Kirk Wallace <[EMAIL PROTECTED]> writes: > > Andrew, > > What kind of machine are you working with? It a 3 cartesian axis mill. What kind of parts do you > want to make? prototypes in plastic, mdf, aluminium and steel
I assume it is a mill. Are the axes moved by steppers or > servos. Servos. Do you have encoders and/or limit switches on your axes? There are rotary encoders on the servos but in production we plan to use linear encoders on each axis. Each axis has 2 limit switches which we also use as home switches. >What kind of tool holder system? We plan to have a linear rack of tools placed at the rear of the machines workspace. The spindle moves to the position above the tool. Then descends. Each tool has 2 teeth that engage in 2 slots in the spindle toolholder. A solenoid activates to fix a screw thread inside the spindle. The spring loading of the tool lets the teeth engage in the slots. As the spindle rotates the tool gets tightened (or released) > It sounds like the tools thread in. Correct >What is used to to run your spindle. AC, DC, stepper or other > motor/controller? 3 phase ac motor open loop ie no encoder > Part of your tool-change procedure is to save positional context, but > your context can be maintained if you have axes encoders or can use > limit switches as references. True we could save the position of the encoders to move back to the starting position. But we need to move to a precise position for the toolchange and as far as I know the encoders 0 position is where it was when it was switched on, I dont believe that the encoder position gets set to zero when the machine is homed. So we need to have a form to do a move to a absolute position x,y,z Im not sure the limit switches would work as there is not 1 toolchange position there is a position for each tool. I think they would only work if the toolchange was always in the same position, or are you saying do a "home" on the limit switches then move a certain number of encoder pulses to get to the coords required. > EMC maintains current tool information so this may be taken care of > already. Ok > If your tools thread into their holders, I would think these to be of > lower accuracy and load capability. If you need higher accuracy and > load, you might consider a different tool holding system, which could > change your plans quite a bit. > One of the problems seems to be that EMC's motion function is only > accessible through g-code and g-code can not be issued by a script or > HAL component. Shame, what needs to be done to implement that? >I believe a component or script, can control anything > that can be controlled by digital signals. So for example, if what you > you are moving uses a PWM signal, you might be able to create a > tool-change mode and use HAL components to output a PWM signal until a > switch closes, or some sequence of digital events. When the tool change > is done, you could go back to normal motion control. If your axis has an > encoder, the good news is that your position information is maintained. > The bad news is you will get a following error. Even if the machine has moved back to exactly the same place? What can be done to avoid this as this makes the "automatic" tool change not so automatic if the user has to recover from an estop in software. > > Basically, the features you can by-pass or reconfigure will depend on > the details of your system. > I hope you have enough information Andy Bailey ------------------------------------------------------------------------- Sponsored by: SourceForge.net Community Choice Awards: VOTE NOW! Studies have shown that voting for your favorite open source project, along with a healthy diet, reduces your potential for chronic lameness and boredom. Vote Now at http://www.sourceforge.net/community/cca08 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
