How do you Home a 4th Axis

Topics related to wrapped rotary machining in Aspire or VCarve Pro
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DesOwen
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How do you Home a 4th Axis

Post by DesOwen »

Hi Folks

I have the latest release of Aspire but this is about the workflow you folk would use when using Aspire to create your rotary gcode and running under Mach 3.

I cannot find out how to home the A Axis using reference all home. The rotary axis turns after the x,y and z have homed but doesn’t stop turning until I hit reset. There is an NPN sensor inside the box and I’m fairly sure I’ve wired it up correctly but I’m stumped. I don’t even know if I need to home it at all.

Can any one advise please?

Des

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TReischl
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Re: How do you Home a 4th Axis

Post by TReischl »

I would look at the pins, etc in Mach 3 to see if you have configured correctly.

That said, I have run a 4th axis under Mach 3 for at least 7 or 8 years now and have never had a real need to home it. I suppose there are instances where it would be handy but I have not run across any yet. Randy does a lot of rotary work so maybe he will weigh in on this.

I just built a new rotary a few months and was thinking about setting up a switch but then I said, "what for?" and could not come up with a reason. Doesn't mean there isn't one so I will follow this thread to see what is said.
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Rcnewcomb
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Re: How do you Home a 4th Axis

Post by Rcnewcomb »

Let's start with the basics:
To home the rotary axis you should have a proximity sensor.
Image

Proximity sensor should be mounted to housing of the rotary stepper/servo.
RotaryHomeIMG_2164.jpg
There should be a piece of metal attached to the shaft of the stepper/servo that passes near the proximity sensor.
RotaryHomeProxSwitch.png
When the metal piece is near the sensor the prox switch should change from closed to open, or opened to closed, depending on the particular sensor.

1. Do you have a proximity switch?
2. Is there a metal bar attached to the shaft that passes near the sensor?
3. When the piece of metal is near the sensor, does the switch change state (open or closed)?
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TReischl
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Re: How do you Home a 4th Axis

Post by TReischl »

Thanks Randall. . . . good info and good pics.

I am interested in hearing how you use yours, benefits, etc.
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Rcnewcomb
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Re: How do you Home a 4th Axis

Post by Rcnewcomb »

The main benefit it to be able to stop and restart a job involving the rotary and not be slightly off.

Since I try to raster along the cylinder it is important to get back to exactly the same rotation to resume a job.
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TReischl
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Re: How do you Home a 4th Axis

Post by TReischl »

Rcnewcomb wrote:
Fri May 22, 2020 1:24 am
The main benefit it to be able to stop and restart a job involving the rotary and not be slightly off.

Since I try to raster along the cylinder it is important to get back to exactly the same rotation to resume a job.
Gotchya. Makes sense.

I am thinking I could accomplish the same thing by using a shot pin and a plate. Not as elegant but I hate wiring and fiddling with settings :shock: Hmmm, now you got me thinking, maybe about 8 positions on the plate, then I could use it easily as an indexer too.
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Re: How do you Home a 4th Axis

Post by nicksilva »

Aspire is not a controller. it is basically a program generator. However, the gcode
G91 G28 A0;
is generally used. Include it in your own gcode.
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Re: How do you Home a 4th Axis

Post by Greolt »

DesOwen wrote:
Thu May 21, 2020 9:11 pm
There is an NPN sensor inside the box and I’m fairly sure I’ve wired it up correctly but I’m stumped. I don’t even know if I need to home it at all.
So you believe the home switch is wired up correctly. First thing would be to see if it is working.

On the diagnostics page look to see if Mach3 is receiving a signal from that home switch.

Whether or not you want or need to home the axis is another question

I have three rotary axis that I use. None of them have a home switch. However occasionally I strike a situation where one would have been advantageous.

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