Each machine requires a little different calibration. In G-Wizard Editor, you have the following adjustments available:
How fast can your machine rapid? This is the value GW Editor will use (acceleration adjusted) in its estimates.
Spindle 0-max rpm time
How fast does your spindle change speeds? GW Editor factors in a time based on this number every time you change spindle speeds. You can measure it easily enough with a stopwatch if you don’t have a spec in your machine manual.
Tool Change Time
Every time the tool is changed G-Wizard charges this much against the clock.
Coolant On/Off Time
Likewise, every time you turn coolant on or off, G-Wizard charges this much against the clock.
Acceleration has a huge effect on simulated timings, but is one of the hardest parameters to get an accurate value for. If your manufacturer won’t quote a number (and even if they will–it can differ from machine to machine depending on a variety of factors), you’ll have to measure the acceleration. The best way is to test with interpolated holes. Use G-Wizard Calculator’s Interpolation Mini-Calc to see what acceleration is required for a particular hole. See if the recommended feedrate results in a round hole. If it’s off by more than say a thousandth (0.001″), your machine is struggling to accelerate fast enough to do the interpolated hole accurately. Reduce the feedrate and try again. Eventually, you’ll go slow enough it is accurate and from that you can determine your acceleration accurately. It’s usually less than you’d think and less than you’d like!
Min Word Time
This is a flat rate per-Word (line of g-code) charge. For commands that don’t involve motion, spindle, tool changes or coolant, G-Wizard charges this much time against that block or line of g-code. This is another number that’s hard to come by. It’ll be slower on older machines and faster on newer machines. Machines with very fast rapids will likely have a lower Min Word Time too.
Sim Time Adjustment
This is a fixed multiplier of the simulator time found on the machine profile:
Sim Time Adj is a fixed % multiplier on the simulated run time of every program for the machine…
Sim Time Adj is a fixed % multiplier on the simulated run time of every program for the machine. Assuming I have calibrated everything I can based on machine specs, I turn to tweaking Sim Time Adj if I don’t have any better information on why the times are off. It’s easy to do. For example, if your program actually takes 2.28 minutes and the simulated time was 1.5 minutes, you need to apply a 152% correction.
Okay, I’ve Played With These Parameters and Time Estimates Are Still Off
First, make sure you’ve got the easy to measure and easy to look up parameters set up right. That would be:
– Max Rapids
– Spindle 0-max rpm time
– Tool Change Time
– Coolant On/Off Time
If you’re sure those are okay, it’s time to move on to harder parameters to set and tune. I would try to measure your machine’s acceleration next. Getting an accurate read on acceleration would help a lot. Next try the Sim Time Adj. If things continue to be off on some programs, try tweaking the Min Word Time quite a bit. You may get it grossly out of balance, but it largely affects non-motion commands. If your estimates get closer, it means you’re on the right track. If they get worse, it means the motion commands are the culprits. Go back and fiddle with acceleration some more.
In the end, it won’t be perfect, but the goal is to get close enough to be useful for cost and time estimation. That means generating some conservative numbers, which ought to be possible.
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