Add z-axis limit/home switch

Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Tue-09-Jun

I was able to add a z-axis limit/home switch this morning. Turned out that it was much easier that I thought once I got a switch and some wire/connectors.

I got a switch from a friend who does pinball repair and soldered some "extra" wire with individueal 0.1" connectors from an old computer to the NC (normally closed) and common pins of the switch. Plug in the connectors to the positions shown below (the order doesn't match as it's just a switch)

z-axis limit switch connection.jpg
connect normally closed (NC) and common to the outer pins of the z-stop connector.
z-axis limit switch connection.jpg (56.59 KiB) Viewed 1563 times

(like how the board can be removed with all wires attached? check out this link: viewtopic.php?f=106&t=3893)

To position the switch I manually turned the z-axis down so it was about 1/8" from hitting the bottom with the printer in its normal upright position. I put hot glue on the back of the switch then positioned it against the side and moved up until the switch "clicked" open and held until the glue cooled. I then put extra glue on the ends to give a bit more strength

z-axis limit switch mounting.jpg
I used a glue gun to attach the switch to the side of the z-axis plate so the y-axis carrier operates the swtich when its almost at the bottom
z-axis limit switch mounting.jpg (47.61 KiB) Viewed 1563 times


Now in Repetier you can use the z home button in manual control. When you click z-home the extruder will rapid move until the switch clicks open then will backup 1mm and do slow move until it clicks again.

The last step is to level the bed to your new home position. Apply whatever surface attachment you use (ie blue printer tape) then repeat the following steps for each corner
1) Click the motor off button to manually move the extruder to a corner
2) Click the z-home button then adjust the bed so there is a small paper-width gap between the end of the hotend and the bed.
3) Click z-home again to make sure the extruder doesn't touch the bed

BTW its much easier to adjust the bed height screw/nut if you move the bed left/right (with motor off), adjust the screw while holding the nut, then move back instead of trying to get a wrench in under the extruder while holding the nut


You can also edit your configuration to issue the z-home command by putting in "G28 Z0" in the printer configuration of slicr
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Last edited by ahaer on 2013-Jun-Wed-12-Jun, edited 2 times in total.
Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Add z-axis limit/home switch

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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Tue-09-Jun

Just realized that I should explain why I only did the z-axis home switch.

The main reason is that its very easy to move the bed all the way right and the extruder all the way forward. Plus there is no need for accuracy with zeroing x or y. With the z-axis is is EXTREMELY CRITICAL that the first layer is height is positioned properly so you get the proper adhesion. Without the z-axis home I found myself constantly adjusting the height as the perimeter was being printed. While I haven't run any prints yet I'm hoping this problem will go away

As an added bonus the z-axis switch was physically very easy to install...
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Last edited by ahaer on 2013-Jun-Wed-12-Jun, edited 1 time in total.
Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby twistedmedium » 2013-Jun-Tue-10-Jun

Thank you very much and for the details! I'll be doing this for sure, I have a ton of switches but I think I'll have to wait until I decide on my final Z axis rod and coupling setup to get it perfect. Also, brilliant to use the motherboard connectors for the wires to the Printrboard! I was about to go run out to try to find those keyed ones the board uses and as soon as I saw your pic I realized it wasn't necessary. Saved me a few bucks and a good bit of time!
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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Wed-09-Jun

I did a few prints with the new z-axis endstop this morning. I got nice even perimeters EVERY TIME with NO z-axis adjustment required.

This is soo much better that I think everyone should add one and it should be a standard feature

With the z-axis endstop printing becomes a very simple and repeatable process. Before I was always restarting jobs because I didn't get the z adjusted properly...
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Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby twistedmedium » 2013-Jun-Wed-09-Jun

Entirely agree. A single end stop is not an expensive addition at all for Brook and will absolutely save a lot of aggravation and error. After a few weeks now the only two aspects of the Simple I can't fix as-is stock are the Y axis droop issue when extended and all of the finickiness of adjusting the Z constantly and while printing. If those two things get nailed in the stock design I think it becomes a whole new printer with a lot more appeal! This simple switch is half the battle. A small screw/slot would be a good option for it so that it could be adjusted and set for each printer and keep with the design of the rest of the printer.
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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Wed-10-Jun

I was looking around to see where people can buy a switch if they don't have one laying around.

