Polished vs. Over-Polished and Time Saved vs. Time Wasted

Polishing Pointers: This article reviews some tips to saving polishing time and increasing profit for the shop owner.

Ask any apprentice polisher what the most important thing about his job is and he will say "Putting on a great, high gloss polish." Ask any veteran and he will say, "Making a profit for the shop."

The veteran is right. Does this mean that the veteran doesn't care about doing a great job? Of course not! The veteran cares more about his craft than most people will ever know. So what's the difference in thinking between the veteran and the apprentice? The veteran knows the difference between time saved and time wasted. Not only has he learned how to put on a great high gloss polish, he also has learned the art of using polishing to make a profit.

There are many places in a polish that can increase your time savings. The following are some tips to finding these places while saving polishing time and increasing profit for the shop owner without risking the reliability, quality or performance of the tool.

Rating the Importance of Areas

If I owned this tool what areas would be important to me and what areas only need to function?

A polish is rarely required to be perfect everywhere on the surface and in all of the areas - even automotive forward lighting only needs to be optically polished in the clear lens area. The sidewalls of a clear lens only need to "look good," which is nowhere near an optic polish in terms of time spent. Some headlights have "serrations" beginning from the edge of the clear lens area that radiate outward down the sidewalls and go all the way around the lens to diffuse the light. Putting a glossy shine right on top of the tool marks, which cut those serrations, has been acceptable to some of the largest forward lighting companies in the country. By asking themselves, "If I owned this tool what parts would be important to me?" veterans can often reap great time savings for the shop owners accurately and with only a minimum of touch-ups.

Note: Yellow turn signals on vehicles have no federal requirements for distance, only the clear and red lenses do. To "gloss" over tool marks in yellow turn signal pillow optics is acceptable for many automotive lighting companies!

Forgiveness of the Material

What type of material is going to be run in this tool?

Die Cast
Die cast material is extremely unforgiving. Even small amounts of EDM on the molding surfaces can cause a build-up of material called soldering. This build-up continues to grow with each shot and eventually - in extreme circumstances - can tear the part in half, which is not uncommon in die cast shops. Therefore, the polisher has little choice but to do a thorough job when removing EDM for die cast material.

High-impact Styrene
High-impact styrene is not a very forgiving plastic material; in fact, it can be considered very unforgiving because it easily highlights scratches by creating long drag marks in the parts - especially in clear and black colors. Generally, marks in white and yellow do not show up as much, but still should be avoided.

Glass-filled Nylon
Glass-filled nylon is without a doubt the most forgiving plastic for two reasons:

  1. All nylon is self-lubricating. This is why it is used in so many applications that must stand up to wear. Take advantage of the properties of the material.
  2. Filling nylon with glass tends to create a finish on the part so rough that nothing shows. The more glass that is added to the nylon, the rougher the finish and the less it requires polishing - because nothing will show anyway. Anyone who gets a glass-filled nylon job can keep the money quoted for polishing or return it to the customer - it's the shop owner's choice.

Soft Plastics and Rubber
Generally speaking, taking advantage of the material's natural properties while polishing boils down to one simple rule: The stiffer the material, the less forgiving it will be. The softer (more elastic) the material, the more forgiving it will be.

With materials such as die cast and high-impact styrene, which are the stiffest and the least forgiving, and soft plastics and rubber, which are the most forgiving, the veteran polisher can take advantage of the material's natural properties to maximize the shop's profits without risking tool quality or reliability.

Mold Construction

What advantages does the construction of the mold offer me?

ABS Material in a Side-Action Mold
ABS is not necessarily a very flexible or forgiving plastic, but when used in a side-action tool where both sides of the cavity are slides and the center cores remain stationary on the back half, (knock-out half) ABS material becomes surprisingly forgiving. However, this is due mostly to the construction of the tool and not to the plastic itself. The side actions are going to pull; the plastic won't stop that. The center core is holding the part in place, so the only real place to polish an ABS job (or any plastic material) in this situation is in any side-action ribs, but only to the point where they won't leave drag marks in the plastic and to the cores as necessary for ejection. Bear in mind that if the core surfaces are hidden from view and the knock-outs are sufficient, you may not need to polish these cores at all.

