OVERTRAVEL  

Re: OVERTRAVEL

Hi Tonio,

each of the four wires, is equally important on the Stepper motors.
positive and negative signals on all four wires are required to cause forward or reverse rotation

regards Joan

Re: OVERTRAVEL

I know that the cables power a coil in pairs, ie the four cables power two coils, correct me if I am wrong. I wish to know which colours power coil A and which power coil B. I would interrupt one of each to halt the motor from coming down on the bed, however one of each of them might be common to a particular poarity (negative or positive feed) , which would make things simpler by interrupting just one lead. I know this goes against the feature of the feature of alignment of the worst warped assembly, but working on high precision cnc machines myself for over 30 years, I understand that the best way to have an absolutely level bed is by using a dial test indicator on adjsuted, spring loaded bed fasteners. I know this is difficult for people who are not proficient in engineering, but that is the BEST way forward. I do not like the idea of any cnc machine ramming the bed and I never had anything doing this in my lifetime. CNC machines are equipped with two safety feature overtravel switches. One position simply is a software controlled limit and the next is an emergency stop limit which prohibits any furthur movement resulting in destruction of the machine. I intend sorting this and will post my modification for the benefit of the owners of this machine....

Re: OVERTRAVEL

Hi Tonio,
I appreciate what you are trying to do. however if you use a mechanical switch to break the two pairs of coil circuits, you are going to have to put parallell contacts in the circuit to re establish the circuits in order to drive the carriage in the opposite direction after the stop condition has been recognised. however at that stage the mini rambo is likely to have lost calibration, so you will have to ensure that the rambo has stopped trying to drive into the bed before you try to take restorative action...

anyway, back to your query.

on my motors red and blue are one coil and black and green are the other coil

regards Joan

Re: OVERTRAVEL

You are right Joan, I have to fit switches to close the contact again to enable the steppers to reverse back. Whatever needs to be done afterwards is much better than damage to the heatbed... I can`t understand how the machine performs well and produces a part, then when I restart the same part, it would take a dig at the bed when doing the initial caalibration...
What I am concerned is if the rambo gets damaged with the motor disconnected... 😳

Re: OVERTRAVEL

Hi Tonio, that is exactly the possibility you are creating with your proposal the motors are not supposed to be disconnected or connected while the circuit is powered!..

would it be simpler all round to put the micro switches in the reset circuit?
problem is this could result in the heated extruder nozzel touching or very close to the printbed whick could be disasterous.

you could consider connecting the micro switches to the filament run-out circuit and enabling that, in firmware but you are now entering custom firmware territory.

so why not write your own interrupt "Plunge Panic" service that backs up the carriage and stops all motors, extruder and heatbed in the event of an error?

regards Joan

Re: OVERTRAVEL

Hi Joan,
I think I iwll not do as I intended. Your reply has prompted me to ook furthur. The Rambo box has an X & Y end stops provision but no Z endstop.
There is in fact an empty socket for same. It has an endstop provision for + and minus directions which is unused...
I have uploaded the original Kit`s instructions screenclip. There is an unused. The next hurdle is obtaining a socket which fits the plug on the mainboard...