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Screw barrel buying guide

Screw barrel buying guide

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Here you will learn almost everything about feed screw & Barrels. Use these Tips & Tricks to get quality with budget.

15 things to know before buying feed screw barrels.

1. Which is best Steel material for screw barrel ?
Answer: In the case of (monometallic) nitriding steel screw barrels, the best material will be any grade of nitriding steel that can be case hardened to 60-65 HRC.
with case hardening, the overall strength is also important, because wear resistance property does not come alone from Hardness, but overall strength. That is why a D2 (tool steel) which has the same hardness is better wear-resistant material than nitriding steel. A frequently used commercial branded hard-facing alloy Colmonoy-56 which is actually used to protect wear loss has less HRC hardness value (50-55) than post-nitriding hardness in En41b made screws. However for screws above 1200 mm in length D2 material is not used due to the unavailability of hardening process, and at the same time it is more expensive than nitriding steel. That is why generally in all standard screw barrel Nitriding steel is used. In india the most successful grade is En41b it is equivalent to 41CrMOAl7 and 38CrMoAlA, in DIN specification it is called 1.8509 steel. It is better than 4140 steel, En19, En24, and En31 because after nitriding heat treatment En41B works excellently in comparison to these other grades. In india several companies produce En41B material but MSSSPL (MUSCO) made En41b is the most used, and most trusted screw barrel material. For more information
 call our technical expert team at +91-8128381431.

In case of Bimetallic screw barrel the answer is not easy to put in few words, because bimetallic solutions are provided according to the nature of compound to be processed, temperature, pressure, heat, abrasion possibility and wear resistance requirement. Bimetallic screw barrels are made up from superalloys, carbides and borides blends with performance alloys. we have created a separate page to understand Bimetallic screw barrel. You can read all details in this page. 

2. What is bimetallic ?
Visit page: Bimetallic screw barrels to get full information.
Or call our technical expert team at +91-8128381431

3. What is the normal life of different grades of steel used for screw barrel manufacturing ?

Answer: For virgin material En41B grade can perform up to 3 years or more and with the blend of reprocess (40%) this grade can perform up to 2 year, but only when no abrasive fillers and additives are used. In recycling this grade works generally for one year, but that too depends on the nature of material we  have to recycle. To increase life during recycling we recommend vented screw barrel set, and to increase output in any process we recommend barrier screw barrel and grooved feed for some specific polymers. For more information call our technical expert team at +91-8128381431.

4. How to increase life of screw barrels.
Answer: Get coating done at very economical price by Raj Engineering Works, we have highest range of screw barrel coatings, where our expert will suggest the best protection for your specific need. 
For more information call our technical expert team at +91-8128381431.
We have highest range of coating technology like HVAF, TPA, Spray and fuse, and Laser cladding etc. 

5. How screw barrel are made in India, Asia, Europe and America, who make the designs of screw barrels ?
Answer: Normally the R&D teams of compound and polymer manufacturers, academic and professional research institutes suggest technical guidelines. By following that guidelines the machine manufacturers makes a commercial machine, after successful trial a design becomes commercial.
Almost all designs are already invented. These already invented (long time ago), commercially proven designs, spreads in the world by copying (they call it the study of that machine) by other machine manufacturers interested to enter in the machine-making business.

Always (and please) ask your supplier to give you an AutoCAD drawing for your (spare parts) screw barrel. Once you or your maintenance department gets this drawing, you can share this drawing with as many as OEM companies to collect their quotations.

This is the best way of collecting quotations from as many manufacturers as you wish.

The drawing mentions all materials (in case of bimetallic), dimensions & machining requirement; so OEM can easily quote their prices with you. Otherwise how will you compare prices? 

Note: Sharing drawing of screw barrel with anyone outside your company is not a thing to worry about, because that drawing has almost no value in it. Why? Yeah because drawing is not a secret but simple document to produce next copy of screw barrel. That's it. When a screw barrel set damage, we have to replace it with new set, so to maintain the originality we keep this drawing. Second thing, everybody has that drawing, because all drawings are easily available or at least screw barrel are easily available to measure and to make a new drawing!

