The Finished Part

Glass Bead vs. Crushed Glass Grit

noreply@blogger.com (Steven Schneider) — Thu, 28 Aug 2008 13:02:00 +0000

We get a lot of questions about the difference between Glass Bead and Crushed Glass Grit. Below are some before and after pictures of a copper pipe after blasting with similar grit sizes of both of these materials. [Note: The pictures are not great but you should be able to see some clear differences.]
Welding burns & discoloration on surface

Glass Bead is a round particle that produces a very smooth, satin-like finish. This media can be re-used multiple times and is typically used in a blast cabinet. Crushed Glass Grit is an angular grit that offers very goood strip rates but breaks down very quickly. Crushed Glass Grit is generally used in portable blasting equipment where collection and re-use is difficult.

Glass Bead - Bright, smooth, satin-like finish

Crushed Glass Grit - Lightly etched finish, very short blast time

Beijing Olympics

noreply@blogger.com (Steven Schneider) — Mon, 25 Aug 2008 12:54:00 +0000

Wow! An impressive show by the Chinese with these 2008 Olympics. Many of the controls the government put in place to control pollution (stopping construction, closing factories, significantly reduced traffic) seemed to work - although a couple days of well 'placed' rain also helped.

A couple of random thoughts now that we are beyond these Olympic games:

China spent A LOT of money on these games. While impressive, most of this $$$ came from western countries buying less expensive Chinese goods (one individual purchase at a time) leading, of course, to China's continuing economic growth. Is this really best for our local and global economies?

Construction and factories were shut down across China to reduce horrible pollution for two weeks. Now that the Chinese have seen what a blue sky looks like again, I wonder if there will be any continuation of this environmental policy. If the Chinese return to the pre-games norm, I suspect that pricing and supply pressures on many materials (Aluminum Oxide, Silicon Carbide and Steel among many others) will be back in full force along with the pollution it generates.

London 2012 has a very tough act to follow. I hope that the world has learned important lessons about balancing the environment, global trade policies and individual consumption to springboard our (collective) path towards a better future.

Crushed Glass Grit

noreply@blogger.com (Steven Schneider) — Thu, 21 Aug 2008 14:32:00 +0000

The 'hottest' abrasive blast media right now seems to be Crushed Glass Grit. This media is sourced from recycled glass - mostly bottle (beer) glass. It is generally a mixture of clear, green and brown glass. Crushed Glass Grit has lots of great advantages:

Clean, white-metal finish
No free silica, heavy metals or other contaminants (like in many coal slags)
Angular shape offers quick stripping (similar to silica in hardness)
Cost effective use

Two issues to keep in mind when using Crushed Glass Grit: (1) Media is considered consumable and is not generally re-usable; (2) Source quality can vary dramatically - we use New Age Blast Media.

What experiences and performance have you had with Crushed Glass Grit?

Reducing Freight Costs

noreply@blogger.com (Steven Schneider) — Wed, 13 Aug 2008 15:43:00 +0000

We sure do understand the pain of an unexpectedly high freight bill. With fuel costs being what they are right now, fuel surcharges can add 70% to an already high freight bill!

Here are a few tips to your freight to keep costs to a minimum:

Consolidate orders, if possible (if you purchase 1,000 lbs. twice a month from a vendor, order 2,000 lbs. once).
Large LTL (less than truckload) shipments are sometimes charged at full truckload prices and surcharges. Splitting a large order into multiple shipments can actually reduce the overall cost.
Deliver freight to an occupied commercial address with access to a forklift truck. A residential delivery with a lift gate as well as delivery scheduling and notification can add as much as $400.00 to a freight bill.
Talk to your vendors and freight carriers. They can assist in uncovering other options to avoid spending more than necessary.

Blast Cleaning Steel - Pictures

noreply@blogger.com (Steven Schneider) — Tue, 05 Aug 2008 14:34:00 +0000

I posted some information about using Crushed Glass Grit a few weeks ago to strip/clean steel. Here are some before and after pictures using Coarse Crushed Glass Grit on a cast iron part to remove some moderate to heavy rust. The total blast time was less than one minute and the total surface area is about 1 cubic foot.

