Z probe problems

Hi,
I've recently finished my DIY version of a I3 Prusa clone and had some good prints so far but I keep having lots of problems with the first layer height.

I've done some investigation and I think it is the Z probe, it's an inductive probe with a blue plastic tip bought from Aliexpress.

What sort of gap should there be between the probe and the bed (3mm heated aluminium) when the probe triggers, I'm getting 2 layers of A4 in the gap when it triggers, I thought it should be about 2mm.

The sensor is connected to a ramps board so fed from 5V, will a 12V feed improve it?

Should I just buy another, is there a make that people are using successfully?

Cheers

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Printers: -
Davinci 1.0 Pro
DIY Prusa Clone
My blog: www.gadjet.co.uk

3D printer instructions that tell you to set the extruder height by using an piece of paper as a feeler gauge.
The thickness of a piece of paper is an undefined height, and the thickness of a piece of paper is not a constant and varies greatly, firmware assumes 0.1mm.

I have my Proximity sensor mounted onto a slide mount with a thumb screw adjustment, this allows me to adjust the height of the nozzle to the bed.
Allowing for layer height requirement and different nozzle heights, this makes for quick micro-millimeter nozzle height adjustments.

Edited 1 time(s). Last edit at 09/09/2017 07:04AM by Roberts_Clif.

Quote
Roberts_Clif
3D printer instructions that tell you to set the extruder height by using an piece of paper as a feeler gauge.
The thickness of a piece of paper is an undefined height, and the thickness of a piece of paper is not a constant and varies greatly, firmware assumes 0.1mm.

I have my Proximity sensor mounted onto a slide mount with a thumb screw adjustment, this allows me to adjust the height of the nozzle to the bed.
Allowing for layer height requirement and different nozzle heights, this makes for quick micro-millimeter nozzle height adjustments.

That's a very good idea but I need the distance between the probe surface and the bed to be greater than that I need between the nozzle and the bed, it also seems to give a different reading across the bed as well ??

Whilst with some patience and persistence and the right industrial proximity sensor, you can get reasonably good results, these types of sensors have their drawbacks. They are large, reasonably heavy (if you're talking about ultra-light corexy/delta printheads especially), they have offsets from the nozzle which mean you are not probing all of the bed in most machines. I've used them a lot.

It was these limitations that prompted me to try DC42's IR sensor which compared to these inductive sensors is a breath of fresh air. However unless you have a clean, evenly IR reflective bed you can get a degree of inconsistency in height readings as well, and there is still an offset, though much less as its a small unit.

In the end work by Leadnglights, and Moriquendi (and later me) coalesced into Precision Piezo (see my sig for website). We make modules that can be added to most printers, I3 machines with groovemount hotends are reasonably easy to convert, which detect when the nozzle touches the bed. No offsets, use any surface you want. Set your 1st layer height to be exactly 0.3mm and print it, then measure it, it will be 0.3mm and this is repeatable time after time (with a clean nozzle). No paper needed, or feeler gauges. Most firmwares support the small tweaks needed to get the most from the sensor including the main branches of RRF, Marlin, Repetier and the edge branch of Smoothieware.

If you don't fancy buying one, that's cool, its an open source project you can make one yourself.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

That looks very interesting, first thing I'm going to do is feed my probe from 12V to see if that improves it but I'm also going to investigate the
Piezo route.

Edited 1 time(s). Last edit at 09/11/2017 01:39AM by gadjet.

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Printers: -
Davinci 1.0 Pro
DIY Prusa Clone
My blog: www.gadjet.co.uk