Setting and Troubleshooting of Compression Machine

This Document describes (Standard Operating procedure) SOP for Setting and Troubleshooting of Compression Machine

SOP for Setting and Troubleshooting of Compression Machine

I. Purpose & Scope:

• The purpose of this SOP is to lay down the procedure for Setting and Troubleshooting of Compression Machine
• This Standard operating procedure shall be applicable for Setting and Troubleshooting of Compression Machine in production area.

II. Responsibilities:

• All production personnel shall be responsible to follow and implement this SOP for Setting and Troubleshooting of Compression Machine

III : Introduction and Procedural Part :

Setting and Troubleshooting of Compression Machine:

 Handling of Dies :

• Both the internal and external portions of the dies should be checked before taking for the setting.
• Dies should be checked for Die rings & cracks from inside.
• Check for compression point during the last run.
• Dies should be placed in die bore by hand and the driving rod should be used to tamp the die in to die bore.
• Torque wrench should be used to lock the dies.

Handling of punches :

• Punches should be stored in case provided; each punch set should be lubricated using food grade oil before placing in ca
• Punch set trolley should be used for transfer of punch set from storage to compression cubicle.
• Care should be taken to avoid the damage to tip of punches during transport
• Punch set should be polished before setting on compression ma
• Care should be taken to avoid the damage to key on upper punch MOC for key is softer than rest of material

Machine set up :

Following basic set up procedure should be followed during compression machine set up:

1. Check punches and dies before beginning the set up
2. Install the upper and lower cam track
3. Install the dies.
4. Install the upper punches.
5. Install the lower punches.
6. Install the feeders.
7. Set the scraper blade and the knock off plate
8. Set the powder hoppers
9. Set up the vacuum pick up feeds
10. Understand and set the punch entry controls and pre-compression thickness controls.
11. A Discussion of The Proper Setting of The Overload Set Point
12. Rotate the turret and listen to your ma

Check punches and dies before beginning the set up:

• Both the internal and external portions of the dies should be checked before taking for the setting.
• Dies should be checked for Die rings & cracks from inside.
• Check for compression point during the last run.
• Punches should be stored in case provided; each punch set should be lubricated using food grade oil before placing in ca
• Punch set trolley should be used for transfer of punch set from storage to compression cubicle.
• Care should be taken to avoid the damage to tip of punches during storage
• Punch set should be polished before setting on compression machine

Setting of fill cam and ejection cam :

Proper fill cam should be selected based on Compression machine (‘B’ tooling or ‘D’ tooling)

‘D’ tooling		‘B’ tooling
Depth of fill	Recommended fill cam	Depth of fill	Recommended fill cam
0 – ¼”	5/16”	0 – ¼” (0 – 6 mm)	5/16” (8 mm)
¼” – ½”	9/16”	¼” – 7/16” (6.2 – 11 mm)	½” (12 – 14 mm)
½” – 13/16”	13/16”	7/16” – 11/16” (11 – 16 mm)	11/16” (16 mm)

Setting of fill cam and ejection cam : 

• Weight cam should be checked for free travel of punches.
• Proper ejection height should be adjusted by Ejection cam and should be checked by making certain punch tips will push tablet completely out of the die.

Installation of dies :

• Ensure the cleanliness of dies for internal and external portions for any cracks or die rings.
• Place a light amount of lubricant should be on the die barrel.
• Dies should be placed into die alignment ring and should be placed by hand. Then use a die driving rod to tamp the die into place.
• Tamp dies tightly into place after using the die alignment ring.
• Lock the each and every dies into place using torque wrench.
• Dies which fall into die cavity will not align properly with the upper punch.
• Die setting should be always double checked by tapping the bottom of the die upward making certain the die does not move.

Installation of upper punches:

• Ensure the cleanliness of punch’s barrel, tip, and punch bore.
• Punch bore should be checked for absence of wear as this may not allow for proper punch alignment & result in tip damage by hitting of punch tip to die chamfer before finally entering in die.
• Dust top should be placed tip area of upper punches to prevent oil and grit from entering the dies and to prevent die contents from leaving the die as the upper punch enters.
• Upper punch entry should be maintained in range of 1.5 – 6.0 mm. below this increase the risk of capping.

Installation of lower punches:

Ensure that lower punches are properly tightened, as It is important to fully tighten the spring, then back off one quarter turn.

• Note: When installing irregular shaped tooling always twists the punch in the direction of the travel of the turret, making sure the key is solid against the keyway while pressing the die into place.

