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backplot time estimate


mikenaturalice
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I was wondering if anyone else is seeing large discrepancies between the time shown in the backplot menu under the info tab and the actual time on machine?? I know machine configurations like tool change and max rapids, deceleration, acceleration all play their part, but shouldn't it be close if you are using the correct machine (in your machine group inside mastercam I mean)? I would like to add up front as I just said this, I don't have my correct machine at the moment (Haas UMC-750) but I am using the generic Haas renishaw 4axis VMC. I can't see there being much difference between the 2 if I am just doing 2axis or 3axis work. I can't post a file or anything due to work rules. I am cutting a 2d high speed path with an 1/8 endmill, 107ipm, 5% max stepover and its is showing a total cycle time of 10min 49sec. I am showing 22min 10 sec on my machine. The machine is at 100% rapid and 100% feed and all that. FWIW my machine only records the time during cycle start so if I feed hold anything (which I did not on this toolpath) it pauses so the machine clock should be pretty accurate. I have never checked it to a stop watch, but at over 2x what Mastercam says I couldn't see the clock being that far off anyways. I just finished the entire program and the difference between mastercam backplot and machine clock is just under 13min. That said, it looks like all the toolpath times are almost twice as long to run on the machine... any ideas? Looking forward to hearing from you guys! Thanks!! :help:

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The times are off on my Haas on dynamic toolpaths because the control can't keep up with the actual feed rates. With the high speed processing (I had the demo for a while) it does a much better job, but with all the short moves that the toolpath gets broken down to, the machine can't process so many lines of code in order to keep up with the feed rate. Perhaps you have a similar situation?

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Thanks for the tip. I just checked and we do have the HSM package on our machine (at least its on the quote!  :laughing: ). The UMC is supposed to have something like 4second chip to chip, but even if I add 10 seconds for toolchange on this particular program that only would account for 1 extra minute. It does not appear to be slowing down visually, but thats a guess. I am going to run again with the smoothness set to rough, corner rounding to .05",  and see if that affects anything....

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Are you using the Haas G187 High Speed Code ?

I did not use G187 in the program, but I changed that parameter to rough and ran it, it shaved about 4 minutes off the cycle. I am running a part now (I ran without a part to check time only) to see how accurate it will be using the "rough" setting. G187 P1 or P2, P3 is just a temporary override for parameter 191, you can also change the setting inside the parameters page.

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I did not use G187 in the program, but I changed that parameter to rough and ran it, it shaved about 4 minutes off the cycle. I am running a part now (I ran without a part to check time only) to see how accurate it will be using the "rough" setting. G187 P1 or P2, P3 is just a temporary override for parameter 191, you can also change the setting inside the parameters page.

 

 

There is also an E argument available for G187.

 

You are fighting the kinematic limitations of the Haas.

It will not get any better than what you have.

The problem is the machine, not Mastercam.

The backplot function does not take into account the kinematics of Acceleration/Deceleration.

It's strictly a theoretical calculation and doesn't even properly calculate drilling cycle time.

You'll get a more accurate cycle time by using NCPlot

http://www.ncplot.com/ncplotv2/ncplotv2.htm

 

The Haas won't do well with small linear arc approximations.

Arc fitting will help but at the end of the day you're still running a Haas.

 

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There is also an E argument available for G187.

 

You are fighting the kinematic limitations of the Haas.

It will not get any better than what you have.

The problem is the machine, not Mastercam.

The backplot function does not take into account the kinematics of Acceleration/Deceleration.

It's strictly a theoretical calculation and doesn't even properly calculate drilling cycle time.

You'll get a more accurate cycle time by using NCPlot

http://www.ncplot.com/ncplotv2/ncplotv2.htm

 

The Haas won't do well with small linear arc approximations.

Arc fitting will help but at the end of the day you're still running a Haas.