McMaster: 7779K61 Miniature Snap-Acting Switch Pin Plunger, 15 Amps, Quick Disconnect $3.14
AdaFruit: Micro Switch - Premium Zippy 3-Terminal $1.95 (http://www.adafruit.com/products/817)

AdaFruit also sells "Premium Female/Female Jumper Wires - 40 x 12in" for $8.95 (http://www.adafruit.com/products/793) that gives you 40 12" wires with individual connectors on each end...

I was hoping to find someone who sells the micro switches with the wires already attached but no luck yet
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Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Wed-10-Jun

twistedmedium wrote: A small screw/slot would be a good option for it so that it could be adjusted and set for each printer and keep with the design of the rest of the printer.

I don't believe physical adjustment of the zero location at the switch location is required. If you position the switch as shown you have some adjustment at the bed using the leveling screws. If you find that the initial position the switch out of range of the screws you can prey the switch off, remove the glug gun and try again. Once you get things setup there shouldn't be any need for further adjustments.

In my opinion too much adjustability increases complication and confusion and can be an additional possible point of failure.
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Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby twistedmedium » 2013-Jun-Wed-10-Jun

I understand where you are coming from, but in trying to keep with the aesthetic and design already in place with the Simple you are limited in options, that was more where I was coming from in my comment. Sure, if the sky's the limit I could come up with tons of great options and solutions. Using the same materials and hardware already in play though I think a slot and screw/nut combo would be good. Hot glue is a fine DIY approach though, and I may go that route so I can add one now and then change the position when my final rod/coupler is in easily. The other option I thought of (for myself and the situation I mentioned where I will likely need to move/adjust it in the near future) that could work as a stock solution as well would be to simply have a fixed screw hole/mount for the switch but then an adjustable plate or arm on the Z axis that contacts the switch. That is easy and also could be done with what we have to work with. For a $1-2 part this has a big potential impact no matter what though for the Simple and should definitely be integrated in some manner by Brook.
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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Wed-14-Jun

Assuming the switch is in a position where it actually works (ie clicks open and closed) you can also use some g-code to make Z0 be at a different location than the mechanical home position. "M206 Znnn" ("Set Home Offset", link http://reprap.org/wiki/G-code#M206:_set_home_offset) will automatically set the z position to nnn after the endstop is reached as part of the G28 commed). The value can be saved to EEPROM configuration with M500 (I haven't tried it yet).

If that doesn't work you should be able to add a "G92 Znnn" command (Set position, link http://reprap.org/wiki/G-code#G92:_Set_Position) to the slicr printer configuration after the "G28 Z0" home command. That is add "G28 Z0;G92 Z-1" using G92 Z-1 means that the current z position is change to -1mm so that the first move to Z0 will move up (untested as well)

Of course software adjustment only works if you want the virtual zero higher than the mechanical home position. If you make it so virtual zero is below the endstop switch it will rip it off
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Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby twistedmedium » 2013-Jun-Wed-14-Jun

That's very interesting, I hadn't even considering compensating in software! Thanks
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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Wed-17-Jun

M206 doesn't work. However G92 does. Here is what I now have in my slicer configuration in the "custom G-code" section of the "Printer settings" tab

Code: Select all
G28 Z0; home z
G92 Z-2.0; adjust home UP 2mm
G1 X0 Y0 Z10 F5000 ; lift nozzle to "warm up" point

This means that using the ZHome button in manual control will go to the mechanical home but when you run a job it will be correct :)
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Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby JasperJ » 2013-Jun-Thu-09-Jun

The problem to look out for is that if you have to go down "too deep" to get the switch, you will be crashing the extruder into the bed every time you home, and if your switch clicks "too soon" then you will always be pushing the switch down "too far". The adjustments you can get are pretty tiny, then, with a standard switch setup. So tiny that simply moving the bed physically up and down is probably easier. With an opto-and-flag setup, OTOH, you can just go wherever.
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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Thu-10-Jun

JasperJ wrote:The problem to look out for is that if you have to go down "too deep" to get the switch, you will be crashing the extruder into the bed every time you home, and if your switch clicks "too soon" then you will always be pushing the switch down "too far". The adjustments you can get are pretty tiny, then, with a standard switch setup. So tiny that simply moving the bed physically up and down is probably easier. With an opto-and-flag setup, OTOH, you can just go wherever.


