Idler Weld Rebuild Procedure {0679, 0729, 4150, 4159} Caterpillar

Caterpillar Products

Machines with Grease Lubricated Track with Swage

Machines with Greased Lubricated Track (GLT)

Machines with Positive Pin Retention (PPR) Track

Machines with Positive Pin Retention 2 (PPR2) Track

Machines with Rotating Bushing Track

Machines with Sealed Positive Pin Retention (PPR) Track

Machines with Sealed Track

Machines with Sleeve Bearing Track

Machines with SystemOne Undercarriage

Machines with non-PPR Sealed and Lubricated Track

Introduction

© 2019 Caterpillar All Rights Reserved. This guideline is for the use of Caterpillar dealers only. Unauthorized use of this document or the proprietary processes therein without permission may be violation of intellectual property law. Information contained in this document is considered Caterpillar: Confidential Yellow.

This Undercarriage Reconditioning Bulletin contains the necessary information to allow a dealer to establish a parts reusability program. Reuse and salvage information enables Caterpillar dealers and customers to benefit from cost reductions. Every effort has been made to provide the most current information that is known to Caterpillar. Continuing improvement and advancement of product design might have caused changes to your product which are not included in this publication. This Undercarriage Reconditioning Bulletin must be used with the latest technical information that is available from Caterpillar.

For technical questions when using this document, work with your Dealer technical Communicator (TC).

To report suspected errors, inaccuracies, or suggestions regarding the document, submit a form for feedback in the Service Information System (SIS Web) interface.

Summary

Idler rebuilding is a profitable operation that provides the dealer and the customer a viable rebuild option at a reasonable expense. This rebuild procedure allows for the idler to be resurfaced to the original dimensions and provide for equivalent wear rates as a new idler. The instructions given in this guideline provide the necessary information to evaluate and rebuild an idler. Considerations have been taken to improve rebuild efficiency and increase idler wear life. Necessary tooling is listed throughout the procedure.

References

Reference: Undercarriage Reconditioning Guide, SEBF8599

Reference: Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers".

Reference: Undercarriage Reconditioning Bulletin, SEBF8585, "Disassembly and Assembly Procedures for Idlers with Conventional Duo-Cone Seals".

Reference: Undercarriage Reconditioning Bulletin, SEBF8582, "Disassembly and Assembly Procedures for Idlers with Inverted Duo-Cone Seals".

Reference: Undercarriage Reconditioning Bulletin, SEBF8586, "Removal, Installation, and Conditioning of Idler Bearings and Track Roller Bearings".

Reference: Undercarriage Reconditioning Bulletin, SEBF8509, "Welding Wire and Flux".

Reference: Service Handbook, PEKP9400, "Custom Track Service Handbook".

Safety

Illustration 1	g02139237

Most accidents that involve product operation, maintenance, and repair are caused by failure to observe basic safety rules or precautions. An accident can often be avoided by recognizing potentially hazardous situations before an accident occurs. A person must be alert to potential hazards. This person should also have the necessary training, skills, and tools to perform these functions properly.

This bulletin may contain hazardous steps. A safety alert symbol like the ones below is used to indicate hazard.

Warning messages identify a specific, imminent, latent, hazard that has a reasonable probability of resulting in personal injury or death if the warning is ignored.

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Personal injury or death can result from fumes, gases and ultraviolet rays from the weld arc. Welding can cause fumes, burn skin and produce ultraviolet rays. Keep your head out of the fumes. Use ventilation, exhaust at the arc, or both, to keep fumes and gases from your breathing area. Wear eye, ear and body protection before working. Protect yourself and others; read and understand this warning. Fumes and gases can be dangerous to your health. Ultraviolet rays from the weld arc can injure eyes and burn skin. Electric shock can cause death. Read and understand the manufacturer's instructions and your employer's safety practices. Do not touch live electrical parts. See "American National Standard Z49.1, Safety in Welding and Cutting" published by the American Welding Society. American Welding Society 2501 N.W. 7th Street Miami, Florida 33125 See "OSHA Safety and Health Standards, 29 CFR 1910", available from U.S. Department of Labor. U.S. Department of Labor Washington, D.C. 20210

Canceled Part Numbers and Replaced Part Numbers

This document does not include all canceled part number and replaced part number information. Use NPR on SIS for information about canceled part numbers and replaced part numbers. NPR will provide the current part numbers for replaced parts.