Body Jewelry Tumbling

noreply@blogger.com (Steven Schneider) — Mon, 28 Jul 2008 18:08:00 +0000

We received a post a couple of years ago about polishing body jewelry in a vibratory tumbler. While very similar to other jewelry there was a concern about the size of the parts and the threads at the ends. The recommendation was to polish the parts using a Precision Ceramic media to be able to get into the finer areas of the part without damaging the threads. Steel tumbling (while also effective) might roll the thread edges. A simple but effective result.

Polishing Aluminum

noreply@blogger.com (Steven Schneider) — Wed, 16 Jul 2008 14:13:00 +0000

Bringing machined aluminum into a highly polished finish is a multi-step and sometimes challenging process.
The first step is to tumble (vibratory usually works best) the parts in an abrasive media such as a Plastic or Synthetic Media. Using as round a media shape as possible - cones vs triangles - will result in a smoother finish producing a better end result.
The second step is a polishing step using a Ceramic Media. Either an Angle Cut Cylinder or a Precision Ceramic Sphere will produce a smooth surface finish - again rounder is better.
In order to burnish the surface (if necessary), a third step can be to dry tumble the parts with a Walnut Shell Grit possibly treated with a fine abrasive such as jeweler's rouge.
It is important to make sure that the chemical compounds you use will not attack the aluminum. Depending on the final finish required, a small amount of hand polishing may be needed.

Blast Cleaning Steel

noreply@blogger.com (Steven Schneider) — Wed, 09 Jul 2008 15:30:00 +0000

Historically, steel has been blasted using silica sand. For obvious health reasons (potential silicosis hazard), silica is not a safe media to use. Many industrial contractors, municipalities and military facilities are now using Crushed Glass Grit to blast steel.

Crushed Glass Grit will remove paint, dirt, soils and rust leaving a 'white' metal surface. Depending on the grit size used, a micro-finish can be achieved so that the steel can be immediately primed and painted with no further preparation.

Produced from recycled bottle (mostly) glass, Crushed Glass Grit contains no free silica, heavy metals and is approved in many of the most stringent air quality districts. Crushed Glass Grit is also considered a green blasting media since it is 'neutral' to the environment.

July 4th BBQ

noreply@blogger.com (Steven Schneider) — Thu, 03 Jul 2008 11:49:00 +0000

Take a look at your wood deck or concrete or stone patio while you are grilling over the weekend. Does the surface need some attention? A few tips to begin the cleaning and restoration process:

Wood Decks -- Dry abrasive blasting with Corn Cob Grit can strip dirt, soils, stains and coatings without damaging the wood or raising the grain. Avoid harder media such as sand (don't ever blast with silica sand anyway) or glass or coal slag as these will definately etch the wood and can cause damage. The main benefit of dry abrasive blasting versus high pressure water is that the dry surface can be re-sealed immediately - a one weekend project instead of two or three.

Concrete or Stone Patios -- Stripping paint off concrete surfaces requires a more aggressive abrasive such as Crushed Glass Grit. Stone which can be softer than concrete might demand Crushed Glass Grit but Walnut Shell Grit may be a better option since it is not as aggressive and stone is easier to clean (typically no paint or coatings to remove).

Final tip -- Enjoy the BBQ first, then start the work!

Aluminum Oxide - Stabilized?

noreply@blogger.com (Steven Schneider) — Mon, 23 Jun 2008 20:18:00 +0000

A couple of months ago I put a post explaining some of the basics of Aluminum Oxide Grit. What I did not mention was that the ore that is used as the source for Aluminum Oxide is sourced from around the world. While a lot of the crude material is actually refined and processed in the US, it still needs to be shipped around the world.

Increasing crude costs mostly due to increased demand from developing countries (read: China) have combined perfectly with increasing shipping costs and the decreasing US dollar to produce price increases like we have never seen. In some cases, the cost to source, ship, refine and package Aluminum Oxide has doubled in the past couple of years.

Fortunately, it seems that some of the cost pressures are stabilizing so that pricing for Aluminum Oxide may soon fall back into the historical pricing pattern. I only hope that is sooner rather than later.

