Removing metal chips from assembly 3

[morkman]

I have a process where I need to remove SS particles (i.e. small chips) from a stainless steel assembly. The assembly is machined after it has been assembled and I need to make sure that no particles are left behind. The chips cannot be blown out because there are no thru holes. Does anyone have a suggestion on a good way to remove these particles, perhaps a rinse of some kind? Any advice would be appreciated.

Thanks

 

[mfgenggear]

morkman

Is there coolant present or is it cut dry?
Can it be penetrated with a vacuum hose.
& can the particles be removed with a simple vacuum?

the other option would be to mask off all the areas to prevent contamination.
prior to any machining.

It is not advisable to machine if there are close interfaces, it will be very difficult to remove the debris.


Mfgenggear

 

[TVP]

What kind of machining are you doing, e.g. drilling, tapping, something else? Can the machining be performed horizontally instead of vertically? Have you investigated optimizing the cutting geometry of the tool with your tool supplier? Use multiple air nozzles with very high velocity?

 

[1gibson]

What type of stainless steel? Using a magnet is too obvious, I assume it will not work with your material.

 

[arunmrao]

A toothbrush was used just yesterday to remove the metal debris in the space shuttle.power systems.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[1gibson]

An apparatus popped into my head: vacuum nozzle with an angled air inlet straw on the outside. The device is on a quick connect (can be rotated). Turn on the vacuum, the air that rushes into the angled straw will blow the chips around so they can be extracted. Rotating the device (just by hand) points the straw into different areas of the sealed chamber.

---(....____
--(....(
-(..O.(
--(....(
---(....-----

Outer parenthesis indicate outer pipe, the O is the angled straw, the inner parenthesis are the vacuum pipe.

Side view:
...|.|..|vac|....|
|.|..|vac|....|
|.|..|vac|....|

Use multiple straws if desired, but not so many to reduce the inlet velocity, it still needs to disturb the chips. I assume you're getting a cutting tool into the cavity so you have enough room for something like this, easily scale down to the point where the vacuum can pass max chip size.

 

[tbuelna]

A toothbrush was used just yesterday to remove the metal debris in the space shuttle power systems.

Metal debris is a serious issue and requires constant attention. Not even super critical applications like manned space system hardware is immune. First, I think arunmrao meant the space station (ISS) and not the space shuttle. It's great to see that the EVA crews have been taught to check threaded fasteners closely for metal debris before re-installing them. Metal chips can easily cause a fastener to seize up, and the worst possible situation in orbit is a fastener that gets stuck partially installed. It cannot be removed and it does no good for carrying loads. The ISS solar arrays have had previous issues with generating metal debris, most notably the rotary joint trundle bearings.

Speaking of the space shuttle and machining debris left behind, here's an incident I recall from a few years back (when I was working on the shuttle program). During a routine radiographic inpection of the cooling tubes on one of the SSME nozzles a broken drill bit was found inside. Never heard if they figured out where it came from, but if that chunk of drill bit had passed through a turbopump it would likely have caused catastrophic damage, not to mention the multi-million dollar costs for repairs and possible mission termination.

Coming up with a process for removing/isolating the metal debris generated during finish machine operations in morkman's assembly is only half of the task. The other half of the job, which is equally important, is establishing a reliable method for verifying the process is resulting in acceptable levels of cleanliness. The best approach, as suggested by mfgenggear, would be to first use masking/plugs/guards/etc. to confine the debris to areas where it can easily be removed. A post machining flush with some type of liquid that is compatible with your assembly materials would probably be more effective at removing any remaining metal chips than compressed air. You might also take a look at the possibility of making changes to the shape of your parts to assist with debris removal, and also to eliminate any crevices/ledges/pockets/etc. that would trap small bits of debris. Lastly, don't forget to consider whether your final machining operation will leave behind any edge burrs that may break free during service. And if so, how will you remove them.

Sorry for the long response. But ensuring cleanliness is definitely a subject that many people fail to appreciate the importance of. Sadly, in my career I've seen many instances where it has caused serious problems. Hope this helps.
Terry

 

[arunmrao]

tbuelna,

Thanks for pointing the error. Blame,my 19 hours layover at Dubai for a connecting flight! It was only to highlight,the importance of metal debris ,that I cited the example.
Can we discuss about similar instances in medical profession?


_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[mfgenggear]

Terry

It is not a long post but a very well explanation.
& Yes I agree debris contamination is a very serious problem.
and my post should have been as yours.

Take Care
Mfgenggear

 

[tbuelna]

morkman,

I had a thought on one possible process for removing machining chips/debris from your assembly that would also de-burr sharp edges. It's a commercial process called Extrude Hone. It involves pumping a highly viscous polymer media containing an abrasive through internal cavities to smooth surfaces and remove sharp edges. Due to the very high viscosity of the polymer media it would also do an excellent job at driving out any metal chips/debris. The polymer media probably doesn't leave behind much surface residue, so a final rinse with a mild solvent or detergent would leave things nice and clean.

Hope that helps.
Terry