How can I improve this process?

r&ddoc,

if I understand this, you want the plating only on the 'hub' and solder joint, not the cannula (needle). You currently mask the cannula with heat shrink tubing.

ALternative 1: you only need to make needle nonconductive- how about a paint or other non aqueous coating. can be sprayed or silkscreened or just mechanically applied. In my reloading hobby, i apply libricant to empty cartridges by rolling them on a pad soaked with lube before sizing them in die. perhaps the needles could be similarly rolled along a flat pad saturated with a persistent resist (vaseline or other water resistant compound) This would be later removed (after plating)with acetone, MEK, Diethyl ether, or whatever is legal in your part of the world as great organic solvent.

Alternative 2: modify the presentation of the parts into the plating bath such that only the hub and joint are immersed in the plating solutions. This is probably upside down to your current method, or perhaps your current method is just random orientation. The needles can be held between two rails using light compression and these rail racks then lowered into bath only as far as necessary. this can be controlled by mechanical or electromechanical means.

I apologize for the novelty, but you are looking for brainstorms, and these mild zephyrs may help nucleate your thinking.

milo I apologize for typos, not wearing my glasses

Thanks Milo!

Alternative 2 was also tried out. Problem is that our plater hungs the needles into the bath by means of a copper wire. He also uses a mechanism to move them in a horizontal fashion in order to achive an even deposit of nickel on the brass. Movement generates small waves, that makes this alternative more difficult.

i'd look into the cost of just making the hub out of stainless..............compared to doing what your doing,....i'm thinking that if you count all the secondary operations, shipping cost, labor costs, etc , stainless would be cheaper and faster..

i won't even mention that you could probably eliminate a head count

i'd look into the cost of just making the hub out of stainless

You are right Reefdiver! That is the obvious solution.

I've already been working on that subject and had the hubs quoted in 304 SS. Problem is that the body of the cannula is a bit more complicated than I described: it also has 2 little handles and a second part called mandrel (wire obturator that fits into the canula) with a little brass button on it. Button has also to be plated. our production is still not large enough to have a run made in CNC at resonable costs. Should sales increase a bit more we will switch to SS in th short term

There is a coating that you can just brush on that is used in plating processes. I believe it is a type of vinyl. I have used it to mask parts for anodize so it will probably work for nickel plating. Your plater should be able to supply you with it.

Yes: there must be a sort of vinil (or acrylic) paint; to be applied on the cannulas... still didn't get it.

I don't know how platers are in your country, but here they are unbearable down here: sort of take what I offer or get out from my sight!

Curious thing is that everybody complains about MD's... but nobody about platters!

I will make a call today and see if I can get the name of the product for you then post the info.

will make a call today and see if I can get the name of the product for you then post the info.

Great!

"everybody complains about MD's... but nobody about platters!"

MD's = Medical Doctors? I can see why people complain about their health providers!

Platters? Why would anyone complain about serving dishes, unless there is not enough food on them!

You say it's shrinkable sleeve, so I'm thinking you place the sleeve over the needle and then you have to heat the assembly to shrink the material? If I'm right, have you considered having the shink material pre-cut to length, placing the needles in a rack all facing the same direction, placing all the shrink on the needles and then place the entire rack in an oven shrinking them all at once.

To remove, have you tried to make a small fork fixture, where you slide the needle onto the fork and pull down, the fingers hold the shrink wrap while the operator holds the needle? Hey, it might work if the shrink material is thick enough.

you are correct Labguy, this is the way we do it!

The description of the process in our manual is very similar to yours; but (from the productive point of view) it is easier to write it than to actually do it: 1- we need to use a shrinkable that is only slightly wider than the steel tube to get a snug fit on it as this is important to prevent fluids from the bath contacting the tube. 2- the shrinkable is quite expensive.

While writing this I recalled a shiny red plastic in which mechanical parts for cars, or tips of bits / drills are dipped into, to protect the tips. Do you know a clue on what material this can be?

