Mold Maintenance Program
All Molders should have some form of mold maintenance program. Regular mold maintenance can help your mold to last longer, to run with less interruptions, and will save you time, money, and frustration in the long run. The amount and frequency of maintenance is determined by several factors: (Mold Material) Aluminum or soft tools will suffer wear and tear in a shorter period of time than tools made of conventional tool steel. (Part material) Plastic materials that have fillers are especially abrasive and will tend to wash away the mold steel after thousands of cycles. Also plastic with a high melt temperature causes more wear than those with low melt temperatures. Higher melt temperatures expose the mold to more heat and enhance material wear. Some materials give off excessive of residue or even corrosive gasses requiring more regular mold cleaning. (Mold Complexity) Molds with intricate mechanisms or parts requiring unusually high tolerances will require more maintenance than a simple open & shut mold, making a low tolerance part. Slides, lifters, moving cores, hydraulic and mechanical systems, hot runners, complex ejector systems or mechanisms with delicate components all add to the maintenance required. (Abuse) Lastly, molds can be abused by excessive clamp pressures, high injection pressures, over-packing/flashing the part, jerking the mold open and closed, not lubricating the appropriate components, multiple ejection, crashing the mold closed or closing up on partially ejected parts are all sure to cause excess wear and tear on your mold.
The 1st kind of mold maintenance you can perform is to reduce in-house tool abuse.
Have a clean operation using well maintained machines and have the right tools
Do NOT use hard tools (screw drivers, hammers, punches, knives on ANY molding surface, parting, or shutoff surface. (We recommend having "soft" tooling like rubber mallets, punches and pliers made from plastic, copper, or brass on hand to avoid damaging the mold)
Use soft or treated water in cooling systems. Blow out or drain the tool when it is pulled from the machine.
Avoid excessive clamp pressures, high injection pressures, and over-packing/flashing the mold.
Don't operate the press in such a way that the mold is rapidly jerked open and closed.
Lubricate the appropriate components
Take great care not to crash the mold closed or close up on partially ejected parts.
Seal the work area and mold storage area from outside environment.
We recommend several different levels of care/maintenance:
Preventative: Every day, and every time the mold is pulled from production or put back into production
Inspection: Every 20,000 cycles (or every 10 days of production)
Maintenance: Every 100,000 cycles (or every 10 production runs)
Major Maintenance: Every 250,000 cycles (or half the anticipated life time volume)
Simple Preventive Maintenance greatly improves the life of your mold. At the end of every shift while the mold is still in the press:
The parting surfaces, core, and cavity should be gently cleaned with a mild, clean solvent and soft, clean towels to remove any buildup from vented gases, greases, and other resins that accumulate. Pay special attention to the parting surfaces. This clean and check procedure should not take more that 10 minutes
Each time the mold is removed from the press you should perform the same type of cleaning plus some additional procedures.
Before the mold is removed from the press the mold should be returned to room temperature - you do not want condensation to form on the mold and cause rust.
All water lines should be drained and blown free of all residual water to avoid build up of rust due to standing water. It is critical that no water be trapped inside mold.
The parting surfaces, core, and cavity should be gently cleaned with a mild, clean solvent and soft, clean towels to remove any residual dirt and grime.
The ejector system should be moved fully forward, then spray both mold halves with light rust preventive lubricant (like WD-40). Retract ejector system and close the mold.
Check and assure all bolts, plates, etc. are in place and tight.
Bag the last shot as an example of the typical quality of this run and store these parts with the mold.
When the mold is being removed from storage and readied for a production run, open the mold and once again clean the parting surfaces, core, and cavity with clean solvent and soft, clean towels. This removes the mold preservative and any remaining dust or particles. This is also a good time to lightly grease the guide pins, the ejection system, and any lifters or slides.
CAUTION: Highly polished mold surfaces should NOT be wiped with a towel. Instead spray these surfaces with solvent and blow off with clean, filtered, compressed air to remove the majority of dirt and residue, then clean with mild, clean solvent and clean facial tissue or cotton balls. Be very careful with polished surfaces, dust or dirt on your fingers, on your tissues (or cotton balls), or in your air lines could potentially damage the surfaces.
Remember, preventative maintenance should be done every time the mold goes into the press to run AND every time it comes out of the press. Inspection is to note small problems and have them scheduled for repairs. This kind of maintenance should be performed by a lead operator or an experienced person in your tool room after about 20,000 cycles, after 10 production days, or at the end of a production run, whichever comes first.
Inspect the tool and look for minor damage or if any "touchup" work is required. Any missing components or blocked off cavities should be noted and attended to. A few samples from the blocked cavity should be retained for the mold maker to make repairs.
The mold should be washed all over with mild, clean solvent to remove the varnish and build up from the molding process.
The vents should be checked for depth around the cavity face.
Bent, worn or broken ejector pins should be noted and the mold should be removed from production and the pins replaced.
Note ANY concerns that you may want have looked into further at the next scheduled Level 3 maintenance.
This level of maintenance should only be performed by skilled Moldmakers.
