Laser perfilometer

[Marcossf]

How possible would it be to interface a laser profilometer (Keyence, Baumer, etc) to Duet3D, to be able to substitute any process Z offset, Z home, heighmaps and other Z measurements.
I mean something with more precision than the "lidar" used by BambuLabs on the Carbon X1E.

I know these sensors are very expensive, but how complicated would it be?

It would be appreciated if anyone has an idea.

[droftarts]

@Marcossf Can you link to a data sheet of a specific one, so we can see the output it produces?

Ian

[Marcossf]

@droftarts Thank you for your interest.

https://www.keyence.com/products/measure/laser-2d/lj-x8000/specs/

https://www.baumer.com/es/en/product-overview/smart-vision/profile-sensors/ox-blue-laser/oxp200-b02c-004/p/45062

It could be something similar to these two profilometers. We are, at the same time, looking for similar cheaper options, because these are exorbitantly expensive.

Our intention would be to be able to set all Z offsets, home Z and bed topography with this kind of non-contact, solid-state solution.
Additionally, to use it for print quality control.

It will be an industrial AM use, so it is far away from consumer solutions, hence it compensates an important economic effort for both HW and SW development.

[timschneider]

@Marcossf these sensors are around 1k€?
e.g. if you use the Baumer OXM with Modbus RTU you can look in the forum on how to communicate with an RS485 modbus inverter. You will find some examples.

I'm in contact with baumer to get my hands on one of these OXP sensors with an SBC setup. The P sensor will give you a point cloud over TCP, so I need to do the curve fitting and so on. The OXM is doing the fitting internally and can give you the results.

[Marcossf]

@timschneider Those operating at a distance of about 30-50 mm with accuracies of less than 0.05mm are priced at about 3-5K€. Mostly designed for PLC environments. We have some experience using RS485, but not much experience with Modbus.

We are convincing the customer to buy a unit that we can use to develop and test this solution, but where we don't quite see the integration is in Duet3D, how to use a certain measurement to get the Z to the right height.

Now we use a zMax endstop (an encoder position) and set the distance to zMin of Z with respect to a retractable probe. We need to be able to remove all physical contact to make home and to calculate the surface of Zmin. That's why we are thinking about the profilometer, and also to be able to make more complex and precise topographies, to ‘3D-dodge’ certain objects in the printing area.

I believe that until we are able to test these lasers directly, we will not be able to draw conclusions about their integration and usefulness.

Thank you for your input.

[Marcossf]

We found a "cheap" version from Micro-Epsilon, 470€, that could be a easy approach to non-contact sensing for Z and bed. Let's see what we are able to achieve.

https://www.micro-epsilon.com/distance-sensors/laser-sensors/optoncdt-1220/

[dc42]

@Marcossf I've looked at the main for that laser distance sensor. It produces a 4-20mA analog output and a RS422 digital output. To interface it to the Duet, it would be best to use the digital output. The following would need to be done:

• Interface the RS422 connection to one of the UART connections supported by the Duet. There are readily available low cost UART to RS422/RS485 converter boards. We plan to support RS422/RS485 natively on some future Duet3D control boards.

• Modify RRF to decode the data that the device sends and make the height available as a new type of scanning Z probe. The UART port would have to be switched into "device" mode to prevent it being treated as GCode input. This facility is already available in RRF 3.6.

We can quote for doing the firmware work if you have funding available for this project, in which case I suggest you email info@duet3d.com. Alternatively, as RRF is open source you can implement it yourself.

[Marcossf]

@dc42 Thanks David.

As a starting point, it seems quite feasible with the clues you provide.

In fact, we were thinking of treating the measurement obtained by the laser as a differential with respect to a known ZMax which is always the same (SMC LESYH16 axes with encoder). With this measurement, we know the distance of the Z axis without the need to create a new type of probe.

But that solves only a part of the possible range. The problem is that we also have to measure the printing tip with respect to that surface and that it also has an offset, so the use of a point laser is not going to solve the problem. We are going to have to think about implementing at least two, one oriented downwards in the Z gantry, and another upwards/sideways to know the distance of the tips. The printheads are interchangeable and several types and shapes.

This is quite complex, and the hardware required is no longer limited to some €470 sensors, but implementing laser profilometers is going to be a major cost apart from software development and RRF.

We will try to do something and see what we can find out. Thank you very much.