Category: AUTOMOTIVE
23. March 2012   5:31 pm
Andy Stecher

Andy Stecher
Elgin, IL

When looking to introduce a coating media into a stream of plasma, one has a major decision to make; do I create an introduction system made up of mass flow controllers or hose pumps? What is the chief goal of the work the system is being built for?

Mass flow controllers seem to be the slightly more common choice. They are easily bought and integrated into a control unit, they come calibrated and there is a variety available to cover almost any chemistry you can think of. They provide precise flow rates and this is essential to fine-tuning any process and verifying it continues to run consistently. The downside is that they are limited in the scope of materials they can handle; a controller designed for an organo-silicon may quickly cog up if fed with a different liquid. You do pay a premium for the precision as well, although there are more cost-effective models available if precision is not as paramount.

Hose pump systems offer a far wider range of potential liquids and typically switching between these is as simple as switching in a different length of hose and recalibrating the pump for the new liquid. This set-up time and the physical arrangement of such a pump do make it inherently less accurate, but it is a cost effective way to provide flows over a wide range of rates for a variety of liquids.

In short, the real question to be answered is whether you want a system for exploration, or are more focused on fine-tuning a known coating chemistry. Once that is known, Plasmatreat has products available that cater to either need!

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Tim Smith

Tim Smith
Vice President Operations
Ancaster, Ontario

Editorial March 2012

I am often asked how can a company verify, in a production environment, that a part has been treated successfully with plasma?   How can they verify post-treatment surface activation?  I will answer these two questions separately as they have two very distinct answers.

Most plasma applications utilize some form of automation to treat a part and some form of fixture to hold the part in a known location while it is being treated.  These systems also run, sometimes for months at a time, without human supervision.

Let’s break down the three key parameters that will ensure that the part has been successfully treated using plasma. 

1- The Plasma

2 – The Robot Path

3 – The Part Fixture

The Plasma

As discussed in my last blog, Plasmatreat equipment has the ability to monitor the voltage, current, frequency and duty cycle of the plasma as well as the incoming and internal jet (optional) air pressure.  In addition to the control and monitoring of all of these parameters, the LCM option allows for the independent verification of the presence of plasma allowing for QS9000 rating.  If all of these feedback signals are present then it can be assured that plasma is present, with the correct operating parameters, at the plasma jet.

The Robot Path

Once a robot has been programmed with a treatment path, it cannot vary from this path without triggering some sort of error.  It is safe to assume that a robot will follow the proscribed path exactly each time and if for some reason it does not, then an error will be indicated.

The Part Fixture

A part fixture must hold the part in an exact location to ensure that the plasma jet, when being moved by the robot, will maintain a fixed and repeatable distance from the part that is to be treated.  The part fixture usually includes some form of mechanical clamping or vacuum to ensure that the part sits properly in its nest.  Through the use of proximity or optical sensors, it can be verified that the correct part is seated in the correct position within the part fixture.

With the abovementioned three parameters verified; the correct plasma, the correct robot path at the correct distance from the desired part, it can be safely assumed that the part is receiving the proper plasma pre-treatment.

Post Treatment Surface Energy Verification

The above steps ensure that the part has been successfully treated with plasma but does not verify that the plasma has been successful in raising the surface energy to the level expected.  One of the largest varibles in pre-treatment that has not been mentioned so far is the substrate itself. 

Even if you have very tight control over your resin manufacturer and supplier, there may be variations in the molded part due to molding machine parameters, mold release agents and/or the environmental conditions present at the time of molding or during part storage after molding.  If you don’t have tight control over the resin you are using then the variation in the properties of the finished part can be even more significant.

These variations due to the substrate can have a negative overall effect on the surface energy of the product before and after plasma treatment.

In order to verify that the post treatment surface energy is sufficient, the only practical method that I have seen, for use on the plant floor, is to use dyne test inks.  The frequency of this testing is usually dictated by the Quality Control department. A part is taken off of the line, its dyne level is measured and checked against the level required and, assuming that the level is sufficient, the part is usually re-introduced into the assembly line for further processing.

To recap, by verifying that the plasma treatment is correct and by further verifying that the resultant surface energy is as expected, a manufacturer can rest assured that their process is performing properly.

Tim

 

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Category: LIFE SCIENCES / SOLAR
8. March 2012   11:25 pm
Mikki Larner

Mikki Larner
Belmont, CA

Hello friends and followers,

I received a quick note from Andy Stecher (PTS President) plus have been following the news that a large solar storm is headed towards earth.   Anchorage Daily News reports:   http://www.adn.com/2012/03/08/2358908/biggest-solar-storm-in-years-hits.html.  Huffington Post has a nice update as well athttp://www.huffingtonpost.com/2012/03/08/aurora-borealis-2012-solar-flare-storm_n_1332255.html.  In addition, I have been watching the sky in the evening on my commute home as Venus and Jupiter have been quite close to the moon the past few nights.

I still owe you all the report from Dyana’s visit toAlaska(and use of plasma for modifying devices) but this late breaking news may allow many in the northern latitudes to experience the same without a trip toAlaska.

Go out and watch the sky tonight!

Cheers, Mikki

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7. March 2012   6:19 pm
Jeff Leighty

Jeff Leighty
Elgin, IL

Hello again,

Last week I attended the Polymers & Plastics in Medical Applications conference in Las Vegas and what a great event it was. Not just because it was in Vegas but because it was a welcomed change from the medical mega-tradeshows. This was a small, industry-focused event where you get to meet just about everyone who attends. The two-day conference brought together device makers, raw materials suppliers, molders and a top-notch slate of speakers. Topics ranged from new substrate materials for drug delivery and bioresorbable materials to new molding techniques to antimicrobial solutions for devices and materials. One hot topic is the embrittlement of plastic materials by the overuse or misuse of cleaning/disinfection chemicals at clinics and hospitals.

In an effort to minimize the impact of hospital acquired infections (HAIs) more aggressive substances like alcohols, bleaches and QUATs (quaternary ammonium cation cleaners) are being used, alone or mixed together in cleaning “cocktails”, to disinfect medical devices. These products can react with the substrate material in the device making it brittle and unable to stand up to rough handling in the hospital setting.

So what does all this have to do with plasma?

One solution to the embrittlement problem is to alloy different plastic substrate materials together to get the best features of multiple materials and blend them together in a new way. While that may solve the embrittlement problem the new material may not  bond with adhesives, inks and coatings.  One of the conference speakers explained how every ingredient in the masterbatch has “give and take” consequences, ie: add something to reduce gas permeability and it increases rigidity or an additive to increase surface energy might decrease biocompatibility. That’s where plasma comes in. By relying on plasma for the downstream assembly issues the engineers can focus their efforts on the main problem–the embrittlement. Chances are, a quick plasma treatment of the new material will make bonding, printing and sealing the device components no problem at all. Plus, why add surface energy modifiers to the bulk material if you only need it at the surface. Plasma treatment goes only where you need it, not where you don’t and plasma will not effect the bulk properties.

The more new materials the engineers come up with the more plasma treatment will be needed for secondary assembly, coating and decorating operations on medical devices. You can bet on that!

‘Til next time…

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