Installation of feeders :

• Before setting the feeder find the “High spot” on turret and position the feeder on higher spot as feeder set on the lower done the high spot result in friction between feed frame and turret.
• Proper feeler gauge or “go/no go” gauge should be used during installation of feeder.
• Clearance between feeder and turret should be 0.0035” – 0.005”.
• Notice the feeder base is about 3/1000 of an inch higher than the die table. This is normal.
• Installing the feeder on this base gives an a clearance of 2-3/1000” and there is no metal contact.
• Feeder wheels should be checked for absence of wear as it may cause the weight varia
• Using a straight edge is a convenient way to check the feeder base must be installed to make certain that the warp edge to the feeder pan will not allow for metal contact.
• Some feeders also have a “seal” strip to restrict powder from leaving the feeder. This is a contact part.
• After setting ensure the clearance between turret and feeder to avoid the damage to turret.

Set the scraper blade and the take off plate :

• If it is the only part that contact the die table.
• There are four main causes of powder leaking off the feeder & die table.

1. Feeder set wrong.
2. Die table worn with too much run Out.
3. Scraper set up wrong.
4. Interaction of all three factors.

• take off plate should touch to the die table
• Angle of take off plate should be adjusted based on the tablet dimension to avoid the damage to tablet.
• To check the clearance between the knock off plate and turret ordinary paper may be used.

Setting and installation of Powder Hoppers :

• Hopper should be adjusted to minimum height.

Vacuum system installation: 

• Vacuum system should be located & installed

Setting of upper punch entry.

• Check & ensure punch penetration setting as in some presses this is controlled by upper roller pressure & in some presses; this is controlled by link between both rolls.
• Tablets should be compressed below taper in case of taper dies.
• Taper are approximately 3mm deep into the die, when using tapered die punch penetration will be deeper than using standard dies.
• Tablets should not be compressed in taper.

Setting of the overload set point :

• Check & control following situation as compression machine may overload in these situation
• A tablets stick to lower punch & does not eject from die.
• A tablets sticks to upper punch and never leaves prior to the next compression event.
• A press part like scrapper plate, scrape spring, nut or bolt vibrates loose & enters in the dies.
• Chunk of granules enter in the die.

 

 Checks during Compression Process :

Weight control :

• Ensure the cam track is installed as per tablets weight.
• Ensure the tablets press speed with respect to cam track as press at fast speed with wrong fill result in under filling.
• Proper Lubrication of lower cam is requiring to active reproducible tablet weights.
• Ensure the freeness / tightness of lower punches.
• As Compression machine doesn’t weigh the power, uniform particle size and density are the key factors for good weight control

 Hardness:

It is not a set point of machine, it just functions. Factor affecting Hardness,-

• M/s. Speed
• Pre-compression station setting : (Punch entry and Hardness)
• Final compression setting : (Punch entry and Hardness)
• Feeder setting.

 Pre-compression:

• It is second compression station; main function is to remove air from granules to avoid the tablets to get cap.
• Pre compression setting controls the Upper punch entry &Tablet thickness.
• Pre compression is not mandatory for all products.
• Punch penetration should be set to 1.5mm or less.

Friability:

Friability should be checked wherever following changes occurs during compression cycle, as this is the single test for assessing tablet capping

• Increasing speed of press
• Alteration in feeder speed
• Alteration in upper punch entry
• Alteration in tablet thickness
• Alteration in pre-compression setting

 

Problems and Troubleshooting of Compression process:

Capping :

• Tablet compression refers to a reduction in the bulk volume of powder blends as a result of displacement of a
• When external mechanical forces (punches) are applied to a powder blend, there is usually a reduction in volume due to closer packing of the powder particles, and in most cases, this is the main mechanism of initial volume reduction.
• As the load increases and the air (gas) is removed, rearrangement of particles becomes more difficult and further compression leads to particle deformation trapping the ga This is tablet capping.

The nine root causes of capped tablets :

• Excessive quantity of fines.
• Excessive press speed.
• Tooling condition (upper punches only, or sticking punches).
• Compressing too low in the die.
• Feeder speed too fast.
• Pre-compressing.
• Thickness is too thin.
• Bad blend.
• Bad milling producing too many fines.
• Tooling design is bad.

On-line prevention of tablet capping/Troubleshooting of Compression Machine :

Check points for prevention:

• Verify main compression upper punch penetration (No deeper than 2 mm in almost all cases).
• Relax pre-compressing tablet thickness. (Thickness should be at least 2X final tablet thickness). Recheck pre-compression station upper punch penetration (The upper punch penetration should be the same or more shallow than the main compression value. Never deeper.
• Verify by performing a friability test.

 Operating Tips :

• Some Formulas Will Both Pick and Cap
• Beware of DC grade materials and dry blend formulas, they can and will both cap and laminate. In some rare cases there are DC formulas that are very sensitive and will pick if the tablets are too thick and will cap or laminate if the tablets are too thin.
• There are hints you have this situation:
• A change in thickness is achieved only after a significant movement of the thickness control.
• Capping occurs after a slight movement of the thickness control.

