Idea for new auto "Z" leveling

So after going through the procedure on my Maker Farm i3 8" to get the nozzle a nice .008" above my heated bed I began to think of an easier and more accurate way of doing things. I noticed that whenever I tell it to home the "Z" axis in Pronterface it will raise the "X" axis up a little bit and then begin to bring it back down until the bolt engages the endstop. Once engaged it will then raise the "X" axis up one more time and then set it to "home". After that is done then I take my feeler gauge and check to see how tight the gap is and then adjust the bolt that engages the endstop accordingly and redo the process until I am happy with things. Its a relatively easy process but instead of going off of a "feeling" I would prefer knowing that my extruder tip is dead nuts .XXX" away from the build platform. So here is my idea...

While watching that screw hit the endstop it occured to me that the only thing that is going on here is a circuit being closed. Once the circuit is closed then the computer knows that it needs to stop the "Z" motors. I then asked myself, what if you were to take off one of the leads from the endstop and attaching it to the extruder nozzle. Then remove the other lead off the endstop and attach it to a piece of shim stock whatever thickness you desire. In my case .008". When I go to home the "Z" axis now it would stop once the nozzle makes contact with the shim stock thus completing the circuit and badda bing, a perfect .008" floating off the top! Wouldn't that work or am I dreaming?

Edited 1 time(s). Last edit at 03/04/2014 10:06AM by Robdizz.

Here is a quick illustration

That is actually a great idea, I do not see why it would not work. Would just have to add/remove the shim off the platform when you feel the need to re-calibrate.

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This approach definitely works, as it's one of the methods commonly used to set the height of cutters on CNC milling machines. Here are a few examples:

[www.youtube.com]
[www.centroidcnc.com]
[store02.prostores.com]

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Kryptonit3
That is actually a great idea, I do not see why it would not work. Would just have to add/remove the shim off the platform when you feel the need to re-calibrate.

Exactly!

You mean something like this? [www.thingiverse.com]

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MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

Nice!

So last night I tried my idea. Unfortunately I was unsuccessful. I went out and bought some aligator clips and grabbed a couple .004" shims I had lying around. I had an extra endstop connector from my recent build so I stripped the ends and attached the alligator clips to them. I then reinstalled the modified endstop connection back onto the board and fired everything up. Through Pronterface I clicked on "Z" home. Instead of the "Z" axis going down it was doing to opposite and going up. Once I touched the two alligator clips together it would stop and begin to go down. Once I released the alligator clips the "Z" axis would stop. So essentially for some reason when the limit switch is removed from the equation, the actions are reversed. Since the "Z" axis goes in the opposite direction when the circuit is open my idea wont work because need the "Z" to go down so it can eventually come in contact with the shim and then close the circuit. Any suggestions?

Abumaia
That idea that you posted would work for my application if it were to be able to stop the "Z" axis once the connection has been made.

endstops usually have normally open and normally closed no/nc connectors I bet if you reverse it, it may work otherwise there is an invert endstop setting in marlin
const bool Z_ENDSTOPS_INVERTING = false; // set to true to invert the logic of the endstops.

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n9jcv
endstops usually have normally open and normally closed no/nc connectors I bet if you reverse it, it may work otherwise there is an invert endstop setting in marlin
const bool Z_ENDSTOPS_INVERTING = false; // set to true to invert the logic of the endstops.

NICE! I will definitely try that. After I posted last nights results I began to think about a solution and I came to the conclusion that no matter how I wired up the endstop, there would have to be a change in the firmware the "reverse" how the computer reacted to the endstops. I was unsure if the firmware could be altered and obviously it can and I think this is the ticket!

Now my next question, how do you go about tampering with the firmware

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Robdizz
how do you go about tampering with the firmware

Have you ever modified or uploaded firmware using the Arduino IDE?

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Surely .008' is double what you should be setting your nozzle gap to?

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NewPerfection

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Robdizz
how do you go about tampering with the firmware

Have you ever modified or uploaded firmware using the Arduino IDE?

I have not. I have only had my 3D printer for less than a week now and the firmware was preloaded.

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waitaki
Surely .008' is double what you should be setting your nozzle gap to?

Ideally, the nozzle gap would be 0. Then for the first layer, the Z would move to the first layer height, ensuring a proper gap. The other option is to zero the Z axis at the required first layer height, and have the print start at Z=0.

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Robdizz
I have not. I have only had my 3D printer for less than a week now and the firmware was preloaded.

Ask for a copy of the firmware that's on your board from MakerFarm. That will be easier to start with than redoing the configuration from scratch with a default firmware source.

Download the required Arduino IDE (also ask for the version of the IDE required, sometimes the firmware won't compile with the newest IDE version). Take a look at the configuration.h file, this is where you will make any necessary changes. Let us know when you get to that point and we can help further.

Edited 1 time(s). Last edit at 03/05/2014 07:55PM by NewPerfection.

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Robdizz
That idea that you posted would work for my application if it were to be able to stop the "Z" axis once the connection has been made.

Just connect it to RAMPS instead of a battery and buzzer, should work. I'd also swap the PCB squares for aluminum foil, and connect the wires to the binder clips.

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MakerFarm 8" Prusa i3v
RAMPS 1.4
0.4mm E3D v6 for 1.75mm

One problem you may find with this setup is that there may be some plastic that gets to cover the nozzle tip at some stage.
If this happens you will not get a connection and the nozzle will keep winding down onto the bed.
Before I started using Auto Bed Leveling, I was using hall effect sensors that overcame many problems with the Z axis limits.
There are no moving parts with the actual assembly as a magnet is used.
You can fine tune the magnet by attaching it to a bolt so that you can screw the magnet closer or further away from the sensor.
When you have the magnet set exactly as you want it, use a lock nut to fix the magnet in place so that the setting doesn't move with vibration.
Hall effect sensors are actually cheaper than micro switches and a lot more accurate.
The magnet that I used was a 3mm diameter by 6mm long and was pretty cheap on ebay.

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