[Darkphoenix]

Hello,
I have a technical question, please have a look at this image:



this image is from: https://www.guhring.com/Tech/endmillcalc


I would like to know how the formula for the "Actual Chip Thickness" is done
In this case, it is 0.104

Using speeds and feeds for this tool:
https://www.guhring.com/ProductsServ...=9067370160000
Using HPC-ROUGHING; Aluminium, Al-wrought alloys, Al-alloys

I managed to replicate all the other formulas in my spreadsheet it's just this one I'm having an issue with. I would like to have this because it seems to affect the (actual) MRR

[deadlykitten]

hy yeah, mathematics ?! is so ...

if ae = tool dia / 2 then chip thickness = fz else chip thickness < fz

in other words, the more ae is different from tool_radius, the more chip_thickness is smaller than fz

as an extreme case, if ae = 0, then chip_thickness will be zero

an analogy is that to a car wheel : for example, if you drive at 100km/h, then :
... wheel center speed is 100 kmh
... wheel point that is on the ground, has 0 kmh
... wheel point far away from the ground, thus located at top of the wheel, has 200 kmh

when it comes to circles, most stuff changes with radius haha

please check atached images :
... 01 simple cad construction, that delivers same values as the ones from your example; i didn't get 0.1040, but 0.1036 and 0.1044, so pretty close
... 02 zooming in the area of chip thikness, so to show how those lines are constructed in the direction of the radius; at this moment i can sugest 2 aproaches :
...... compute 2 segments, one above ae, and other below ae, then avergae their lengths
...... compute a single segment, that has his middle on the ae line ( the one sketched with blue )
... 03 your initial data fz 0.13 generated a thickness of 0.104, smaller than 0.13, so the software sugests increasing fz to 0.16, in order to get a thickness of 0.13, that is identical with your inital data; such a sugestion pops up only under a safety rule : ae < dia / 3

i hope is ok now please feel free to ask whatever you wish / kindly

[Darkphoenix]

Hayo, you seem to know what I'm talking about, YAY!

Ok, so to divert from the topic a bit here is the formula for how they are calculating the optional 0.16 FZ (in the image I gave)
Attachment 478166

The information is sourced here: https://www.machiningdoctor.com/calc...ng-calculator/

Here is my excel interpretation of RCFT

=1/SQRT(1-(POWER((1-([@[Width of Cut]]*2/[@Diameter]));2)))

and the new FZ

=[@rctf]*[@[Feed per tooth per revolution]]

Back to the topic What I would like to know is how to calculate the 0.104 Fz value in a formula (I think 0.1044 is the correct value because that is the point where the tool engages with the material IMO because I have drawn it out too, i think they just rounded it down TBH)
I want this because I want to calculate the actual MRR using the 0.104 Fz value and then see if it is going to be a massive improvement or if I should just let it be when calculating my tools

[Darkphoenix]

Update I got this formula, but I don't know how to solve it for Hex. (i have Fz,D and Ae) im not that big a math boy

Attachment 478168

[Darkphoenix]

Update again i figured it out... hehehe boi
Attachment 478176

[deadlykitten]

pls check sugestions from attached image

here is the formula for how they are calculating the optional 0.16 FZ

maybe ... i don't have time to check it, nor interest ... i mean, just undersand the idea, and replicate in your own way

=1/SQRT(1-(POWER((1-([@[Width of Cut]]*2/[@Diameter]));2)))

excel tips - instead of
... SQRT() use ()^0.5
... POWER() use()^2
example, distance in plane is ((xa-xb)^2+(ya-yb)^2)^0.5 or ((xa-xb)^2+(ya-yb)^2)^(1/2) but not ((xa-xb)^2+(ya-yb)^2)^1/2

I got this formula, but I don't know how to solve it for Hex

actually, if you go that way, the truth is that you can not find a solution using static formulas, because the motion is compound between circular and linear, and that is a cicloid diagram

not impossbile, but a bit more tricky than common geometry; idea behind, is to use a static alternative, that can deliver a precision that is still tolerable to you

for example :
... think local : stop messing your head with cicloid, but simple lines as described in attached image; thus use an aproximation, with an error that you being satisfied with
... think wider : instead of messing your head with one revolution that generates a shape that looks like a nail and has an area a bit hard to compute, think of motion from start to finish that actually cuts into a rectangle

thus don't look into it from tool perspective that cuts many small bits, but look at it from process perspective, that simply crops a rectangle

and another idea is this : circlea area is pi*r*r, or area of a rectangle [r] * [pi*r], thus the circumference of the circle, or if you wish, asociated with the mrr/tool revolution, can be developed, aproximated with a linear segment, in order to reduce math

[deadlykitten]

I want this because I want to calculate the actual MRR using the 0.104 Fz

hello again actually fz is not needed to calculate mrr; in other words, for your initial example, any tool that has a diameter >3.2 will deliver same mrr, as long as ap and mm/min is the same

fz is simply a side value, non critical for mrr calculation, so my sugestion is do not corelate them, don't regards them as dependent when it comes to mrr

of course, i sugest to continue and build your excel, because there is a tendency for many to understand how aplications for cutting specs work, but pay atention to those that require more inital data than necessayry, and put out data values that are corelated between them ... is needed to understand the separate things that an aplication does, even if it uses same form to input/output ... is like a comercial for fast-food near one for losing weight and have a healtyh life ... thus even if data makes sense, values are correct, one should separate them


my sugestioon :
... use ap*ae*feed for mrr, thus 3 values
... use attached table, as a guidance, to corect feed when ae<>radius
... if you wish to futher hunt for fz, consider also what other values are related to it, and futher hunt them down, in methods that may not involve excel ?! thus move math from excel to real world feedback ... if you wish, i will develop on that / kindly

[Darkphoenix]

If you want then I can post my excel sheet here then you can modify it as you want and redistribute it as you wish, I feel like not a lot of Machenest's does this type of calculation, and they may find it useful. I mean these calculations are useful for a beginning feeds and speed setup and they can improve on that at their own pace using trial and error. because I found for instance if you have an ae and ap of like 0.2 (for finishing complex geometry) you can give it some strange feeds and speeds and get great results, at the cost of increased localized wear. give me some time to finish it and ill post it....

[deadlykitten]

hey darkphoenix, just go on with that, finish it as you desire, etc

off course, if you wish, i will take a look, who knows ?

because I found for instance if you have an ae and ap of like 0.2 (for finishing complex geometry) you can give it some strange feeds and speeds and get great results, at the cost of increased localized wear

please, can you develop a bit ?

I feel like not a lot of Machenest's does this type of calculation, and they may find it useful.

not everyone is into such calculations, and there are different perspectives when it comes to pushing cutting values, some for example rely on their senses, some like to be aggresive, other preffer smooth, other use spindle diagram for localized torque, others don't have time/patience to try something new because that setup worked last time; almost each one has it's idea, but there are a few that stand out

go on with what resonates with you, and when youll consider it done, see what others think about it ?!

for example, some consider the calculus to be correct, while others say that there is too much detailed mathematics into the mecanics, and mecanics is much more than cutting

[Darkphoenix]

Okay here is that excel file if you want to edit the formulas go to "Review>unprotect sheet" there are no passwords in this sheet. enjoy!

[deadlykitten]

hey, it looks nice