Soda Blasting

noreply@blogger.com (Steven Schneider) — Mon, 09 Jun 2008 13:36:00 +0000

Soda blasting is a specialty process that is used for applications where surface 'sensitivity' is critical. Soda (actually sodium bicarbonate or baking soda) blast media is a very soft media that can be used for stripping on a variety of surfaces including thin metals, aluminum, fiberglass, wood and glass without causing warping, etching or pitting. Many abrasive blasting media can also be used for these applications but different types may be needed for different applications.

The major reasons that soda blasting is not more popular include the cost of the media itself, the non-recyclability of the media (it can only be used once) and the requirement for specialty blasting equipment.

Baking soda (and anyone with a box in their refrigerator know this) absorbs all kinds of things including moisture very quickly. Super dry air is a necessity for soda blasting. Air driers and chillers also add to the difficulty and cost of soda blasting.

Abrasive Blast Polishing?

noreply@blogger.com (Steven Schneider) — Wed, 28 May 2008 13:24:00 +0000

I wish there was a way to polish metal, plastic and wood surfaces using abrasive blasting. Unfortunately, using abrasive media (no matter how soft or round) just doesn't produce a polished finish. Glass Bead will result in a uniform, satin-like finish on some metals and Steel Shot can 'almost polish' hardened steel surfaces.

So far, we have not identified a media and process to consistently create a high polish using a blasting process - especially on plastics and wood.

Have you had any success in this area?

All-Time High for Steel

noreply@blogger.com (Steven Schneider) — Thu, 01 May 2008 14:49:00 +0000

In a February post I explained the origins of the steel scrap surcharge. Basically, the base price of steel shot and steel grit is fixed but a surcharge is added (and changed each month) to bring the price of steel to current market value.

Well, the demand for steel in both Asia and Eastern Europe continues to grow and much of the scrap is being sent overseas to satisfy this demand. Obviously, increasing demand leads to increased pricing and even product shortages.

The current scrap surcharge is up about 500% in the past 5 years and has nearly doubled in the past six months. In addition, the lead times are continuing to extend for certain sizes and grades. Unfortunately, it does not look like this is going to be a short term problem unless steel manufacturers can figure out a way to make a lot more steel.

We're at an all-time high for steel prices but I fear we will continue to say the same thing many times in the near future.

Matching Nozzle Size and Grit Size

noreply@blogger.com (Steven Schneider) — Fri, 25 Apr 2008 12:28:00 +0000

Question: I would like to know if there is a standard for matching Nozzle opening size to media size. I am just starting out and I am not sure what size media I can use with my sand blaster. The literature on the blaster doesn't say. Can you help?

Response: Generally, the nozzle size you use should be at least 3-4 times the diameter of the grit size.

{If the grit is still getting stuck in the nozzle, try reducing the blasting pressure (psi) and making sure there is no moisture in the system.}

Mass Finishing Basics (Part 4)

noreply@blogger.com (Steven Schneider) — Thu, 10 Apr 2008 15:56:00 +0000

The art of mass finishing really shows itself when trying to select a tumbling media. Media is the material ('stones') that parts are tumbled with in either a vibe or barrel tumbler. The types of media available are as varied as the parts that can be tumbled in a mass finishing process.

Ceramic Media is available in bonds or formulations that range from super aggressive, cutting to non-abrasive polishing. The most popular preformed shapes are triangles, cylinders and variations of these shapes. Ceramic media is typically used with hard metals such as steel. Softer metals such as aluminum can be tumbled with ceramic media but care should be taken so the process is not too aggressive. Precision Media is a high density version for specialty applications.

Plastic Media and Synthetic Media have a lower density and are thus less aggressive than ceramic media. These media are typically used with aluminum, copper, brass and other soft metals. Popular preformed shapes include cones, pyramids and wedges.

Steel Media is used primarily for polishing and burnishing operations in barrel tumblers. Some vibes can be set-up to handle the weight of the steel media which is 3-5 times as heavy as the other preformed shapes.

Other types of tumbling media include Hardwood Media (dry tumbling of wood and some plastic parts), Aluminum Oxide (surface finishing and etching), Walnut Shell (burnishing) and Corn Cob (burnishing) as well as many other specialty media.

Choosing the proper type, size, shape and bond is critical to making sure that the required finishing is achieved. Common problems include excessive media wear, poor and/or inconsistent surface finish, too much (or too little) edge rounding and media 'jamming'.

