I am designing threads for prototype parts which are to be produced using SLS.

So far I have been using a "hemisphere" design - one part is threaded, and the corresponding part has 2 little hemisphere knobs which the thread screws onto. It's a double entry thread, the 2 hemisphere bumps are on opposite sides.

I have had good results with 30mm, 50mm, and 65mm diameter parts. But the 90mm diameter part doesn't hold together well.

Are there any better ways of designing threads for SLS? (I have have bad experiences with regular type threads)

Or are there any slight design tweaks that will create a stronger connection. ie. making the thread steeper or shallower? Increasing the number of bumps etc.

Many Thanks.

Can you make it a three-start thread?

"Art without engineering is dreaming; Engineering without art is calculating."

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Quote:

sodium lauryl sulfate (SLS) is an organic compound with the formula CH3(CH2)11OSO3Na. It is an anionic surfactant used in many cleaning and hygiene products. The salt is of an organosulfate consisting of a 12-carbon tail attached to a sulfate group, giving the material the amphiphilic properties required of a detergent. Being derived from inexpensive coconut and palm oils, it is a common component of many domestic cleaning products.

source: wikipedia

 

NX 7.5
Teamcenter 8

Quote:

Selective laser sintering (SLS) is an additive manufacturing technique that uses a high power laser (for example, a carbon dioxide laser) to fuse small particles of plastic, metal (direct metal laser sintering), ceramic, or glass powders into a mass that has a desired 3-dimensional shape. The laser selectively fuses powdered material by scanning cross-sections generated from a 3-D digital description of the part (for example from a CAD file or scan data) on the surface of a powder bed. After each cross-section is scanned, the powder bed is lowered by one layer thickness, a new layer of material is applied on top, and the process is repeated until the part is completed.

source: also Wikipedia

"Art without engineering is dreaming; Engineering without art is calculating."

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A 3 start thread won't really work with this design.
Have made tolerances tighter, enlarged bump, and made a bit steeper. Any other suggestions?

Also sodium lauryl sulfate, despite being ubiquitous is a pretty nasty chemical and a carcinogenic - so I won't be using that. Laser sintering however, is wicked!

I was already wondering how you were going to make prototypes out of coconut oil. Did you put the lime in?

NX 7.5
Teamcenter 8

Quote:

Also sodium lauryl sulfate, despite being ubiquitous is a pretty nasty chemical and a carcinogenic.

Yes, absolutely - just like dihydrogen monoxide.  An evil conspiracy has developed, putting SLS into all kinds of consumer products.  It's the main component in baby shampoo, and now even toothpaste.  Soon, it will be government-mandated in tinfoil hats too.  

[snark mode off]

What a load of crap.  The stuff is safe enough to drink, though it'd taste lousy.


"Spurious onLine Sources (SLS) are being quoted more and more often in attempts by ignorant people to seem less so in online forums."

- source: me.

SLS, great, however what material?

Pay attention KENAT, we're clearly talking about threaded shampoo here..

NX 7.5
Teamcenter 8

nylon

At the larger size can you just have a course pitch conventional thread in the mating part?