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Height Measurement Sensor

Posted by Karthik.pdy 
Height Measurement Sensor
July 20, 2018 02:49AM
Hi, I'm using Marlin filmware with Arduino mega+Ramps for my DLP 3D printer
I like to add a height measurement sensor to Z axis to position the build plate in accurate resin level.
kindly suggest/Help
Re: Height Measurement Sensor
July 20, 2018 07:20AM
The 3dsystems SLA machines used a laser to measure the resin height. The time of flight might be an issue for a small height differential though.

Assuming it is the resin height that you want to know:

I think if you put a capacitive sensor on the z carriage you could have the machine "probe" the resin height without too many modifications, assuming that the resin shows enough of a difference in capacitance to the air.

If it is a bottom up SLA though do you not just want to set the platform to vat position ? That should be a fixed distance and just be an offset from the Z home position.
Re: Height Measurement Sensor
July 20, 2018 08:05AM
Just use a ballcock (stop smirking and look it up) on a variable resistor, floats on the surface and adjusts the resistance to reflect the level.
Re: Height Measurement Sensor
July 21, 2018 03:41AM
You could use open loop control as long as you have an accurate resin dispensing system and a consistent cross section of your vat.
Re: Height Measurement Sensor
July 21, 2018 05:20AM
Thanks for your feedback,

I like to use this device "https://www.amazon.com/GP2Y0A21YK0F-Sharp-Distance-10-80cm-Compatible/dp/B00IMOSEJA/ref=sr_1_4?ie=UTF8&qid=1532164632&sr=8-4&keywords=distance+measurement+sensor+for+arduino"
please advise how to code to measure a Z height using this devise


Edited 1 time(s). Last edit at 07/21/2018 05:20AM by Karthik.pdy.
Re: Height Measurement Sensor
July 21, 2018 06:15AM
needs a reflective surface... and most resins are transparent so the laser or light can get to all of it...

also it uses IR, if resin cures in IR... you may have an problem

Its the same device as [www.pololu.com]
There are 3 arduino demos how to use it in the blog section of the page.

As for adding it into marlin... no idea.
Re: Height Measurement Sensor
July 21, 2018 06:37AM
My differential IR sensor will probably work with resins. See [miscsolutions.wordpress.com]. It will pick up the reflection from the surface, even if the resin is transparent to IR. An ordinary IR sensor such as linked to 2 posts previously will give varying trigger heights depending on the colour of the resin, if it works at all.

I think most resins cure with blue light, so IR should be OK.

Edited 3 time(s). Last edit at 07/21/2018 06:39AM by dc42.

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Height Measurement Sensor
July 30, 2018 06:36AM
Hi, Thanks for your feed back and suggestions. can help me to integrate in Marlin filmware
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