine.<\/li>\n\n\n\n<li>Keep <strong>wall thicknesses uniform<\/strong> to avoid heat accumulation and warpage that drifts your tolerance stack.<br><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Hollowing, Powder Escape, And Thermal Balance<\/strong><\/h2>\n\n\n\n<p>Large solid blocks are the fastest route to warped parts and high material bills. Hollowing not only saves powder; it also equalizes thermal behavior, which keeps your tolerances in check. Plan escape paths like a fluid system, not an afterthought.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Hollow thick regions<\/strong> and add <strong>at least two escape holes \u22656\u202fmm<\/strong> on opposing faces to flush powder.<\/li>\n\n\n\n<li>Place escape holes <strong>high and low<\/strong> to use gravity and compressed air during de\u2011powdering.<\/li>\n\n\n\n<li>Keep <strong>internal channels \u22652\u202fmm<\/strong> wide so powder does not cake and trap heat.<\/li>\n\n\n\n<li>Maintain <strong>consistent wall thickness<\/strong> in hollow shells, and avoid long, uneven transitions that create thermal gradients.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Strength And Stiffness Optimization (Ribs, Shells, Lattices)<\/strong><\/h2>\n\n\n\n<p>Using ribs, shells, and lattices correctly lets you cut mass without compromising durability. Treat ribs as structural features that need fillets and thickness, not thin cosmetic fins. For lattices, prioritize manufacturability and de\u2011powdering over exotic cell patterns that look good in renderings and fail in production.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ribs<\/strong> should be <strong>60\u201380% of the wall<\/strong> they support and filleted at the root (\u22650.5\u202fmm) to prevent crack initiation.<\/li>\n\n\n\n<li><strong>Shell + lattice<\/strong> strategies work well: a <strong>1\u20131.5\u202fmm shell<\/strong> over a <strong>15\u201325% gyroid\/diamond<\/strong> core is a common, robust pattern.<\/li>\n\n\n\n<li><strong>Bosses for inserts<\/strong> need extra meat: follow the heat\u2011set insert vendor\u2019s pilot and wall thickness recommendations to avoid cracking.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Designing Assemblies And Moving Parts<\/strong><\/h2>\n\n\n\n<p>Printing assemblies in one shot is tempting, but fused joints are expensive to reprint. When you do it, give every contact surface enough air to survive the thermal cycle and the breakout process. Validate a single sample set before committing to production volumes.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Leave <strong>0.25\u202fmm clearance per side<\/strong> between moving surfaces to prevent fusion.<\/li>\n\n\n\n<li><strong>Orient parts<\/strong> to minimize long, parallel close faces that can sinter together.<\/li>\n\n\n\n<li>For <strong>snap fits<\/strong>, model <strong>+0.15\u202fmm clearance per side<\/strong> and confirm stiffness with real prints, not solely FEA.<br><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Surface Finish And Post\u2011processing<\/strong><\/h2>\n\n\n\n<p>MJF parts come off the machine with a matte gray finish and a typical Ra around 6\u20138\u202f\u00b5m. Every finishing step alters geometry slightly, so build clearances and tolerances around what you will actually apply, not what you wish you could skip.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>\u0627\u0644\u0633\u0641\u0639 \u0628\u0627\u0644\u062e\u0631\u0632<\/strong> even texture, but can remove a few hundredths of a millimeter\u2014budget for it on tight fits.<br><\/li>\n\n\n\n<li><strong>Dyeing<\/strong> (often black) penetrates roughly a quarter millimeter, so don\u2019t rely on it to mask loose clearances; design them in.<br><\/li>\n\n\n\n<li><strong>\u062a\u0646\u0639\u064a\u0645 \u0627\u0644\u0628\u062e\u0627\u0631<\/strong> improves surface integrity and watertightness; add <strong>0.05\u20130.15\u202fmm<\/strong> extra clearance on critical interfaces.<br><\/li>\n\n\n\n<li><strong>Secondary machining<\/strong> (drill, ream, tap, face) is often the cheapest way to guarantee CTQ dimensions.<br><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Quality Assurance And Documentation For Repeatability<\/strong><\/h2>\n\n\n\n<p>Repeatable MJF production depends on documenting more than just nominal dimensions. Capture how you nested, oriented, and finished each part, then lock that into your drawings, traveler, or MSA files. The more regulated the application, the more this matters.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Freeze build orientation and packing density<\/strong> for production runs; keep annotated screenshots in your release package.<br><\/li>\n\n\n\n<li><strong>List CTQ dimensions and gauges<\/strong> (CMM, structured light scans, or go\/no\u2011go) to avoid ambiguous inspection.<br><\/li>\n\n\n\n<li><strong>Track material lot numbers and post\u2011processing recipes<\/strong> when regulatory or medical compliance is involved.<br><\/li>\n\n\n\n<li><strong>Record annealing or smoothing parameters<\/strong> (time, temperature, chemistry) to ensure lot\u2011to\u2011lot consistency.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Common MJF Design Mistakes And Quick Fixes<\/strong><\/h2>\n\n\n\n<p>Teams often repeat the same preventable errors: thick solid masses that warp, razor\u2011sharp inside corners that crack, undersized bores that never get reamed, and assemblies with near\u2011zero clearances that fuse into expensive paperweights. Fixing these requires simple, codified rules in your CAD checklist.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Don\u2019t model solid bricks<\/strong>\u2014hollow thick zones, add vents, and keep walls uniform.<br><\/li>\n\n\n\n<li><strong>Fillet every inside corner<\/strong> that sees load or heat concentration.