Machine to make Bath Bombs

[alr]

I have recently been asked to design and make a machine for the production of “Bath Bombs”. These are perfumed foaming blocks that are used in spas and baths.

The ingredients (consisting mainly of Epsom salts) are mixed dry and a very small amount of water is added. They can be pressed into the mould by hand (i.e. exerting approximately 10 psi). The machine is to press them directly into the mould, where they can be de-moulded almost immediately and the hopper needs to hold sufficient for 100 units (about 500 cubic inches).

Because of the dry nature of the material, it will not flow and compressing it, hardens it. It is similar in nature (but much finer) to the dry mix used to make concrete slabs. An Auger feed could be used, but my client would prefer a cheaper and easer to clean, design.

I am open to all suggestions.

Tony

 

[CanEngJohn]

Trust me, it will flow. Track down some people in powdered metal I am sure they can assist you with hopper and shoe concepts.

You can probably do this easily with a compacting press or a machine based on a similar concept. You premix the powders in the appropriate mixture then drop it into a hopper which gets placed on a stand above the machine. Use gravity to feed the powder down to a shoe. Let the machine do the rest. Given the forces you can probably get 20 strokes per minute easily.

 

[johnwm]

Vibratory hopper? usually prevents powders & fine mixes from 'bridging'

Good Luck
johnwm

 

[griffengm]

There are small air operated vibrators for such applications. They are ususally mounted on the cone area and are fairly inexpensive.
McMaster Carr carries them.

Griffy

 

[CanEngJohn]

Actually not vibratory. Does not work as well.

As I mentioned, talk to someone with more experience in Powedered Metal than myself (only 4 years) and I am sure they will have lots of insight.

 

[automatic2]

A small amount of water would then make it a mastic?. Pump it with a peristaltic.

 

[CanEngJohn]

I would add the water down at the die cavity instead of in the hopper.

 

[alr]

Thank you all for your interesting insights, specially adding the water last.

Tony