Z axis probe to limit switch swap??

[jknightandkarr]

Is it possable on the Printrbot Simple 1405 to get rid of the z axis probe n use a limit switch? This probe thing isn't working for me at all and with the design, is also a HUGE P.I.T.A to adjust!!! So hopefully someone can help me on this. It is all original minus Ubis 13 hotend and heated printbed, but everything else is the same.

Joe

[RetireeJay]

It's absolutely possible. How to do it depends on which specific model of Printrboard you have.

The original circuit, before the probe came out, used a 4.7k pullup resistor, and the end-stop switch held the pin at ground until the switch was touched. On Rev D boards, the 4.7k pullup resistor was actually built-in to the ATMEL chip. On Rev F boards, you have a transistor in between the external pin and the ATMEL Z sensing input pin, so there's a inversion. Depending on the model, there may or may not be a pullup resistor in the circuit on the input side of the transistor (some probes have "open collector" outputs; others have active pull-up and pull-down circuitry). You will have to do a bit of research.

If you want to avoid having to modify the firmware, then you'll need to emulate the probe's high and low states depending on whether or not you are "triggered". Once you do that, then simply never issue a G29 command. A G28 Z0 will suffice to lower the carriage until it triggers your switch. You will want to have a convenient way of precisely adjusting the trigger point. And it will be up to you to get the plane of the bed parallel to the plane of X-Y motion of the hot end.

Several of us old-timers don't have probes and don't want them. A good switch and a trammed bed work just fine with ultimately less hassle.

[jknightandkarr]

I have the Printrbot Rev F4 board. Thanks for the help. I definatly need it. I flipped the probe to outside of its original loc, but now the screws will hit it if i try it. Lol

Joe

[Sagbot]

The thread's a bit stale but Joe, if you haven't already solved it, one thing you can do is move the inductive probe to the back of the bot and use it as a Z switch (with G28 Z0 as Jay says). I saw one person mount the probe on Z-Y blocks, next to the Y motor and sensed the steel base below. Then you don't have to make electrical changes. The bed can be shimmed with washers or springs or rubber spacers.

[jknightandkarr]

No, I haven't messed with it yet, been WAAAAY too busy/stressed out/felt like crud. I am looking at it now. Thanks for the help!

I thought I could just move the Z-Probe to the outside of the housing, but while that DID free up ALOT of room for the adjustment nuts, the bed screws hit n no room on one side to sence with out mods, next thought is original location but cut out part of the <Y> bracket to open up the room I need to adjust the probe.

Joe

Edit: So far the only good place I have found to mount the probe to is the Y/Z Top Back plate near the Z-Axis lead screw. Just gotta figure out the mounting of it and the metal sensor plate that the probe needs. A Z-Axis limit switch directly from Printrbot would have made this much simpler......

[jknightandkarr]

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Well i got my z probe moved to a solid location n this was the result. The brackets are straighter then they look, tonight i'll set the height of the z axis then print, adjust, reprint till the stupid thing works right!

Anyone have any suggestions for settings for a 1405 w/heated print bed n Ubis metal hot end? Using Repeater Host. Thanks!

Joe

[jknightandkarr]

Well can this be moved to the hardware troubleshooting section please??

Good news is I got the printer working again. Bad news is stuff once again is NOT sticking to the print bed. Good news there is I know what the issue is. Bed front sits higher then the rear of the bed does. The rear of the bed is at a good area to work from. The front is TOO high n as a result nozzle clogs, stuff don't stay on. The whole bed frame looks like its been tweaked or something, so I see 2 fixes here.

1) Rebuild the whole print bed frame so its straight n true. Maybe someone has designed plastic replacement parts??

2) Easier and simpler to deal with, being get longer screws to hold the bed down n place a spring under each corner of the bed, so it can be adjusted much easier. I have some assorted springs, but no screws, so I'll have to get some.

Has anyone else ever had this happen with the 1405 Simple Wood printer before?

Joe

[RetireeJay]

There are many who have worked on various methods of leveling (actually tramming) the bed. I'm a proponent of shims rather than springs. You get a more rigid structure and less tendency to creep.

I think this thread is in the right sub-forum now: Hardware & mechanics - Mod talk.

[frankv]

Limit switches also have problems. There's some Z movement of the nozzle needed to trip the switch. One of my printers (not a PB) had the switch mounted above the nozzle, so that the nozzle itself pressing against the bed tripped the switch. This didn't work very well.

On both my printers I've manually levelled the bed and I manually set the height using the tried and true "firm grip on a piece of paper" method.

[jknightandkarr]

Well, I have tried to level the bed and no luck. I noticed that the Z/Y axis assembly sags WAYYYYY too much, stupid zip ties.... so found an easy $3 solution to my problem that made a SERIOUS improvement to my axis sag problem. 19 gauge wire! Looped it through each hole 2 times like I was sewing a patch, then twisted the ends togeather. Only have 1 set of bearings left to redo, but I already tried to move the assembly and now there's almost NO movement in the assembly! So when I finish that and level the bed will try printing again. These 2 mods should fix my issue quite well.

Joe

[RetireeJay]

To carry that no-sag saga even further, check out the many posts from Jon Lawrence. He built a new frame for the carriage that moves in the Z direction, giving it better support. viewtopic.php?f=113&t=7647&p=49808#p49808
But replacing wire-tires with wire sounds like it's going to do the trick for you at much less expense and trouble.

[jknightandkarr]

Thanks, I will check his mods out n upgrade mine further. I do have a new 3d printer a friend bought me, but owe him $150 before I can get it. I'll make the new parts with the new printer or my current one if I get it fixed. So far it should help pretty well metal wires that aren't going to give out as easy as easy as plastic will.

Joe

Edit: Got the machine's body back togeather, and while sadly there is still some sag, it's a HECK of ALOT less then before. I guessed previous be like 4/10ths of an inch movement, now maybe 1/10th of an inch at most, so I am MUCH happier now. Now just gotta reassemble the electronics portion of it.

[jknightandkarr]

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Picture is worth a thousand words! After since September 2015, my 3d printer is working again! No more ziptied bearings! Had to cut 2 notches out of the Y/Z axis bearing holder so stuff would clear. Had to remove springs n adjust print bed. Little cleaner, little photo safe glue stick n I got my first print since Spring/Summer 2015! Now time to adjust, print, repeat till I hit the diamond zone! Oh it feels soo good to get it going again! 2016 & most of 2017 sucked to the point I didn't care, but after a divorce n a NEW n much better woman in my life, I am back to normal again n happier then ever!

Joe

[TutherJay]

Several of us old-timers don't have probes and don't want them. A good switch and a trammed bed work just fine with ultimately less hassle.

Uh-oh.... I was hoping for LESS hassle, not MORE!