Parting Line Magic

I was looking at Teague’s new website today and something struck me about the computer they designed and is their current showcase project.

Have a look at the attached image which is a screen capture from their site.

What it seems to show is a part that, by old-school thought processes, is a no-go. There is a radius on all corners of the cross section.

Now, while this isn’t the part that confuses me so much. You can achieve that through a stepped part line. Toolmakers grumble about it, it costs a bit more, etc…but it is achieveable.

What does confuse me is that there is no flashing where I would anticipate the partline to be.

Now, I anticpate this part is injection molded and then painted. But even with a good coat of paint, I would expect to see a faint flash line.

Am I just following too old school notions of parting lines and finishing, or is there some kind of hocus pocus occurring here? Did they do some kind of polishing out of any flash partlines? Can the paint be applied thick enough to not show flash lines?

Or is this ID showing an ideal design and not the reality of the final product?

I am not picking on Teague for this…I see it all over the place and my first boss stuffed “good tool design” techniques in my ear till they bled. I would actually like to eliminate some of those “good tool design” laws he taught me with updated ones if they exist.
partline_teague.jpg

It’s “ID” or they have used a low temp powdercoat.

Could just be a hard model…

Could also just be too difficult to make out in the image. Might have been photoshopped out in the glamour shot, could have also been photographed in such a way to avoid it. Or it might just not be there at all - either it was tooled differently then you’d expect.

From what I’ve seen in my short time working most tool makers are ultra conservative, but can be pushed to go against their intuition and develop a tool that does what the designers want without any terrible calamities.

Brett_NYC…I would be very surprised if it wasn’t a model.

That said, my question still stands. Is this ID hocus-pocus? Having those rounds on the design definitely sells it better. It looks more finished. It looks cleaner. But to my eye, it doesn’t look RIGHT.

And that’s where I stumble. I tend to find it wrong to show a client something that can’t be manufactured. Or, along the same ilk, something that isn’t manufacturable in a manner that doesn’t cause exorbitant tooling and part costs.

So, let’s go down that road a second and say that this is a cosmetic model. How “wrong” is it that a product is shown like that? While a small round is not something most people would really notice. Or flash lines, or anything of the sort. But they are the kind of things that separate a good design to a finely polished design…except that its not really achievable.

What does this kind of presentation do to the credibility of designers? It definitely perpetuates the angst from the Engineering Department for not being able to design manufacturable product. It also undermines the argument we (I?) have with Marketing on a daily basis that ID is a skill that has a firm grasp on technical issues. I don’t like playing the bait and switch game…

…but it makes damn good eye candy, and that sells the design.

Ask forgiveness later?

Absolutely toolmakers can be pushed. Especially nowadays. CNC and CAD design has changed the landscape in a manner that can’t be described. I am old enough to have seen both hand blueprint product design all the way through AutoCAD to today’s tools. You think toolmakers are conservative now? Think Zippy on steroids.

What doesn’t change are physics. High pressure pushing plastic into tools with part lines makes for flash. There are tricks, and tweaks. But you still just can’t lose the reality of a plastic part…

or can you? That is part of what I am trying to get at. If there is some other technique being used here…or planned on being used if this is a cosmetic model…what are they?

ip_, it’s always possible that its a model but in any case it is not a problem. The two edge radii in the direction of pull are no problem of course and there may not be a radius on the back or more than likely it’s very small, maybe less than .015 in. It’s also possible that there is just a little hand work done on that edge prior to paint.

Maybe someone from Teague will spill.

The four sides of the part could be made on sliders, then standard core/cavity for the inside and back sections, so the part-line would be on the inside edge after the radius. If you look just above the section line you drew, you can see a recess which would have to be made on a slider…

Or, it could be that the part line is well controlled open/shut to the point of not being an issue.

This kind of thing is really quite simple in small tools, we do it all the time on our phones. It just requires good tool design and moulding control. For the best examples of very well concealed to the point of being almost invisible part-lines, look at the iPod ear phones.

I see no reason why the same can’t be achieved in larger tools too.

iPods, etc. go to extents most companies aren’t willing to pay for. As I recall reading, Apple is not against the idea of hand polishing out flash lines, etc.

Large tools with side action becomes very pricey very quickly. You need one helluva press to handle that tool. Not only tooling costs are high, but part price goes up due to the larger press.

Most of which, I tend to think isn’t worth the expense for that added radius. At least, most every client I have dealt with wouldn’t equate the worth of a small rad, even though it polishes it up to the eye, with the added expense.

So where it leaves me is should that kind of design practice be shown to clients? I tend to lean on the side of, no…it shouldn’t. I find it embarrasing at best if I having to talk my way out of a “design feature” that I added to sell the design when I know it won’t, or even worse, shouldn’t be part of the design in the first place due to my understanding of the project’s budget.

I hope that I am not misunderstanding the quandary, but couldnt the parting line be along the color break? It could be along the inner fillet radius. That would put the flash lines in less visible area.

I agree with Masterblaster–that’s exactly where I’d expect it to be. Unfortunately that’s a really nasty place to leave a witness-line.

Do we know this is a molded part and not cast or formed?

Do we know this is a molded part and not cast or formed?

Wow … . . I can’t imagine the cost of a cast, or formed part, especially the latter; a routed, or milled radius? And casting is notoriously imperfect.

Looking at the images from Teague’s website I think MB is correct. It also appears (to me anyway) as though the black face stands proud of the edge of the case slightly. This feature combined with the “reveal” between the face and case, and the witness line at the bottom of the radius probably conceals it to a great extend.

Teague’s gallery images are not exactly shall we say, crisp . … .

http://www.teague.com/flash.html