Need Help!- Question about the accuracy and setting changes for cycle time estimates in backplot

[CJH]

Hi all,

I have a question about the estimated cycle times presented in the backplot details/info. I have been having a conversation that has been ongoing with a coworker of mine about the accuracy of the backplot cycle times info. He has told me that there are big differences in what are estimated in MC vs what are actually at the machine. so today I paid closer attention to this and found out that there can be as much as 25% or more difference in what MC says vs what the actual machine cycle time states. MC says the cycle should be shorter.

I ran a program that MC said was 30 or so minutes and the actual machine time was more like 46 minutes.

Is there a setting that can be tweeked in MC that can more accurately reflect what we are actually expiriencing at the machine?

Chris

[ObrienDave]

My experience with backplot time accuracy is pretty close to what you are describing.
There are a number of things to consider when calculating estimated machining times.

1. Rapid rate.
Since the machine must accelerate and decelerate for every rapid move, the actual time for the move is longer than calculated.

2. Canned cycles. i.e., peck (deep hole) drilling, boring, etc.
In my opinion, peck drilling is the worst offender.
MasterCam calculates time by dividing length of move by feed rate.
This works fine for G1, G2, or G3 type feed moves but does not accurately reflect the actual number of peck retracts and returns each hole requires.

These errors in time multiply as you get into programs that have a great many retracts, peck drilling, etc.

There are settings in the post file for the machines rapid rate.
You can adjust this value by opening the .pst file in a text editor like 'notepad' and looking at the 'numbered questions' area at the end of the file.
Question #38 is the one you want to adjust.
I believe there are similar settings in the machine definition area for the 'X' versions.

[Aquatic]

I once cut a part with 672 M2 tapped holes. MC estimated just over 12 hrs to complete. 26 hrs later it finished machining.
The rapid moves most definately affect the time.

I had a look and found this
http://www.cobham.com/media/111652/hga-8000%201.3.pdf

It was the chassis for this baby