Note: The true center line must be kept on all idler rebuild procedures. All idler width dimensions are based off center line of the idler. Measure from machined retainer surface on hub to establish the true center line of hub.

Tooling and Equipment

Types of Idlers

There are three types of idlers utilized for machines equipped with tracking undercarriage

1. Fabricated

2. Cast

3. Center tread

Illustration 2	g02367577
Fabricated idler

Illustration 3	g02367579
Cast idler

Illustration 4	g02367580
Center tread idler

Same weld procedure and settings can be applied to all three types of idlers. Welder adjustments will be necessary for each idler to allow for variances in idler wear profiles, idler condition, and weld consumables.

Note: The true center line must be kept on all idler rebuild procedures. All idler width dimensions are based off center line of the idler. Measure from machined retainer surface on hub to establish the true center line of hub.

Center Tread Idlers (CTI)

The procedures listed can be used to rebuild center tread idlers. Information critical to the CTI has been added to the following welding procedures.

Illustration 5	g03711895
Center tread idler dimensions (A) Angle (B) Width from Center Line (C) Width from Center Line

CTI dimensions that must be maintained during a rebuild procedure are:

(A) Tread taper - Angle

(B) Width - Outside from Center Line of Idler

(C) Width - Inside from Center Line of Idler

(D) Tread diameter uniformity - not shown

These dimensions are necessary to allow the idler to engage between the track links. The tread diameter uniformity is necessary to ensure that the tractor ride does not vary due to variances in the tread diameter. Refer to Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers" for the necessary dimensions.

Always keep the true center line on all the rebuilt idlers. Center lines of the idlers never change.

Idler Weld Rebuild Procedure

Introduction

The procedure to rebuild idlers is a profitable operation. The idlers can be rebuilt to the original dimension and maintain a wear rate that is equivalent to factory idlers. This reconditioning bulletin provides a proven procedure that will produce quality results for individuals that execute the procedure effectively. Special attention should be given to make sure that the entire procedure is followed and that the correct equipment and weld consumables are used.

Note: Successful idler welding dependents on the operator. The operator should manage the variables of the welding operation.

Variables of the Welding Operation

• Types of idlers

• Idler wear patterns

• Welding adjustments

• Idler measurement and assessment

• Supply of consumables - quantity and quality

• Proper preheat (thermal expansion)

• Proper idler cool-down (thermal contraction)

• Time management (work flow)

• Welder maintenance

Idler Evaluation and Preparation for Weld

Follow the steps below to evaluate and prepare the idler for reuse. Make sure that you identify potential modes of failure before performing work on the idler.

1. Clean the idler for inspection. Use a high-pressure washer or steam system to clean the idler thoroughly. Make sure that all debris has been removed from the idler.

2. Review service information for the idler that is being serviced.

3. Use a needle peen to remove packed material from around the bolt heads.

4. Disassemble idler. Refer to "References" section for the procedure to disassemble the idler being serviced.

5. Evaluate the idler for damage that cannot be repaired. Examine the idler for cracks, spalling, and bent sidewalls (fabricated idlers).
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   Illustration 6	g02367582
   Measuring the wear of the idler using a large caliper.

6. Measure and record the wear of the idler. Use a large caliper to measure the diameter of the idler. The idler wear should be greater than 70% or less than 120 %. Refer to the Service Handbook, PEKP9400, "Custom Track Service Handbook" for the percentage of wear indicated by the dimensional measurement. Idlers that have less than 70% wear should not be rebuilt. Rebuilding idlers that measure above 120% wear can create repair-cracking problems.

   Note: Idlers that have wear that exceeds 110% should be built up to 100% with softer weld wire Lincore 35. This procedure will reduce the amount of stress caused from the idler welding process.