Another example of how mold design can help save time in polishing is a core for a plastic riding mower hood which has several bosses - two to three inches deep, each one supported by four strengthening ribs all burned in by EDM with a fairly good finish. Each boss has a core pin to create a center screw hole and a sleeve knock-out for ejection at the bottom of each boss.

Question
How much polishing needs to be done to make these bosses run on the first shot?
Answer
None. By adding up the draft on the boss and ribs and subtracting the roughness of the EDM divided by the "forgiveness" of the warm plastic and multiplied by the effectiveness of the sleeve knock-out, the final equation clearly concludes that no polishing is needed to make this part of the job run perfectly on the first shot. The customer is happy he received his parts on the delivery date and the shop is happy that it was able to maximize its time savings.

Color

What color(s) will the job be run in?

Many repair jobs have come in with the steel terribly damaged, but surprisingly the damage that the steel may suggest does not show in the plastic part. This explains the first rule of time savings, "The tools are talking to us everyday, but are you listening?" Any veteran polisher who gets a repair job in at 2:30 p.m. on a Friday that the customer requires back by 5:00 p.m. knows the first thing to look at is what's showing up bad in the part, not what's wrong with the steel!

To fix everything that is wrong with the steel may be a major overhaul - including welding and reburning - but to only fix what looks bad in the plastic part could get the job back to the customer and running by 5:00 p.m. as the customer requested. This veteran knows how to use polishing to help the customer maximize his profit.

  • Clear plastic is not always as unforgiving as people may think.
  • Translucent (semi-clear) tends to be more forgiving than clear - mostly because it is harder to see through. Generally, translucent plastics don't require as good a finish as do the dark colors. They also offer the veteran a good opportunity to save time.
  • If a part is going to be molded in white - and especially if the finish is only around a 320 stone - hardly anything will show up in the part. White is always a very forgiving color with which to work and of which to take advantage.
  • Yellow and green are almost as forgiving as white.
  • Red, dark blue and black are the least forgiving of the colors.

Generally, the rule when taking advantage of plastic colors is: The lighter the color, the more forgiving it will be. The darker the color, the less forgiving it will be - white being the most forgiving and black being the least forgiving. Clear can go either way - depending primarily upon the softness of the material.

Heat

Finally, even the temperature of the plastic and the speed of production at which the molding machine will be set can help the polisher save time. Generally, the warmer the temperature of the plastic parts, the softer and more forgiving the parts will be, the more easily they will eject and the less polish that will be required.

Quality

The customer is the only person who can define what quality is and every customer defines it differently. However, most customers only want two things from a polisher:

  1. They demand that the job run perfectly; and,
  2. If it's an appearance job, they want a professional appearance.

The easiest way for the veteran to satisfy the customer's quality requirements is to look at parts he is already producing and copy the quality level for level in all of the different areas of the part. This will ensure that the veteran comes out on top every time with a satisfied customer and a profitable job for the shop owner.

Conclusion

There are many areas on every job that can increase your profit and time savings and below are three secrets to achieving this success:

  1. The polisher must ask himself, "If I owned this tool what details would be important to me and which details would only need to function?" This question alone will add tremendous time savings to any job. Smart shop owners may even require their toolmakers and designers to begin to ask themselves this same question. This is proper time management.
  2. The veteran will always ask himself what help he can count on from the properties of the tool and the materials being run. A true veteran keeps all of his past experiences at his fingertips and is ready to apply them to every new project.
  3. Every time a veteran gets his hands on a part that has come out of a "banged-up" mold, he will examine it to learn what the tool is really capable of and then will find out what the customer is accepting as quality. Veterans know that by looking at parts running from a "banged-up" mold, they will learn the secrets to increasing profit and time savings.

 

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