The below article excert originally appeared in Advanced Manufacturing magazine.
You can read the entire article at the title link at the bottom of this page.
Medical parts are often delicate, which can create problems when they are picked off with the subspindle for backwork. It is important but difficult to apply just the right amount of pressure to hold the part in the subspindle. And once the optimum gripping force is determined, it is not easy to communicate to other operators how the adjustment was made.
Machine tool accessory maker Masa Tool Inc. (Oceanside, CA) has developed a collet system that makes this process easier. The collet is set using a special tool with marked graduations that enable precise adjustments to the gripping force of the collet.
“You can document the micrometer-like adjustment for the collet closure in your setup plan,” said Matt Saccomanno, CEO. “It’s done the same way every time, regardless of operator skill and without relying on feel.”
One of the more challenging Swiss applications is making dental implants because of their small size. Saccomanno said that Masa recently helped a customer broach a dental implant on the subspindle with the Masa collet system holding only a small land. Considering how much force is applied to the workpiece during a broaching operation, this might have seemed impossible to accomplish.
The reason it is possible is that the Masa collet system applies the gripping forces directly over the area where the collet grips the part. The collet system has two main parts, a cartridge that replaces the standard machine collet and a smaller collet made by Masa that is installed into the cartridge. These components are held to a high accuracy and are made by Masa with proprietary grinding methods. Concentricity variation is held to 0.0002″ (0.005 mm).
“This particular broaching application used an over-grip collet,” Saccomanno said. “The process change moved an operation from the main-spindle to the subspindle and so allowed some simultaneous machining not possible previously. Before they used our system, the part was made entirely on the main spindle.”
An over-grip collet opens up to pass over a shoulder or some other feature on a part in order to grip the part past the shoulder. Masa makes over-grip collets that can open up to 4 mm over the chucking diameter. This is the largest difference in diameter in the industry and still holds 0.0002″ TIR, according to Masa.
Read the entire article by clicking the link below
Special Thanks to Mark Hurst from HiTech Industrial for bringing this application solution to their attention.
Matt Saccomanno, the inventor of the Microconic Workholding system discussed how it works at IMTS 2016.
Masa Tool has developed the Microconic™ system specifically for holding workpieces from Ø0.15mm to 10mm (Ø0.006" to 0.390") in any machine that has a collet-type chuck.
The system consists of two major components: The Microconic™ cartridge, which fits into your CNC machine spindle replacing the standard 5C, TF20 or TF25 collets, and the Microconic™ collet, which fits in the Microconic™ cartridge.
The Microconic™ system has unsurpassed concentricity: Our manufacturing tolerance is 3µm (.0001") and we guarantee our cartridges to be within 5µm (0.0002") in production use in your machine.
The Microconic™ system works with either draw-type or push-type standard collet systems that are in any machine.
The Over-grip collet capabilities of Masa Microconic™ System, introduces a whole new world of time saving opportunities awaiting. Our Overgrip Collets open up to 4mm (0.157") diameter larger than the clamping diameter.
Make plans now to visit Masa Tool at the IMTS 2016 Booth W-2232 and learn about our new Microconic Workholding System.
The Microconic™ work holding system is a mechanically actuated micro-workholding system for use in high precision, small diameter CNC turning applications.
The system consists of two major components: The Microconic™ cartridge, replaces the standard TF20 collets and fits into your CNC machine with no modifications to the spindle required. The second component to the system is the Microconic™ collets which have capacities of 0,22mm - 10,00mm ( 0.0086" - 0.3949") and -Over-Grip collets which can open up to 4mm over the chucking diameter and run within 5 µm/.0002" TIR
It's the first and only workholding system for the micro-machining industry.
"Every time the collet would chuck on the parts with chip wrap, it would leave an impression in the collet. Sometimes the chip would stay lodged in that impression and the parts run from that point on are scrapped due to the chip impressions on the part and once noticed, the collet would need to be replaced."
Avinger Inc., based in Redwood City, California, designs, develops and manufactures precision medial device technology with the goal of helping patients keep their legs. Recently they began testing the Micoconic system on their Citizen L20 (7M8) Swiss Screw Machine using a Utilis 3000 series cutoff holder and an 1/5mm X 10mm insert. The bar stock was .225" OD round.
They where kind enough to share their test results with us.
A Swiss CNC machine shop presented us with several problems related to long cycle times and poor tool life with a high-volume group of Dental Surgical Drills, Taps, and Counterbore Drills with standard ISO shank configuration.
Before Microconic: The Workholding Problems
Before implementing the Microconic solution there were a number of problems:
Our customer was machining 6Al4V Titanium dental implants and scrap rates increased the longer our competitors collets where in use.
This root cause was primarily result of cutting the threads in the main spindle. Chips wrapped around the finished threads before the implant was handed over to the sub spindle collet for machining of the head hex and internal thread.
Collet wear & bad parts
The unpredictable periodic clamping on the wrapped chips on the workpiece embedded chip impressions in the collet (Fig. 3) which in turn marked the next part when it was chucked on.
As a result the competitor's collet workholding lost it's chucking power from the bell mouthing in the front. By becoming out of round, parts lost their concentricity.
When you need to make small parts, the size range of the 5C collet is where the best variety and value exist in machine tools and accessories. You don't want to sink capital into expensive, specialized machinery that will run nothing but small parts. But a 5C collet is pretty big compared to your 1/8-inch diameter part.
An adapter is available, however, that renders a common 5C machine tool capable of handling very small diameter parts. The new small parts adapter, manufactured by Masa Machine Tool Accessories, Oceanside, California, fits in any machine's 5C collet closer, just like a standard 5C collet, without any modifications or special mounting procedures.
Here you will find the latest press releases, news coverage and technical information about our Microconic™ system