While writing this I recalled a shiny red plastic in which mechanical parts for cars, or tips of bits / drills are dipped into, to protect the tips. Do you know a clue on what material this can be?

I think the stuff you're referring to is the insulated paint that people drip there tools in. You can probably find them in the electricial catalog. I will try to find the name and post in here later.

MidniteFighter

http://www.paigewire.com/pdf/3Mscotchkote.pdf

http://www.3m.com/product/information/Scotchkote-Electrical-Coating.html

I think this is stuff you're looking for.

MidniteFighter

Hi MidniteFighter,

Since it has "good adhesion" to metals, wouldn't that be a little hard to remove?

And if I'm not mistaken (I very well could be), the protective coating on drill bits and such is a more "waxy" material....I think...no?

You may be right about that. I was thinking once it is applied to the needle, maybe the "paint" can be slit and peel off. Anyway, I was answering his question about the red protective coating bit.

MidniteFighter

No problem,

I sometimes find it hard to get the right words. When it is written and not spoken, it can come across as "pretentious" but be assured that it wasn't the case. English is my second language (french being the first) so my "bank" of words is somewhat limited...

later,

Rick.

The waxy material your referring to is hot tool dip. Its used by a great many grinders to put on the sharpened face or tip of drill bits and machine tooling. It is very cheap but much like candle wax it is very susceptable to heat. It is a parafin based material and probably wouldn"t work well in your application as it would fill both inside and outside the needle you are referring to.

Hey R&DDoc

Can you stick the needles in a silicon or "cork like" block during plateing? You could reuse the block and would not be as time consuming.

Hi Yani,

should we do the plating inhouse, your suggestion would be OK... but we depend on a bad tempered plater (they are wery few, by the way) not willing to introduce changes

Hi r&ddoc,

In PCB production, We use something called "temporary mold seal" or "peelable solder mask" when we want to protect certain components from being exposed to the wave of molten solder (480 degC). It is applied as a viscous liquid and some are air dried, some are UV cured. The cured product is easily peeled (consistency of cured silicone but with much less adherence).

Take a look at Dymax and or MG Chemicals. I think these products could be of some use for you. Funny enough, we use your "needles" to apply these products to the boards (syringe on an XYZ machine).

Good luck,

Rick.

What's the point of the brass alloy and nickel plating if the needles are disposable? One would think molding the cannula into a plastic or composite would be much more cost effective being they're disposable.

What's the point of the brass alloy and nickel plating if the needles are disposable? One would think molding the cannula into a plastic or composite would be much more cost effective being they're disposable.

We also have disposable needles with a molded plastic handle, but there are MD´s that do not want to use them.....

As you know: customer is always right!

Here is contact information for a company that supplies automated welding equipment and developed welding processes for welding stainless steel hypodermic needles. They also will set up and do production runs for clients.

Process Welding Systems, Inc.
72 Buchanan St.
LaVergne, TN 37086
Ph: 615-793-7020
E-mail: proweld1@gte.net
Fx: 615-793-7557
http://www.pwsweld.com/

I´ll check this!

I would look at swaging the needle in to a stainless steel hub. Cutting out the plating all together. I am not sure what the application of the needle is. The swaging should hold good pressures. Would all so save time and materials. Tube can be cut, swagged and sharpen. product done

I would look at swaging the needle in to a stainless steel hub.

If sales increase we will replace brass for SS.

The needle is for bone biopsies, and is hammered into the bone by means of a surgical 300 gramm hammer. We tried swaging, but welding is (unfortunately) much more reliable.

The problem sounds very like selective plating of PCBs (although they tend to coat with a range of materials). Typically, they silk-screen the plating resist; but from your description I can see no reason why your part could not be dipped. The only additional issue is to choose a resist that you can easily remove when you finish the plating process (PCB photoresists that are used as etch barriers might be ideal)

Regarding plating subcontractors - I think it goes with the territory, particularly for those working in the general market. Companies I have worked with often do the plating in-house for just that reason. You might find a local PCB company that has spare capacity in their plating shop who would be interested to do something a little different; alternatively, specialist platers for quartz crystals and electronic hybrids enclosures may be able to meet your needs - and some of them may even be equipped to remove the resist when you finish.

