Last Thursday, I completed an initial series of 4 carves (pockets, slots, holes, etc) to test the setup and accuracy of my newly assembled 750 mm X-Carve.
On the first one, I went through the “homing” sequence (my machine has the three limit switches), and then used Easel set the work home to X-0 and Y-0 and the Z-probe to set the Z-axis. The carve went fine! On the subsequent three carves, I again was using Easel and the Z-probe but just used the “use last X-Y” for the X and Y settings. These 3 carves also went fine. I shut the machine off and as I recall pushed the gantry and spindle to the center of the work surface so I could measure the results.
On Friday, my planned test carves involved text and irregular shapes. This time, when I turned the machine on, I did not go through the homing sequence, the gantry and spindle was where I left it the previous day, but simply starting the carve using the “last X-Y” setting. The result was TOTALLY unexpected! Rather than move normally to the X-0 and Y-0 point, the machine moved very rapidly in a “jerking” motion toward the lower left. This all happened so quickly, the machine “clipped” one of the hold downs on the X-axis before I could hit the emergency stop button.
I then restarted the machine and went through the same processes I had used the day before to run my test carves and they went fine!!!
Along with running test carves to check alignment and accuracy, I am trying to develop a repeatable work-flow process, so my questions are:
What did I do wrong, or what went wrong???
When starting an X-Carve session for the day (using Easel), does one need to go through the “homing” sequence???
I have not been able to find any clues in my searches through the forum over the weekend, so any advice (including criticism) is helpful and appreciated!!!
Yes you can home in Ugs
Th g code is $H (I think)
And there is a button with $H in the main panel.
The machine will be in an alert state after it gets power. So you always have to home the machine first or quit with $X out of the alert state.
You should always home the machine after the controller gets power you unexpectedly run into something or hear strange noises from the motors and when you manually moved any axis.
There’s a lot of good information here. Robert hit the nail on the head as to what happened.
Homing establishes a machine zero point. When you power up, wherever the spindle is becomes the new machine zero until you run a homing cycle.
The GRBL command is $h entered into the console. It’s not technically Gcode. Not sure if you’d ever want to put $h and gcode together. That smells like a disaster waiting to happen.
This button, at least in the Platform (which I highly suggest) has changed and is now more plainly labelled “Home Machine”. It may be the same on Classic. Just letting you know so you don’t tear your hair out looking for $h.
Only if you have $22 set to 1. Otherwise, it doesn’t care. I would hope that Easel would change this value but if not, don’t be surprised if you don’t have an alarm state.
I’m sorry to confuse the commands with g code (what makes total sense after your explanation)
I’m new looking into what g code commands are.
Still wanted to give my 2cents.
I definitely look more into it before giving some false information next time.
It’s still a good habit to home the machine when something funky happens
first things first. NEVER NEVER NEVER. And if I haven’t already said it. NEVER move your machine by hand!! Stepper motors act as generator’s when moved without supplied power. They will back feed into your controller. That’s never a good thing.
Your machine has two coordinate systems. Machine & Work. When you tell the system where your zero point is of your material. That’s work coordinate. That can be where ever you set it. Machine coordinate is a set system that should never be messed with. It’s what everything references off of. Soft limits G28. & G30. Etc. when you power down you system it forgets where it is at. So when you power it back up it assumes it’s at machine zero. When you home your unit you physically tell it where machine zero is at. I always home my machine just before I shut it down for the night.
I’ve seen this mentioned a lot on this forum, but you’d have to spin the motors faster than the machine can move them and generate a voltage greater than what the driver can handle. Even then, a decent controller will have a large cap on the power supply that will, at minimum, provide you done resistance in spinning the motor. Depending on your controller, you may even power the enable pin on the driver which will actually brake (not break) the motors. I’m sure there is someone here who knows a guy who knows a guy that fried something, but I think this is an overrated caution. Many CNC machines have hand wheels for this purpose. Sorry for going off topic.
And for not reading further as my point was already made by someone else.
Unless you want to move it faster than your controller can. I’m not recommending you try to damage your drivers, but I think moving the machine by hand, to get it closer to home before you switch it on or to install a 3D printed pen holder, should be ok.
99% of my knowledge of cnc has been learned from this forum. That being said, I move my gantry to square up by hand, every time i power up. In doing so I worry that i may damage the controller. Is this OK to do?
Like Robert I move mine by hand all the time and have yet yet to have a problem.
I understand the “theory” behind this caution BUT is there anyone here that can directly attribute damage to this practice? I am asking for first hand knowledge not my brother in law’s neighbor heard about…
Usually - when there is an actual need. When there is no need it is often called paranoia.