Wood Stripping

noreply@blogger.com (Steven Schneider) — Fri, 28 Mar 2008 16:14:00 +0000

Question: I’m renovating a house built in 1917 and I would like to remove the years of built up paint off the 6 panel doors and trim that was used in the house. There are 15 doors and probably a 1000 lineal feet of various finish boards. Which Machine and Media should I purchase? Approximately how much media will I need?

Response: Either the KF110DM or the KF65DM will work with the Corn Cob Grit or Walnut Shell Grit. The Walnut Shell Grit will offer a more aggressive stripping action but the surface may require some sanding depending on the surface finish you require. Corn Cob Grit will be more ‘sensitive’ to the wood surface but will not strip as quickly.

The quantity of media required will depend on how aggressive the blasting that is required. Multiple layers of durable paint will demand more media; however, both Corn Cob and Walnut Shell are re-usable. If you are blasting in a clean area you can pick up the media and re-blast it a few times – just be careful to not pick up anything that could be blasted and damage the wood surface.

Motorcyle Parts

noreply@blogger.com (Steven Schneider) — Tue, 25 Mar 2008 12:59:00 +0000

Question: I want to clean /polish an aluminum motorcycle engine. Would walnut shell be the best media for the job? I want a clean, lightly polished look typical of stock bikes.

Response: Walnut Shell Grit will clean the surfaces relatively well but will not have an impact on the surface finish. A Medium-Fine or Fine Glass Bead will clean the metal and leave a satin-like finish on the surface.

Aluminum Oxide

noreply@blogger.com (Steven Schneider) — Mon, 17 Mar 2008 17:19:00 +0000

Aluminum Oxide (a.ka. aluminium oxide, alumina, aloxite, corundum) is generally sourced from bauxite ore. While bauxite is the primary ore for aluminum metal, Aluminum Oxide is extracted using the Bayer Process to remove unwanted impurities.

Aluminum Oxide is a very hard, versatile blasting media that can be used in a variety of applications for removing oxidation and scale off metals to etching stone and glass surfaces. The pure (>99%) White Aluminum Oxide is used when surface non-contamination is critical like when blast cleaning medical parts.

The hardness and large grit sizes available also make Aluminum Oxide an excellent choice for non-skid flooring. Aluminum Oxide is commonly used as an abrasive for sandpaper.

I'll bet you didn't know that precious stones like rubies and sapphires are simply Aluminum Oxide (corundum) crystals contaminated with other metals like chromium, titanium and iron.

Mass Finishing Basics (Part 3)

noreply@blogger.com (Steven Schneider) — Mon, 03 Mar 2008 18:32:00 +0000

Vibratory tumblers come in all different shapes and sizes. Bowl style vibes include both round bowl and oval-bowl shapes. Tub style systems look kind of like bathtubs. In general, vibes are produced in sizes as small as 1-2 gallons up to 150 gallons (and much larger). Both systems force the tumbling media and parts to vibrate and rotate around the vibe.

Tub style vibes force the parts (and media) to vibrate and rotate around the center axis of the tub. This creates a similar sliding and rolling action to a barrel tumbler but adds the additional vibratory energy working against the parts resulting in shorter cycle times. Since tub style vibes can be very long in length and diameter extremely large large parts can be tumbled.

Bowl vibes add circular movement around the bowl in addition to the typical tumbling and vibrating. Since the entire load is moving around the bowl, this system allows the option for a separating screen (either above or below the load) to automatically remove the parts from the media. Unlike tub style systems, bowl vibes can only process parts smaller than the bowl channel width.

Polishing Eyes

noreply@blogger.com (Steven Schneider) — Tue, 26 Feb 2008 14:41:00 +0000

An interesting thread (edited slightly) on the ShopTalk Forum:

Question: We are looking to for a way to polish parts made from a clear urethane casting resin, shore hardness 85D. We currently do all hand polishing and the result is a high glass type polish and looks good.

