Hi, I have suddenly started having problems with my K40, if I try to engrave an outline (in line mode) it seems to work normally, but if I use fill mode the X axis goes crazy, sometimes it starts normally then shoots left and right at random. I have tried adjusting the tension on the X axis belt but it made no difference. (thinking maybe a worn belt, but the machine has not had heavy use)
if it is the belt what type and size will I need?
Not sure if the problem is hardware or software, using the Amazing Tech Mini Gerbil 3 controller.
You can hear one of the axes (sounds/looks like X) that is either being bound or has too high of an acceleration value resulting in a loss of steps. If it looses steps, it doesn’t know where it is.
Since this has been working, it’s likely a mechanical issue. So examine the X axes for any kind of binding or mechanical issue.
If it worked on a previous version of Lightburn, it’s realtively easy to downgrade to one of the earlier versions and run the job again.
If this just started, it’s unlikely that the settings have changed in your controller, unless you changed them.
You could have a mechanical issue with the motor themselves or with the back to the controller where the actual step signals are sent to the motor.. Usually referred to as the Stepper motor driver. Most of these grbl ones are a small daughter board on the controller.
You should be able to swap the X and Y motor driver chips and see if the problem follows the swap.
Start with the simple things.
How fast are you asking the X axes to operate and is this normal for your machine.
Nothing has changed in the setup or software, worked one day and failed the next, I have a new X axis belt on order (may take a while to arrive though) speed is around 60 - 80mm/sec, has worked fine at that speed for about 4 years. It “feels” like a mechanical problem, but I don’t understand why I get no problems in line mode, only in fill (I suppose the head is moving faster and more often in fill, that may explain it) Moving the head feels normal, can’t feel anything binding, but when the new belt arrives I will strip it down and clean and lubricate everything.
I doubt you have a failing belt. These are automotive timing belts and are more than very tough, they are nearly indestructible. Doubt you’d wear one out in a lifetime of use, let alone a few years.
Are you running your cut at the same speed as your cut… I kind of doubt it. If not you really can’t compare them.
Shouldn’t hurt anything to try a vector cut at your scan speed, won’t cut, but it might help with diagnosis.
I suspect you have an issue with the hardware in the X axes somewhere.. Either mechanical or electrical. It’s more likely mechanical, but electrical failures also occur.
Did you build this controller? Or I should ask did it come assembled, these usually need the motor driver current setup.
Thanks for the prompt replies, after more testing, engraving large letters in line mode it is clearly slipping in the X direction, the first letter is correct but the next one is either too close to the first or actually overlaps it, it now does this at slow speeds (10mm/sec) I think it’s getting worse!. Tomorrow I will try removing the gantry and have a good look.
The controller is a Mini Gerbil 3 less than a month old
A quick update, I just tried a filled circle on piece of scrap card, 50mm/sec speed.
You can it start ok but after a few seconds you can hear a noise from the machine and the head moves to the right, a little later it shifts to the left.
Hi, SUCCESS!!!
I reduced the X axis acceleration from 12,000 to 5000 and so far it has worked perfectly for over 5 jobs (still testing)
No idea what changed, it has been at 12000 for a long time, but at least this fix saves me from having to remove the gantry then the hassle of re aligning the mirrors!
Thanks again to everyone who made helpful suggestions
Most of the normal co2, such as my China Blue had an X acceleration of around 8,000mm/s^2, most k40 can’t accelerate that fast as they have smaller motor (NEMA17, mine are NEMA23).
What determines these values are basic physics, you need larger motors to accelerate the same amount of mass faster.
There are a number of videos out there about speeding these up, but what you find is that they start failing at a certain point. You want dependabiity, lower the acceleration.
The head on mine has been modified to have a lot less mass and my acceleration values for the X axes is 45,000mm/s^2. Although it does allow a higher speed, where it pays off is the gets up to speed quicker spending less time not over the object.
I really don’t know the values for a K40, but you should be able to find it out somewhere, just not by me.
