I have just completed the build of a new 54" x 120" machine using fabricated parts and openbuilds motors, blackbox, etc. Travel in the X and Z axis is smooth (I have increased the acceleration rate), however, travel in the Y axis is not consistent. Sometimes it moves fine through a range of travel and occasionally the motor loses traction and it sounds like a slipping clutch. I have increased the current in the Y, Y2 motors and this has helped somewhat. Can anyone give me an idea of what the problem might be. Also, can you suggest typical accelerations rates for this size of machine using nema 23 motors? The X and Y axis are belt driven.
Tune your Acceleration and Max rate values in Grbl Settings (instructions in the Grbl wiki at github.com/gnea/grbl/wiki) Being a heavy gantry, untuned acceleration or Max rate set too high leads to stalling.
Not about mechanical tightness. Referring to grbl parameters, software settings. Tune down acceleration and Max rate to prevent stalling
I have toyed with the settings but I need to approach the problem from first principles. In the attached photo, the bottom-Left corner is where the machine homes to - you can see the sensors at the top of the z-axis, left of the x-axis, and right of the y-axis. The bottom left is where I intend to mount any work and place the work coordinates. I have X+ moving to the right, Y+ moving to the far end and Z+ moving the router up from the table. So as near as I can tell the router is physically moving in the correct directions. The first thing I need to accomplish is the setup of steps/mm. When I used the wizard for the x-axis and followed the guide, instead of moving 100mm, the x axis carriage moved to the right as expected but travelled all the way to the right and I had to abort the setup. So if we start with that problem and fix it then I can move on to the next issue.
The motors are openbuilds 1.8 degree, the pulley has 22 teeth, the microstepping is ? (where is that value), the belt is 3GT (POWGE Arc HTD 3M Open timing belt). Rick
So 1.8 deg motors = 200 steps per rotation (360deg / 1.8 deg = 200) Microstepping, we'll assume 1/8th (Blackbox default, see you mentioned BlackBox in first post while back). 200 * 8 = 1600 microsteps per rotation 22 teeth * 3mm pitch (GT3) = 66mm per rotation. Thus 66mm in 1600 steps. Getting back to "steps per 1mm" we simply 1600steps / 66mm = 24.24 steps per 1mm That gets you in the ballpark, entered in Grbl Settings > Steps per mm (Remember to save, and reset). Once you are approximately there using theoretical numbers, THEN you calibrate (fine tune) using the Wizard Once you are spot on with the steps per mm, then you tweak Acceleration and Max rate as described in the Grbl Wiki
Peter, Thanks for that excellent lesson and calculation. I entered the 24.24 value into the settings saved and reset. Then I went to the wizard and ran the test for the x-axis. The amount of movement was 55mm and when I made the correction the steps were 2.2 steps/mm which I intuitively knew was wrong. So I am still puzzled as to what is wrong. My first thought is to do a total reset of the controller to factory settings and start over. If this would be your recommendation what settings for my machine should I tackle first - steps/mm?
If the info you gave me is correct, its 24.24 steps to be about 99% accurate. What have you got for acceleration and max rate, perhaps you stall out at 55mm before you got to 100mm Attach your Grbl Settings backup (CONTROL > Grbl Settings > Backup button on top toolbar)
I have played with the settings and have almost established a fully functional machine (which may need a bit more tweaking). The one glaring issue right now relates to the Y-axis. The y-axis has about 2.6M of travel. When I set the motion to continuous, the most the carriage will travel is about 1000 mm and near the end of that travel (in either direction) I get a slippage-like response from the motors which shakes the table and the carriage stops. I do not have soft limits enabled just yet. This is a consistent feature no matter where on the y-axis I start from. Are there any suggestions as to what might be causing this issue?
