Having a hard time understanding primary vs seconary axis

[lowcountrycamo]

At first I read somewhere that the primary axis is connected to the machine and secondary is connected to primary.  Like a Okuma  millac head head, B would be primary and C secondary. Or a common Haas trunnion add on for a 3 axis, the A would be the primary and B would be secondary. 

 

But then I watched a video on about 5axis generic post and at about 25 seconds in it show a description that has confused me.  Does anyone have a simple way to describe this to me. I very much want to understand this.

 

For the record I don't program full time, only when something special is needed. However, I am trying to give management a reason to elevate a young machinist to a full time programmer, which would be unusual for our shop.  I feel I am almost there. In fact, I am the only guy in the shop that is  trying to learn post editing or really anything new.  Thanks to you guys at emaster I was able to sort out some post problems one of our guys was having last week.

 

 

Thank you

 

Steve A

[crazy^millman]

When you get in your car and decide you are going to go some where you normally have a primary place in mind where you want to go. When you start driving down the road and your wife decides we should stop here you now have gone to a secondary place. Your goal was to go to the primary place, but her goal was to go to the secondary place. Now you can sleep on the couch and not pull over and go to that place she wanted to go or you can stop and let your secondary place be your new primary place correct?

 

Primary and secondary is like this on Multi axis machines. The logic is about the same as what I described above. The primary axis controls all the movement of the other axis it is supporting or driving, but the secondary axis is really the one deciding what is being done where the tool or part comes into contact with the tool. Now if the primary was not headed in the direction it was headed in the secondary would have not happened, but it could have happened if the primary was already in a place where the secondary was already in place to be where it needed. Most times in 3+2 work this is the case, but in full Multi-axis work this is not the case and if the secondary cannot get to where it needs from the original primary position then the primary potions needs to move to allow that position to happen or work. Problem is all the limits and possibility of where and how that can happen. Each machine and each configuration creates it on unique problems or issues to solve and figure out.

 

Now the post is a math formula be it a very complex one, but at the core of any post it is just a math problem. Make enough logic for the problem to solve itself and it will, but when it can't solve the solution then that is where you need to help it along. Most posts in Mastercam need this help and that is where the switches and all the other things come into play. If they were kinematic aware and knew all of this information during toolpath creating then the post would not need all of this help. If you look at the Moduleworks toolpaths you can spend the time and define this and then the toolpaths will respect the kinematics of the machine. I have not taken the time to dive into those capabilities because I have programmed 5 axis for well over 15 years in Mastercam so I am aware of enough to think of all the possible traps. Not that I do and not that I really fight sometimes creating 5 axis toolpaths, but when you make a machine dance a like a ballerina and the customer just stands there with their jaw dropped watching the machine run one of your programs it makes the job and the process worth it.

 

Primary controls just that the primary motion of the axis. The secondary is slave to the primary and if it not in a place to allow it to be where it needs to do what it needs then it must tell the primary to get where it needs to do what it is trying to do. That can be with a Head-Head where the one axis of the head need to move to a different place or it can be on a table-head where the table need to move to a place where the head and do it's thing or where the head needs to move to it's place and allow the table to be where it needs. Then there is table-table and now it comes down to what and how can one help the other put the part where you need to reach that area of the part you are trying to machine.

 

I could get all technical and bring out abstracts and such, but would rather put in terms hopefully that make sense and help you wrap your brains around something we all do everyday when we drive a car, eat our food or even just walk from place to place. Our Hands are 9 Axis or more of movement and if you sat down and mapped all the movements your hand can make and then wrote out the math for what we do in seconds without thinking and just sat there and thought about the formals to make a machine do what your hand just did in just typing a response to this thread you would see what we do in 5 axis is really no different. We are just telling a machine to do what we do all the time, but we just need to do it in a way it understands.

[jlw™]

Ron, what then is singularity in the driving situation with the wife?

 

LOL!

[Watcher]

I guess that would when you need to visit some friend in the back street but your wife says no problem to visit Joe, but we've got to go to the shopping mall first. You eventually get there, but only after burning a quarter of the gas tank...

 

[Watcher]

A mild example of singularity and the effect on feed rates on primary.. 

 

https://youtu.be/g7p1umVBQ08

[So not a Guru]

A mild example of singularity and the effect on feed rates on primary.. 

 

https://youtu.be/g7p1umVBQ08

How was the improved path created?

[Watcher]

How was the improved path created?

Apparently it's a thesis from someone... I don't know... I simply searched for 5 axis singularity on YouTube...

 

Mild singularities can be treated by the post sometimes... Most high quality posts have logic in MP to attempt to treat it...

 

I don't know which system that code was created on, but it's possible that the PP was enhanced within the possibilities to treat it...

 

The more axis you have involved in the motion, the more prone to bump into it...

 

But it's as Ron said a mathematical problem... Most cases tilt the part and move on... on 5 axis machines...

 

Now think about robots, 9-11 axes moving.. they are far more prone to it and tilt the part may not solve it because there far more than 2 solutions like in 5 axis... so developers solve this with advanced path planning algorithms... Octopus and Robotmaster are good examples of sophisticated motion planning / calculation to avoid singularity...

[Watcher]

I shared the video because we often talk about singularity but it's difficult to understand it without a video...

[Zoober]

Ron, what then is singularity in the driving situation with the wife?

 

LOL!

That's when you both agree on the destination, but argue about how to get there.