Controling jerk and setting stepper motors

#1
I am a beginner to 3D printing yet understand the background behind it(I have background in machining, design and engineering). I believe i'm having trouble with the calibration of the stepper motors (X,Y) the Z axis runs extremely smooth when actuated manually, i would expect that the x,y would respond the same, they jump quite a bit while turning the dial even at .1. I have only tried printing a couple times and they seem to start smooth then things go crazy. It almost acts like the x axis loses its position which seems to start with the hard jerking motion while doing infill. Any type of setting suggestions would be great and calibration tips for the motors. Also on the motors, they all move freely while moving by hand. Infill tips and any other tips for this machine would be appreciated.

Thanks all
 

GORDON.LAPLANTE

Administrator
Staff member
#2
The stepper drivers can be tricky to set and once you are sure you finally have everything running well it's best to leave them alone.

The stepper drivers come with two potentiometers on them. One is an overheating shutoff (which we fully engage to turn off) and the other adjust the current to the motors.

When adjusting the motor current pot it's a balance between too high and too low:

Too high:
-The motor will get hot and eventually start skipping
-The motors will hum loudly
-The stepper driver heatsink will be very hot to the touch

Too low:
-The motors will skip during fast movements.
-The motor may skip and 'click' while standing still.
-The motor and heatsink will be much cooler.
-The motor will be almost silent

When you first set your stepper drivers run the printer for 10 minutes or so and try to notice any skipping. This includes the extruder motor which is noticeable by the poor printing quality.

While the printer is running you can slightly adjust each of the stepper drivers. Don't worry this is safe for the motors (if you are adjusting) and it's the easiest way to see direct changes as you print. After you are satisfied, run a new print with much faster movements to see how the printer holds up and adjust accordingly.

As a last resort you can take the stepper driver from E1 (which is extruder 2) in the electronics case and swap it with the stepper driver you are having problems with. This driver was included with your kit to make future dual extrusion upgrades much easier and its possible the stepper driver may be bad.


Note:
We suggest using slic3r or any similar slicer that utilizes 'acceleration' control. This will slow the extruder as it approaches corners and it will slow down the print head during jerky movements.

Also note:
The gMax has a large bed and a heavy extruder (since the motor is on the extruder). This means we can print very large models with little stringing but it also means the print head moves a little slower than other printers and it can complete very fast movements. That being said you can see from the quality of the printed parts in your kit that our printers are dialed in (using the methods mentioned) and we are not using any other special components. Actually some of our printers are old prototypes with sub-par parts compared to the kits.
 

KSL

New Member
#3
I just (mostly) finished my build. At first I was having erratic choppy motion on the Y axis. I tried to adjust the pot but didn't have any luck.

I swapped the stepper controller as you suggested and now everything is working well.

However, while pulling and swapping the stepper controllers, I accidentally pulled the green/white thermistor connector. It's fine, I just don't know where it goes. I assume that's what's causing the Min Temp error I'm now seeing on the LCD.

So, three questions:

1. Where does the thermistor wire plug into the board?

2. Is there a wiring diagram with all the plugs shown at the board?

3. No rush at the moment, but at some point I'd like to order a replacement/backup for the 'extra' stepper controller. Any suggestions for a supplier, and what's the part name/number?

Thanks!
 

GORDON.LAPLANTE

Administrator
Staff member
#4
In the build manual there is a wiring diagram showing the locations of each wire. It's page 5 of the latest manual.

Replacement stepper drivers will be available in our online store (in the future) or they can be ordered from www.gadgets3d.com for the time being.

These are the drivers we use (http://gadgets3d.com/index.php?route=pr ... duct_id=71).

As you mentioned, if anyone else has problems with stepper drivers, take the unused one from E1 (which is the 2nd extruder driver) and use it to replace the bad driver for the time being.
 

KSL

New Member
#5
Whoops, there it is. Don't know how I missed it. Thanks!


GORDON.LAPLANTE said:
In the build manual there is a wiring diagram showing the locations of each wire. It's page 5 of the latest manual.

Replacement stepper drivers will be available in our online store (in the future) or they can be ordered from http://www.gadgets3d.com for the time being.

These are the drivers we use (http://gadgets3d.com/index.php?route=pr ... duct_id=71).

As you mentioned, if anyone else has problems with stepper drivers, take the unused one from E1 (which is the 2nd extruder driver) and use it to replace the bad driver for the time being.