   Note: Idlers that have less than 70% wear can be machined (idler grinder or lathe) to 70% wear. Ideally, the undercarriage system will be managed to avoid this circumstance.

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   Illustration 7	g02367584

7. Drill a 9.53 mm (0.375 inch) hole or larger in fabricated idlers. Mark the hole to indicate that the hole has been made in the idler as shown in the Illustration 7. Drill a hole in fabricated idlers to prevent a possible explosion during preheating or welding.

8. Use a suitable lifting device to lift the idler into the idler welder. Refer to Table 3 for the weight of disassembled idlers.
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   Table 3

   Approximate Weight of Idler Shell
   Model	Fabricated	Cast	Center Tread Idler
   D3 D4	67.9 kg (149.69 lb)	-	60.6 kg (133.59 lb)
   D5	134.6 kg (296.74 lb)	-	89.5 kg (197.31 lb)
   D6	127.5 kg (281lb)	-	126.1 kg (278.01 lb)
   D7	218.2 kg (481.05 lb)	-	188.4 kg (415.35 lb)
   D8	-	312.9 kg (689.82 lb)	216.0 kg (476.19 lb)
   D9	-	367.2 kg (809.54 lb)	-
   D10	-	492.6 kg (1085.99 lb)	-
   D11	-	752.6 kg (1659.19 lb)	-

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   Illustration 8	g02367585
   Removing surface contaminants using a wire brush or an abrasive disc.

9. Remove all surface contaminants from the tread and center flange. Use a wire brush or an abrasive disc to remove surface contaminants.

   Note: Do not allow the debris from the idler to contaminate the weld flux. Typically, surface contaminants are removed while the idler is positioned in the idler welder. The flux recovery tray must be covered to prevent the debris from contaminating the weld flux.

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   Table 4

   Idler Crack Repair Guidelines for Cast and Center Tread Idlers
   Area	Item
   (A), (B), (C), (D)	Repair visible cracks in this area
   (X) to (Y)	Repair visual cracks in this area. Cracks that extend through the rim are repairable
   (G), (H), (J)	Weld repair not permitted within G,H, and J. Weld is permitted 10 mm past each side of radius G and J.

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   Illustration 9	g02367596
   G and J = Radius length + weld permitted 10 mm on each side of radius For other item reference, refer to table 4 (K) 100% wear depth (L) 1/2 of C (M) Tread thickness

10. Inspect the idler for cracks or abnormal wear. Refer to Table 4 and Illustration 9 to determine if the crack is repairable.

11. Machine out the crack with a grinder, carbon arc, or other suitable machining operation.

12. Preheat the idler before welding the crack. Refer to Table 6 in the "Idler Preheat" section.

13. Weld the machined cracks with a mild steel filler wire. Use an E7018 stick electrode or E70T wire electrode. Refer to Table 5 for recommended electrodes.
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    Table 5

    Recommended Electrodes
    Electrode Type	AWS Class	Size
    Stick	E7018	1/8
    GMAW	L-56	0.035
    FCAW	E70T	5/64

14. Grind the weld repair smooth to prepare for the weld build-up.

15. Mount the idler in the idler welder. Make sure that the idler hub will not be damaged during the welding process.

    Note: Current flow from the idler to the cone can arc and cause damage if the idler bore is not clean and clamped securely in the idler welding machine.

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    Illustration 10	g02367597
    (N) Visible stickout 3/8" (P) Distance (1) Flux delivery

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    Illustration 11	g02367598
    Measuring offset

16. Use a level to determine the top dead center (TDC) of the idler or locate the vertical center-line of the idler.

17. Measure distance (P) and position the electrode (wire) 31.7 mm to 38.1 mm (1.25 inch to 1.50 inch) ahead of the top dead center as shown in Illustration 11. This distance is typically referred as “Offset”.
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    Illustration 12	g02367599
    (Q) Stick out distance 31.75 mm (1.250 inch) (2) Welding tip (3) Wire (4) Tread (5) Center flange

18. Position the torch tip 31.7 mm (1.25 inch) above the idler tread. The correct torch tip position will establish the correct stick-out distance. Make a tool that will allow you to check this distance during the welding operation. The stick-out distance will need to be adjusted during the welding operation to compensate for the build-up of weld material.

