"The concept seems very interesting. However, I think it can be a lot more successful and popular with 3D printer users if there is a rigid mount to maintain a fixed position on the print head and the device directly interfaces with the controller card probe interface.”
We considered a tapped M3 hole on the back of alignG. You can simply mount it using a M3 screw and simple mechanical structure. You can even glue it to the surface if you need a permanent attachment.
Remember that there are two very important advantages for alignG when comparing with any dial indicator: (1) dial indicators in the price range of alignG always apply a (spring loaded) force to the surface, roughly about 1 Newton (100 grams). To make sure that the force is not displacing the dial indicator, you need a very rigid mounting for the dial. When speaking about 15-micron displacement, 1 Newton force is huge. (2) a dial indicators in the price range of alignG weights about 100-150 grams. So, you need to consider that in the structure of the mounting fixture. In addition, the weight of mounting structure is often more than the weight of dial indicator, take that in account!
alignG is a non-contact measurement device; so, no worries about the spring-loaded force to displace it. In the other hand, it weighs only 20 grams. A strong magnet tape can simply keep a 20 gram gadget in place for a long time, except if you want to intentionally displace it. For sure, there are many ways to permanently attach a 20grams gadget to your extruder, if you want to install it for one time and leave it there.
“The device should have the option to trigger at some set height above the bed and it should have an output signal that can be directly connected to most 3D printer probe endstops. If it can do that and maintain accurate/repeatable readings, it would be a great contact-less bed leveling tool that can use the automatic bed leveling systems already built into most modern firmware like Marlin, Repetier, DuetWifi, etc. The location of the probe in reference to the tip of the nozzle is critical and must be a fixed distance. Without a rigid mount, the measurements would not be repeatable if the device moved.”
We considered an option for the output port of alignG, providing analog/I2C/USART interface for creative developers to integrate alignG into their system. The precision value reported for alignG (25 micron for alignG-I & alignG-II and 15 microns for alignG-III) are the standard deviation of the measurement. Standard deviation also represents the repeatability of the measurement system. Using alignG, you will have a repeatable reading.
There is no way that somebody compares a 15-micron precision sensor with an IR sensor or inductive proximity sensors, commonly used in the auto bed leveling systems. Even a high precision premium brand inductive sensor still lack the necessary accuracy. Inductive proximity sensors are limited to the conductive (or magnetic) target materials. If you have a glass bed, probably you need a conductive tape on top of that. Proximity sensors are not measuring the distance; So, your measurement is dependent on the accuracy of the Z-Stage. While using alignG, there is no need to move the Z-stage; because it measures the distance. Inductive proximity sensors have a large hysteresis problem, sometimes up to 20% of their sensing range, look at their datasheet. What inductive proximity sensors measure depends on the target material and even its thickness. If you have a thin aluminum bed, the measurement will depend on its thickness uniformity. It is a small dependence; but when talking about micron precision, it is counted.
“I honestly can't forsee myself doing a manual bed level each time I print with a separate software on a device that is attached to a magnet. Watching the video, the locations indicated for each spot is not even clear. Do you randomly pick a spot? The firmware in Repetier can probe over 40+ points on a bed and create a contour profile of the entire surface if needed. It can also do it without user interaction. Some beds are concave or convex and not planar. The leveling software in the video demo assumes the bed would be flat. I run an automatic bed level probing routine each time before I print. The height can change slightly just with temperature deltas between the hot end and the heated bed. Some of the changes can be enough to cause poor or too much adhesion on the first layers.”
Even if you are always using an auto leveling mechanism, it is always recommended to keep your bed leveled. If the miss-leveling in your bed is comparable with the backlash of the Z-stage, auto bed leveling will not result in an excellent finished surface. So, having an instrument that can check the four corners of the bed in few seconds is always useful.
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