lukewang Posted August 16, 2012 Share Posted August 16, 2012 Hi, I came cross a feedrate higher than programmed one when running an arc with huge radius. Then I found the following explaination in PMAC manual: "If the specified feedrate causes a move time of over 223 msec (about 2 hours 20 minutes) to be calculated, the move will be executed in 223 msec, at a higher speed than what was programmed." It is really beyond my comprehension. How come feedrate control be affected by block length? What's the theory behind? Thanks. Luke Link to comment Share on other sites More sharing options...
Sina.Sattari Posted August 16, 2012 Share Posted August 16, 2012 Please see the following paragraph from Turbo PMAC Users Manual: Maximum Move Time The maximum time for one programmed move is (2^23)-1 or 8,388,607 msec, approximately 2 hours and 20 minutes. This is the maximum value that Turbo PMAC will accept with a TM command. It is also the maximum value Turbo PMAC will compute for a feedrate-specified move when it divides the vector distance for the move by the feedrate. If the vector distance for the move divided by the feedrate yields a time greater than 8,388,607 msec, Turbo PMAC will use 8,388,607 msec as the move time, and the speed will be higher than what was programmed. Please let me know if it is still unclear. Link to comment Share on other sites More sharing options...
lukewang Posted August 21, 2012 Author Share Posted August 21, 2012 Hi Sina, Is that because intergal length issue? TM command can only have 23-bit integal? Cheers, Luke Link to comment Share on other sites More sharing options...
Sina.Sattari Posted August 21, 2012 Share Posted August 21, 2012 Luke, That is correct. The resolution of the TM register is 0.5 msec and it is a 24-bit register, allowing a maximum 8388607 milliseconds for move time. Regards, Link to comment Share on other sites More sharing options...
lukewang Posted August 22, 2012 Author Share Posted August 22, 2012 Thanks, Sina. Now it is clear. Link to comment Share on other sites More sharing options...
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