Andy Pugh wrote: > 2009/6/20 Rob Jansen <r...@myvoice.nl>: > > >> how would EMC know how to move back to the last >> programmed position/ >> > > I don't think it needs to, it will either do the next G0 (which is no > problem at all) or do a G1 which might get a bit boring. You do need to do something special. An automatic tool change would first move to a safe height (clear away from the work piece in the Z axis), move to the tool changer, grab the new tool, move to the safe height, move to the old XY position and only then move to the wanted Z position again before continuing the code.
As least for simple 3-axis movements. For 5 - or more - axis movements the tool could even be in a side pocket and I have no idea how EMC could figure this out all by itself. So if you would stop and so some MDI actions you do need to bring the tool back to an approximate, or even the exact same, position before continuing. Otherwise your tool may collide with the work piece. This is especially true when current actions are taking place in small deep pockets - otherwise the tool or collet could come in unwanted contact with the work piece. I know - this happened to me a few times with desastrous results (not fun with EUR 200 end mills ...) I'll try to create the 'manumatic' tool change I suggested next week and post the results on this list. Things should be easy: zero the first tool, go to the tool height indicator and determine the offset (i.e. -5). Indicator and tool change position should be at a reachable location and such that all tools can be fitted (enough Z height). Now determine the offset with the new tool - for example +10 - this means the current tool is 15 longer than the old one and the Z=0 position should be moved 15 up. We now program the new position Z-height (for this coordinate system) to be the current height - (new offset - old offset). If we moved 10 mm clear of the tool indicator probe then this means Z-current = +5 and Z-new = 5 - (10 - -5) = -10 (new Z=0 is 15 higher than the old one). Now store +10 as the old offset to use for the next tool change. I know that doing this my result in longer milling times since the probing is taking place (at low speed) and the moves to the tool change/indicator position but when it prevents any stupid mistakes resulting in hours of lost work (or broken tools) it is worth the time. Most of my current milling involves the milling of molds for carbon products. Here (http://www.myvoice.nl/prototyping/prototyping.php#fork?lang=en) is a nice example of a mold that took about 3 days to complete (I know - my machine is too slow) a manual tool change followed by an accident after a full day of work would be a real waste Rob Note to self: add telephone allert to trigger the operator (me) to do a tool change :-) ------------------------------------------------------------------------------ Are you an open source citizen? Join us for the Open Source Bridge conference! Portland, OR, June 17-19. Two days of sessions, one day of unconference: $250. Need another reason to go? 24-hour hacker lounge. Register today! http://ad.doubleclick.net/clk;215844324;13503038;v?http://opensourcebridge.org _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
