Rodriguez t4c Medical Welding Systems

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MEDICAL WELDING

SYSTEMSAssignment in Industrial ElectronicsRodriguez, Karen Joyce M.

T4C


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WELDING SYSTEMS

WELDING, the fusing of the surfaces of

two workpieces to form one, is a precise,reliable, cost-effective, and high-tech

method for joining materials.


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MEDICAL WELDING SYSTEMS

Three most commonly used welding systems for

medical applications:

1. Orbital Welding

2. Laser Welding

3. Ultrasonic Welding


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ORBITAL WELDING

SYSTEM


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ORBITAL WELDING SYSTEM

In environments that require extremely hygienic

and sterile conditions, orbital welding has been

proven to be an effective method for joining

stainless steel tubing for systems in which

products flowing through them must be free of

contamination.

It has the capability of making smooth, crevice-

free welds that maintain uniformity and

consistency for thousands of joints


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Orbital welding, ideal for pipes or round objects

requiring a strong, secure weld, is performed by

contract manufacturers to join components in

medical device manufacturing.

In the continuous orbital welding process, a

welding arc is rotated 360 degrees around an

object, using non-consumable electrodes and

tungsten inert gas to produce clean, low particlecount welds.


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Open welding heads use flexible hoses to

supply power, gas, coolant, and filler wire, which

is sometimes required when welding thicker tube

walls or difficult materials.

Closed chamber weld heads are often used on

larger diameters to position the torch precisely

and to securely hold the pipe.


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LASER WELDING

SYSTEM


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LASER WELDING SYSTEM

Two Categories:

1. Macro-scale seam sealing

2. Micro-spot


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Macro Welding: Implantable devices

End-effector attachements for surgical tools

Require excellent weld quality with minimal heatinput

Seam Welding of implantable devices requires 300-

600 micron core beam delivery fibers to provide

maximum process stability and weld speed

Key: integration of motion with laser control to create

the contour weld, such that the pulse repetition rate

is tied to the speed, and weld nugger spacing and

energy input are consistent


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End-effector attachment is usually a fillet

weld requiring smooth transition between the

two material thicknesses such that no dirt or

debris can accumulate


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Micro welding: Reducing spot size, and therefore rapidly increasing

peak power density, is great for drilling applications

but presents significant obstacles for welding

When creating micro-welds, methods of heat sinking

and means to avoid material balling around the joint

are critical.

Balling occurs when the joint material simply melts

and forms a ball under surface tension pulling awayfrom, rather than wetting, the other interface.

Laser needs to operate around 100-500mJ, and down

to as little as 20mJ.


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Laser welding of polymers in medical device

manufacturing has special requirements as

related to:

colors of the materials

process control

documentation of the process parameters

The usage of laser-based plastics joining brings

in some aspects which make this joining method

for particular applications advantageous

compared to classical plastics joining methods

like ultrasonic or heat-stamp.


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Advantages of laser welding of polymers:

its excellent welding quality

the protected welding zone (inside welding) the clean surfaces (no particles)

the high optical quality of the seam

the minimal thermal load to the work piece

easy designs (flat surfaces e.g.) the contact-free welding process (no deterioration of

the welding quality)

the online closed-loop process control and

documentation.


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The colors of the materials involved determine

the degree of the complexity of the process itself.

The laser is used to generate a melt pool in-

between the interfaces.


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Except for the welding of two transparent materials, all other

material combinations are joined using a sandwich of a laser-

transparent part on top of a laser absorbent part (Figure 1).


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Due to the absorption time and the generation of the melt pool, as wellas for the wetting process of the melt pool onto the transparent plastic,

such a process needs a certain time frame and cannot be done infinite

fast (Figure 2).


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The contour welding method is rather slow but allowsthe controlled dosing of the applied heat to the work piece.

The simultaneous welding method, however, is suitedfor fast and high-volume processes, but has thedisadvantages of inflexibility and inhomogeneous heating

along the contour. Mask welding is also inflexible since for each contour a

new mask is needed and it consumes much more laserpower than needed, making the process inefficient.

The quasi-simultaneous welding method combines the

contour welding with a fast galvo-scanning process. Incombination with a pyrometer the quasi-simultaneousmethod allows fast and precise welding with controlledheat and simultaneous storage of the relevant process datafor quality control and traceability.


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The various

methods (Figure

3) used in laser-

based plastics

welding.


