Feed screw Conveyor Design Formulas

Hi people!

I want to ask about a design procedure about feed screws.

We want to design something about 2500 miligram feed in 4 revolution with accuracy +-50 mg.The density 0,8-0,9 gr/cm^3

Max shaft diameter is 16 mm

the other things will be determined by us

in conclusion I need formulas of determining screw conveyor.

And am going to design a screw conveyor.

Can you help me abaout this design problem


Screw Feeder Design

Posted on 5. Aug. 2008 - 11:37

My first thoughts are that, if you have to ask, you should'nt be doing it but if you want to have a go - see 'Guide to the design, specification and application of screw feeders', published by The British Materials Handling Board.

Re: Screw Feeder Design

Posted on 5. Aug. 2008 - 01:00

Originally posted by Lyn Bates

My first thoughts are that, if you have to ask, you should'nt be doing it ...

Sometimes these things just have to be said... :-))

Re: Feed Screw Conveyor Design Formulas

Posted on 5. Aug. 2008 - 10:26

Thanks for the replies.

I am going to buy your book Mr Lyn.

I want to ask one more question. Is there a section about accuracy of the screw feeder. As I stated 2500 mg +- 50 mg means max %2 tolerance.

What effects the accuracy of these systems.

Best Regards.

Re: Feed Screw Conveyor Design Formulas

Posted on 5. Aug. 2008 - 11:21

You could also buy the screw conveyor publications from here :


But most of the real knowledge is NOT in published books, but resides within companies who MAKE screw conveyors and feeders. This is their commercial lifeblood so is unlikely to be issued to competitors. At some point you will have to make your own way in the world as others have had to before you.

Re: Feed Screw Conveyor Design Formulas

Posted on 6. Aug. 2008 - 11:02

I think this design must be done by a professional. Because we do not have enough experience doing this and this screw will be done only once. But our managers said that we have to do it in a short time period. We have some designs and machine is working.But there is no standart designs done by trial and error method and tolarance is +-200 mg. Now we have to reduce it to +-50 mg.

So I started to make a standard screw.This is why I need the formulas. And besides that accuracy is most important thing.

I see a design of 3 parts. Outer dia(15mm) is quite high with shaft then 2nd part reduce to 9mm suddenly and then 3rd part is shatfless part on the screw is it correct.

Having %2 tolerance in 2500 mg can be done by such a design.

or is it feasible having %2 tolerance in feed screws

Re: Feed Screw Conveyor Design Formulas

Posted on 6. Aug. 2008 - 11:16

One more question to mr Lyn.

Is there a soft copy(pdf format) of your book.

Screw Feeders

Posted on 7. Aug. 2008 - 12:22

The book on screw feeders is only available in hard copy at £ 50 plus £ 8 o/sea post and packing. I can arrange for a copy to be sent by the British Materials Handling Board if you forward your full postal address to lynflow@btinternet.com.

The batch discharge accuracy of a screw feeder is determinate on many factors of the screw geometry, speed and nature of the bulk material. In the first instance the screw should be delivering material at a consistent rate and in a consistant condition. This is mainly dependent on the design of the inlet section of the feeder, where mass flow is a great asset for any products that tend to vary in density. In general, a two speed discharge is desirable for accurate batch dispensation, with the bulk of the quantity, say 90%, being fed in roughly half the total time and the remaining period dispensing at a lower rate to give a more precise teminal quantity.

The main vaiables at the discharge point relate to the cyclic form of the screw, which tends to deliver in surges, according to the rotation of the screw, and the state of the bulk material. If the bulk material is cohesive there will be a tendency for the material to hold together and fall off in erratic clumps. On the other hand the repose surface of a free flowing material will avalanche at low feed rates and inhibit a sharp cut-off unless a quick-acting valve is fitted. The techniques available to overcome these phenomena are therefore different and a close knowledge of the design and material are required to secure optimum results.

The degree af attention merited ultimately relates to the importance of the results required. Short cuts are at the expense of predictability.

Re: Feed Screw Conveyor Design Formulas

Posted on 9. Aug. 2008 - 09:21

Really no point in spending that kind of money on a book. Any reputable conveyor company will have everything you need in their catalog, complete design criteria. You just need to study the data and go from there.

I hold patents on several screw feeders, if I can help, let me know.

Ted Key

Ted Key

Re: Feed Screw Conveyor Design Formulas

Posted on 11. Aug. 2008 - 01:09

Dear Sirs,

Thanks for the replies,

When I am searching the internet I found some suppliers but minimum diameter is 4".

I need very precise and small screw conveyor. So I need parametric design formula.

The main idea of our design is 2500 mg+-50 mg. Other parametres can be changed.

If it is possible I want to see your patents.

I will search again.

Thanks for advices.

Best Regards.