Objects and methods of grinding in Carding Machine.

It includes the following topics

1. Object of grinding.

2. Metallic wire grinding procedure.

3. Grinding Roller

Object of grinding:

As a card operates, the action of fibres and dirt with it, gradually wear the points of wire causing them to become poor  cleaning point. The purpose of card grinding is to maintain the card clothing in a sharp condition.

Metallic wire grinding procedure

Cleaning the card:

Remove the lap and strip the cylinder & doffer

Run the card until all the flats are stripped out

Remove the flat strips

Remove all the trash from under the card for they may cause a fire.

preparing for grinding:

Take off the main belt and guide.

Remove the doffer driving belt and dis engage the doffer driving gear.

Remove the flat driving belt. Br Remove the belt from cylinder to lickerin. -   Disengage the calender roller drive,

Remove the doffer comb bands. - Replace the main belt and guide to drive the cylinder back wards (in opposite direction) most motors are fitted with reversing starters and the change of direction can usually be obtained by means of special key.

Connect the cylinder and doffer pulleys with an open belt.

put the grinding roll in the cylinder stand with the driving pulley on the opposite side from the main driving belt.

Put on the grinding band to drive the grinding roll, so that they turn in the same direction as the cylinder. This causes the surface of the emery covered roll to run against the back of the card wire.

In the case of fast grinding, the driving connection is given as shown in the figure, assuming the cylinder speed of 170 rpm then,

Grinding Roll speed = 170 x (18/4) =755
Doffer speed =170 x (18/12) =255 RPM

In the case of slow grinding the following driving connection is given as shown in the fig.

Assuming 170 RPM as the speed of the loose pulley on the cylinder shaft, then Doffer =(170 x(16/95) x (5/100) x (40/216) =13. 2 RPM

Cylinder =13. 2 x (2 / 18) =8. 8 RPM

Grinding roller =170 x (16/9. 5)x (9. 5/4) =680 RPM

Start the card -The card is now so arranged that the cylinder,

doffer and grinding roller are the only parts moving.

Brush out the cylinder very care fully by holding the brush firmly and press it into the wire of the moving cylinder.

Stop the card and lift & correct any bent or jammed wire with special hook.

Before grinding, the setting should be noted so that an indication of amount of wire height removed by grinding can be obtained, when these settings are re-checked after grinding,

DURING GRINDING

Start the card running, listening for contacts. If either grinding roll touches it will cause a brushing sound.

Set the grinding roll down gradually until slightly brushing -action is heard.

The adjusting of the grinding roll during grinding against the cylinder is usually a matter of judgement.

Spark should not exceed 50 mm on cylinder and 30 mm on doffer.

Set the grind stone about 0. 15 mm clear off the surface of the wire at each end of traverse.

After 6-8 min, stop the grinding and the sharpness of wire points should be examined through micros cope. The presence of serrations on the wire and majority of points showing clear grinding, striations with a fine burr at the leading edge can be taken as an indication that the grinding has been done well.

Worn out grinding stone & deep meshing of grinding stone on wire would break or damage the wire and may lead to hooked or bent wire points.

The grinding stone used in grinding a card is aluminium oxide vitrified bond 46/L 7v or WA 80 /PE 31. It is a emery having a granular formation.

Starting up after grinding:

Remove the grinding band and Roller Remove the belt from cylinder to doffer Engage all the card drive connection as usual Reset all the settings Put on the main belt and bring the normal direction to cylinder after grinding. Turn the card parts by hand and listen for any contacts of surfaces. tart the card care fully and listen for contacts

Put the lap and reengage the side shaft gear

Start the calender roll when the web is in good shape.

Discard the first few yards of sliver on account of dirt and light weight.

Grinding Frequency;

Generally, grinding of cylinder and doffer should be carried out once in 6 month or after taking 40000 kg production and card should be reclothed once in 3 to 4 year or after 1. 5 lakhs kg production in one card.

Generally frequency of grinding depends upon the rate of production, quality of material, type of wire points and level of neps in the cad web.

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Grinding Roller For Carding machine | How it works?

Two types of Grinding Roller are available

i) Long roll grinder ii) Traverse Grinder.

1. Long roll grinder:

It is a steel shaft about 7 inch in dia and 42 to 47 inch long. The roll is carried on a shaft about 1. 125 " in dia. The grinder roll is entirely covered with emery fillet.

It is equipped with, a traverse motion to give a short (endwise) traverse. The usual length of traverse is 3/4 inch. The. drive to long roll grinder is given as shown in the fig. 2. Traverse Grinder:

This consists of a narrow roll, 3. 5 " wide and 7" in dia (mounted on a hollow steel shell 46" long. Within the hollow shell is the traverse screw, a long central shaft in which are cut two wide threads, one right hand and one left hand, which join at the two ends. This makes art endless spiral path around

the shaft which reverses at each end and returns. There is a follower which projects from the narrow grinding roll, through a long slot in the shell into the thread of the screw. By turning the shell the grinding roll is turned for grinding. By turning the screw at different rate of speed than that of the shell, the grinding roll is made to traverse to and for across the card.

The shell is driven by a band from cylinder pulley and so turns the 22 gear. The 16T and 15T gears are fast together and are driven from 22 T gear. The 15 T gear turn the 23 gear, which engage with the end of the screw.

so, for one one rotation of shell, the turns of the Screw is (22 X 15)/(16 X 23) = 0.897

This means screw losses 0.103 turns for every turn of shell. Pitch of the screw is 1. 5 inch. So, for one turn difference between screw and shell, the grinding roller moves 1. 5 inch. But here difference is 0. 103 turns. So 0.103 x 1.5=0.1545 inch is moved (Grinding Roller) for one turn of the shell.

By changing the gear we can alter the traverse per minute of Grinding roller.

BACK OF POINT GRINDING:

The direction of rotation for metallic wire grinding are normally arranged so that the Back edge of the tooth is first to pass under the grind stone.

This method of grinding is safe to use in practice and is by far the most widely accepted method used in mills, giving perfectly satisfactory results.

But with the disadvantage of leaving a temporary rough edge or burr, on the important leading edge of the carding tooth.

This burr tends to mask the real condition of the true leading edge so that experience is necessary to access the precise state of leading edge when making microscopic examination following grinding:

AGAINST THE POINT GRINDING:

In this method of grinding whereby the leading edge of the tooth is first to pass under the grind stone, so that the grinding burr is formed at the back edge of the point.

This leaves the leading edge clear for examination of the true condition after grinding. However, a marked disadvantage is the real danger of serious accident to operators because the points are leading during grinding operation and this method is sot to be recommended.

TOP GRINDING: This consists of grinding away the top of the wire to make the top end of every wire flat and in the sake plane as all other. This gives what is called a chisel point.

SIDE GRINDING OR NEEDLE GRINDING: This consists of grinding away the little from the side of- each point making it some what narrower at the point.

PLOW GRINDING: This consists of grinding the sides of each wire so as to leave more space for the cotton fibres, this gives a tapered point.

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