PRODUCTION MICRO MOLDING
11/26/12 Micro molding is an exciting field to work in. You are working with cutting edge technology to create products that have never been made before! The medical field is one of the major fields that is using this technology to increase human comfort and speed up recovery time. Some examples of Micro Engineering Solutions work is seen and explained in the attached Production Micro Molding video clip from our website.
MICRO MACHINING VALIDATION USING CT SCANNING
11/19/12 Ct Scanning (X-Ray Scanning) has come a long way in the last few years. This technology was originally developed for use in healthcare facilities whereby a person lays flat on a table while a CT scans specific parts of the body, however CT scanning is now being used for inspecting ultra-high precision micro components and assemblies.
These critical components, along with many others requiring micro features and surface finish are ultimately validated using many metrology methods. Validation time lines for Phase 1 clinical trials can be lengthy but shortened with extremely fast CT scanning equipment. This equipment can measure a 3-dimensional part or assembly in <3 hours and compares the fully 3D model to the actual scanned part or assembly (see Figure 1.1).
The CT Scanning (Xray Scan) scans the entire part in 3D (see Figure 1.2), creates point cloud data which with software turns the scan into a 3d CAD model. This model can then be compared to the original part solid model, which when drawn at nominal can be used as a fast, and accurate comparison from planned to actual part geometry.
In fact, the smaller the part, the more accurate the CT scan can be due to the pixel sizes of the scan.
• Actual CT Scan vs. CAD Nominal Model Comparison
• Surface finish imperfection recognition
• Accuracy of non-contact metrology between sub-micron to ten nanometers
• Metrology fixtures simplified (Save time and money on multiple fixtures to “present” parts to vision source)
• Feature inspection and recognition
• Bonding surface inspection and analysis
• Accurate Volume calculation for costly materials
• 100% 3d component and assembly scanned in hours vs. days or weeks
• Micro Machining, Micro Molding, Micro Assembly Defect Analysis
CT scans a singular part or an entire assembly, showing the bond surfaces, the tiny interactive surfaces, and separate thin walls designed into surgical instruments, implants, and pharmaceutical devices.
Figure 1.1 CT Scanned Endoscope Micro Machined Component (Tan) compared Metal Injection Molded Component (Blue)
Figure 1.2 3d Scanned Endoscope component, scanned once from the top down, showing top and bottom scans
Validating with First Article Inspections is tedious, time consuming, and costly. CT scanning, whicle not cost effective for all parts, is a no-brainer when it comes to critical, high value components and assemblies such as implants and pharmaceutical devices.
Micro milling, grinding, and swiss turning are micro machining methods that create critical components for implants and pharmaceutical components such as:
• Cardiac Implants
• Trauma fixation Implants
• Orthobiologics
• Reconstructive join replacements
• Insulin Delivery Pumps
• Neuro stimulation Devices
• Glucose Monitors
• Ophthalmic Instruments
Medical and Pharmaceutical device companies can speed up the clinical trial process with validation and metrology methods such as CT scanning. Three hours to part and assembly CAD data compares to most first article inspections that can take days and weeks because of the fixturing necessary to view the entire part and assembly in many different planes, using many different datums. It is then not possible to stitch all of this data together in a visual way for engineers and research scientists to determine how far off the parts are from their original models.
It is also physically impossible to look inside orifices, tubes, and inside geometry without cutting parts in half or sectioning them. This can produce distortion of the actual parts and split the features needed for full metrology and validation. Guesswork such as datum re-establishing and solid model stitching is taken out of the equation when CT scanning is used.
CHALLENGES IN MICRO MOLDING WITH BIO-RESORBABLES
11/12/12: Micro Molding in bio-resorbable PLA and PGA materials creates challenges with small gate sizes for these highly shear sensitive and highly moisture sensitive materials, such as shear stress through small gates, humidity control for extremely small shot sizes, and integrating macro to micro technologies to produce near micron level geometry in precision, micro molded bio-resorbable components.
The first challenge encountered by processors of bio-resorbables is material handling, which is the single largest area for error. PLA/PGA materials are highly susceptible to moisture and heat. They must be stored properly at a specified temperature in nitrogen-sealed foil pouches. They must then be used according to the processing run quantities needed and material drying cycle. The material usage must be matched with the injection screw and shot size in an injection molding machine so that the material is not sitting in an improperly sized machine where over-drying and over-heating can occur due to the prolonged temperature and drying exposure.
A mold design with a properly sized gate and a very small runner and sprue (if any) is critical to product quality and cost.
Mold venting is also important as clogged vents will also degrade the polymer prematurely and cause burning of the implant during processing.
Lastly, micro molding machines are a key component to processing resorbable polymers. Because they are highly shear and heat sensitive, proper fit of the shot size to the screw and barrel is critical. The residence time (time the polymer sits in the barrel) can affect the IV of the material.
You can see some of the components we have worked on here.