IMM 3/99

We are a plastic injection molding company having trouble with dirty pinmarks. We have tried several types of lubes and different ways to lube our knockout pins and still have a dirty pin problem coming out onto the part. Most of our material is nylon 6/6. Is there a good dry lube solution out there?

We never had any luck with "blemish-free" lubes. Our solution was to determine when we would be running a light-colored part and schedule the mold for a thorough cleaning before the run. We would clean every part ejection pin and use pipe cleaners in all part ejection pinholes. Although this took a couple of hours, we would then have a virtually defect-free production run. Keep in mind this won't last forever. Our combination of cold molds (50F) and normal humidity in the shop will always leach out contaminate over a period of time.
-R. Webb, Adept Custom Molders, Kokomo, IN, (765) 457-8225.

We mold some white, FDA-approved polypropylene. I had some similar problems with lube contaminating the material via ejector pins. We thoroughly cleaned the core half and installed self-lube ejector pins. The molds run quite frequently. The pins have been installed for about five years, and we still do not have ejector pin flash or a contamination problem.
-J. Lutes, American Plastic Molding, Scottsburg, IN, (812) 752-7000.

This one is easy. Do not lube knockout pins. Remove them, clean all lube, crud, etc. from pins and holes, and dry the pins before replacing them in the mold. Put nothing on the pins; it's not needed, and anything you use will bleed onto the part.
-J. Broughton, American Greetings Corp., Corbin, KY, (606) 528-5851.

The pins should not be lubed at all as long as the mold is constructed properly. The mold should be disassembled after each run and the pins, along with the pinholes, should be cleaned. Also, cool the ejector half if possible. The rising temperature of the mold will cause bleeding.
-D. Harbit, Royce Plastic Molding, Elwood, IN, (765) 552-3972.

Remove your ejector pins from the mold, then place them in an oven at 300F for about 10 minutes. Then, dip the pins in Slick 50 for about 30 seconds. The Teflon will attach itself to the steel. Remove the excess oil, and you will get about 50,000 cycles before you will need to re-dip the pins.
-L. Stires, Sanford/Koh-I-Noor, Bloomsbury, NJ, (908) 479-8234.

A company called Dicronite Dry-Lube Northeast has a process to surface impregante a dry lubricant to metal surfaces. The phone number is (413) 562-5019. I have used this treatment successfully to run molds with no grease on the pins. This should successfully eliminate dirty pinmarks due to lubricant.
-D. Laing, Santin Engineering, Peabody, MA, (978) 535-5511.

We have had great success using Progressive Components' Ultra Pins.
-D. Schwab, Polymer Conversions, Orchard Park, NY, (716) 662-8550.

Try a product called Viscotene produced by the Wynn Oil Co. I have used it successfully for five years. It has the added benefit of lasting three to five times longer than conventional, moly-based lubes.
-K. Gravesen, Coils Inc., Dwight, IL, (815) 584-1145.

If your part is demolding without problems, then your mold release is adequate. However, too much mold release will liquefy and absorb itself into your pin pockets via movement and heat transfer. Try cleaning off the knockout pins with extra clean towels and compressed air. Use your "dry" mold release sparingly. Also, some additional cooling time might help you demold without using a mold release. Stoner provides various mold release and tool cleaning products. Give them a call at (717) 786-0804, and they will help you out with your needs.
-J. Stastny, Tecnico, Anaheim, CA, (714) 632-8938.

Remove the pins from the holes. Degrease all holes with a bottle brush and a safety solvent followed by a metal degreaser. Degrease all pins. Then apply a very thin film of USPI 50 EP grease. It is a PTFE-based, white grease that helps eliminate pin-to-hole wear, a major cause of pinmarks. Upon startup and following a series of cycles, this grease will bleed until all excess is gone. The grease is available from U.S. Petrolon Ind. Inc. at (800) 755-4572.
-S. Hatfield, Accent Plastics, Corona, CA, (909) 273-7779.

Not a week goes by that we don't coat hundreds of ejector pins with WS2, primarily for medical molders where wet lubes cannot be used because of contamination. WS2 is applied at room temperature, so no warpage is experienced, and dimensional change is less than .00002 inch per side, which allows for the pin to fit into its original hole without modification. The dynamic coefficient of friction is .03 (Teflon is .06 to .09, so WS2 is two to three times slicker). Once applied, galling and markoff caused by wet lubes are both eliminated, and under normal operation the life of this economical, NASA-developed coating is about one year. For a no-charge sample on your pins, contact Russell Products at (800) 567-8887 or the sales office at the following number.
-D. Brown, Russell Products Co. Inc., Dayton, OH, (937) 846-1873.

There are two primary causes of pinmarks on parts. The most obvious is the residue from lubricants used on your knockout pins. A popular product used by many toy and medical molders is Zip-Chem Products' ME-2345 EZ Pinlube. This product is a clear lubricant with high film strength, which does not contain silicone and is FDA compliant. It will not carbonize, varnish, or bleed out onto your parts. The product is easy to apply by merely spraying your pins while in the forward position.

Another source of your pinmarks may be the use of a penetrating corrosion preventive or mold protector. A penetrating product can get into your mold, burn, and bleed out through your pins. We would recommend a nonpenetrating mold protector like Zip-Chem's ME-5050NS. This is an easy-to-use, nonpenetrating protectant, which offers the user daily or monthly protection from corrosion and moisture. The product is easy to remove and has a built-in acid neutralizer.
-A. Peabody, Zip-Chem Products, San Jose, CA, (800) 648-2661.

Melting grease from ejector pins is a very common problem that can be overcome by using the right grease product. Super Grease from Slide Products Inc. is a clear, nonyellowing grease that will not freeze, melt, or gum up. Colorless and odorless, Super Grease has good load bearing properties and provides mechanical stability even when sudden temperature changes occur. Super Grease contains no silicones and is approved for use on food machinery. The operating temperature range for Super Grease is -60 to 650F. Super Grease is available as an aerosol, in 14.5-oz tubes that fit a standard grease gun, and 4-oz cans. Free samples are available.
-M. Muth, Slide Products Inc., Wheeling, IL, (800) 323-6433.