Unfortunately, I can't be more specific, because the company that I used to work with was bought by the principle user...

Idea #1. Look at other bonding processes besides soldering. If you can spin-weld the cannulas to the hub after the hub has been plated, then you wouldn't have the problem. (at least not the same one)

Idea #2. Look at a different coating besides plating for the hub. A differen epoxy coating may protect oxidation of the hub, and permit a inverted dip type application.

Idea #3. Look at constructin the hub and cannulas from a single material, drawn for the barrel, and forged or pressed for the hub. then you wouldn't need to plate at all.

Question? How do you prevent the plating of the inside of the hub currently, if at all?

Hi chrisg!

We started working on this project about 3 years ago: it took 2 years to test all imaginable (and unimaginable) assembly methods, until we decided to do them the way we do.

The only remaining alternative is "Idea 3", but this requires larger sales.

Idea 4 is use only stainless steel and do the welding with a laser machine (30,000 bucks!)

As needles are for medical use, we have to deal with a lot of GMP standards, like type of materials, type of coatings, mechanical tests (compression, traction, twisting), etc.

Plating fluid gets into the cannula, but it does not get plated because (I guess) it behaves as a Faraday Cage; and no metal is deposited on the inner surface

Not a Faraday cage as such - though one of the possible mechanisms could be related. If the tip of the tube gets plated and needs to be cleaned or removed, then it's either the current flowing to the surface and depleting the conduction of the solution (because it is unstirred in there) or the inside is protected by hydrogen accumulation. Otherwise, it's likely that there simply isn't enough plating material within the tube to make a significant coating without it being stirred.

Alternative ideas. I wonder if you can use the tubular 304 stainless to make the entire item, by winding and forming the hub. (as follows)

1. at the point where the hub would start, make a radiused bend, leaving a length of material trailing. (length to be determined experimentally)

2. Make a hole in the wall of the tube on the outside of the radius, equal to the ID of the tube.

3. Insert a mandrel that is the shape of the inside of the hub, with pin into barrel.

4. Wind the trailing tubing around the mandrel. trim excess.

5. option A - die press and electrically heat hub material to 2700 F. to make hub.

6. option B - die press material to form hub then remove and micro weld to finalize hub.

7. option C - as the tubing is being wound around mandrel, use flame and profiled roller to shape the hub. flame would have to be exact temp to achieve plasticity of 304 stainless.

Chris

Alternative ideas.

Hi Chris,

You are right, this might be an alternative too, but I am afraid it will require new tooling, and some time to put it to work... problem is I have to deliver products to our customers YESTERDAY.

I will discuss it with our plant manager and also compare this with the quotes for SS hubs.

r&ddoc,

I spoke with the platers here where I work and they use a type of lacquer. It's known as a "stop-off" coating. The stuff is made by Miccro Products, yes there are 2 c's in the name. The stuff our platers use is called Miccro Super XP2000 stop-off lacquer.

They use it for both electro-less nickel and electrified nickel plating. Parts can be dipped, painted, or whatever, with the stuff. It can air or heat dry. It peels off after your done with it.

Here's a link for the company that makes it and other products. http://www.tolber.com/products.htm#Miccro

Hope this helps.

Gideon

Hi Gideon,

YES!!! this is the kind of stuff I was searching for.

I will contact this company tomorrow to ask which of their products is the most appropriate for the intended use, and to have one bottle sent right away!

Thank you a lot! Cosme

I called my plater and they said they would call me back with the info. Of course they didn't. The Miccro sounds like the right stuff. Good luck

I called my plater and they said they would call me back with the info

Never believe in what a plater promises!