Lamination:

• When we compress a ta If on removal of the load the deformation is to a large extent reversible, i.e. it behaves like rubber, then the deformation is said to be elastic. (All solids undergo elastic deformation when subjected to external forces.)
• In other powder blends, an elastic limit is reached, and compressing force above this level results in deformation not immediately reversible on the removal of the applied force. Bulk volume reduction in these cases results from plastic deformation which forces particles into available void spaces, resembling the behavior of molded clay.
• Because plastic deformation is a time dependent process, rapid force application leads to the formation of fewer “new” clean surfaces resulting in weaker or incomplete tablets and “lamination”.

 The Six Causes of Lamination:

• Too many dry granules
• Too many dry fines.
• Not to enough binder to hold granules
• All above combined.
• Compressing tablets to thin having material with characteristic
• Lowe punch damage, sticking or inadequate lubrication

On line prevention of tablet lamination/Troubleshooting of Compression Machine :

• First, make which side gets lamination
• Tablets having no letters/numbers it can be difficult to determine which side has the problem. Verify with the batch record, do not rely on memory.
• Verify the lower punches are free to move and well lubrication

Follow below procedure for online prevention/Troubleshooting of Compression Machine :

Test 1: Increase tablet hardness by 1-3 Kp.

If lamination increases, you are over compressing.

If lamination decreases, but does not go away, you have

too many dry fines or not enough binder or both.

Test 2: Decrease tablet thickness.

If lamination decreases, you are over compressing.

Increases pre-compression and back off main compression. If lamination not go away. Granules are with too many dry fines or  not enough binder or both.

Note: If tablet press with equally sized pressure rolls at both the pre and final Compression stations try this:

Have the press compress the tablet with exactly the same tablet thickness values at both stations. This is essentially a ‘double hit’.

If this works, you actually have a sticking problem, not a lamination problem.

STICKING & PICKING :

Powder sticks to the punches or dies resulting in defective ta This is different than “picking” which is material sticking to letters and numbers.

On-line Prevention of Tablet Sticking & Picking/Troubleshooting of Compression Machine :

• Before press start up: Fine polish your tooling and verify.
• Do not ‘wash” tooling with IPA immediately before installation in the tablet press
• Consider using Pre-pick tooling.
• Consider micro finishing of the tooling.
• During Production: – compress a or two just below or at the overload set point, discard the tablets and review for picking. Or Pull the tooling, repolish and reinstall.
• Try an external lubrication system

Preventing Picking: Types of Tool Coating :

• Electro polishing
• Teflon coating
• Nylon coatings
• Hard coat anodizing
• Nickel plating
• Chrome plating
• Titanium Nitrite
• Aluminium Nitrite
• Zirconium Nitrite
• Microfinish coating
• Chromium Nitrite

Physical Vapor Deposition (PVD) Coating to tool :

• Physical vapor deposition (PVD) forms a mechanical bond between the punch tip and coating and is suitable for punches.
• Common PVD coatings are:
  • Titanium nitride (TiN)
  • Titanium carbonitride (TiCN)
  • Chromium nitride (CrN)
  • Aluminum titanium nitride (AITiN)
• The minimum coating thickness for metal stamping and forming applications should be no less than 4 to 5 micrometers.

 

Spots on Tablets :

• Spots appears on tablets are either due to raw material being compressed or oil from tablets press.
•  On Line Prevention of Spots on Tablets :
• Preventing grey spots, grey means dried lubricant:
  • General: use dust cups./ Replace dust cups.
  • Do not over lubricate the upper punches.
  • Vacuum the tablet press more often.
  • Fines are mixing with the lubrication and falling into the die.
• Preventing dark black spots, black means oil mixing with powder creating grit:
  • Check the granulation for these spots.
  • Check the upper cam track Fines are being trapped in the upper cam track, migrating into the upper punch bores and then dropping Into the die.
• Reduce or eliminate fines:
• Long term: Incorporate a relief on the upper punch while using a dust cup.

Tablet Edge Chipping :

• The tablets periphery chips during exiting the tablet press or during friability testing.
• This is a physical defect caused by physical abuse on a tablet press.

On Line Prevention of Tablet Chipping /Troubleshooting of Compression Machine :

• Check your ejection cam for excessive wear.
• Check your knock off plate for correct installation.
• has it vibrated into a – different position?
• Verify the high point on the press turret.
• Do you know where the high point is? See press set up.
• Review friability results. Is this really a friability problem ?
• May be do more friability tests.
• Reduce the distance/angle between the press table and the drum/bin.
• Is this distance inordinate?