Printer Exceeds Travel Limits

Hey all,

I am very close to getting my printer working but there is one major problem. When I hit the print button the bed heats up and the extruder and the x y and z axis all move to hit their endstops and once they hit them they back away then slowly go back to hit them. All normal. Then the printer will go kind of wild and the x or y axis will move way out of the way for some reason just try to keep going way beyond where the machine can physically go so I have to shut it down so it doesn't destroy itself. I'm not sure if this is related but when I turn the machine on and plug it into printrun to test out the axis they wont move past the position they were in when I plugged the machine in. They move gladly in the other direction completely willing to smash into their physical limit The way I download my files is by getting the stl from thingiverse, then going to cura and turning it into gcode then loading that file onto printrun. When I load the gcode onto printrun from cura the object is way off to the side off of the build platform even when it was in the middle in cura, so I have to put the piece in the corner of the cura platform. Does my printer know how big it is? I even changed the limits on printrun and cura to a lot smaller than what my printer could do but for some reason this does not help. Once the printer went way off the bed and just sarted gushing out plastic into the table.... I've done a lot of research about endstop possitions and I know mine are right b/c the printer purposely tries to hit them when it homes....
All help is appreciated
thanks!

Don't know which printer you've got. But the Mendel (and thus the Prusa I assume) don't have a max-sensor, only a home sensor.
IIRC the slicing software (cura?) should have a limit range in it's setting details, but if you give the printer a command that is too big it will attempt to do it as there doesn't seem to be any limit checking in the firmware either (probably relies on the slicer to give good data to keep the firmware light)

I also ran into similar problem when printer catches on anything (print job, wire snag, random item in path) because the program/sensors are Open Loop, so the printer assumes the printer is in the spot it thinks it is, and doesn't use a closed loop to check during the print. Usually one collision leads to several more.

They generally only have a min sensor, but they also generally know the limits of travel - the firmware is usually set up with the size of the bed.

Either the firmware is not correctly configured, or the microstepping jumpers do not agree with the configuration. If you tell your firmware that you are using microstepping, but do not install the jumpers, the carriage will go beyond the limits of the machine.

Have you set your #define DEFAULT_AXIS_STEPS_PER_UNIT?
What happens in Pronterface/printrun when you tell an axis to move 10mm? Does it move 10mm or more?
When you tell an axis to home in Pronterface/printrun does it travel toward the end stop?
Do you have all 3 jumpers under your drivers?

Steve

Thanks for the replies,

This is what I have for the #define DEFAULT_AXIS_STEPS_PER_UNIT but I'm not sure how to know what the steps per mm (don't even know if it's mm) is for my nema 17s, also factoring in the belts and threads of the z I foresee that that number may not be easily reached.

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,78.80,4000,660}  // 660 was 760 * 1.1 calibrate extruder per slicer

When trying the print I set up Cura with an even smaller length width and hight than what my printer can handle just to see if that would work but it didn't do anything. I thought there might be a place in Marlin to put in bed size but I guess not.

I just did some testing to see if my printer was accurately moving the distance I asked it to and I'm surprised yet somewhat pleased by the results. It seems that for every axis of the machine when I ask it to move 10mm it moves 15mm, very odd. Do I multiply my steps per unit by 2/3? Also, I'm not really sure what any of you mean by three jumpers under by drivers. Nothing like that in my set up. What are these jumpers? What do they do? Also, when I ask my printer to home all the axis do move into their end stops.

Thanks again.

Edited 1 time(s). Last edit at 11/29/2014 01:48AM by erikn.

On a RAMPS card at least, there are jumper pins beneath the stepper drivers. The normal configuration is to have all 3 sets of pins with a jumper installed. This gives 1/16 microstepping which, basically, turns your 200 steps/rev stepper into one that has 3200 steps/rev. The number of steps figures into the steps per millimeter configuration. Each combination of jumpers gives a power of 2 multiple, so I'm not sure why you are getting 15 for 10. I would expect 20 or 40. This tells me that the value you have in steps per millimeter is incorrect.

For more on the pololu drivers and microstepping, see here.

For more on the ramps board and the jumpers, see here.

For help with the calibration calculations, see here.

great links from jbernardis.