Moving the bed to match the mechanical home position is what I did...

You are right, software corrections probably won't make much sense with this type of switch and its current location. If the switch is too low to be adjusted with the bed you will crash the head before hitting the switch. If the switch is too high, you will (probably) push of the switch going down to the bed after mechanically zeroing
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Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby cap60552 » 2013-Jun-Fri-01-Jun

I created a mounting bracket using TInkerCAD and added my own Z-Axis switch tonight. It makes homing the Z-Axis SO MUCH EASIER.

You can find it on Thingiverse as thing number: 99922
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Bracket With Switch Mounted to printer
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Re: Add z-axis limit/home switch

Postby JohnSL » 2013-Jun-Fri-10-Jun

This is awesome. I was thinking about how to design and mount a Z axis switch and thinking I would do that this weekend. Then I found your design, John. Here's the link to his part since he wasn't able to add link:

http://www.thingiverse.com/thing:99922

I'm currently printing this, and will install it after work. Thanks again John, and welcome to the forum.
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Re: Add z-axis limit/home switch

Postby ahaer » 2013-Jun-Fri-10-Jun

great part!

twistedmedium will like that you made slots so the position of the switch can be adjusted...
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Original PrintrBot Simple Beta Owner, upgraded to V2 with
- 360mm GT2 belt-driven X axis (thing:215294 + thing:24061)
- 160mm GT2 belt-driven Y axis (thing:229854)
- 360mm x 160mm bed for GT2 belt-driven X axis (thing:240601)
- 160mm Z axis (thing:215625)
- LED light ring and 40mm fan mount (thing:217224)
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Re: Add z-axis limit/home switch

Postby cap60552 » 2013-Jun-Fri-11-Jun

ahaer wrote:great part!


Thank you, I'm pretty pleased with it, especially considering it's my first design. :D

ahaer wrote:twistedmedium will like that you made slots so the position of the switch can be adjusted...


Well, I wanted to be able to adjust it as well, that's also partly why I made the arm to wrap around the switch. By using Self Tapping screws passing through the plastic into the switch body I can adjust the switch if I need to w/o having to remove the whole mount. (Plus there really isn't enough clearance for screw heads or nuts between the plywood and the switch.

I may still have to extend it and wrap back around the other end of the switch and have a lip that sits back onto the deck to increase the firmness, I've noticed a little more flex in the mount than I would prefer. So far though it doesn't seem to be a major issue.
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Re: Add z-axis limit/home switch

Postby twistedmedium » 2013-Jun-Fri-12-Jun

hah! I hadn't noticed when I viewed the image on my phone the first time, bravo! :)
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Re: Add z-axis limit/home switch

Postby owens » 2013-Jun-Fri-15-Jun

Looks good, and I'll be printing one tonight too. I do have one observation though - you soldered three wires to the switch, presumably the common and both NO and NC contacts. I'm hoping that you didn't connect all three on the other end, though, because that would short the 5 v rail to ground when the switch is pressed. . .
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Re: Add z-axis limit/home switch

Postby cap60552 » 2013-Jun-Fri-15-Jun

Nope, there are only two wires. You are just seeing the motor wires behind it.
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Re: Add z-axis limit/home switch

Postby owens » 2013-Jun-Sun-14-Jun

cap60552 wrote:Nope, there are only two wires. You are just seeing the motor wires behind it.


Oh, good, just a perspective problem ;)
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Re: Add z-axis limit/home switch

Postby briankb » 2013-Jun-Mon-23-Jun

Has anyone be able to add a X and Y axis limit switch on the simple?
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Re: Add z-axis limit/home switch

Postby JohnSL » 2013-Jun-Mon-23-Jun

Personally I haven't even thought about X and Y limit switches since it's so easy to just move the X and Y to the front left with the motors off.
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