Are end stops necessary?

Are end stops necessary? As I understand it, the computer tells the printer exactly what to do. So It seems to me, that if you keep the printer properly calibrated, the end stops wouldn't be necessary. This is why I'm wondering if they are necessary, and why, if they are.

Endstops give the computer that controls the printer a reference point to the real world. It tells the computer what physical position is software 0 so that it knows that position 30 is 30 units away from that reference point. End stops arent needed at all ends but at least one on each axis is needed.

Since 3d printers using stepper motors always print relative to their origin, yes you definetly need them. You need to reset the origin every time you start a new print so that it keeps printing in the right area. Almost no printers use absulute servo motors so your computer has no way of knowing where the extruder or the bed is inside the machine if not for the origin at the end stops.

Ask yourself this to:
-So how does the computer know where the different parts are when you move them around manually?
-How does the computer compensate for wear?
-How does the computer compensate for skipped steps?

I don't use end stops or homing switches at all, you do have to watch the z-axis as to not crash the nozzle into the bed, but have had no real issues without them at all.

Running Mach3 with a TB6560 controller, no homing gcode.

Quote
Dirty Steve
I don't use end stops or homing switches at all, you do have to watch the z-axis as to not crash the nozzle into the bed, but have had no real issues without them at all.

Running Mach3 with a TB6560 controller, no homing gcode.

So how did you do the initial calibration? And what do you do when you move the head manually?

My 0,0 for XY is the lower left corner of the bed, end stops have nothing to do with XYZ step calibrations. With the controller powered off, I run Mach3 from 0,0,0 so where ever I place the nozzle becomes 0,0,0 for the print.

Calibrations done with a dial gauge.

Edited 1 time(s). Last edit at 05/23/2014 11:50AM by Dirty Steve.

You nudge the head in pronterface till it's roughly at the low end of X and Y, and spend a bit more time positioning it on Z. Since Z rarely moves by hand on most machines, this isn't as much hassle as it sounds, just have your end.gcode position the head at a known level at the top and your start .gcode uses G92 to restore that Z coordinate when the next print starts.

I don't have endstops configured. I use Pronterface to jog the head to the center of where I want to print and a paper-width above the bed and send a G92 x0 y0 z0.1, and have my slicer set up to center on 0,0.

Thanks Andrew--I hadn't thought to park at a standard Z height.

I do bed leveling and checking with the same paper feeler gauge, using the Pronterface jogging control and some M114s. Also I occasionally check the thickness of the skirt to confirm Z positioning.

I also do not use limit switches for homing on my machine.

X,Y zero also bottom left.

So jog it X,Y over and then lower my Z-Axis so nozzle nearly hits piece of paper I have placed under it.
Then disconnect/re-connect in Pronterface and every thing is where it should be.

When I finished printing for the day I send the machines all 3-axis's to zero point and turn off.
Next day when powered up Pronterface connects and knows everything at zero.

Cheers

Sean.

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I ran my machine without endstops for about a year. In fact, I just got around to installing them up a few days ago.

I installed them because a I wanted to run an LCD interface and free the computer for other uses. The LCD, as far as I know, requires end stops. Even if the LCD did not require end stops, I would not want to be without them. It's great.

I can stuff in an SD card, select "print from SD", select file, and it prints like an appliance. Fantastic. I've printed as much in the last couple of days as I did the previous year.

I used to run without end stops. Setup is much easier now I have them - unless there is a good reason, I'd install them.

On some of the more exotic designs (delta) they may be required since the amount to move the three axes changes depending where you are.

I've heard of the ability to add a decoder to the end of your stepper motor. This will confirm to the controlling computer the exact location of the stepper motor axle.

However, as you might have noticed, there is always some kind of encoding/decoding of analog 'real world' information into a computer so it knows where all the zero points are.

Encoders typically only know the position over 360 degrees - they still need a rough starting point to know what turn they are on.