Thanks anyhow!

I called Miccro and purchased 1 gallon of some stuff + the same amount of stuff stripper (total for both: 100 bucks).

If it doesn't work, I will be back to ask what to do with it (replies will be obvious!)

Best regards, Cosme

Sounds like "MechTech Gid" has the answer to your immediate problem, easily applied to your current process.

However, my suggestion would be to plate the hub separately. Barrel plating is much cheaper, with less labor involved. Then attach your needle with a process that does not use soldering. Years ago I saw an ultrasonic welding process for attaching dissimilar (or similar) metals. Most thermal welding processes require the materials to be similar, for example ferrous versus copper-based versus aluminum, but this process created a mechanical joint by forcing the micro-structure of the two surfaces to interlock through ultrasonic energy.

The process had been developed primarily for good, solderless, electrical connections between, for example, nickel-plated contacts and un-plated copper wire.

Thank you too STL!

Prior to implementing soldering we did a lot of tests (including interlocking, and other mechanical means like a Morse cone, etc)... but nothing worked as good as soldering.

Due to the intended use, this needle has to be 100% reliable, and capable of withstanding abuse: don't forget they are used by physicians!

Samples of finished products are sent to a technological institute to perform a lot of mechanical tests.

In house we also take samples to determine if the needle gets detached from the tube (worst scenario): needle is held in a wise. Once tight (no matter if tube collapses) a torque meter is applied to the hub, and turned 360 degrees. If properly soldered, tube gets completely twisted, or splits. Hub is then cut in halves, and a special ink is applied to determine fissures in the solded interface. Fortunately we have a team of geniuses doing this job, having had no problems since this method was implemented.

If sales grow a bit more, we will have the hubs made in stainless steel, so we can get rid of plating!

Best regards,Cosme

i'm still really confused as to why the quantity is SO important........the brass pieces all already being machined, correct? the same machine process can be used for the stainless, 304 is not that much harder to machine than brass.......the speed may be a little slower, but it will still be faster and cheaper than what you are currently doing..

what am i missing here?

Could it be the equipment costs and subsequent requalification for welded stainless?

Fyz

Hi Doc!

I hope this suggestion isn't too way out!

Why do it at all?

Plate the hub, then shrink the needle into it, got to be much quicker than soldering?

(heat the hub or cool the needle, then press in, this should be very secure and fine for a disposable item).

I sometimes find removing the problem is easier than solving it!

Is that hot hub, cold needle? It needs precise dimensions for the hole and for the OD of the needle* - but it could be extremely effective if the tube walls are thick enough

*On the basis that you probably need to be within a factor 2 of the maximum pre-cracking pressures

PS1 It would probably be advisable to have a slow taper at the entrance to the hole to minimise strain discontinuities.

PS2 Isn't that similar to a method used with optical fibres? - but they are solid in the middle, so there's no issue with tube collapse.

I've been reading some of the other suggestions.

Maybe best is a combination!

Make hub out of stainless and press fit (shrink fit) the needle.

My previous sugestion would require the hole in the hub to be masked to maintain the tight tollerance for a shrink fit...this puts us back to the orignial masking problem!!! D'oh...never met that effect before have we guys? (Joke, 'cos it happens all the time).

Yup, there's no need for plating if the hub is stainless...

I had assumed you were proposing to use thermal expansion to allow an ideally tight fit. Did I get that wrong?

Your assumption was right I was suggesting heating the hub, or cooling the needle or both! Maybe need to press too!

Shrink fit with heat/cold is obviously better with parts of a bigger diameter and a good coeficient of expansion e.g. Fitting bearings into aluminium castings, as the bigger the diameter the more the expansion, also aluminium has a much greater coeficient of expansion than steel etc.

That's why I hedged my bets by saying heat & cold & pressing!