You need to calibrate your printer.
First if it's a RAMPS board check the jumpers - power everything off before removing the driver boards.
Next take the pulley type (usually a GT2 but could be T2.5) and the number of teeth on it and use the calculator jbernardis has linked to.
This will give you the correct DEFAULT_AXIS_STEPS_PER_UNIT value.
compile/upload and see what 10mm or 100mm from Pronterface/printrun gives you.

Steve

I just realized that I actually did receive some jumpers with my kit, I feel like I should have realized this late in the game. I only got one jumper per driver though so I installed them in the 1m slot, i.e. the 1/2 step slot. Then I went to measure the travel of the printer and it went 7.5mm per what is supposed to be 10mm. I guess the jumpers did their job. I'm going to use to calculator to try to get the right values for the firmware. I jumped the gun and tried to print a cube and still when the bed finished heating and it went to start printing the y axis just tried to go way past it's travel and the x axis went way off to the side to a point where the extruded wasn't even over the bed anymore. I think this issue has to do with cura and the object location in the bed in the gcode. I think it's telling the printer to print the object in some crazy location. What software do you use to set up (scale and what not) your prints?

Thanks a lot

Quote
erikn
I just realized that I actually did receive some jumpers with my kit, I feel like I should have realized this late in the game. I only got one jumper per driver though so I installed them in the 1m slot, i.e. the 1/2 step slot. Then I went to measure the travel of the printer and it went 7.5mm per what is supposed to be 10mm. I guess the jumpers did their job. I'm going to use to calculator to try to get the right values for the firmware. I jumped the gun and tried to print a cube and still when the bed finished heating and it went to start printing the y axis just tried to go way past it's travel and the x axis went way off to the side to a point where the extruded wasn't even over the bed anymore. I think this issue has to do with cura and the object location in the bed in the gcode. I think it's telling the printer to print the object in some crazy location. What software do you use to set up (scale and what not) your prints?

Thanks a lot

Each driver needs 3 jumpers under it.
I use both cura and slic3r for slicing and pronterface to actually setup the printer.
Cure slices some objects better than slic3r and vice-versa.
I always print from the SD card

Steve

I got the accuracy thing fixed but now my printer just goes absolutely wild when I ask it to print a cube. It wont go past its limits anymore but it will be going all over the place when the cube is only 10mm^3. Could this be an issue between the Cura to Printrun gcode transfer?

Quote
erikn
I got the accuracy thing fixed but now my printer just goes absolutely wild when I ask it to print a cube. It wont go past its limits anymore but it will be going all over the place when the cube is only 10mm^3. Could this be an issue between the Cura to Printrun gcode transfer?

Have you checked and set the voltages on your stepper drivers?

I have been doing some research on how to check voltage on the drivers and from what I have been seeing it seems like you probe between the trimpot and the ground pin on the driver, and also that there is a Vref test point. Yet when I try this nothing is read on my multimeter. Once I figure it out how do I set it? Do I adjust the trimpot to get the right resistance across all of them? I measured the resistance between the trimpot and ground and it was around 6.5 for all of them +- about 0.2. I later realized that I need to find the Vref test point to measure the voltage but I could not find it on my stepper driver.

Thanks

Also, the motors do vibrate when they move and make a lot of noise. I have found a great calibration page on the wiki that I am going to follow and see how things progress.

Quote
erikn
I have been doing some research on how to check voltage on the drivers and from what I have been seeing it seems like you probe between the trimpot and the ground pin on the driver, and also that there is a Vref test point. Yet when I try this nothing is read on my multimeter. Once I figure it out how do I set it? Do I adjust the trimpot to get the right resistance across all of them? I measured the resistance between the trimpot and ground and it was around 6.5 for all of them +- about 0.2. I later realized that I need to find the Vref test point to measure the voltage but I could not find it on my stepper driver.

Thanks

Use a multimeter on DC volts (0 to 2v range).
neg lead onto the 12v ground lead that comes from the PS (I just stick it against the screw in the green plug-in) and the pos lead to the trimpot itself.
Turn the 12V powersuppply off when checking and adjusting the trimpot - just leave the USB power to the Arduino. Turn the 12V powersupply back on to test the motor movement.

Steve

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