Finicky optical z-axis endstop - Leapfrog Creatr

Machine: Leapfrog Creatr (a new machine from a new company in the Netherlands, so the Creatr-specific community is VERY small at the moment...), which comes fully assembled, calibrated, and (supposedly) ready to plug-and-play print.

Software: Slic3r and Pronterface

Problem 1: the z-axis endstop (optical; x- and y-axis minimum endstops are mechanical) doesn't always work, which leads to the print bed running into the hotend when homing.

Problem 2: I am brand spanking new to 3D printing, and unfortunately have no background in programming, electronics, or any of those nifty skills that would help with both troubleshooting and modifying the printer.


The machine worked pretty well out of the box, all things considered. The first problem we noticed right off the bat is a bit of a z-wobble. I understand this is a problem for a lot of machines, if the threaded z-axis screws are not perfectly straight. To correct for it, we designed rudimentary bumpers, which would stop the plate from moving in the X and Y axes, while still sliding in the z-axis. This worked, reducing but not eliminating the wobble (from ~0.8mm to <0.3mm). Then we added another bumper, which, to the naked eye, appeared to completely eliminate the remaining wobble. Great. So I hit "home all" in pronterface to get started with the next text print. Next thing I know, I'm diving for the power button while the glass build plate tries to grind itself into the extruders.... Best guess (and it is a wild guess) based on timing is that the bumpers are working TOO well, and the build plate is now held too far away from the sensor - it seems that the optical sensor only trips when the plate passes within fractions of a millimeter, and taking out that extra 0.2 mm wobble means the plate is now 0.2mm too far... Except that sometimes it still works, once or twice in a row, just long enough to trick you into thinking that it has resolved, before speeding right past the sensor the next time I hit "home". Argh.

Options I have come up with so far include:
1) Manually move the optical sensor in 0.1mm increments, until it works consistently. Hopefully this won't result in the plate smacking into the sensor.
2) Add layers of reflective tape (the sensor only seems to respond to metallic objects, so I don't know if it is a magnetic sensor or an optical/shininess sensor) to the relevant part of the plate. Again, hopefully this won't result in it hitting the sensor.
3) Reprogram the sensitivity somewhere in the firmware (??? No clue where to even start doing something like this...) so that it will detect the plate when further away (if that is possible...)
4) Replace the optical endstop with a mechanical endstop. Major problem here is that it would require not only rewiring but reprogramming...
5) Remove all the bumpers and just deal with the wobble (ugh...)


Anyone out there want to weigh in with advice? especially anyone with (positive) experience with the Creatr? I can upload pictures of the setup if that would be helpful.

Hi Littlebutterfly,

It is unfortunately to hear about your problems. These issues are solved in the newest version of the Creatr and we want to help you solve this as well. Could you send a few pictures of your issues and your bumpers to support"at"lpfrg.com? Our support department will contact you to see how we can solve this together.

Kind regards,

The Leapfrog Team

My guess would be that you are using the printer near a window with direct sunlight. This is not good for the optical flag. Any direct light for that matter might cause similar problems.

I don't know if you're still have this problem, I hope not. I just got my Creatr this week and after a day of messing with settings and calibrating the plate height, I was having the same problem. I don't think the issue is light, and the sensor position seems fine. What I've noticed is if you lower the plate less than a few centimeters, and definitely if you only move it a little so that the sensor is still part way across the plate, if you hit "Home" at that point it goes right past. If I lower it at least 5cm, it's fine when homing. It doesn't happen after a normal run, just when I move it in increments trying to figure out the Z offset. If you're still having problems, you can always try lowering it more before homing. I'm going to look into it more tonight.