Pressing is probably fine on it's own especially if there is the tapered lead in which was suggested. The tubular needle will be in compression so it will be able to exert a high hold-in force

(heat the hub or cool the needle, then press in, this should be very secure and fine for a disposable item).

Hi Del!

Yes I tried that as well: it does not work either!.

Main issue here is the difference in the masses of both components, and it´s sizes. As the wall of the tube is extremely thin, the hot hub tends to collapse it when cooling, causing the mandrel (obturating wire) not to pass trough the tube.

You may say it is just a matter of finding the correct match for ID of the hole in the hub and the OD of the needle... you are right, but we did not find it either!

We also tried glueing both parts together using high tech glues, also making a flange on the tube, etc, etc (I´ve spent 2 years fooling around with this!)

There are some companies that also manufacture this products, and the only needles that work are those which are welded by acethylene as we do, or with laser (as we would like to do).

Best regards, Cosme

Your reply aroused my curiosity about how much time you would have available to place the tube if you relied on thermal contraction to make a force fit. The answer somewhat surprised me - that this should be perfectly feasible with a suitable taper at the entrance to the hole, and using reasonable fixtures for pre-alignment and placement. Even the tolerance (~50-um diameter range) doesn't look untoward. But it's not the sort of thing that can work in a manual trial.

The thermal diffusivity of austenitic* stainless steel appears to be in the order of 0.05 cm^2/sec. Now, I'm not a tubing specialist, so I couldn't work out what you meant by '3-mm = 0.97" OD', so I've calculated on the basis of a 3-mm OD tube with a wall thickness of 0.1-mm; but I can easily recalculate if I know the actual thickness. That allows something in the order of 2-ms contact time between the tube and the hub before the temperature difference was substantially reduced. You have, of course, significantly longer than that, because until the OD of the tube matches the ID of the hub, they can't touch all the way around simultaneously. I would estimate that this gives you about 20-ms to place the tube before the clearance reduces drastically. I know that doesn't sound long, but I imagine that you need a contacting overlap between tube and hub of at most 10-mm, so the components will only will need to be close together for about 15-mm of movement. That corresponds to a speed for the placement of less than 1-m/second, which should be quite easy to achieve with suitable fixtures.

*Preferred because of it's relatively high expansion coefficient - approaching that of Aluminium

Refinements, or other thoughts?

Fyz

Are you using electrolytic or electroless nickel? If the former, you might try the latter. With proper fixturing, you could mask the parts from the solution. How thick is the plating? if it is thin, EN plating depositis at about .0007 in/hour and it is controllable. Using wire to rack parts is the cheapest way to go, but if you are doing this long term, or in high quantites, you can save money by creating racks made of Titanium that have a hole that you would insert the tube into. Building racks would add a few cents to the cost of the parts that would be amortized over a number of parts.

EN plating is an autocatalytic process that requires you to have solution flow at a given rate. If the flow is too fast, the part won't plate. If you prevent exposure to the solution you also prevent the part from plating. You could mask several hundred of these in 15 minutes or so and, most likely, reduce your overall cost to plate the parts and get a more consistant plating. Additionally you might simplify the production of the product.

Another option might be to make the hub out of stainless and eliminate the entire plating process. If you wish to have a nickel rich surface, you could passaviate (Mil. Std. QQP-35) the stainless and leave it nickel rich by eliminating surface iron. This would have the effect of reducing surface corrosion if that is a concern. If you were to make it of SS, you could sterilize the units by heat and package them in a sterile package.

Hi sixsigma,

thanks a lot for your advises! I will discuss this with the platter (if he lets me!). Problem is platters behave like alchemists of the middle ages. No idea if he uses electrolytic or electroless nickel. Plating is 20 microns thick.

Today I ordered a run of SS hubs to see what we get for the price that was quoted. If it works, we will discontinue our previous production method.

regards, Cosme

I believe there is a liquid that they dip in to make tool handles that can be removed

Try

http://www.tools-plus.com/safety-and-protection-tool-handle-dipping-liquid.html