the windpipe (trachea) and the throat (oesophagus). Air, pow- ered by the lungs, is diverted into the throat, which vibrates and results in fluent speech. Traditionally the valve is made from silicone rubber, but the material is exposed to a hostile and non-sterile environment and a biofilm develops on the surface. Tis biofilm causes valve performance to deteriorate, necessitating an uncomfortable and costly valve replacement procedure about every three months. Te company was seeking a way to replace the silicone
with ceramic, a more attractive material because of its stability, biocompatibility and compliance. With its hard, impervious surface, ceramic is more resistant to the hostile environment found in the throat. Te medical device company had a design concept for the
new valve, a three-piece component with a front and a rear casing and a dart-shaped component inserted into the top and bottom casing. Te dart moves forwards and backwards to close the valve. Te overall size of the valve is less than 10 mm. Te unique valve design called for precision manufacturing for the parts to work together.
Morgan Steps In Morgan became involved in the project about two years ago,
when Avoco Medical sought out the Rugby, UK, plant for their experience with ceramics, design, and precision manufacturing. Te plant, which manufactures advanced ceramic components, began by developing five scale prototypes of the valve. Te ma- terial used, Zyranox, is a very high-purity zirconia-based mate- rial. It contains 99.9% zirconium oxide (ZrO2 ide (Y2
), with yttrium ox- O3 ) and hafnium oxide (HfO2 ) in combination. Zyranox
zirconia ceramic was initially chosen because it has proven to be highly resistant to biofilm during extensive laboratory testing. It was originally designed in the 1980s for use in femoral heads for hip joint replacements with toughness in mind. But the material also has another distinct advantage—Mor-
gan already had an FDA master file and ISO 13485 approval for the Zirconia material, so they could demonstrate the material’s biocompatibility beforehand, a boon to the design process. Te material also exceeds the requirements of ASTM F1873 and ISO 13356. Te demonstrated biocompatibility meant that the company did not have to go through a full validation process demonstration; they simply had to prove that the device is safe and performs as specified. Morgan was able to show a failure mode analysis (FMA) to
support the use of the material for a medical device. Tey had ex- amined all the potential hazards and had a risk mitigation plan in place. “When we design a new component we look at all the key criteria and features, testing to see that the design meets require- ments,” said Yannick Galais, commercial manager for Morgan’s Rugby site. “We make sure that every aspect of risk is satisfied.” “Te new speech valve includes three ceramic components that must be precision-manufactured so they work together
properly. Te difficulty here was to design an assembly that would encapsulate the dart but allow it to move freely,” added Galais. He noted that the tolerances are tight and must be pre- cise. “Controlling the fit and clearance between the different components is critical. Morgan has the ability to manufacture the parts to tight tolerances and complex geometries, which is essential to providing high-quality, reliable valves.” Similarly the surface finish of features is key to ensuring
the component can slide without catching. Morgan worked on tooling to achieve the most appropriate surface roughness parameter (RA) to permit the proper motion of the dart.
No Secondary Operations To avoid secondary operations that add to costs, Morgan
had to develop a manufacturing process that would result in a finished product, with the proper fit, with one machin- ing operation. Tis was a challenge, since each of the three components was manufactured individually, but had to fit together. Te goal was to achieve repeatable tolerances to make the assembly work. To meet this goal, Morgan did a significant amount of preliminary work mimicking the fit and evaluating the surfaces in contact without the full as- sembly to make sure that each worked. Tey did a mockup of one part, then another and then the third. When they were sure that all the design experiments worked together, they completed the full assembly. Te front of the dart provides a curved sealing surface
that prevents fluids from the throat going into the lungs, so designers had to make sure there were no leaks in the front face of the dart. Another challenge was that the back of the dart contains the three flanges that move in the valve body. Te designers prepared a number of iterations on the shape of the flanges to make sure they could move without sticking to the housing. Mockups were prepared of different phases, then a full-scale assembly was made to test that all the previous concepts worked. Tis meant they could fine-tune or tweak the design without having to change other components. During the yearlong design process, Morgan worked on
a number of design iterations, as they realized that some features were not achievable or would not meet the origi- nal movement requirements. Tey reshaped the features in collaboration with Avoco Medical, working on amendments needed to achieve the final product. Zirconia ceramic components have a hard and impervious
surface, which discourages the biofilm that reduces standard silicone rubber valve performance. It has proven to be highly resistant to biofilm during extensive laboratory testing and the ceramic valves should last more than two years—at least eight times longer than silicone ones.
This feature edited by Yearbook Editor Michael Anderson from information provided by Morgan Advanced Materials.
Medical Manufacturing 2014 55
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164 |
Page 165 |
Page 166 |
Page 167 |
Page 168 |
Page 169 |
Page 170 |
Page 171 |
Page 172 |
Page 173 |
Page 174 |
Page 175 |
Page 176 |
Page 177 |
Page 178 |
Page 179 |
Page 180 |
Page 181 |
Page 182 |
Page 183 |
Page 184 |
Page 185 |
Page 186 |
Page 187 |
Page 188 |
Page 189 |
Page 190 |
Page 191 |
Page 192 |
Page 193 |
Page 194 |
Page 195 |
Page 196 |
Page 197 |
Page 198 |
Page 199 |
Page 200 |
Page 201 |
Page 202 |
Page 203 |
Page 204 |
Page 205 |
Page 206 |
Page 207 |
Page 208 |
Page 209 |
Page 210 |
Page 211 |
Page 212 |
Page 213 |
Page 214 |
Page 215 |
Page 216