Thursday, September 7, 2023

Simple calipers and vernier calipers, method of uses and calculations


The calipers are very useful instruments. These instruments are used to measure the diameter of the cylinder, bore, bearing size, and small distance accurately. There are two types of calipers used in the industry:

1- Simple calipers
2- Vernier calipers

Simple calipers:

These calipers are used to measure the inner and outer diameter of bigger size cylinders. Suppose that we have measured the outer diameter of a big size solid roller or cylinder and there are pivots on each side of the roller. This roller rotates on its pivots. In this case, we can not use a measuring scale for diameter measurement. The role of simple callipers comes into play now. You can measure the outer diameter of this roller accurately with the help of the simple callipers. See the below diagram:

There are two simple callipers used to measure the cylinder Or roller diameters. You can see clearly in the above figure. 

The simple calipers consist of two legs bent at the bottom. The top ends of both leg are connected to each other with the help of a leaf springs. This leaf spring tends to keep both legs close to each other. A adjusting screw fitted near the top of the calipers helps to increase or decrease the gap between two legs as per requirement. 

The calliper having legs bent inside the instrument is used for outer diameter measurement. The object ( cylinder or roller) is fixed between the legs ( jaws) and the screw is tightened gently. The bent end of each leg ( jaw) just touches the cylinder Or roller surface. The jaws should just touch the surface not put pressure on the surface. Now, the instrument is taken out and the distance between two jaws( legs) is measured with the help if measuring scale graduated in the millimeters. 

The calipers having bottom ends of legs (jaws) bent outside direction of the instrument are used to measure the inner diameter of cylinder. The measuring procedure is same as stated for outer diameter measurements. 
You can easily measure inner and outer diameter by following the given picture as above. 

Vernier caliper:

This instrument is used to measure small dimensions accurately. We can measure inner diameter, outer diameter, and depth of cylinder accurately  by this vernier caliper. The structure of this instrument is given below:
1- It is constructed of two scales. 
2- A fixed scale graduated inver millimeters is called main scale. 
3- A sliding or moving scale graduated in certain no. Of divisions is called vernier scale. 
4- The number of divisions in the vernier scale is more than one of the smallest divisions present in the main scale. If the vernier scale has 50 divisions then these 50 divisions of vernier scale will be equal to 49 divisions of main scale. 
5- It had two upper jaws. These upper jaws are used to measure inner diameter of a cylinder. 
6- It has two lower jaws. These lower jaws are used to measure outer diameter of a cylinder or a roller. 
7-  A depth measuring blade is used to measure the  depth of a cylinder. 
8- A sliding screw helps to move the vernier scale left to right or vice versa. 
9- A fixing screw helps to fix the position of vernier scale during dimension measurements. 

Measurement procedure:

1 - First of all see carefully the whole instrument. 
2- See the least count of vernier calliper written on it. 
3- If the least count is not mentioned, we calculate the same by formula. 
4- Close the fixed and movable jaws of instrument. 
5- Zero point of main scale gets matched with zero point of vernier scale. If there is found any error, this zero error is rectified first. 
6- The upper line of the main scale is graduated in inches and lower line of main scale is graduated in millimeters. 
7- Count the number of divisions marked on the vernier scale. 
8- Fix the object between lower jaws if we are measuring outer diameter. 
9- If you are measuring inner diameter of an object, fix the object between upper jaws. 
10- Use depth measuring blade in case of depth measurement of a cylinder. 
11- Finally, fix the fixing screw. 
12- Now, read the main scale and vernier scale readings on a note pad. 


No. of divisions in vernier scale = 50
Value of one division of vernier scale = 1 mn


Least count= (Value of one division of vernier scale) / (No. of divisions in vernier scale) 
                        = 1/50
                        = 0.02 mn
Main scale reading = 25 mn

Vernier scale reading = 38 no. Division( it means the 38 number division is getting matched with any division of any one division of main scale) 

Cylinder dia ( mn) = main scale reading + ( vernier scale reading x least count)
          = 25 + ( 38 x 0.02) 
          = 25 + 0.76
Diameter= 25.76 m.m.

