Reason for use:
Repair worn bearing seat without recoating the print roller with new rubber
EQUIPMENT
Metallisation Mark 61 Flamespray System
MATERIALS
Metallisation 99E Molybdenum (Mo)
Exhibits excellent adhesion to ferrous substrates. The spraying of molybdenum using the Metallisation Flamespray Equipment gives the unique ability to produce a range of coatings between 250 and 800 HV.
METHOD
Cleaning
(A) Remove bearings from roller ends
(B) Degrease by solvent vapour process if equipment available
(C) Inspect for cracking and longitudinal distortion
Pre-Machining
(A) Rough turn or grind diameter being sprayed to a depth of 0.25mm (0.010″) giving a parallel work surface
Note: On this type of application, 99E Molybdenum will only require a minimum thickness coating as it has excellent adhesion to ferrous substrates when applied by the Flamespray Process and the ability to be ground to a feather edge.
Cleaning
(A) Degrease by solvent vapour process if available
Preparation
(A) Mask all machined surfaces adjacent to area requiring treatment with heavy duty masking tape
(B) Thoroughly inspect for contamination prior to blasting
(C) Thoroughly blast with clean no. 30-36 grade aluminium oxide grit
(D) Ensure that area to be treated is thoroughly blasted.
Application of Sprayed Coating
Masking
(A) Apply Sprayshield masking fluid, using a small paint brush to all areas adjacent to the area being sprayed (small amounts of masking fluid on areas to be sprayed can be removed with emery cloth)
(B) Check thoroughly area to be sprayed for contamination
(C) IMPORTANT: Area to be sprayed should not come into contact with chains, rope slings, hands or any other form of contamination. Delays between blasting and spraying should not exceed 20 minutes.
Spraying
Spraying should be as soon as possible after preparation and before any visible sign of deterioration occurs.
The roller should be mounted in a lathe chuck and rotated at a surface speed of not less than 18 metres/minute (60ft per minute).
Note: If rubber cover is in good condition and to be left intact during the spraying operation, it is essential that roller temperature is kept as low as possible during spraying and should not exceed 85°C.
Bonding
A deposit of Metallisation Molybdenum (99E) Wire is applied to a deposit thickness of 75μm-100μm (0.003”-0.004”) at a range of 75mm (3”). The spraystream should be at 90° to the surface being coated and traversed by hand to give an even coating.
Main Deposit
Continue to spray the main deposit of 99E using the same parameters as the bond coat but increase spray range to 100mm-150mm (4”- 6”). Complete the spraying of the main deposit traversing the spray head to give a uniform coating over the bearing seat.
Using pre-set callipers, check final deposit thickness including grinding allowance. i.e. Finish ground dimension plus 0.375mm-0.5mm (0.015”-0.020”)
Spraying Parameters Metallisation Mark 61
Acetylene Pressure 1.03 bar 15 psi
Oxygen Pressure 1.9 bar 30 psi
Air Pressure 4.5 bar 65 psi
Flowmeter Point Settings
Gas 5.5
Oxygen 2.25
Demasking
(A) Remove all masking tape.
(B) Remove all overspray taking care to prevent coating damage
(C) Remove all traces of Sprayshield with solvent
Finishing
(A) Grinding wheel type n° 46 grit blue V grade
(B) Wet grind to final diameter taking light cuts using feed and speed in accordance with grinding machine manufacturer’s instructions
Inspection
(A) Check dimensions
(B) Check for cracks, defects in sprayed coating, i.e. large pores or protrusions and loose particles.
Finish Cleaning
(A) Clean to remove any traces of grinding abrasive and loose particles
(B) Wash with petroleum spirit/paraffin
(C) Dry the surfaces with clean, disposable cloths or paper towel
(D) Final inspection prior to refitting bearings
REFERENCE TECHNICAL BULLETIN N°S :- 2.2.4 Metallisation 99E Molybdenum
