Kerf Crossing / Anti Dive

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19 May 2019 00:12 - 19 May 2019 00:13 #134228 by rodw
Replied by rodw on topic Kerf Crossing / Anti Dive

tommylight wrote: Rod, do you feel lucky? :) Could you please try to get some data at all the fastest your machine can do while cutting some thin 0.8 to 1mm sheet at say 45 degree slope and 30 to 50 Amps ? Nah that is to much I think but it would be nice.


Funny you say that Tommy, I spent some time yesterday reviewing some maths that Dewey Garrett shared with me to calculate the velocity and acceleration required to cut corrugated iron. Its these Z axis limits that determine the maximum velocity you can cut at.

My maths sucks but Dewey calculated that corrugated iron at 6100 mm/min with 2" peak to peak and a 1" depth required a velocity of 9600 m/min and acceleration of 2019 mm/sec/sec . Fortunately in Australia, our profiles are a bit easier to navigate as they are 76mm peak to peak and 17mm deep. But yes, I have been thinking bout testing this!
Last edit: 19 May 2019 00:13 by rodw.
The following user(s) said Thank You: phillc54, tommylight

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19 May 2019 08:14 #134251 by phillc54
Replied by phillc54 on topic Kerf Crossing / Anti Dive
It is easy calculate on the fly as to the maximum angle the machine could handle at its current speed but I am guessing there is a practical maximum angle that someone would actually cut. Is that corrugated sheet? If so what is the maximum angle of corrugated profile?
I also think that torch profile could have a limiting effect on the maximum angle a machine is capable of.

Cheers, Phill.

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19 May 2019 08:34 #134252 by rodw
Replied by rodw on topic Kerf Crossing / Anti Dive
Phil, this was Dewey's maths

I was thinking about machine Z axis requirements for thin
corrugated material.
Example:
1) thin material, mfg says use 240in/min = 4in/sec
2) sinusoidal height (Z) pattern of corrugation:
period: 2 in (distance between peaks)
height: 1 in (peak-to-peak, so Zmax=0.5)
3) time between peaks:
2 in/(4 in/sec) = 0.5 sec
4) frequency: f = 1/0.5sec = 2 Hz
5) Zamplitude:
Z = Zmax*sin(2*pi*f*t)
= 0.5*sin(2*pi*2*t) = 0.5 * sin(12.6*t)
6) Zvelocity = V = d/dt(Z)
V = -Zmax * 12.6 * cos(12.6*t)
Vmax = 0.5 * 12.6 = 6.3 in/sec = 378 in/min
= 160 mm/sec = 9.6 m/min
7) Zaccel = A = d/dt(V)
A = -Zmax * 159 * sin(12.6*t)
Amax = 0.5 * 159 = 79.5 in/sec^2 = 2019 mm/sec^2 = 0.2 g

So folks aren't kidding when suggesting that high performance
is a requirement for Zaxis motion when cutting thin materials


I started to spreadsheet this this morning but then had to leave it. I have a mistake somewhere...

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19 May 2019 08:40 #134254 by rodw
Replied by rodw on topic Kerf Crossing / Anti Dive
So i think its hard to get a stepper motor to do better than 3000-3300 mm/min on a 5mm/rev ball screw and max acceleration is probably going to peak out at 700-900 mm/sec/sec. but Dewey's dimensions are out as mentioned on an earlier post so the real world is not as extreme. I gues the question I had is there anytjing in the tuning of plasmac that limits velocity and acceleration to less than the Z axis settings?

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19 May 2019 23:42 #134303 by tommylight
Last plasma I built had two Z axis with nook ball screws at 5mm/rev driven by Nema 17 motors @1.5A driven by Lam Technologies drives. It could do 9m/minute @ 2000mm/s/s acceleration.
Good drives do wonders for stepper motors. Have not tried the "hybrid" ones yet, might be quite good by now.

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20 May 2019 04:46 #134324 by rodw
Replied by rodw on topic Kerf Crossing / Anti Dive

tommylight wrote: Last plasma I built had two Z axis with nook ball screws at 5mm/rev driven by Nema 17 motors @1.5A driven by Lam Technologies drives. It could do 9m/minute @ 2000mm/s/s acceleration.
Good drives do wonders for stepper motors. Have not tried the "hybrid" ones yet, might be quite good by now.


Tommy, thanks for that. None of the good stuff ever seems to come to Australia!

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23 May 2019 02:53 #134652 by tommylight

rodw wrote:
Tommy, thanks for that. None of the good stuff ever seems to come to Australia!

I would venture a gues that you have it much better than me. It is disgraceful to be in Europe and not be European, but as history has proven time and time again, this part of Europe does not deserve to be in Europe ! To many f@#$%& wars, by some magnificently dumb people, that use their brains only as a means to keep the equilibrium while walking. Luckily, breathing and heartbeat are reflexes, otherwise most of them would forget to breathe.

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23 May 2019 03:37 #134656 by rodw
Replied by rodw on topic Kerf Crossing / Anti Dive

tommylight wrote: I would venture a gues that you have it much better than me. It is disgraceful to be in Europe and not be European, but as history has proven time and time again, this part of Europe does not deserve to be in Europe ! .


We really are spoilt here. We are essentially have only had one language to contend with until recent multicultural arrivals and no wars on home soil. I read the history of my customers countries sometimes and its quite amazing! Like Greece, Mauritius and several others.

Just we are so close to China everything is Asian and the freight is so cheap!

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24 May 2019 00:04 #134752 by Grotius
Replied by Grotius on topic Kerf Crossing / Anti Dive
Tommy,

Your country has a war history down side, i know. I worked with a bosnie war man for a while, 25 years ago.
He would kill me if i did something wrong to him. His name is Netzart.

I have perfect connection's for you for plasma related stuff and equipment. Near by your country. Special connecion.
Are you interested? When interested pm me. You won't regret it.

Last plasma I built had two Z axis with nook ball screws at 5mm/rev driven by Nema 17 motors
Nice pitch !! I use them alway's with Nema 34 type with 80 volt's step drive. This can handle load's up to 25 kg's, nice for milling also.

None of the good stuff ever seems to come to Australia!
If you read the new's. The special metal mine's in Australia are worth a fortune now because China will regulate export to US.
So Rod, do you already have a big backyard to dig in and extract some special metal's? If you can participate in this extraction process, they need in Australia a fast chemical way to extract the metal. So Rod, think about that !!
The following user(s) said Thank You: tommylight

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24 May 2019 00:39 #134756 by tommylight
Thank you, Grotius.
Last September a friend got the exclusive dealer contract with trafimet in Italy so I am good as far as consumables and torches go, got a 12 meter long cable and torch for 486 euro with tax, torch only for 139, consumables 4.6 euro a set, all this is for autocut A141 torch.
Another problem I have to live with here is nobody wants to pay for new stuff, so only used plasma power sources going for around 600 to 1200 can be sold. That is one of the reasons I awoid selling them, I sell only the CNC machine and wire in the plasma that they got.
@Grotius
Did you get my last email regarding costs here? Have not heard back so I wonder....

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