To engrave or NOT to engrave? STAINLESS STEEL

Copyright © 2006 by Davis Multimedia, Int'l. All Rights Reserved.
As Printed in October 2006, Volume 32, No. 4 of The Engravers Journal
 
 
  Figure 1: We’ve clamped this switch plate into the corner with the clamp that came with the engraver then we used an additional plate to make sure it doesn’t move during the cut.  


     Along time ago, in the early days of G.L.G. ART Custom Engraving, I decided stainless steel engraving and paint filling was not my cup of tea. These things were just too difficult to do. Then, through conversations with my customers, I learned that other engravers also thought this was too difficult to do. However, because of the demand for color filled stainless steel engraving, eventually the light went off, or it should be said “went on” and the words of JFK, “We choose to do them… not because they are easy, but because they are hard” came to mind. Engraving stainless steel and paint filling is no moon shot, but it is one of the more challenging jobs around the shop.
     In the business world I’ve been taught that there are niche markets and also that supply and demand dictates prices and profits. Translated another way, if you’re willing to do difficult things and are in tune with their market value, you can make a reasonable profit for your efforts. I realized this and invested time and money to learn and equip my shop to do and promote these tasks. Our Yellow Pages ad lists the materials we engrave and includes stainless steel, aluminum, brass and plastic, in that order. The most difficult is first on the list indicating to potential customers our comfort level in dealing with this material.

Figure 2A: We’ve created an automatic liquid coolant recirculating system with a Rubbermaid storage container, an aquarium pump and some tubing.

Figure 2B: Here you see the coolant delivery tube coming in from the back and going down the spindle to flood the stainless steel surface.


     A manufacturer of elevator control panels dropped into our shop one day and said he would bring hundreds of stainless steel “call station” panels for engraving if I would commit the resources to do a job of this magnitude. A long discussion ensued and he was very technologically helpful in starting us down this road. Additionally, all of the panels would need to be paint filled after we engraved them. The learning curve began and those tips and experiences are what this article is all about.
     Some of the “must-dos” when engraving stainless steel are: always use a sharp cutter and have a good mechanical grip on your material. In my early days, I didn’t have a cutter grinder to resharpen my cutters. Every day I had to ship 10 cutters to Antares for re-sharpening. We had 50 cutters in the rotation and spent a lot of money on shipping, as well as sharpening services. Believe me when I say that once a cutter is dull or chipped, you can’t engrave another letter with it and get a good result. It didn’t take long to decide to buy the sharpening grinder and learn to do my sharpening in-house. The added advantage of having in-house sharpening capabilities for all of my other jobs also became invaluable. We’ve used solid carbide and high speed steel cutters. More recently we switched to the Bruce Diamond EH cutter, which has a longer life. In our experience, the carbide cutters do a nice job, but when they fail, the tips chip and break off. This sudden failure immediately causes unacceptable engraving. The high speed steel cutters wear down over time but remain relatively sharp while they are wearing. This means the quality of the engraving will lessen, but it will not be abrupt. The EH cutter can wear away but still remains sharp although it will chip under extreme loads. It is, however, the best cutter I’ve used.

 
Figure 3: Using a Scotch-Brite pad to buff the surface eliminates depth nose-related shadows and burrs around the mouth of characters. Always clean in the direction of the finish grain on the material.  

     To give you an idea of cutter life, the switch plate job shown (Fig. 1) had thirty-seven plates. Each plate had the words “SLEEP LIGHT” engraved on it. That is ten characters per plate for a total of three hundred seventy characters. We used two cutters to complete this job. Nineteen plates were engraved with the first cutter. That’s 190 characters. We probably could have done a few more, but knowing the first cutter was not going to come close to finishing the job, the decision to replace it mid job made good sense.
     Holding the steel object firmly is imperative. Use whatever clamping device that comes with your engraver and then use more of your own if necessary (Fig. 1). I’ve read many articles over the years and talked to salesmen about spindle choices for engraving stainless steel or other hard materials and they always recommend using a collet spindle. This is a spindle where the cutter is gripped at the bottom close to the nose cone by a locking collet. This goes along with the idea of holding the material firmly. Rigid is always better. Now having said this, I’ll tell you I’ve engraved somewhere in the neighborhood of 100,000 pieces of stainless steel and have never used a collet spindle. All of our spindles are the standard top loading spindles. The spindle bearings wear out faster when engraving plastic and, over time, the fluid we run on the Vision machine also plays havoc with the bearings. We just accept these realities and get our spindles reconditioned whenever they need it. A spare spindle is kept on hand so there’s no down time due to shipping spindles back and forth to the repair shop.

