You need a 3D design package eg SolidWorks or Inventor to model the screw and then automatically generate the drawing sections. ■

If you are not able to calculate the flight blank sizes, it seems to me most unlikely that you will have the tooling needed to press out the individual flights, so why not go to a screw manufacturer to get the job done properly?

The dimensions suggest that this is for a compaction application, rather than for progressive extraction from a hopper outlet, but even so, continuous taper over the whole length raises the question of linlet length for establishing the potential compression ratio and other issues concerning the end construction. A reputable manufacturer would probably also advise on the screw design. ■

Originally Posted by louispanjang

You need a 3D design package eg SolidWorks or Inventor to model the screw and then automatically generate the drawing sections.

Either will produce pretty pictures. I don't know about SolidWorks, but if you're looking for a flat pattern, Inventor won't produce one for a pitch of screw flighting.

If you want an approximate flat pattern then you can use SketchUp with a couple of plugins.

Of course even with a flat pattern you've still got the problem of pressing it to the correct shape ■

Here's a rough sketch of a constant pitch, variable O/D flight.

Attachments

screwflight (PDF)

■

Just work it out from basic geometric principles. When I started as a draughtsman 32 years ago I would have been laughed at or fired if I couldn't work this out from first principles on a piece of paper taped to a drawing board.

Just imagine that the OD of the flight is drawn on a cylinder, then unroll the cylinder.

Don'r rely on software for everything. It is a tool, and only as good as the operator. ■

Alas engineers these days seem to have lost the ability to think from first principles which is why they come asking others for formulae or computer programs to do their work for them.

One pitch of a screw conveyor flight is not hard!

http://www.mcadforums.com/forums/vie...SCREW+CONVEYOR ■

Assuming linear increments, it would theoretically take 10.86 progressive pitch flights to cover this length. However, experience shows that a properly designed blank extends to more than one pitch when formed, so 10 flight blanks will be more than adequate for the screw. This information would be redundent to an experienced supplier and probably useless to one without experience, but answers one part of the enquirers query. ■

I am sorry that I am unable to advise on detailed constructional dimensions as this is a commercial feature of the equipment made by my company. It does beg the question as to who will actually form the flights as, without some form of tooling, it would be awkward to attain a smooth finish on the flight shapes. Anyone with tooling would presumably know the blank sizes required.

I would normally recommend a slightly different form of construction to the geometric increase in extraction that this design generates. ■

You can calculate all of the developments with this program https://www.youtube.com/watch?v=E4sfkIU2xPU. It is very accurate. ■