Digital vernier caliper: 

This instrument measures dimension accurately. It gives direct reading of dimension of the object. A digital display is mounted on the vernier scale. Remaining procedure and structure are same as that of simple vernier caliper. 

Tuesday, September 5, 2023

Gears rotational speed and cylinder surface speed calculations ( spur gear, bevel gears, Worm, and worm gears)


Gears rotational speed calculation( spur gear, bevel gears, Worm, and worm gears)-step 1

Motor rpm(M) = 1400, Motor pulley dia(A) = 40 cms

Machine pulley dia(B)= 20 cms, Machine pulley rpm=? rpm

Rpm (B) = (Motor rpm(M) * Motor pulley dia(A)/Machine 



 =(1400 *40)/20

Machine pulley(B) rpm= 2800

Gears rotational speed calculation( spur gear, 

bevel gears, Worm, and worm gears)-step 2

RPM gear( C ) = RPM ( B)= 2800, No. of teeth (gear C ) 


No. of teeth (D )=60, RPM gear D =? RPM

RPM gear D = (RPM gear C * No. of teeth gear C )/No. of 

teeth ( gear D )

 =(2800 * 25)/60

RPM gear D = 1166.66

Gears rotational speed calculation( spur gear, 

bevel gears, Worm, and worm gears)-step 3

RPM bevel gear E=RPM gear D=1166.66, 

Since bevel gear E is mounted on gear shaft of D, therefore rpm 

of bevel gear E = RPM of D = 1166.66

No, of teeth in bevel gear E and F are equal to each other, 

therefore rpm of bevel gear F = RPM of bevel gear E = 1166.66

Gear G is mounted on F, therefore rpm of G = rpm of F= 


Gears rotational speed calculation( spur gear, 

bevel gears, Worm, and worm gears)-step 4

Rpm gear G = 1166.66, No. of teeth grar G=25

No. of teeth gear H = 60, RPM of gear H = ?

 RPM of gear H = (Rpm gear G * No. of teeth grar 

G)/No. of teeth gear H 

 =(1166.66 *25)/60

RPM of gear H = 486.11

Gears rotational speed calculation( spur gear, 

bevel gears, Worm, and worm gears)-step 5

Since the single worm I is mounted on the gear shaft of H, 

therefore rpm of single worm I = rpm of gear H = 486.11 

No of teeth in worm gear J = 42, rpm of worm gear J = ?

rpm of worm gear J = (rpm of single worm I * 1 ) / No of teeth 

in worm gear J

 rpm of worm gear J =(486.11* 1 ) / 42

rpm of worm gear J = 11.57

Gears rotational speed calculation( spur gear, 

bevel gears, Worm, and worm gears)-step 6

Since the worm gear J and roller K are mounted upon same shaft, 

therefore the rpm of Roller K = rpm of worm gear J = 11.57

Dia of roller K = 75 cms

Surface speed (K) = Rpm of K * 3.14 * dia of K

 = 11.57 * 3.14 * 75

 = 2724.73 CMS / Minute

Surface speed (K) = 27.25 meters / minte

Monday, May 8, 2023

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Monday, April 17, 2023

Table screen printing process

 Table screen printing process

The table screen printing method is widely used to print various types of fabric. Fabric is printed on the table that is why this method is called table printing. Flat screens are used in method therefore it is also called the table screen printing technique.

Advantages of table screen printing:

1- This fabric printing technique is a cost-effective technique. 

2- The design repeat size is bigger than any other fabric printing technique. 

3- The wastage of colours and fabric is very low. 

4- The edges sharpness of the design results is excellent. 

5-Minimum order quantity is very short. 

6- We can even print one meter of fabric sample in table screen printing.

7- The printed fabric is dried by sun drying therefore drying cost is very low.

Disadvantages of table screen printing technique:

1- The number of colours in table screen printing is limited.

