When do you start caring?

Let;s say you’re designing a mid-level consumer product.
And you know of Round fillets as well as Continuous curvature fillets (blends).
When do you start caring of what the small details look like?
What I’m curious about is the size of that surface(fillet). So the size of the detail/feature, not the part.

I usualy start caring at 1mm dimension and up.

Just curious if that’s too small.

Whay I ask? Well because nicer surfaces usualy take longer to make and are heavier on the machine(CPU and CNC later on).

Thanks for your replies.

Hi Design DUDE,

If I understand you correctly - Not a straight forward question and whose answer perhaps depends on your agenda / perspective / role.

If you are a product designer who works on a conceptual level i.e. you are a serial visionary of how things could be better then you would probably not give a hoot … in fact you would not waste the brain time with a CAD package.

However, if you are a designer who is more concerned with aesthetic and quality of user experience you would probably agonise over it. You have to get it just right as ever detail of shape and form combines to make the best product it could possibly be.

If are the later, you perhaps understand how such details influence a products success on the market (favourable marketing factors allowing of course) the consumer will acquire a product with which they will grow to love because, even if they are not aware of it, every aspect of the product oozes quality. The commercial consequence is greater sales and brand equity.

Bastardising a well know UK comedy show (The Fast Show) “Designing a product is like making love to a beautiful woman” … you need to get know every surface, feature and form and make it scintillating to the touch, and eye.

Anyhow, back to cold reality i.e. time constrains, cost (both self-explanatory) and manufacturing. I read somewhere that design for manufacture is not so much a process as a state of mind. That is as you are designing that curvature you are being intuitively informed by a spectrum of project specific information and previous experience e.g.

  • how will the light bounce of this edge,
  • how does it frame adjacent surfaces,
  • will molten plastic flow into it / quickly enough / can it then be removed
  • will it impinge health and safety standards
  • will it slow down / speed up the development / production process (as you mention)
  • can you save a few critical cents by changing it one way or the other
  • etc …

One other consideration - if you don’t worry beyond a certain limit and leave it out of your specification (manufacturing handover pack) you are leaving the detail to an engineer who may have absolutely no appreciation for aesthetics, user-centric design, brand integrity, etc … Which could ultimately leave you looking bad - the devil can be in the detail.

So in a nut shell, detail design matters right down to smallest increment and variable … but only if it is your responsibility or indeed you care. Just think of some design classics the detail is usually tighter than average.

Saying that there is also the 80 / 20 rule which translates as - you have a deadline that can not move, you are running out of time but the project is largely complete (80%) - it works and so it can be signed off. The remaining 20% (resolving those not critical issues) will have to be left out. As designer I hate this rule because it compromises the ideal but have found it wise to incorporate it whenever planning a project.

Ramble over :slight_smile: - a good question and other views would be interesting.

Ok that kinda answers my question from one point of view. (I’d LOVE to hear others on this)
I’d consider myself/my position as the later description (i do care, I am required to care)

And another thing that i’d like to know, somewhat in the same direction, is that What is the smallest toolbit (diameter) that moldmakers use (on average) to create overall shapes(not details like holes and such)? Because perhaps it would be wise not to obsess about any surface that will only be approximated by the mouldmaker anyhow because of the tooling limitations. (Of course there’s a way to do a RP model with .001" ‘resolution’ and then just investment cast that into a mould…)


You should care from the start if you are in a position to affect the tooling. More importantly, you recognize the fact that there are certain fillets, drafts, ejection points, gates, etc. that MUST be built into a tool to produce a part. The more aware you are of what these requirements are, and how it affects your concepts, the closer you’ll get your design to come out as you conceived it.

I have been on both sides of this issue, and it boggles my mind that so-called “Senior” designers conceive of detailed solutions without any regard for their manufacturability.

I’ve been a designer for 25 years.(BSD in product design). I also have been involved in all of the detailed engineering component design, tooling approval, and integration into manufacturing for most of those 25 years.

I’m currently working with a designer within our corporation who thinks he is hot, yet he has no clue as to manufacturing constraints. (He claims to be designer from a big consultancy with 30 years experience). He conceived a very geometric die casting design of an aluminum part approx. 14"x12"x8", and demanded vertical sides, no fillets, no gate marks, etc. This is a product mounted on the side of a building viewed from a minimum of 20 feet up.