Dear Littlebutterfly and Bbonish,
more information on Creatr issues can be found at the official forum of Leapfrog (unfortunately not public, so one has to register for reading it). The sensor is capacitive, reacting best on conducting materials and it indeed has some reliability issues. It appears that ensuring that none of the electric wiring can get near it solves it. Also, the repeatability (accuracy) of the resulting z-position is a bit lousy, so in order to obtain best results, one could better use (literally) manual control using the bottom driving belt while the printer prints the initial circumfering loop around the object's footprint.
On the z-axis wobble, this problem was known early on and has been solved since november/december on some of their printers by using decent ball bearing spindles instead of threaded rods and nuts. (The new system can be seen in their recent unpacking videos and product photo's.) But, due to apparent supply problems, they were shipping the threaded rods system again untill very recently (I can't look in Leapfrogs crates at the moment, this claim is based on forum posts of recent recipients).
I would suggest that the person behind 'The Leapfrog Team' takes a closer look at the systems they momentarily actually ship, before unintentionally claiming better performance than is physically delivered to their customers.
Apart from this problem, the printer ain't bad, it is just a shame that promises made are not always met.

bbonish - That is definitely a user error that we have noticed, making sure that the plate is well below the sensor before hitting home, or as you said, it will continue to go up. However, we were also running into the issue of missing the sensor even when the plate started below the sensor. We appear to have since fixed that issue, or at least patched it, with the "bumpers" that attach to the metal plate and slide in the frame grooves. Once we adjusted them so that the plate was held within 0.5 mm of the sensor (closer than the 1.0mm leapfrog team claimed they needed to be, but it consistently missed the sensor at 0.6 mm...), the sensor started working consistently, and our z-wobble has gone away to boot. We may have just gotten a bum sensor - leapfrog has offered to send us a replacement if it continues to be a problem.

mr distel - Interesting that you point out that the wiring getting near the sensor can throw it off. I hadn't found that to be problematic, but its worth taking a look at. Some of the wiring does drag awkwardly across the build plate, depending on where the print head is, but I haven't noticed any issues with it. I will keep it in mind. Also, thanks for the suggestion about correcting for the accuracy by manually tweaking the height during the circumference loop. It seems that, as long as the bed is level, if it starts out at the wrong height, aborting the print, lowering the bed, bringing it back up, and restarting the print usually seems to correct the starting height.

An update on the sensor issues: on the new and independent Creatr forum a solution is presented by one of the users, for the sensor failures and accuracy. The principle is as easy as turning the sensor by 90 degrees. Now approached axially, the sensor can't miss the table anymore and since sideways table movements make no difference anymore, the repeatability has improved as well. Read about it on: [creatrtips.freeforums.org]
This forum also offers tutorials on printing with the Creatr and lots of other stuff the companies forum couldn't provide.

We are having an issue with our z-axis which is effectively this. The is an error present in the z-axis so that as the printer lays down each new layer the table does not drop enough. This error effect builds over the course of about 10 layers which results in the extruder touching the material. With each layer after this initial collision, it keeps getting worse; leading to the head slowing compressing and squishing the material more with each layer.

I have tried several methods to fix this error; they are as follows:
Changing the z-axis offset
Changing the Layer height of both the first and other layers
Changing the amount of material extruded
Changing the speed of material extrusion

I have done each of these separately and in different combinations and have obtained a very good extrusion of the first few layers. Yet none of these changes solve the overall issue of the extruder head colliding with the material after about 10 layers.

What I need to know is this:
Is there a ratio controlling the z-axis adjustment that can be slightly off with each layer?
Could the stepper motor be mis-calibrated by the EEPROM firmware and be slightly off that way?
What are the steps in the z-axis stepper motor for our printer?

Our Printer Information:
Creatr Dual Head Extruder 3D printer
The Z-axis screws dimensions are:
ID: 14.00mm
OD: 16.00mm

It DOES NOT have the following:
A chain guide for the lines and wires going to the extruder.

I have also attached the firmware that is currently installed on our printer.

Probable causes are:
0. Z axis steps per mm configured wrong - Is it calibrated?
1. Running too fast, for the Z axis try 30mm/m. If you no longer have the problem then you can try 50mm/m or 100mm/m. The unlike the X and Y axis the speed of the Z axis is not that important for fast prints.
2. Stepper driver current set TOO LOW.
3. Stepper driver current set TOO HIGH.

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Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
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