2 - Almost 6 - 7 colours design can be printed by table screen printing.

3- The fitting accuracy of the colours in the printed fabric design gets low.

4- if continuous fabric or yardage is printed in the table screen printing, the repeat joining line may appear in the fabric.

5- It is labor intensive printing technique.

6- approximately, 30 - 35 meters of fabric can be printed on the table screen printing at a time on one table. 

7- The depth of the printed colour may slightly vary due to manual striping.

8 -  This printing technique has width limitations as well.

9- Productivity is low.

Table screen printing process:

The whole printing process gets completed in the below steps:

1- Screen preparation

2- Table preparation and setting

3- Fabric mounting upon the table

4-Colour preparation  and matching

5- Fabric printing

5- Fabric drying

6- Fabric curing 

7- Fabric checking and touching

8- Fabric folding and packing

Screen preparation:

Screen preparation is a very critical task in the table screen printing process. this task is performed by a well-trained person. The screen preparation takes place in the below steps.

  • The printer receives either printed fabric samples or artwork.
  • If he receives a printed fabric sample, the artwork is developed by the printer.
  • Now, the tracing of the each colour is prepared.
  • The tracing is prepared upon the transparant plastic sheet having good flexibility and strength.
  • The area having colour is painted with black colour in each tracing paper.
  • The blank area is left unpainted in the tracing paper.
  • Now, blank screens are prepared.
  • Very fine and perforated polyester fabric is is mounted on the round pipes square or rectangular iron frame securely and tightly.
  • One blank screen is prepared for each colour.
  • Now all these screens are coated with photo emulsion and dried well under sunlight.
  • Now, these photo emulsion coated screens are exposed to high intensity light as per tracing.
  • The tracing is placed over exposing table then the photo emulsion coated screen is placed over the tracing. Now, the photo emulsion coated screen is covered by plan metal or plywood sheet.
  • The exposing table light is switched on now for definite time.
  • Thanks the photo emulsion coated screen exposes with high intensity light. The light falls on those areas of screen directly where the blank area of the tracing allows to pass light. The areas exposed with High intensity light gets hardened. 
  • Now, these screens are washed in weather by high pressure water supply. The the hardened areas of photo emulsion in the screen remain fixed in the screen but unexposed areas of photo emulsion with light get washed out and the photo emulsion is removed. 
  • Now, each screen is checked. If required, touching of photo emulsion is done on damaged areas.
  • Thus, the all screens get ready for use.

Printing table preparation and setting:

  • Two types of printing tables are used in table screen printing.
  • Cushioned (bed type) table is used in some printing unit while adhesive bonded tables are used in the other Printing units.
  • In the cushioned (bed type) printing table, few layes of fabric are spread out over the printing surface of the table.
  • In the adhesive bonded table, the top surface of the printing table is covered with good quality non woven bonded cloth made of synthetic fibres.
  • A layer of adhesive is coated upon the top surface of this table.
  • In case of adhesive coated table, it is washed thoroughly before start printing.
  • The screen positioning elements are fixed as per design properly. 
Fabric mounting upon the printing table:

  • Now the fabric is mounted upon the printing table.
  • In case of cushioned (bed type) printing table, the fabric is fixed with the help of steel pins. 
  • The steel pins hold the fabric at the both selvedge.
  • In case of adhesive coated printing table, the fabric gets stup upon the printing surface due to adhesive coating upon the surface.
  • The fabric is mounted straight.
  • The wrinkle free fabric mounting is assured.
  • The fabric is mounted tightly in the both directions.
  • The side margin in the table is kept as per fixation of screen positioning elements.
  • Thus, the fabric gets ready for Printing.

Colour preparation and colour matching:
  • The colours paste is prepared in the colour kitchen.
  • Each colour is prepared separately and as per colour recipes.
  • A band of fabric in each colour is printed in each colour till proper matching achieved.
  • Now, our colours pastes get ready for use.

