One Case of HSM Machining: HSMAdvisor vs. AllApril 2, 2016, 7:41 pm
April 2, 2016, 7:41 pm
September 7, 2016, 11:19 pm
Sat August 15, 2009, 4:00 pm
Tue March 28, 2017, 12:39 am
Look for the HSM machining of the round central pocket in the beginning.
Here we have a 12mm 6 flute Coated hi-performance endmill, cutting 1" deep at 0.047" (10%) rWOC.
at 10000 RPM and 300 ipm feedrate. the chipload works out to be 0.005". Material is 4140 pre-hardened steel.
Impressive isn't it?
Those results have been achieved with uber-expensive BlueSwarf tap-test technology.
This is one video that caught the eye of one of my HSMAdvisor trial users:
Being a geek and wanting to help the user make the right decision I immediately punched the numbers into my HSMAdvisor app.
Here is what I've got:
Not too bad huh? My Speed and Feed calc suggests almost the same chip-load.
But because it is caring about your tool life, HSMAdvisor suggests slower cutting speed. 4464 RPM versus BlueSwarf's 10000 RPM
Now, if we wanted 15 minutes of tool life (what the tool on the video is probably going to have)
We could have entered 10000 RPM and voila!
We are getting almost the same feedrate at the expense of tool life.
86% of Tool Life versus 18% - You decide which is better. HSMAdvisor gives you that ability.
You can also decide whether super-expensive technology like BS is really worth the hype and the money spent.
But we are not over yet.
Let us try another calculator. The HSMAdvisor's direct competitor.
Introducing the G-Man(real name hidden).
This series of screenshots was sent to me by a user of that software, who showed me the okuma video to try and make sense of his results.
He entered the same tool numbers with the same material to see what the Goliath of the S&F business suggests:
All the tool data is absolutely the same.
We can see that G-Man really cares about his customer's tool life because his RPM is really low.
However his Feedrate seems kind of HIGH....
How high - I do no know. What's the Chipload? 0.003" or 0.005".....hmm OK.....
Then the user set RPM to 10000 like in the Okuma Video at the top of the article:
HOLY FLYING CUPCAKES!
10000 RPM and 650 IPM !
Why is the Feedrate so high?
Isn't there something in the calculator that should prevent the machinist from leaving the Endmill inside the pocket once the E-Stop is pressed and Z-Axis is retracted?
Yes, everything is set to "Rigid" and "Rough" but you would not normally expect such mild words to cause much trouble, would you?
I am starting to realize that something is very very wrong here.
In the last screenshot his Chipload(IPT) shows 0.0108". Please note in the previous screenshot he has 0.003".....
How does a mere fact of changing the RPM change the Chipload so much?
I am going to the previous screenshot and start doing some math. Something that G-Man should have done for him:
185.9ipm / 6 flutes/ 2640 RPM = 0.0117" Chipload.
Where does 0.0117 show on that screen? Nowhere!
Whelp. Perhaps before "...considering over 60 variables..." G-Man should get his basic math in order?
Or a program workflow. I don't know - I am not an accredited IT engineer to advise on that.
Also note that aside from the Deflection nothing shows us how hard we are really pushing the Endmill.
What if I told you that the endmill in question WILL NOT survive 0.004" deflection at all?
How does my HSMAdvisor know it? Math. Not even some hard-core science. Just a high-school level.
Does G-Man know it?
Dohis customers it?
HSMAdvisor users learned to trust the Limits I have put in place to protect their tools.
If it says "Can't do it" there is a really high chance that you really should not!
What do other people who run HSM machining toolpaths for a living say?
Here I assembled the cuts posted for 4140 PH or similar steel with a similar tool diameter on Rizzo's Dynamic Database :
At the bottom of each column I calculated the actual chipload the comparable tools were making.
These results by real people are in fact more in line with HSMAdvisor's default suggestion than with the Okuma Video.
And shure as hell none of them goes any close to 0.011" per tooth in such situation.
It is not my job to point to my competitors mistakes (though he probably should thank me for finding them).
But it is a word of caution for those who use Speed And Feed Calculators, that do not consider the endmill's strength and do not show you how hard you are pushing your tools and machines.
A user who does not see what he is doing is bound to break something.
So the big question everyone is having: Is G-Man plain wrong?
I seriously, do not know. His calculations seem just too wonky to be even sure this is the intended result.
Here is what I have when I try to simulate G-Man's results:
It is possible! With Torque Limit almost at its maximum (190% is no joke)
For a minute or two! Then you will likely hear an unmistakeable sound of the endmill snapping.
Only a mad man would run his tools like that. I mean who has the time and the money to replace his tools like that?
Unfortunately for his customers G-Man does not tell them that kind of information.
What did I advise the customer? I sent him a link to this article, so he can decide.