 

I am aware of the E value, it was changed to .05" , although I am not sure what the threshold is before I start getting crappy toolpath corners or gouging. I also know the drilling is not correct, but I expected the milling to be a little better than 1/2?! As to the comment "Arc fitting will help but at the end of the day you're still running a Haas."  well, that really doesn't have much to do with my question I think. I know it has limitations and I really don't want to go into the "Haas Hating", I was merely asking a question about the backplot time. So I guess in turn I have to ask, what is the value of the backplot time if it doesn't reflect something close to what the machine can do?? I just now changed the machine and it went from 5min 32sec (remember I doubled the stepover from the 10min cycle) to 15min 44sec. The only noticeable difference I see is that the max feedrate on the machine I swapped in was 300 ipm vs the 500 (on the back feedrate in the 2d highspeed path) that was programmed for the Haas, so I could see maybe the time going to 8 or 9 min, but it tripled by changing machine so Mastercam must be doing some calculations based on the machine vs. just calculating linear inches and feedrate... right?

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I can't, but I can tell you the original size (in the toolpath display inside the Op manager) was about 2990k. I changed my stepover to 10% which more or less halved my file size to 1484.2k.

I was looking to find out if there are a lot of long straight moves in the toolpath or a bunch of tight corner pickin....

Basically, does the toolpath allow room for the machine to get up to programmed feedrate.... for the most part, or is it restricting the machine with tons of direction changes

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I am aware of the E value, it was changed to .05" , although I am not sure what the threshold is before I start getting crappy toolpath corners or gouging. I also know the drilling is not correct, but I expected the milling to be a little better than 1/2?! As to the comment "Arc fitting will help but at the end of the day you're still running a Haas."  well, that really doesn't have much to do with my question I think. I know it has limitations and I really don't want to go into the "Haas Hating", I was merely asking a question about the backplot time. So I guess in turn I have to ask, what is the value of the backplot time if it doesn't reflect something close to what the machine can do?? I just now changed the machine and it went from 5min 32sec (remember I doubled the stepover from the 10min cycle) to 15min 44sec. The only noticeable difference I see is that the max feedrate on the machine I swapped in was 300 ipm vs the 500 (on the back feedrate in the 2d highspeed path) that was programmed for the Haas, so I could see maybe the time going to 8 or 9 min, but it tripled by changing machine so Mastercam must be doing some calculations based on the machine vs. just calculating linear inches and feedrate... right?

 

You're incorrect. It has EVERYTHING to do with the answer.

You need to understand how a CNC works kinematically.

Not Haas hating at all.

 

Backplot doesn't take into account the Acceleration/Deceleration of any machine.

Changing the Machine in Mastercam is meaningless.

The machine is slower than the programmed feedrates because the machine is incapable

of actually reaching the programmed feedrate for 50% of your program.

Very short linear moves with changes in direction are a problem for the Haas control.

Arc-fitting can eliminate some of that.

The machine simply doesn't have enough processing power coupled with the fact it's servos, drives and screws

are inferior to more expensive machines.

 

If you want to get accurate times based on your actual machine then you need

a product like Vericut or NCSimul to run a complete G-Code based Machine Simulation.

The machine environment in these applications can and do take the kinematics into account.

You will never get an accurate cycle time by using Mastercam only.

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I see K2csq7. It's a relatively small area with some funky corners. Now that you bring it up there is probably not room to ramp up to full speed, but it is a 1/8 cutter, so I dunno... looks like the longest feed move would only be about 1.3-1.5". 

 

FTI2007 - I don't have a whole lot I can say at this point. I am waiting to get our MCX seat upgraded to multiaxis and get the UMC-750 post and machine simulation. So right now I am mostly just programming it more or less like a rotary axis and doing alot of hand editing <yay>  :ouch: . I do know a few things I will pass on - (1) The pendant design sucks on this, you can clearly see they did not put any thought into this and just tacked on the same thing as they use on the VF series and lathes. If you have run older Haas, remember when they changed the pendant from the overhanging to the kind that is like a medicine cabinet that swings open and has shelves behind it? In the closed position you faced the control and doors in the same direction. That was awesome because you could swing the control 90deg (kind of boxing you in ) and have nice access to it and be able to work inside the enclosure. Well, on the UMC they just tacked it on the side so when it is in the closed position it is 90deg AWAY from the operator and when you open it all the way up it faces at you, meaning you need extra long arms to reach the control and be inside the enclosure. We did get the remote jog handle with the fancy LCD screen, but even that seems awkward for some reason.... (2) The door is really really heavy. Seriously, when loading/unloading alot of tools and you have to close and open the door for each one it gets old fast.

