This issue’s articles:
• Your Smartphone as a 3D Printer
• Mammography machine
• Sensor Tip: Selecting best stroke length
• Underwater actuator

Featured video: Windvane Application

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Last fall this news column announced breakthrough layerless 3D printing using Continuous Liquid Interface (CLIP) Technology. We reported a company named Carbon 3D harnessed oxygen and UV light to selectively trigger or inhibit photopolymerization of an object being grown.

Now a new company has furthered this technology to harness your smartphone for the light source and to integrate the 3D information for the object to be printed.

This new company is called OLO and they have found a way to get this technology in everyone’s hands by using almost any smartphone, with their 3D CAD file app, placed in an OLO printing engine. The engine is the shape of a smartphone only taller to hold the liquid polymer, motor and other engine parts. OLO reports X,Y resolution is to 42 microns and Z resolution is 36 microns. OLO claims it is only months away from delivering this product at $129.

See it work! Source: http://www.olo3d.net

First, it helps to define the terms we are using. Referring to Figure 1, that represents a position sensor track, L1 indicates the defined electrical travel. L2 indicates the continued travel to where the track and bonding material begin to overlap, which becomes a nonlinear connection region as detailed in Figure 2. This is included in electrical stroke length but not defined electrical stroke. L3 indicates the total electrical contact travel of the potentiometer. L4 indicates the mechanical travel.

Requirement 1: total electrical stroke length (L2) should be a minimum of 5%, and preferably 10%, longer than the maximum stroke length your application requires. This ensures overrun errors and damage to the sensor are avoided.

Requirement 2: The closer the defined electrical stroke length can match the application’s actual required mechanical stroke length, the larger the change in signal will be over the range of motion. This will give you the maximum signal to noise ratio. If you try and match a small mechanical stroke length to a large electrical stroke, the output voltage change of the signal (or current change) would likely be very small and result in large resolution steps when run through a 10- or 12-bit A/D converter. In closed loop applications, this can cause dither of an actuator, imprecise positioning and overruns of the targeted position.

Linear position sensors are available in dozens of stroke lengths in small enough increments for virtually any application. For example, Novotechnik’s TLH has 20 different stroke lengths available– for short strokes in 25 or 50 mm steps between models and above 1,000 mm in 250 mm steps. Things are even easier with noncontact linear position sensors: many of the short and long stroke sensors come in different mechanical stroke lengths that can be individually programmed to - shorter than specified - strokes by the factory or – individually – by the customer, without special hardware or software.

Actuators

Completely submerged at a depth of approximately 13 feet, a butterfly valve manufacturer found the RFD 4000 touchless angle sensor met their specifications. Since they are sealed to IP 69K, constant immersion is not an issue. These angle sensors are very compact and use touchless technology. The sensing base component accurately tracks the position of a magnetic pickup attached to the moving valve stem, providing flexibility in placement and usability in a tight space.