    Note: The weld deposition rate is related to the amount of wire stick-out (distance between tip and work). As the stick-out is increased, the deposition rate will also increase. Longer stick-out reduces the positional control of the electrode (wire). The electrode may begin to “Whip”.

19. Make sure that there is sufficient amount of weld wire and flux to begin the welding process. The wire and flux should be clean and free of rust, oil, moisture, or other contaminates.

20. Determine the rebuild dimensions for the idler being serviced. Refer to Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers" for the correct rebuild dimensions.

Idler Preheat

Idlers must be preheated to reduce potential stresses that are created during thermal expansion and contraction. The solidification of the weld deposit will create tremendous “hoop” stresses around the circumference of the idler. Preheating the idler reduces the “hoop” stress by expanding the idler and then allowing the idler to contract with the weld deposit.

Preheat of idlers will provide the following benefits:

• Remove moisture, oil, and grease

• Reduces stresses between parent material and weld deposit

Preheat Temperatures

Preheat temperature depends on the following factors:

• Idler size

• Idler type

• Idler rim thickness

Idler Preheat Methods

Illustration 13	g02371377

The method used to preheat idlers will have an impact on the cycle times, quality of process, and safety of process for idler welding.

The following principles should be reviewed when selecting a method to preheat idlers.

• Efficiency - preheating the idlers before mounting the idler in the idler welder can reduce cycle times. This process can be accomplished by fabricating or purchasing an oven to preheat the idler. The oven can preheat the idler during a previous shift or during the welding process of another idler.

• Safety - the use of an open flame increases safety hazards for operators and can damage components on the idler welder. If an open flame is used, special consideration should be given to the types of gas used to heat the idler. Typically, propane or natural gas is the safest and most efficient for this process. Acetylene is not a recommended gas for this process.

• Heat Soak - particular concern should be given to preheating the entire idler. Preheating the rim only is not sufficient. The entire idler must be preheated to specified temperature. The areas that are not preheated properly will act as a heat sink and draw heat form the rim. For example, if a D11 idler rim was preheated to 316 °C (600 °F), the hub could potentially draw 93 °C (200 °F) from the rim before the welding process began.

• Temperature Measurement - Temperature crayons provide a reliable temperature reading. Infrared thermometers may also be used to check various parts of the idler to ensure that the idler is preheated to the specified temperature. Infrared thermometers can be ordered from the Catalog, NENG2500, "Dealer Service Tool Catalog".

Welder Settings

Illustration 14	g02371380
Weld controls that allow voltage and wire feed speed to be adjusted.

The following parameters will need to be set on your welder before a weld is initiated:

• Voltage

• Wire feed speed or Amperage

• Travel speed / Idler rotation speed

Note: Before you begin to make adjustments, determine how your welder controls wire feed speed. The operating amperage is the result of the voltage and wire feed speed. For example, when wire feed speed is increased at a constant voltage, the resulting amperage will go up.

Two types of adjustment are:

1. Adjust the voltage and the wire feed speed - the amperage is the result - not set.

2. Adjust voltage and amperage - as the amperage is increased the wire feed speed is increased - not set.

The consumables (wire and flux) that you are using will dictate specified welding parameters. Table 7 lists the welding consumables that are available from Lincoln Electric. Table 8 contains manufacture recommendations for the Lincoln Electric consumables.

Travel Speed (Idler Rotation Speed)

The travel speed is the rate at which the idler rotates. The operator must adjust the travel speed to reflect the weld settings, consumables, and the location that is being welded on the idler. Table 9 provides a starting point for the different sizes of idlers. Once started, the operator will need to determine if further adjustments are necessary.

Next to current, travel speed has the greatest impact on weld penetration. Reasonably, travel speed can be adjusted to control weld size and penetration. The effects of changing the travel speed are categorized in general patterns.