<br><\/li>\n\n\n\n<li><strong>Assume holes print tight<\/strong> and plan to ream or drill.<br><\/li>\n\n\n\n<li><strong>Give moving parts breathing room<\/strong>\u2014treat 0.25\u202fmm per side as your default starting point.<br><\/li>\n\n\n\n<li><strong>Normalize wall thicknesses<\/strong> and use ribs for stiffness, not random thickness spikes.<br><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Material Choices For MJF&nbsp;<\/strong><\/h2>\n\n\n\n<p>PA12 is the default, but it\u2019s not the only option. Material decisions influence strength, ductility, chemical resistance, color, and even surface finish. Select intentionally, then adapt your design rules (wall thickness, clearances, post\u2011processing) to match the chosen polymer.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>PA12<\/strong>: balanced strength, stiffness, and accuracy; ideal general\u2011purpose production.<br><\/li>\n\n\n\n<li><strong>PA11<\/strong>: higher toughness and impact resistance; good for snap\u2011fits and living hinges.<br><\/li>\n\n\n\n<li><strong>Glass\u2011 or mineral\u2011filled nylons<\/strong>: higher stiffness and temperature resistance, but more brittle\u2014add generous radii.<br><\/li>\n\n\n\n<li><strong><a href=\"https:\/\/en.wikipedia.org\/wiki\/Electrostatic-sensitive_device\" target=\"_blank\" rel=\"noopener\">ESD\u2011safe<\/a> grades<\/strong>: for electronics housings; confirm surface resistivity ranges with your supplier and test parts, not just coupons.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>DFM Checklist To Run Before You Upload The CAD&nbsp;<\/strong><\/h2>\n\n\n\n<p>A short, enforced checklist prevents 90% of reprints. Run it internally before you send files to your bureau, and ask your vendor to confirm it on their side. This is the cheapest quality control you\u2019ll ever implement.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Are all walls \u22650.8\u202fmm<\/strong>, with load-bearing or tall walls at 1.2\u20132.0\u202fmm?<\/li>\n\n\n\n<li><strong>Did you hollow thick regions<\/strong> and add \u22656\u202fmm escape holes on opposing faces?<\/li>\n\n\n\n<li><strong>Did you allocate +0.1\u20130.2\u202fmm<\/strong> for any holes that need tight tolerances post\u2011print?<\/li>\n\n\n\n<li><strong>Are moving parts spaced \u22650.25\u202fmm per side<\/strong>, and are snap fits given +0.15\u202fmm?<\/li>\n\n\n\n<li><strong>Have you documented orientation, packing density, and post\u2011processing steps<\/strong> needed for production?<br><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>\u0627\u0644\u062e\u0627\u062a\u0645\u0629<\/strong><\/h2>\n\n\n\n<p>Great outcomes come from designing with the physics of the process\u2014heat, powder flow, and finishing\u2014in mind. Balance your walls, create real powder escape paths, budget for machining where it saves headaches, and document orientation so every batch behaves the same. Do that, and you\u2019ll control quality, slash rework, and keep unit costs predictable as you scale from prototype to production in the USA. If you want a fast DFM pass or a second set of eyes on your next build, <a href=\"https:\/\/eli-tec.com\/ar\/\"><strong>\u0642\u0627\u0644\u0628 \u0627\u0644\u0646\u062e\u0628\u0629<\/strong><\/a> is ready to review your CAD and suggest the most economical way forward.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>\u0627\u0644\u0623\u0633\u0626\u0644\u0629 \u0627\u0644\u0634\u0627\u0626\u0639\u0629<\/strong><\/h2>\n\n\n\n<p><strong>Is there a single minimum wall thickness I can always rely on?<\/strong><\/p>\n\n\n\n<p>0.8\u202fmm is a widely used safe minimum for short, non\u2011structural walls. If the feature is tall, load\u2011bearing, or sees heat, increase to 1.2\u20132.0\u202fmm.<\/p>\n\n\n\n<p><strong>Can threads be printed directly?<\/strong><\/p>\n\n\n\n<p>Yes, for larger sizes (M6 and up), but for durability and repeatability, most teams print a pilot hole and use heat\u2011set inserts or post\u2011tapping.<\/p>\n\n\n\n<p><strong>How accurate will flat sealing faces be out of the machine?<\/strong><\/p>\n\n\n\n<p>Plan \u00b10.2\u202fmm and use vapor smoothing or machining if you need tight sealing.<\/p>\n\n\n\n<p><strong>Will vapor smoothing change my dimensions?<\/strong><\/p>\n\n\n\n<p>Slightly. Add 0.05\u20130.15\u202fmm clearance to interfaces where precision matters.<\/p>","protected":false},"excerpt":{"rendered":"<p>If you\u2019re figuring out how to design parts for MJF, you probably care about three things: reliable, repeatable quality; tolerances that don\u2019t surprise you after post\u2011processing; and unit costs that still make sense when you move from ten prototypes to a few thousand production parts. Multi Jet Fusion is forgiving compared to many processes, but [&hellip;]<\/p>","protected":false},"author":4,"featured_media":13480,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[58],"tags":[],"class_list":["post-13037","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cnc-machining"],"acf":[],"_links":{"self":[{"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/posts\/13037","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/comments?post=13037"}],"version-history":[{"count":3,"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/posts\/13037\/revisions"}],"predecessor-version":[{"id":13482,"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/posts\/13037\/revisions\/13482"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/media\/13480"}],"wp:attachment":[{"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/media?parent=13037"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/categories?post=13037"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/eli-tec.com\/ar\/wp-json\/wp\/v2\/tags?post=13037"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}