Figure 4A: When adding additional engraving to a pre-engraved piece, you can place tape on the blank plate and do a trial run. Figure 4B: Here’s the pre-formatted plate partially engraved.

     Another thing we do is lubricate the stainless steel surface while it’s being cut. In our shop a Vision Phoenix 1212 machine is dedicated to stainless steel engraving. (Fig. 2A & 2B) This machine has been modified to incorporate a lubrication system. We have our machine on a table with a 5° back to front tilt. We keep a 12" x 18" x 5" deep Rubbermaid storage container on a shelf below the engraving table, with a Powerhead 301 submersible aquarium pump in the container with a clear aquarium airline tubing attached to it. The tubing is routed out the back and up to the engraving spindle. It’s guided down along the spindle by a Plexiglas bracket. During the cut Tri-Cool Synthetic Based Premium Metalworking Coolant is pumped continuously on the stainless steel. The solenoid switch that came with the engraver and is normally used to run a chip collecting vacuum is now used to turn the pump on and off as the engraver starts and stops. The fluid runs off the front of the table and back into the Rubbermaid container which forms a recirculating system. We do the vast majority of our stainless steel engraving on this machine. However, some special jobs are done on our Gravograph IS7000. This machine doesn’t have a coolant system. We use Tap Magic cutting fluid for these jobs. We dab the fluid onto the specific engraving area before cutting and then wipe it off with a paper towel after completion.
     When engraving stainless steel and other hard materials, the cutter rpm is set to maximum, and the vertical (plunge) speed and x-y speeds are reduced. Generally we run our machines at the lowest speeds available when engraving stainless steel. Brass and aluminum are run at medium speeds. Sometimes if a “clean-up” pass is required, the speed is increased because only a very small amount of material is being removed as the cutter passes over letters which have already been engraved.


Figure 5A: Here’s a close up of the finished plate with the paint filling. Figure 5B: The finished paint-filled switch plate.

     Another technique we use to achieve good quality cutting is careful font selection. We prefer a font that traces each letter forwards and then backwards without lifting off the surface. This gives a better result than engraving the same letter twice in the same direction. We actually created our own font for the Vision machine. If you have the capability of using TrueType fonts, ABlock is a font which traces forward and back. I don’t know if any engraving machine fonts offer this, but you can check with your machine manufacturer. We get better results when using this kind of font.
     When engraving an object for subsequent paint filling you should maintain a known and consistent depth. We engrave most stainless to a depth of 0.006" unless the customer has a specific requirement for some other depth. We like this depth because it’s deep enough to paint fill easily but not so deep that it slows down the cut.
     The most common way of regulating the depth is by using a depth nose regulator and allowing the depth nose cone to ride on the material. Sometimes this may cause shadowing or scratching on the surface, but it’s a lot better than trying to maintain uniform depth without a nose! Some of the stainless steel we engrave, such as the switch plate covers in Figure 1 are engraved with the nose riding over the stainless steel surface. To fix this, we use a Scotch-Brite abrasive pad to buff the switch plate surface. Stroke the pad in the same direction as the finish grain on the material and most of the marks will disappear (Fig. 3). Bear in mind these are industrial plates and should look good, but are not works of art.

Figure 6A: Here’s the switch plate with the chips still in the engraved grooves. Figure 6B: And the switch plate after cleaning.