A barrier screw is barrier screw no matter which brand/country machine you buy. An American, European, Asian, African and Australian machine has the same barrier screw, same grooved feed technology & same vented screw. If there is any difference than the difference will be due to their specific diameter and length. For example a 90 x 2400 mm barrier screw will be slightly different from 89 x 2410 mm. This difference is meaningless because both are same screw.

That is what a drawing tells about! A drawing just tells the exact value of each measurement in your screw.
It is like suppose a tailor makes Men's shirts, now he may or may not have your shirt's dimensional measurements, but he can make the shirt for you if either you give him a sample of your shirt, or fresh measurement of your upper body, or a drawing of your shirt made by previous tailor. Providing drawing will save not only time but he can quote more accurate price, because now everything is clear to him. The drawing of your shirt is not a secret; this is about your fitting. This fitting in terms of screw barrel is called precision.  So if you have drawing, share it fearlessly. In this case we are that 'tailor' and the only difference (for you the confidence) is we have highest range of world class fabrics (steel material) and a R&D team to ensure you get No.1 fabric (steel material) only.

In case of injection molding machine users, in a same machine brand and in the same series there are multiple designs available for the same polymer. How?

Because the machine manufacturing company alters the dimensions at very small level (almost negligible) every time to maintain their monopoly.

So it is better to provide a drawing when asking quotation rather than just sharing the machine's model number/name. 

In the whole world no screw barrel manufacturing company invent/design screw and barrel for any machine. It is a machine manufacturer who designs (or get a design by copying) screw barrel for a particular process. But when they (machine manufacturer) share that drawing with OEMs like our company; they generally change the drawing in such a way that no one can get idea about the application of that screw barrel, output, machine name, model number etc.

Only few screw barrel OEM companies in world has an R&D center which include few from USA and China and Raj Engineering Works from India where we can change a particular zone in the screw for lowering shear heat or managing Intrinsic viscosity by adding new mixing zones or something else etc .etc.

Most screw barrel manufacturer do not studies what they do or make, but at Raj engineering works, since day 1 it is our constant endeavor to understand A to Z of what we do and why we do that. That is why our R&D is now capable of doing the same thing which a top class research institute can do, after a 3 year extensive research about bimetallic screw barrel, we started in-house manufacturing of all kinds of bimetallic screw barrels.

6. While purchasing a machine from the manufacturer if you do not get drawings, make drawings with the help of a draughtsman or engineer for you. Always insist on drawing of the screw barrel, nose cone, head grooved feed bush etc. 

7. Always keep spare screw barrel with you for any emergency situation.

8. Never run the screw barrel without loading any polymer, never run screw barrel in cold condition.

9. Always filter the material before loading into the hopper to remove any hard material like stone or metal to enter the screw barrel damage it.

10. Increasing the diameter of old screws barrel does increase the production in most cases.

11. Introducing barrier section in the screw does increase the production, but will draw more current; hence gearbox motor should be able to take the excess load.

12. Most grades of bimetallic screws can be used with a gas Nitrided barrel.

13. Avoid making drastic design changes in the screw barrel.

14. Do not increase rpm of the screw than the recommended speed by the manufacturer of your machine.

15. Keep good relations with the machine manufacturer.

16. T-conditioning (Tempering hardening) which is actually a pre-heat treatment Is necessary to process on raw material to ensure strength, because it is strength + hardness which works against wear resistance and alone hardness (gas nitriding).

17. When you repair a barrel, forget the term repair because actually, it becomes a new barrel at a lower cost. So it is better to procure a new screw along with the repaired barrel. 

18. The recommended clearance for a new 2-inch screw and barrel is 0.004 to 0.006 in.

A rule of thumb is one thousandth per inch per side. Screws should be rebuilt when they exceed the maximum clearance.


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