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Tiny Medical Device Validation – Designing or Success

9/20/17     This is a blog from isomicro.com:

VALIDATION

Picture this – your medical device is designed and you’re ready to validate the tiniest component – the technology piece that enables your intellectual property. You dive in head first, knowing your part has +/- 5 micron tolerances on a plastic part. You start like any engineer would start – with a solid stack-up tolerance plan and <20% gage R&R – you should be fine, right?

Consider this general micro molding rule of thumb – BEFORE you even design the injection mold. If you work backwards with the numbers, you’ll have ~0.0004” total tolerance

Total   10 microns = (0.000397”)

Tooling = 20% of 10 microns = 0.00008” (wow, really? This is difficult to do but SO critical to hitting the final Cpk.

Cpk of 1.33 or better on this tolerance means you need ~20% of the tolerance left (and be tightly controlled) to hit your CPK.  The error breakdown generally speaking is:

Tooling 20%
Gage R&R 20%
Molding process 20%
Material lot to lot variation 10% – melt flow, venting
In the bank- 10% for some unforeseen couple of microns

Starting with the tooling (it’s almost always about the tooling), anything we can do to reduce the 20% of steel tolerance in a critical tolerance will increase the numerical dance of success as explained above. Achieving steel tolerances of +/- 0.0002” is fairly straight forward in the precision mold-making industry, however achieving 20% of this is not straight-forward and requires some good research to make sure you have one that can. Selecting the right tooling supplier is the #1 absolute critical contributor to overall micro molding product success.

It’s equally important to understand the gage R&R error in the still measurement as well as the end plastic component. Creating the steel may require EDM, milling, wire EDM, or grinding. Validating steel or pieces of steel that make up a critical feature requires that the metrology equipment is capable of one more resolution higher than the tolerance. For example 20% of 0.000397” = < 0.00008” which requires 0.00001” or better in measurement capability in both steel and plastic. If the tooling supplier doesn’t have this capability, there’s no way to quantify the very start of the process to creating a micro molded part. If the tooling supplier has this capability, you are off to a great start in achieving the final goal of CPK 1.33 or better – a necessary requirement for many medical and drug delivery devices.

Micro Expert to speak at upcoming conference

9/8/17     Medtech notable Donna Bibber, Vice President of Sales and Marketing for Isometric Micro Molding Inc. and President at Micro Engineering Solutions Inc., will be the keynote speaker at the medical extrusion conference. A University of Massachusetts-Lowell graduate with 25 years of experience in micro manufacturing, Bibber has published technical papers on micro and ultra-precision manufacturing topics worldwide. She was named one of 100 notable people in the medical device industry by sister brand MD+DI in 2008. Bibber was president of Micro Engineering Solutions at the time.

The conference, scheduled for Nov. 7, 2017, in St. Louis Park, MN, will address a range of technical issues related to medical extrusion, including:
• Manufacturing micro-medical devices using precision over-molded tubing;
• the role of pellet size in process stability of PA-12 micro-extrusion;
• medical tubing die and process optimization;
• jacketing of discrete guidewire lengths and automation of secondary processes;
• vacuum sizing small-bore tubing; and
• processing semi-crystalline materials

Speakers include Anthony Walder, Global Technology Manager at Lubrizol Corp.; John Perdikoulias, PhD, President of Compuplast Canada Inc.; Jonathan Jurgaitis, Senior Extrusion Engineer at Apollo Medical Extrusion; and Dave Czarnick, a tooling expert with 25 years of experience who holds five extrusion-related patents.
This conference is designed for individuals interested in extruding medical tubing and performing secondary operations such as braiding, over molding, surface treatment and laser drilling for catheters and delivery systems.

The Fall Spotlight Medical Extrusion & Secondary Operations Conference is hosted by Graham Engineering brand American Kuhne.
For more information and to register to attend, click here.