If the travel speed is increased:

• Power or heat input per unit length of weld is decreased.

• Less filler metal is applied per unit length of weld resulting in a smaller and typically narrow weld bead.

Excessively slow travel speeds produce:

• Convex bead shape that is subject to cracking.

• Excessive arc exposure which is uncomfortable for the operator.

• Large molten pool that flows around the arc, resulting in a rough bead and slag inclusions.

Flux Depth and Width

Illustration 15	g02371378
(6) Flux recovery (7) Contact tube (8) Consumable electrode (9) From flux hopper (10) Granular flux blanket (11) Base metal (12) Arc path (13) Molten weld metal (14) Solidified weld metal (15) Slag

The arrow indicates the direction of travel.

The use of a granular flux is coherent with the welding process “Submerged Arc”. An optimum depth of flux exists for any set of welding conditions. This depth can be established by slowly increasing the flow of flux until the welding arc is submerged and flashing no longer occurs.

Typical results from flux coverage can be categorized in general patterns.

If the granular layer of flux is too deep:

• Produces a weld that appears rope-like.

• Arc is too confined and gases cannot escape.

• Surface of weld becomes distorted irregularly.

If the granular layer of flux is too shallow:

• The arc is not submerged.

• Flashing and spattering occur.

• Results in porous appearance.

Removal of Fused and Unfused Flux

Dust and unnecessary handling of flux can be reduced by removing the unfused flux a short distance 51 mm (2 inch) after the weld zone. Illustration 15 shows the concept of vacuuming the flux after the weld.

Typical Rebuild Order

Rebuild Center Flange Width

Note: Make sure that idler is at the specified preheat temperature. Refer to Table 6.

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Illustration 16	g02369116
Idler profile gauge

1. Use the appropriate idler profile gauge to determine the parts of the idler flange that require build-up.

   Note: Idler profile gauges can be fabricated. Refer to Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers" for the necessary dimensions.

   Note: The idler profile gauge does not measure percent of wear. The diameter must be measured to determine the percent of wear.

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   Illustration 17	g02369117

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   Illustration 18	g02369118
   Cast idler

2. Build up the center flange of the idler based on given center line dimensions. Rotate the idler to an angle that allows the weld to be stepped up the side of the flange. Refer to Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers" for the correct dimensions.

   Note: The true center line must be kept on all idler rebuild procedures. All idler width dimensions are based off center line of the idler. Measure from machined retainer surface on hub to establish the true center line of hub.

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   Illustration 19	g02369119
   Center tread idler in buildup process

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   Illustration 20	g02369120
   Center tread idler build-up completed

3. Complete the build-up of the center flange width. Make sure that you build up both sides according to the reconditioning dimensions.

Rebuild Idler Treads Diameter

Note: Since the CTI only has a center tread, this step is not necessary to rebuild a CTI.

1. Treads that have concave surfaces should first be filled so the surface is level. Use stringer beads to fill the concave tread surfaces.

2. Use both idler welding heads to weld on the treads. The welding should start at the tread edge.

3. Set the step over to allow 1/3 to 1/2 bead overlap.

4. Continue welding until the weld bead ties into the center flange. The last bead will require the operator to monitor the weld head. Manual adjustment may be necessary for correct bead placement.

5. Continue welding and reverse the step over direction without interrupting the weld. Allow the welder to continue the step over toward the outside edge. Make sure that the last bead does not roll over the outside edge. The operator may use a “dam” to control the weld and flux flow. The last bead will require the operator to monitor the weld bead. Manual adjustment may be necessary for correct bead placement.

6. Continue welding until the reconditioning diameter is at the correct dimensions. Refer to Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers" .

Rebuild Idler Center Flange Diameter

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Illustration 21	g02369121
Fabricated idler

1. Use both weld heads to weld the center flange.

2. Finish the build-up of the center flange with one head to avoid interference.

3. Continue welding until the reconditioning diameter. Refer to Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers" for the correct dimensions.

