Losing track of Z starting position

[Joymaker]

This is a recent development: my Creator Pro has started losing track of its Z starting position. I will launch a print job, the platform comes up to starting position, and then it makes this awkward tick-tick-tick noise, hitting its vertical end stop without knowing when to stop. After that, we can be fairly confident that my Z positioning is badly off, and the model will print too high or too low. Usually too low, practically grinding the plastic into the plate.

Until recently I could get around this problem by giving the "Home axes" command from the menu before printing. But now even that command is having the same problem.

Clearly some piece of hardware is failing. What piece could it be?

[jfkansas]

Probably a switch, or the cable. The cable doesn't move so there isn't really any wear on it so I would say the switch most likely.

[Geoff]

Probably a switch, or the cable. The cable doesn't move so there isn't really any wear on it so I would say the switch most likely.

Yep, that would be it. Unfortunately I don't know an easy way to send Gcode commands to the flashforge (simplyfy3D maybe? or some convoluted USB s3g conversion...)

Normally you would send M119 to the machine and check the status of the endstops, but in your case the light should be coming on when it's contacted. If no light then yeah problems. Check the voltage from the wires, if no voltage then connection and if voltage yes, but light no, then end stop. They are $2 to replace tho, it's nothing to worry about.

[warkmal]

If you have OctoPrint and the GPX plugin, you can send M114 in the terminal window and it'll return what the bot thinks its current position is and whether the endstops are activated.

[Joymaker]

Thanks, guys. Sorry I was taken with more urgent work for the past couple of weeks. But a couple of questions:

1. Where is that switch located? And what part should it be replaced with? Sounds like you're saying it's a standard, off-the-shelf part.
2. Where is that light that I should be looking for?

Thanks for your help! -Ken

[warkmal]

The endstop switch is attached to an endstop board. It's behind the Z lead screw such that the platform that is behind the Z lead screw will run into it when your platform moves upward.

I googled for an image of it in-situ. Most of the hits are for the shim people put on the platform when they add a glass bed (like me). I found this one of a broken Dreamer endstop: https://3dhubs.s3-eu-west-1.amazonaw...2-16-23-05.jpg It's similar, but the Creator Pro has a little metal tab instead of that red button.

[Joymaker]

Hey, warkmal, that's really helpful. Not to mention that I've been hearing people advise adding a glass bed – but I wouldn't know where to get one of the right size, or how to go about it. Can you tell me how you did it, or point me to a good link on the subject?

[warkmal]

I actually use 0.03" PEI (Ultem) stuck to cheap mirror glass using 3M 486MP double sided tape. One of my kids had a 12x12 decorative mirrors in their room that they decided to get rid of. I got rid of the frame and then used a glass cutter to cut it down to the size of the bed. I used a metal straight edge and a glass cutter to score the glass and flipped the glass over on a couple of silicon baking mats (has some give) and pushed down on the score and it broke nicely. A lot of people use borosilicate glass because of the heat, but since it heats up and cools down fairly slowly and evenly I haven't had it break due to thermal shock. It's fairly thin though so it'd probably be easy to break by driving the nozzle into it.

I printed a shim for the back to hit the endstop. I used a different one, but if I was doing it over, I'd probably print this one so it'd stay in place better: http://www.thingiverse.com/thing:515065

I don't clip mine with binder clips because I don't wanna fuss too much avoiding having the nozzle hit them, so I printed two corners that "frame" it sorta, but what holds it laterally is "gino" pads that are for fastening thermal heatsinks, but work great for this. I bought a 12x12 sheet from Amazon and cut it to the size I needed. Most folks cut it into say 2" squares and distribute around the bed with space between.

[Joymaker]

Some answers to my own questions, after processing what's been said here:

1. The end stop. For others who may come searching here, it's actually called an "axis sensor" on the Flashforge USA parts shop. And it only costs $2, and for a creator pro you want the "regular" variety. Now – if only I didn't have to wait for shipping!!

2. The glass. They sell one on their store for $11. I bought one. They say it's 1/4 inch thick. Soon I will know whether it works as nicely as advertised.