Thread: waterjet cutting a certain shape

Hello! I am interested if you think it is possible to waterjet cut an edge as shown in the images using 5-axis machine (omax 80x). The green triangle part is apparently problematic.

paralelna.pngstranica.pngtrikotnik.png

Thank you for your answers

Absolutely no waterjet knowledge, but my first instinct is that the sharp internal corner is an issue because the jet will be stationary at one point while it tips the head which might end up blowing out the corner.

Could you modify it slightly to blend the 45 degree edge smoothly into 90 degrees as it comes around the corner?

Can be done, you’ll need to find somewhere that has a machine with the ability to rotate the cutting nozzle to an angle.
Assuming the return on the bottom is part of the same assembly, that will need to be made separately and either bolted or welded on.

Not a good idea for ground engaging equipment.

What is shown is two flat planes intersecting to an internal corner, finishing with a sharp edge.

It screams out to me " cracks start from here".

That is not an if its going to break type statement, but a when.

Never put a stress raiser in an internal corner (as per your illustration)

Irrespective of the process you cut it with, do not leave the finished item like that . Probably some weld fill should be applied as well to improve the sweep of the radius.

With a disk ,then a flap wheel, blend those two flat planes smoothly into one another.

I spent my apprentice ship in building the accoutrements for earth moving equipment and crack repair on the same.

Grahame

Originally Posted by elanjacobs

Absolutely no waterjet knowledge, but my first instinct is that the sharp internal corner is an issue because the jet will be stationary at one point while it tips the head which might end up blowing out the corner.

Could you modify it slightly to blend the 45 degree edge smoothly into 90 degrees as it comes around the corner?

Yeah, that sharp internal corner is apparently problematic. I do not understand why it can't be done in 2 passes. For exaple, in the first pass a sharp edge is created going from bottom to the top. In the second pass, the machine stops the water flow, keeps the sam tilted angle, moves to side and makes another pass horizontally up to the end of the problematic triangle.

two_passes.png


Most probably I'll go with blending the sharp edge smoothly into 90 degrees. If would be a challenge to draw such geometry in solidworks.

Originally Posted by Grahame Collins

Not a good idea for ground engaging equipment.

What is shown is an internal corner finishing with a sharp edge.

It screams out to me " cracks start from here".

That is not an if its going to break type statement, but a when.

Never put a stress raiser in an internal corner (as per your illustration)

Irrespective of the process you cut it with, do not leave the finished item like that . Probably some weld fill should be applied as well to improve the sweep of the radius.

With a disk ,then a flap wheel, blend those two flat planes smoothly into one another.

I spent my apprentice ship in building the accoutrements for earth moving equipment and crack repair on the same.

Grahame

Thank you for your insight. I'll do as you suggest.

Originally Posted by potato

If would be a challenge to draw such geometry in solidworks.

I've never used Solidworks and I've never done anything like this in Turbocad before, but just did this easily so Solidworks should handle it no problem.

merge.png

Originally Posted by Grahame Collins

Not a good idea for ground engaging equipment.

What is shown is two flat planes intersecting to an internal corner, finishing with a sharp edge.

It screams out to me " cracks start from here".

That is not an if its going to break type statement, but a when.

Never put a stress raiser in an internal corner (as per your illustration)

Irrespective of the process you cut it with, do not leave the finished item like that . Probably some weld fill should be applied as well to improve the sweep of the radius.

With a disk ,then a flap wheel, blend those two flat planes smoothly into one another.

Even relatively small stress raisers can have big implications.
In the Late 90's a well known maker of heavy trucks made a change to the 20mm thick plates on the ends of the crossmember that supported the rear of the cab. Trucks that had been in service for well under 6 months began returning to the dealership with these plates cracked through and both the cab and crossmember floating around in the breeze. What was the change that brought this about? Simply changing from flame cut plates to plates punched or sheared with the resultant scratches and gouges in the edges that allowed cracks to propagate. That was one of the best lessons that I ever learned as an apprentice. Smooth lines and smooth transitions make for a smooth life.