Fabric printing:
  • Each colour is printed one by one.
  • Lightest colour is printed first.
  • The darkest colour is printed at the last.
  • Printing starts from one end of the fabric and finishes at the other end of the fabric.
  • The screen is placed over the fabric and is aligned with the help of screen positioning element.
  • Now, the colours paste is dropped at the one side of screen.
  • The colour paste is wiped out from one to other side of the screen. The colour paste penetrated through the fine holes of the screen and gets stuck upon the fabric.
  • Now, other colours are also printed in the same way.

Fabric drying:

  • If the steam heated table is used, the the fabric gets dried after my some time and it was s taken out from the printing table.
  • In case of cold table printed fabric is left for drying by natural moisture evaporation.
  • Ceiling fans air helps to accelerate the speed of drying there.
  • After some time, the fabric is taken out from the table and is hung upon strings tied in the walls of the shed for further drying.
Fabric curing:
  • This printed fabric does not show proper colour fastness.
  • This fabric is passed through a heating chamber where hot air blows.
  • The polymerization process takes place and the colour fastness gets improved.
Fabric checking and touching:

  • Now the fabric is checked for any printing defect.
  • If any unprinted area appears after printing, the colour is painted by touching brush or pen .

Fabric folding and packing:

  • Now, the fabric length is measured and rolling if the fabric is carried out.
  • The rolled fabric is packed in the polythene sheet and then in hussian cloth .
  • Thus printing fabric gets ready for dispatch.

Sunday, December 4, 2022

Siro spinning system, objective, properties of siro spun yarn, advantages and disadvantages of siro spun yarn

 Objectives of Siro spinning:

· The main objective of the Siro spinning is to achieve a weavable worsted yarn by capturing strand twist during twist insertion on the ring-spinning frame.

· To reduce the cost of production in the spinning stage up to half by increasing production per spindle by roughly two times.

· To eliminate the yarn doubling process cost.


What is Siro spun yarn?

· Siro spun yarn is a virtual - two-fold yarn in which the two components are untwisted strands rather than twisted singles yarns.

· It builds on the concept of self-twist spinning up to some extent.

· In elf-twist spinning, two drafted strands have cyclic false twist inserted by a set of oscillating rollers.

· One strand is made to follow a longer path so that when the two strands are brought together their twist is out of phase.

· In trying to untwist, the two strands twist about each other, capturing oscillating twist in each strand.

· Production rate 200 meters /minute is possible and the yarns could be used for knitting.

· However, to be weavable the yarn had to undergo a real twisting in a separate twisting step (ring doubling or two-for-one twisting process) as with normal two-fold yarn production.

Concept of Siro spinning:

· The initial steps were taken at CSIRO in the mid-1970s (Plate and Lappage, 1980).

· Two strands were fed side-by-side through the drafting system.

· These strands were passed through a further pair of rollers after leaving the front rollers.

· This pair of rollers was intermittently blocked the twist from propagating up to the nip line.

· The two strands were brought together by the twist to form a large, long spinning triangle (the ‘vee’).

· The twist-blocking rollers caused the twist running into the two strand arms to increase and decrease.

· This intermittent twist becomes trapped in the yarn below the convergence point, which is held fixed by a guide, as alternating twist of the strands relative to the rotating point of contact (i.e. the mean folding twist).

· The alternating twist enables surface fibers to be trapped between the two strands.

· Plate and Lappage (1980) showed that the amount of trapping is proportional only to the alternating strand twist and is independent of the two-fold twist.

· An alternative method by Lappage (1973) achieved a similar result by vertically oscillating the convergence guide without the twist-blocking rollers.

· Even though twist is observed in the strands during Siro spun spinning, if it is constant then none of it is trapped in the yarn.

· Real (net) twist cannot be introduced, only alternating twist.

Yarn model of Plate and Lappage for real two fold and virtual two fold yarn

· This is illustrated in the model of below Fig.  (following Plate and Lappage, 1982) in which the two singles strands are represented by long rubber cylinders.

· One of the untwisted cylinders has a black line along its length Fig. (a), representing a surface fiber. 