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Laser welding systems used for manufacturing

medical devices are generally automated and

require custom:

Software

Motion

Vision

Tooling


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Software Development

Has 2 parts: the graphic user interface (GUI) and

the underlying code

GUI must provide a method for SPC and FDA

data collection

GUI and control code require the user to define

functionality and precisely how and what needsto be seen and controlled


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Motion System Encompasses the required positional accuracy

and repeatability and the orientation of tooling

and support structures to allow sufficientaccessibility for welding and loading


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Vision SystemAn essential component in medical laser welding

systems

It can offer correction in all three orthogonal axeswithin a predetermined field of view ofinterst

based on stack up tolerances

Lighting for vision, along with software

configuration of what is expected to be seen iscritical to the system reliability


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Tooling Use of remote diagnostics via PC and modem

connections permits monitoring and

implementation of modifications


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A Classic Product of LaserPlastic Welding:

Ostomy bags of this kindhave been mass produced usinglaser welding since 2003. The

joint line is hidden in the interiorand satisfies the highest hygieneand quality specifications.

Another plus point for lasertechnology in this application is

the minor, easily controllableenergy input. Welding machinesfrom the LQ-Integration seriesare equipped with a pyrometer foronline process monitoring.


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99 RNA Sensors in anExtremely Compact Unit:

This laser-weldedmicrofluidic cartridge is partof a complete, highlyspecialized mini-laboratory.

This opens up a whole newrange of opportunities forsurgeries and clinics lackingsophisticated laboratoryfacilities. LPKF was selectedto make this product because

of the specified two-meter-long joint line, particle-freeand additive-free contactsurfaces, complete tightness,and guaranteed channelcross-sections.


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ULTRASONIC

WELDING SYSTEM


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ULTRASONIC WELDING SYSTEM

Ultrasonic welding is an industrial technique

whereby high frequency ultrasonic vibrations are

locally applied to work pieces being held together

under pressure to create a solid-state weld.

It is commonly used for plastics and especially

for joining dissimilar materials.

In ultrasonic welding, there are no connective

bolts, nails, soldering materials, or adhesives

necessary to bind the materials together.


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It does not introduce contaminants or

degradation into the weld and the machines can

be specialized for use in clean rooms.

The process can also be highly automated,

provides strict control over dimensional

tolerances and does not interfere with the

biocompatibility of parts.


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Items such as arterial filters, anesthesia filters, bloodfilters, IV catheters, dialysis tubes, pipettes,cardiometry reservoirs, blood/gas filters, face masksand IV spike/filters can all be made using ultrasonicwelding.

Another important application in the medicalindustry for ultrasonic welding is textiles. Items like

hospital gowns, sterile garments, masks, transdermalpatches and textiles for clean rooms can be sealed andsewn using ultrasonic welding. This preventscontamination and dust production and reduces therisk of infection.


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For joining complex injection molded thermoplastic parts,ultrasonic welding equipment can be easily customized tofit the exact specifications of the parts being welded.

The parts are sandwiched between a fixed shaped nest

(anvil) and a sonotrode (horn) connected to a transducer,and a ~20 kHz low-amplitude acoustic vibration is emitted.

When welding plastics, the interface of the two parts isspecially designed to concentrate the melting process. One

of the materials usually has a spiked energy director whichcontacts the second plastic part. The ultrasonic energymelts the point contact between the parts, creating a joint.This process is a good automated alternative to glue,screws or snap-fit designs.


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It is typically used with disposable medical tools but it can

also be used on parts as large as a small automotive

instrument cluster.

Ultrasonics can also be used to weld metals, but are

typically limited to small welds of thin, malleable metals,

e.g. aluminum, copper, nickel.


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Ultrasonic welding of thermoplastics causes local melting

of the plastic due to absorption of vibration energy. The

vibrations are introduced across the joint to be welded.

In metals, Ultrasonic welding occurs due to high-pressuredispersion of surface oxides and local motion of the

materials. Although there is heating, it is not enough to

melt the base materials. Vibrations are introduced along

the joint being welded.


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The benefits of ultrasonic welding are that it is much fasterthan conventional adhesives or solvents.

The drying time is very quick, and the pieces do not need toremain in a jig for long periods of time waiting for the jointto dry or cure.

The welding can easily be automated, making clean andprecise joints; the site of the weld is very clean and rarely

requires any touch-up work.

The low thermal impact on the materials involved enablesa greater number of materials to be welded together.


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All ultrasonic welding systems basic elements: A press to put the two parts to be assembled under pressure

A nest or anvil where the parts are placed and allowing the highfrequency vibration to be directed to the interfaces

An ultrasonic stack composed of a converter, an optional booster anda sonotrode . All three elements of the stack are specifically tuned to

resonate at the same exact ultrasonic frequency (Typically 20, 30, 35or 40 kHz)

Converter: Converts the electrical signal into a mechanicalvibration

Booster: Modifies the amplitude of the vibration. It is also used instandard systems to clamp the stack in the press.

Sonotrode: Applies the mechanical vibration to the parts to be

welded. An electronic ultrasonic generator (US: Power supply) delivering a

high power AC signal with frequency matching theresonancefrequency of the stack.

A controller controlling the movement of the press and the delivery ofthe ultrasonic energy.

Rodriguez t4c Medical Welding Systems

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