Comments on New Project

Hi All

I am doing to some planning on a possible project. The machine is a x-ray system for scanning the welds on dished ends. I have made a sketch - see attached PDF.

The purple box is the scanning head and the orange cylinder is the x-ray source. The scanner has to be 50mm from the plate and the x-ray source 700mm from the scanner.

The machine in the current state of design has 2 x Horizontal axis(RED in the PDF), 2 x Vertical axis(BLUE in the PDF) and 2 x Rotational axis(GREEN in the PDF). I have drawn a few positions for the scanner and x-ray source. I left out the vertical and rotational axis twice else the drawing would be to cluttered.

The operation idea is that the operator inputs the dimensions according to the drawing of the dished end. The top axis with the scanner will then 'find' the left, center and right by approaching the end until a proxy is triggered. This will tell the PLC what the actual size is (there is quite a big tolerance) and adjust the dimensions accordingly. The scanner will start on the left and finish on the right.

I am planning to use SEW Movidrive B with SEW servo motors and a SEW MoviPLC to do the positioning.

Now the kicker: I have two options on the scanner.
1) The first one is well known technology and has to move 100mm and the stop to take a picture and then move to the next position. This should be relatively easy as how it moves in between stops does not matter.
2) The second option is rather new technology and snaps a picture every 50µm! (so 20 times per millimeter). The scanner either has to move a constant speed in relation to the dished end or it has to be triggered every 50µm.

That was a lot of typing!

I am trying to get some ideas on possible problems and if I use the second scanner HOW DO I GENERATE THE TRIGGER?

I have not used the Movi-PLC before but an familiar with the Movidrives.

Any comments and suggestions are welcome.

Thanks
Bestbier

I think a geared reduction drive using an encoder at the motor may work for this. X pulses = Y um moved.

The one thing you did not mention is the size of the ends. This will equate to how long it takes to do all the Xray evaluation.

Because I have worked in industry where X ray was done nuclear plant and submarine overhaul I wonder what these are for?

Dan Bentler

Hi

I forgot to mention that the dished ends are between 1500mm and 2600mm diameter.

They go onto barrels to from a ISO tank container - it's a standard shipping container frame with this tank for liquid. 95% of the world production is in South Africa and China.

I was thinking along the line of a gearbox with a ratio in the region 100:1 and then have the encoder on the motor - for SEW you need to have the encoder on the motor.

My problem is with generating the 50 micron pulse - I am thinking I can generate it with the MoviPLC, but because 3 axises will be moving at the same time it becomes a little tricky. I will contact my SEW guy to see if he can help.

Regards
Bestbier

I think your term 50um pulse is confusing you. I would call it 50um initiate xray or something else.

You have it right there in the encoder.

Distance traveled ie um proportional to motor RPM which is proportional to pulses. You can do the math and come up with ratio
Z encoder pulse to A distance traveled (um).
So for 50um initiate is equal to 50 x Z pulses on encoder.

Dan Bentler