is there any tips on how to avoid draft angle? Im trying to design a 1 part tube shape product around 30cm height and I want to avoid draft angle as much as I can.
I see that there are several product with a very minimum or no draft angle ( apple products ) how they do that? is it as long as its glossy its ok?
Some injection molding companies offer air-assisted ejection. The part shrinks around the core when cooling but then becomes pressurized from the inside to aid mold release. 0 draft angles are possible that way however I havenāt heard of these large size parts. Some companies can do 0.25 degrees draft but anything larger than that becomes noticeable. I imagine this humidifier was done with two mold halves and a collapsible core though.
-Ralph
Moving this to materials and processes.
I assumed the same on the humidifier. Without seeing it in person it is hard to know, but Iād look for subtle tooling part lines. I would assume the top circle has a slide (they need to mold all those vents), the body was done in two half, and as Ralph said a collapsing core.
One thought on the Ć draft trendā¦ who is this for? Does the consumer/user care or is it to impress other designers? I tend to be more impressed by working with the constraints instead of against them. Maybe it is an attempt to signal quality and purity. Perhaps there is another way to do that without driving your factory partner crazy 
Aesthetically as a designer Iām drawn to it as well so Iām trying to figure it out.
On the apple example, Iām not sure how they do that (I hadnāt heard of the shrinking around the core process, but it sounds like something apple would do) ā¦ I always assumed they had a fairly large reject rate for parts that came out of the mold scratched and that it being apple they just didnāt care.
They probably doā¦
with shrinkage I simply meant that any polymer molding will shrink and as a result it clamps onto the core - something to take into account.
I am still looking for a factory that can do the 0 draft feature for a product that has been in the āconceptā labeled drawers for a good little while but I can accept the .25 as well. The length of the 0 draft is a big factor too, you may want to design to reduce this area.
adding adraft on my design would totally change the look and feel, draft angle would make it looks like its using a skirt ; )
How about extrusion?
Whatās the material you are looking at?
You can get zero draft with parting lines but those would be visible and you wouldnāt get the āAppleā look.
As for Apple, I am suspecting maybe polish and painting/coating? But I am not sure if you need PC for that or if you can also achieve this with ABS.
I agree with Michael. Try to design around the constraints of manufacturing. Itās a fine art.
For example, see if you can put features and design elements along the parting lines in a meaningful way. Like a battery door or vents.
I have seen some pretty neat work around this where designers managed to hide the parting lines almost completely by designing the product with the tooling in mind.
I found apple patent relating to zero draft angle:
also another zero draft patent, by western digital:
I couldnāt understand both, anyone get it?
Only briefly looked at the Apple one, theyāre looking at making the cylindrical body of something like the Apple pencil.
It looks like theyāre purposely having the part shrink and cling onto the the centre core of their mold. Where they got clever is that the centre core is actually made of two parts. One is a thin tube with a slot in it and the second one is a solid cylinder with a key that matches the tubeās slot. When theyāre molding the plastic part, the cylinder is inside the tube, thus making a nice circular inner surface. When demolding, the plastic part clings onto the two core parts. They then push the inner cylinder out, that leaves the plastic part onto a tube with a slot in it. Since thereās a slot in that cylinder, itās allowed to shrink a little bit and relieve the pressure from the plastic part, thus allowing it to pop out.
Sounds like a collapsible core.
I agree on being true to the manufacturing process as well, however I love those ingenious molding solutions.
The most important thing is that we do not want to see any molding features on the product, somehow it makes it looks low-end, dare I say Asian.
If you can do away with additional detailing, extrusion is the way to go however you do need to color coat the plastics to hide the marks.
The choice of material makes a significant difference on the draft angle required. Iāve made 5cm long (2.5") parts out of a polypropylene where the toolmaker was happy to make the tool with 0.2 draft. When I say happy, I mean he considered there to be wiggle room in there and so was happy to just make it with so little draft from the get go. I was pleased with the resulting parts.
On the tooling for this polypropylene part, were there any special features to pop it off, or were ejector pins enough?
What is draft angle? Sorry for this stupid question
Hi there, draft angle is the slight taper put on parts so they can easily pop out of a mold. Engineers will typically push for more draft angle as it allows parts to be popped out of molds faster, more reliably, and with less defects.
Here are a few illustrations that will help explain it. Also there are many articles and videos explaining it out there.
Crayonne Plastics (UK, ā70sā) produced a range called āInputā that made quite a thing out of a zero draft aesthetic, especially their bins and ice buckets. Moulded in ABS, with a slow cycle time, they had ~4mm chunky wall thicknesses and were super glossy. The parallel sided bins were pushed off the core by using sleeve ejectors that pushed on the thick wall edge.
No doubt the glossy finish helped with demolding though the chance of scuffing would be increased. Maybe theyād throw out every other molded part, a la Apple Cube.
Thank you so much