All plates are separated and their faces cleaned. CAUTION: Highly polished mold surfaces should NOT be wiped with a towel. Instead spray these surfaces with solvent and blow off with clean, filtered, compressed air to remove the majority of dirt and residue, then clean with mild, clean solvent and clean facial tissue or cotton balls. Be very careful with polished surfaces, dust or dirt on your fingers, on your tissues (or cotton balls), or in your air lines could potentially damage the surface.
ALL components are checked for wear. Any excessive wear is noted and a determination is made to repair, replace or continue to use.
Any cavity detail area with dings, dents or other signs of wear or abuse should be considered critical and should be carefully analyzed before any other replacements or repairs proceed.
All moving parts are to be lubricated. Use lubricant sparingly on all moving parts which make contact with plastic parts.
Vents should be checked for depth, width and land and a determination made if repair is needed. Maintaining good venting prevents fill problems, excessive fill pressures, material "burning", etc. They should also be checked for corrosion and vent burns to see if additional venting may be required.
"O" rings, seals and gaskets should be checked for integrity. A list of the required seals as well as one complete replacement set should be kept on hand.
All water lines are to be pressure tested for leaks and for flow capacity. Water lines that have built up scale and are restricted should be pressure cleaned with a descaling agent and if necessary redrilled
The ejector system should be examined for proper alignment. If the ejector pin holes seem "sloppy" or have become egg shaped it must be determined if they could simply be replaced with oversize pins or if they should be drilled and reamed to the next larger size and the existing pins replaced with the next larger size pins.
Guided Ejection bushing should be checked for wear and any broken return springs should be replaced
Determine if Re-plating or Resurfacing (as a result of the material eroding the mold surface) is necessary
Determine if Replacement/Re-sizing of gates or gate inserts, new runner blocks etc. are necessary.
Replace all springs after 50,000 cycles.
Major maintenance should only be performed by skilled Moldmakers and it should be done when triggered either by the mold fulfilling the required number of cycles for maintenance, or by excessive wear or damage to the tool. Before maintenance begins, there should be at least 2 of the most recent, complete shots (Parts, sprues and runners) from each cavity delivered with the tooling for examination. It is also very helpful if an earlier shot, that represents "good" parts, is available for study.
All components determined and authorized to be replaced should be removed and new components constructed and installed in accordance to the original designs if previously certified spare components are not available.
Worn leader pins, bushings and all bearing moving surfaces (gibs, wear plates, wedge blocks, etc.) should be checked for wear and replaced/repaired as required.
All return springs in the ejector plate should be replaced with new springs to avoid fatigue.
All water lines should be flushed with descaling agent to remove scale build up.
All "O" rings, internal plugs, seals and gaskets should be replaced.
Plates and mold cavity surfaces should be checked for parallel and ground flat if required.
Mold cavity surfaces should be cleaned and polished as required to the original surface requirements.
Any dings, dents, or scratches should be worked out until the surface is fully in compliance to the original print specifications.
The cavity surface is to be inspected for wear or erosion of plating or texturing. When determined necessary, the cavity surfaces are to be stripped and re-plated, or the texture is to be polished off and then new texture applied.
All components not meeting the part print's original specifications (to be noted by the molders QC department) should be repaired/replaced as required
All components that have been plated should be stripped and re-plated where required. All components that have had special surface treatments for corrosion resistance, lubricity, hardness and the like should be retreated to insure the original intent of the tool.
All moving components should be checked for ease of movement (ejector box, slides, lifters, etc.). Adjustments should be made as required.
For tools requiring high production, the cavities should be removed and stress relieved to remove work hardening and material embrittlement. The entire mold/cavity set must be re-inspected and made as "like-new" as possible.
The mold base is to be inspected for cracks, work hardening, corrosion, etc. If the mold base was plated or painted for corrosion resistance, the coating is to be stripped, the base cleaned and the coating reapplied. The tool should be re-stamped indicating when the tool was rebuilt.
Suggested tools available for proper tool maintenance:
Assembly table, should be able to handle a minimum of 5,000 lbs.
(2) Heat-treated parallels/rails 36" x 1" x 1" for molds to slide on.
(2) Pry bars (Aluminum, or Brass)
Rubber or hard plastic mallet and a light weight machinists hammer (Ball Peen).
(2) Hex wrenches sets (an extension pipe is also handy)
Cleaning tank, with clean cleaning solvent.
Compressed Air, filtered, with standard shop air pressure.
A set of polishing stones (fine), to remove burrs or scratches on mold inserts. Be careful to protect the cavity surface.
Medium bench stone, to remove burrs or scratches on mold plates.
File, to remover burrs or hobbed corners and edges on mold base.
Set of soft aluminum or brass pins, to use as punches, to remove ejector pins, to remove plastic material left in sprue bushing, etc.
Ratchet wrench with 7/16 and 9/16 deep sockets for removing water line fittings and Teflon tape.
Containers for storing all loose parts.
All-purpose Grease (minimum temperature 500 degree F)
Duct tape: Used to protect all critical corners and edges on cavities and cores. Tape should also be used on other components like ejector pins, ejector sleeves, slides, and lift cores to protect edges. Use tape wherever there is a sensitive area on tool which can be easily damaged. Be diligent to protect ALL sharp edges!
Although we recommend ALL of the above maintenance, at the very least, eliminate mold abuse and perform preventative maintenance and you will noticeably improve mold life!