Manufacture an helical auger flight from steel plate 4

[15EA]

Hello,

I'm trying to manufacture a steel auger flight these are to be screwed into the ground and act as an anchor, the outside diameter of the flight is 700mm and 20mm thick and are to be welded to a 90mm diameter shaft and the pitch is 125mm.

I’m wondering how to manufacture these auger flights. I know the plate is cut with a profile burner but how do a get it to the helical auger shape?

 

[L17Aurora]

I think each pitch is a complete circle. They are then pressed apart & welded up. google Srew feeder/auger etc.

 

[15EA]

Yeah I'm neally 100% sure the first step is to cut a circle and the diameter would be a bit bigger ie od = [(700^2)+(125^2)]^0.5 = 711mm and the id is alos a bit bigger [(90^2)+(125^2)]^0.5 = 154mm. I'm guessing they are pressed a part just a bit more than the pitch to allow for sring back - i'm wondering if any one has come accross a machine that will do this.

 

[CorBlimeyLimey]

To achieve a circular auger section after 'twisting', both the outer and inner profiles of the flat blank would need to be elliptical.

 

[15EA]

I'm pretty sure they are just two circles.

 

[CorBlimeyLimey]

Circles would probably be good enough for a ground anchor auger, but as a test, cut the split circular shape from a piece of card, twist it, and note what happens.

 

[15EA]

I must try the card. It's getting the cut steel split circles into the helical shape that i can't figure out.

 

[kelowna]

It is simple really. It is an ellipse with the smaller diameter given by the diameter of the auger and the large diameter given by the square root of the diameter squared plus the pitch squared

 

[15EA]

You would think it would have to be an ellipse but i'm 99% sure its just two circles the od is square root of od squared plus pitch sqaured and the id is sqaure root of id squared plus pitch sqaured. This then gives me a flat spilt ring plate - how do i get this into a helicoil shape you would think there bound to be a machine that can do this.

 

[CorBlimeyLimey]

You could use a regular brake press, bumping the blank with many angular hits. this would give a multi-faceted surface though. Again, probably good enough for a ground anchor.

If you need a smooth surface, you will probably have to use a more specialised tapered-roll rolling machine.

 

[15EA]

Yeah I think an ordinary press brake would do the job - only thing is I have 200 of these to make and it would be very slow and they would all be slightly different just look very amateur. I was thinking of a former type template then place in the split ring on it and and then press it between to formers. But I'm thinking the split ring would then lie along the slope of the former and not press right. There is a machine that can roll flat strip into into a helicoil shape but it will not do my job as there far to big a difference in the radius's the strip would simply tear as it was being rolled - heating would be no good even if it did work as the would then be far to thin.

 

[JStephen]

You can develop some shapes, such as a cone, from flat plate and all it requires is bending the plate. Other shapes, such as a sphere, will require actually stretching or compressing the plate in areas to form the shape. I think an auger screw is going to fall into the second category. You won't know the exact shape to cut without some trial and error, and it would depend on the forming process as well. The force required to form the plate will be a lot greater than a bending-only process as well. It might be easier to do the forming hot. I would guess that the people that make smaller auger screws have specialized forming machines for the job. Larger ones might be done on a hydraulic press.

 

[insideman]

Everybody has missed a point: A helicoid is not developable!
A closely related surface appropriately called a "developable helicoid" exists. The straight line elements are not radial as in the helicoid, but are tangent to the inner cylinder. A real excercise in descriptive geometry. I think descriptive geometry is not taught any more.

 

[Compositepro]

Different manufacturing techniques are required for different designs. Since your application is a ground anchor, I assume that you only need one turn. Thus you can make it from plate. The I.D. would be an ellipse with the minor axis about equal to your tube. The major axis would be the tube diameter divided by the cosine (I think) of you helix angle. Since you want a uniform flight height the O.D. will be the I.D. plus the height. Cut that from plate, cut the ellipse open along the major axis, then bend and twist.

 

[unclesyd]

Here is the basic information on the making of a screw conveyor flight.

http://www.engineersedge.com/

http://wwwboard/posts/9034.html

I would also look at purchasing you flights from companies like the ones below. Both companies have the helicoid flights which is cheaper and very easy to install.

http://www.tfcflighting.com/index.htm

http://www.falconindustries.com/

 

[SincoTC]

15EA,

The auger you describe is quite a serious bit of bending and welding; can't you get them made for you by someone who already makes helical earth anchors and has all the right equipment and knowledge, I expect something this size is probably quite small in the offshore oil industry. It may be worth searching for something there or looking at helical foundation piles which are very similar apart from reversing the axial load. Like here>

http://www.foundationsupportworks.c...lical-pier-systems/technical-helical-pile.php

If you must make them yourself, have you considered making a wooden pattern and getting them cast in steel?

 

[15EA]

I know it going to require a bit of heavy duty cutting and welding - I'm looking forword to getting started on this project. I'm 99.99% sure to create the sectional helical shape I need to cut two concentric circles - the formaula for 700 od and 90mm tube and 125mm pitch is plate od = [(700^2)+(125^2)]^0.5 = 711mm and the plate id is also a bit bigger [(90^2)+(125^2)]^0.5 = 154mm. Note each secation helicoil will be approx 350 degrees or so. But how do i get this in to the helical (helicoid) shape.

 

[PeterCharles]

This is widely discussed topic in various places.

Here's one extensive discussion

http://www.mcadforums.com/forums/viewtopic.php?t=7481

and another

http://www.bulk-online.com/Forum/showthread.php?threadid=9504

and another

http://engineersedge.com/cgi-local/anyboard.cgi/

http://wwwboard/?cmd=iYz&aK=2123&iZz=2123&gV=0&kQz=&aO=1&iWz=0

 

[15EA]

Yeah its a common enough item you see them everywere, but i can't see a machine that can make them.

 

[PeterCharles]

Well try here ....

http://www.lenham-uk.com/production.htm