Idler Cool Down

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Illustration 22	g02369122
Insulated modified parts tub, slow cool-down box that will hold a D11 idler.

Note: This parts tub has been modified and insulated to be used as a “Slow Cool-Down” box. Inexpensive and allows the idler to be moved with a fork truck while in the cool down box.

1. Use a grinder to remove all rough edges and weld runs from the edges.

2. Place the idler in a “Slow Cool-Down” box to allow the idler to cool slowly. The idler should remain in the cool down box/compartment until safe to handle or touch with the bare hand. If the cool down box/compartment is properly insulated, the D11 idler will take several days to be cool enough to remove.

   Note: Rapid cool down will negatively impact the success of idler rebuild process.

   Note: Never place two idlers in the same cool down compartment. The idler that is cooler will rapidly draw down the heat of the idler that is hotter.

Idler Welding Cycle Times

Table 10 provides approximate weight of weld metal divided by deposition rate = hours arc times needed to rebuild an idler that measures 100% wear. Table 10 uses recommended consumables and parameters. Times for welding are for normal wear patterns and does not include building up the center flange. Use the times listed in the table 10 to gauge the efficiency of your idler welding process.

Rate 1 Lincore 42-S, 1/8 inch wire, 100 inches per minute, 28 V.

Rate 2 Lincore 42-S, 1/8 inch wire, 125 inches per minute, 29 V.

Idler Bushing/Bearing and Idler Bore Measurement

The weld build-up procedure may cause the idler bore to shrink. Many variables affect this procedure and require that the idler bore or bushing/bearing inside diameters be measured and resized if necessary.

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Illustration 23	g02369123
Determining the shaft-to-bearing clearance using a feeler gauge.

1. Use a feeler gauge, or an adequate measuring tool to determine the shaft-to-bearing clearance. Refer to Table 11 for the acceptable shaft-to-bearing clearance for the idler that is being serviced.
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   Table 11

   Clearance Between the Shaft and the Bearing
   Sales Model	Clearance Minimum / Maximum
   D11N D11R D11T	0.49 mm to 0.61 mm (0.019 inch to 0.024 inch)
   D10N D10R D10T D9N D9R D9T D8L D8N D8R D8T 578 583R 583T 587R 587T D7E D7H D7R 572R	0.44 mm to 0.56 mm (0.017 inch to 0.022 inch)
   D6K	0.13 mm to 0.69 mm (0.005 inch to 0.027 inch)
   D6H D6R D6T 527	0.30 mm to 0.40 mm (0.012 inch to 0.016 inch)
   D6M D6N D5R D5H	0.30 mm to 0.52 mm (0.012 inch to 0.020 inch)
   D5M D5N D4H 561H 561M 561N	0.26 mm to 0.48 mm (0.010 inch to 0.019 inch)

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   Illustration 24	g03711920
   (L) Inside diameter of the bore of the idler (M) Width of idler hub from center line (N) Bearing assembly inside diameter

2. If the measurements are not acceptable the idler bushing/bearing, idler shaft, and idler bore should be evaluated. Refer to Table12 and Table13 for the dimensions of idlers and shafts that have conventional Duo-Cone seals. Refer to Table12 and Table13 for the dimensions of idlers that have inverted Duo-Cone seals.

   Reference: Undercarriage Reconditioning Bulletin, SEBF8571, "Reconditioning Dimensions for Idlers".

   Reference: Undercarriage Reconditioning Bulletin, SEBF8585, "Disassembly and Assembly Procedures for Idlers with Conventional Duo-Cone Seals".

   Reference: Undercarriage Reconditioning Bulletin, SEBF8582, "Disassembly and Assembly Procedures for Idlers with Inverted Duo-Cone Seals".

3. Instructions for honing the bushing/bearings are available in Undercarriage Reconditioning Bulletin, SEBF8586, "Removal, Installation, and Conditioning of Idler Bearings and Track Roller Bearings".

Note: The true center line must be kept on all idler rebuild procedures. All idler width dimensions are based off center line of the idler. Measure from machined retainer surface on hub to establish the true center line of hub.