· If real twist is inserted then the surface fiber traces a helical path Fig. (b). 

· Every turn of singles twist leads to a trapping point of the fiber after two-folding Fig. (c). 

· If the strand twist remains constant then there is no real (alternating) twist of the strands relative to each other. A fiber that starts on the surface always remains on the surface Fig. (d). 

· This is the basic reason why ordinary singles yarns (or Siro spun yarns at small strand spacing) are not weavable. 

· In such yarns there is a small amount of fibers migration, due to varying spinning tensions and movement of the delivery positions of fibers, but overall many surface fibers are poorly trapped and will be easily rubbed up along the yarn during weaving. 

· Constant strand twist above the convergence point just leads to fibers maintaining their relative positions in the two strand yarn; removal of the two-fold twist will leave two untwisted strands. 

· When two strands are held at both ends insertion of real twist is not possible and only varying twist can enable trapping.

Schematic diagram of two fold Siro spinning system with break out device:

The changes needed to the ring spinning frame to produce Siro spun yarns are as below:

1- A double roving creel (for twice the number of roving packages)

2- A double set of roving guides.

3-A wider middle (apron) roller recess, modified front zone condensers (if used).

4- The break-out device. 

· The yarn count per spindle is doubled and the amount of twist inserted is usually the same as would be inserted in the two-folding operation (a metric twist factor of 120 to 130) which is similar in turns per meter to that put in the singles yarn. 

· The recommendation is still to have the same total number of fibers in the yarn cross-section as the equivalent two-fold yarn (e.g. for wool, at least 2 ¥ 35 = 70, given the accepted spinning limit of 35 fibers in the yarn). 

· This twist level and number of fibers are needed to ensure good spinning performance by avoiding drafting of the strand arms. 

· Studies (Plate and Feehan, 1983; Plate, 1983a) have shown that the optimum strand spacing is a balance between improved abrasion properties and poorer evenness and spinning performance. 

· It was found that yarn abrasion resistance increases linearly with strand spacing, hairiness drops rapidly at first, then slowly, and yarn evenness, tenacity and elongation improve at first, then plateau and later decrease. 

· The standard strand-spacing of 14 mm has been adopted for worsted spinning (Plate, 1983a).

Properties of Siro spun yarn:        

· Siro spun yarns have higher tenacity and elongation.

· Siro spun yarn has lower hairiness.

· On average Siro spun yarn have marginally poorer evenness, possibly due to correlations between the drafting of strands through the same drafting zone and due to occasional strand-arm drafting.

· Siro spun yarns are not quite as abrasion resistant as the equivalent two-fold and more likely to fail on the loom under extreme conditions, such as in the selvedge.

· Siro spun yarns have more thin places than two-fold yarns produced from the same material and observed that extreme thin places are associated with higher spinning tension.

· It is much better to think of Siro spun as a singles yarn with improved binding of the surface fibers.

· As singles, Siro spun yarns are leaner than the equivalent two-fold yarns.

Disadvantages of Siro spun yarn:

· One drawback is that winding and clearing are carried out on the final yarn rather than the singles.

· The joins (splices) must survive weaving unaided by a good (un spliced) yarn. The performance of splices in weaving is so critical that Siro spun could not gain wide commercial adoption until improved wool splicing (the Thermo splicer™) was available.

· This is a potential cause of more visible streakiness in plain-weave piece dyed fabrics where the uniform colour and simple pattern provide the least hiding of the yarn irregularity that is always present.

You may also be interested in the below articles:

Objectives of compact spinning system, different types of compact spinning systems advantages and limitations

Friction spinning method, main features, limitations, basic structure and working principle of friction spinning machine



Siro spinning system, objective, properties of siro spun yarn, advantages and disadvantages of siro spun yarn

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Simple calipers and vernier calipers, method of uses and calculations

Calipers: The calipers are very useful instruments. These instruments are used to measure the diameter of the cylinder, bore, bearing size, ...