When confronted with this task of “engineering” it for the project, I added the draft, fillets, and such and was immediately told-you must make his design as conceived.

So the tooling went from a single axis male/female cavity die to one with two second axis slides and a whole lot of concern from the vendor over tool life due to sharp corners in the cavity (the designer finally agreed to a .015" radius, reluctantly).

Guess what happened? Less than 500 shots in to the tool, it blew apart in the cavity along the sharp corner. Cost? $15K for a new cavity, a boatload of down time, and the real kicker…the replacement is being made exactly as the first!

If you want to really, truly be a good designer, pay attention to the details, learn the processes involved in making your concepts realities, and don’t be so stuck in your designs that you can’t adjust them to make them manufacturable.

Remember, design is more than art, its about mass production of that art.

my $.02

I recently attended a lecture by a well known and very hot right now designer at a local design/architecture school. It was intended for the product designers, by was open to the public. This designer’s entire 2 hour long lecture was a rant on working with engineering and manufacturing. He flat out said “If you design a product for low-cost mass production you are not a designer you are a drafts man!” Went on to say how he is so proud that 90% of his products never reach the shelfs becuase they are to expensive to manufacture. Braged about this watch that he worked on for 2 years and 3 mil Euro before the company told him to stop. He never made it past the sketches in that time because he said it was too hard to deal with the engineers who said they could not make gears that small. It was sickening to listen too, especially since I new that there were about 100 students listening to this, as well as the public.

For me the inital brainstorming is constraint fee, near blue sky stuff. From there on out 3-4 rounds of refinement I focus on increasinly more details. First focusing on the surface continuity and overal form (keeping in mind the material constraints and rough idea of parting lines and peice parts), then ending with the placement of internal support and ribbing to compliment the exterior lines and shapes (should minor shrinkage accure).

design is more than art, its about mass production of that art.

Well put.

Regarging your question about CNC tool sizes, it depends on your depth of cut. You can get ball endmills down to 0.025", but you can’t cut very deep with them. If you want more specific info let me know and I’ll talk to my machinist.

WIRE EDM is your answer, typically very close to 0.005" res., ability to do near-perfect square corners that mold just great…

Seriously now, some very good advice here for our younger friends starting out in mfg. An experienced designer with no clue about manufacturing limitations is inevitably blind to the opportunities offered by various technologies as well. But most of all that person is a qualified idiot selling the profession short.

Even sculptors and fine artists are limited by the constraints of the physical world. And a designer is not?

Choose your influences in life very carefully.

Wow, thanks for the great response.

My education focused on manufacturability (even more so than aesthetics) and user experience (ergo, semantics…).
Recent graduate, worked at several jobs at different companies already (each job hotter than the last, why I switched).

However my recent exposure to ‘design’ was that of aesthetics above all.
I’ve heard of those ‘designers’ before, but it just baffled me.

Glad to see these responses in sync with my views. (reassuring).

Just can’t help but to ask myself if it’s only the people who think like us that answered.

It’s funny that you ask that because in my experience it totally depends on the type of project it is, at what stage its at and the resources available… Ask an enginner, or better yet, a toolmaker to help determine the appropriate radius depending on the material and the type of part intended. This is a sort of detail that is best hashed out in the development stages.

As far as industrial design goes, well, how defined is the target specs and how much time is there to complete the surface geometry alongwith textures, scnarios, interfaces etc that all go into clearly communicating what the thing is and how it’ll be used and why the design is profitible and neccessary.

This resolution of detail is important without question, yet there are a hostof factors like the type of product, the type of client, type of users, time, resources, target specs and/or mrd that play into the level of resolution you’re going for. NAmely using a .25 mil round compared to a 1mm.

btw, if a surface model requires(?) a .5 round and it bogs down the machine using alias or rhino, it’s easier to transfer the igs/stl to SW or ProE, make solid, shell then asign radius. Either that or specify it in the design controll drawings. Most of this minute detail stuff is more defined in the design development anyways whisch, as we know, is hashed out with and through the client and the design development team; eg eng, materials and time all effecting COST.