     In the case where no shadow or scuffing is allowed at all, we apply Laser’s Edge to the surface before we begin engraving. This tape is very tough and is three mils thick and allows the nose to ride on the tape as it protects the metal’s surface. We’ve used this method on polished stainless steel and polished brass and the integrity of the polished finish has been maintained. Another use for the tape is demonstrated in Figures 4A & 4B. Here we’re engraving data onto a stainless steel plate which has a standard format of pre-engraved information with blank areas for additional data. If you look closely you’ll see a line of data that needs to be added which was not originally on the pre-engraved plate. In order to check alignment we placed tape on the blank plate and set the depth of the cut to cut .001 inches. Then we engraved the added data onto the tape without going through the tape. Don’t forget to do your alignment checking and proofreading. You can make small adjustments before doing the final engraving. For the final engraving, set the depth nose to the desired depth remembering to add three mils for the tape’s thickness.
     Well over 95% of the stainless steel we engrave requires paint filling. The examples shown in Figures 5A & 5B are the paint filled engravings shown earlier in Figures 1 and 4B. Your engraving must have smooth edges if you want to achieve good results when paint filling. Earlier we showed you how a Scotch-Brite pad was used to remove depth-nose related shadows. At the same time, it also removed minute burrs on the edges of the engraved letters. You’ll also need to clean all dirt, fluid and filings out of the engraving before you begin painting. Figure 6A shows the engraving before the cleaning and Figure 6B shows it after cleaning.


 

Figure 7A (left): Here’s Kathy using a syringe to paint fill the plate.

Figure 7B (right): This close-up gives you a better feel of how to do the syringe painting.

 

     A future article will deal extensively with paint filling, but for now, only paint filling the stainless steel examples shown here will be addressed. We prefer an oil-based enamel paint. “RUST-OLEUM protective enamel, oil-based” or “ACE Indoor/Outdoor RUST STOP for metal substrates only” are two brands we find suitable. In this example we used ACE Gloss Black. We apply the paint into the grooves of the engraving (Fig. 7A and 7B) using a 3ml 21g 11/2" long syringe. These are common medical syringes with the tip ground off, (Fig. 8A & 8B). The paint slops over a little bit and that’s fine. We set aside the freshly painted plates for about 40 minutes to let the paint start to set.
     As the paint starts drying, you’ll see that some of the slopped over paint shrinks back into the engraving. The rest of the paint adheres to the plate’s surface. We use a common white multifold paper towel to clean the excess paint off the surface. Then, using an artist’s paint brush, we dab mineral spirits onto the towel until it’s saturated. Let the towel dry for a few seconds so that it’s not excessively wet. Then gently brush the towel across the engraving and remove the paint from the surface (Fig. 9). You’ll notice that some streaking will occur on the plate, but don’t be too aggressive.
     Let the plates set for another 10 to 15 minutes and then repeat the procedure. The second wiping should remove all the minor streaks. Allow the plates to dry for 24 hours and then clean them with Favor furnisher polish. This last step makes sure any residue from the whole process has been removed and will give it a final touch of quality.

Figure 8A: Here are two syringes, one as it comes from the store and the other with the tip ground off for our paint filling needs. Figure 8B: And here’s a close-up of Fig. 8A.

     Throughout the course of this article very specific products and processes have been mentioned. These are the results of testing many readily available products, such as other kinds of cutters, tape, paint or furniture polish. These are the things we have found that work for us. You may already achieve great results by other methods you’ve learned over the years by trial and error just as we have. If so, that’s good and maybe you would like to share your experiences with EJ. If you’re new to engraving and paint filling stainless steel, these techniques work, but do require some practice for you to become comfortable and confident using them.
     In any case, engraving and paint filling stainless steel can be rewarding. The absolute minimum commitment you must make is to have a supply of sharp cutters. After that, you can fool around quite a bit. Some of the reward is monetary because, as I said earlier, stainless engraving is not always trouble-free and a lot of shops steer clear of it. Those who do it charge a premium. However, some of the reward is just plain fun in knowing you have accomplished something the less hearty have feared to brave.

 
Figure 9: Kathy uses a white paper towel to make the first cleaning pass on the switch plate.  

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