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You're incorrect. It has EVERYTHING to do with the answer.

You need to understand how a CNC works kinematically.

Not Haas hating at all.

 

Backplot doesn't take into account the Acceleration/Deceleration of any machine.

Changing the Machine in Mastercam is meaningless.

The machine is slower than the programmed feedrates because the machine is incapable

of actually reaching the programmed feedrate for 50% of your program.

Very short linear moves with changes in direction are a problem for the Haas control.

Arc-fitting can eliminate some of that.

The machine simply doesn't have enough processing power coupled with the fact it's servos, drives and screws

are inferior to more expensive machines.

 

If you want to get accurate times based on your actual machine then you need

a product like Vericut or NCSimul to run a complete G-Code based Machine Simulation.

The machine environment in these applications can and do take the kinematics into account.

You will never get an accurate cycle time by using Mastercam only.

I stated in my original post about accel and decel... I understand it plays its part and that was my question. You answered first about using a G187, and then your 2nd post went into I was fighting the "kinematic limitations of the Haas" and "the problem is the machine, not Mastercam" "it's servos, etc are inferior to more expensive machines" I never said anything bad about Mastercam, I just asked why the big difference... and I thought it would be close if I was using the correct machine, which I stated I wasn't but I thought it would be pretty close since it was still a Haas. So you say Mastercam doesn't account for any of that, then why bring it up?? I do however thank you for the link, I will check that out. Again, I was just asking the question of why they are different. I am well aware a Haas will never perform up to a Mazak or Matsuura...

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I stated in my original post about accel and decel... I understand it plays its part and that was my question. You answered first about using a G187, and then your 2nd post went into I was fighting the "kinematic limitations of the Haas" and "the problem is the machine, not Mastercam" "it's servos, etc are inferior to more expensive machines" I never said anything bad about Mastercam, I just asked why the big difference... and I thought it would be close if I was using the correct machine, which I stated I wasn't but I thought it would be pretty close since it was still a Haas. So you say Mastercam doesn't account for any of that, then why bring it up?? I do however thank you for the link, I will check that out. Again, I was just asking the question of why they are different. I am well aware a Haas will never perform up to a Mazak or Matsuura...

 

Trying to educate you about the issues involved so you might understand where the issue actually lies.

 

Obviously you know it all already.

Have at it.

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I see K2csq7. It's a relatively small area with some funky corners. Now that you bring it up there is probably not room to ramp up to full speed, but it is a 1/8 cutter, so I dunno... looks like the longest feed move would only be about 1.3-1.5". 

 

 

Watch the machine control while the program is running.... I bet you don't see the actual feedrate top 50IPM

There is your 2x cycle time on machine vs. mcam backplot.

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The Haas high-speed option is a joke. It only has 40 blocks lookahead using a single processor, unlike a higher calibre machine. As many others have pointed out, the machine is the limiting factor. I agree that Mastercam's reported cycle time is off somewhat, but on our Makino's and Mikron's, it is reasonably close.

 

Carmen

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Watch the machine control while the program is running.... I bet you don't see the actual feedrate top 50IPM

There is your 2x cycle time on machine vs. mcam backplot.

Good suggestion, I will look next time. I do know it moves pretty rapidly between the backfeed of 500ipm and the feed of 107ipm. I don't know how accurate this will be either.

I appreciate all the input, but none of it really addresses why it is so far off.I completely understand that the Haas cannot accel/decel fast enough to actually get to the programmed feedrate. I understand that completely, but my basic question then goes back to why isn't any of that addressed inside the backplot? Or I should say inside the software when you choose your machine.  If this is something that can't be overcome, then fine so be it.

 

SO I guess if the backplot time is off, can I trust the machine simulation??

 

Again so I am clear I am not "blaming" Mastercam, I am asking why it does not reflect the issues that keep the Haas machines from reaching their programmed feedrate. I'm not saying it's Mastercam's fault that the Haas cannot do what is programmed, just wondering why it is not compensated for. Also, I would love some clear answer to this so I can present it to the boss. When I backplot something I don't need him to see that time estimate and plan my work around it...

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