Response: Urethane is designed to be very resistent to abrasion and does not polish the way most plastics do. Most of the work must be processed in a wet operation with a ceramic or porcelain polishing {Precision Ceramic} media in order to provide enough pressure to abrade the urethane. If the starting finish is rough, the {first step using general purpose} ceramic and abrasive (i.e., pumice) will smoothe out the surface. The "pre-polish" would be done in the porcelain media using a fine Aluminum Oxide powder - 100 to 150 grit. Start the water level very low (30% ) and then after 6hrs, raise the water level to even with the top of the load. Run overnight. The final high polish would be achieved using a dry process with wood pegs and {Microlyte} polishing cream . It may take 6-12 hrs to achieve the final polish.

Why a Steel Scrap Surcharge?

noreply@blogger.com (Steven Schneider) — Wed, 20 Feb 2008 14:07:00 +0000

Steel Grit and Steel Shot primarily use scrap steel as the source raw material. The scrap is melted, the chemistry is modified and then solidified into small particles using a high pressure stream of water. Back in the early 1970's (as well as today) the scrap steel market was very volatile with significant monthly swings in prices. This made long term purchasing difficult for large shot and grit users.

A pricing scheme for steel shot and grit was developed that fixed the base price and added a surcharge to that base based on the ups and downs of the market. The Iron Age Scrap Price Bulletin has been used as the standard for setting the monthly steel scrap surcharge.

In the last 30+ years the pricing scheme has become the accepted standard. As such, the base price of Steel Grit and Steel Shot remains consistent and the applicable steel scrap surcharge is applied at the time of shipment. It's a strange but fair system that gives everyone - suppliers and purchasers - an opportunity to get the best value.

Mass Finishing Basics (Part 2)

noreply@blogger.com (Steven Schneider) — Fri, 15 Feb 2008 20:00:00 +0000

The two types of barrel finishing systems are rotary barrel tumbling and centrifugal barrel tumbling. Both mass finishing techniques use tumbling media, water (usually) and compounds to tumble parts inside a closed barrel. The similarities end there.

Rotary barrel finishing is an abrasive process that involves a sliding and rolling motion of the media/parts load. Filling the barrel 50-60% full allows the upper layer of the load to slide down (due to gravity) as the load is turned-over. Changing the load size as well as the ratio of media to parts to water to compound will create more or less aggressive operations. This ancient mass finishing technique is a highly economical, time-tested technique.

Centrifugal barrel finishing creates more sliding action at higher rates as the individual barrels spin independently of the turret rotation (think of the carnival ride with individual cars that spin while the entire carousel of cars are spinning) . The high centrifugal force created inside the barrel compacts the media/parts load and results in low part to part interaction. These high forces also lead to lower cycle times and very smooth, consistent surfaces finishes.

Getting Aggressive with Tumbling

noreply@blogger.com (Steven Schneider) — Tue, 12 Feb 2008 20:40:00 +0000

Barrel tumbling is a time tested method to deburr, polish and create a desired surface finish. Vibratory tumbling is a new (well...newer) technology that also works great and has replaced barrel tumbling for deburring and surface finishing for lots of reasons. The aggressiveness of a vibe is largely limited by the tumbling media being used.

Welcome back - barrel tumbling. Extremely aggressive processes can be achieved in barrel tumblers. Rough cut, laser cut, parts with lots of slag and scale, heavily rusted parts can be tumbled successfully part-on-part in a barrel tumbler. The weight of each part acting on the others creates an environment in the barrel that will clean these parts in a way that a vibe never could. Adding a grit to the process will add to the cutting action.

Sure, it's a loud process. It can even be a little dirty. But the results speak for themselves.

It's the Economy!

noreply@blogger.com (Steven Schneider) — Fri, 08 Feb 2008 19:03:00 +0000

The economy has been getting a lot of attention as the presidential candidates and Congress argue about the best way to 'fix' it. While all these macro-economics discussions are interesting on a "micro" level we continue to see inflationary pressure on our raw materials.

It seems that every new year brings a new round of price increases from our suppliers (along with a cheery 'Happy New Year'). We are analyzing everything we are doing to minimize the effect for our customers. So far, for most products we have been able to keep any increases to a selective few products.

2008 should end up being an exciting year and we will continue to work hard to do things Right From The Start!

Tumbling with Steel Media

noreply@blogger.com (Steven Schneider) — Tue, 05 Feb 2008 17:17:00 +0000

Polishing all types of metal with steel media is an established procedure for many industries. As the price of steel increases (especially stainless grades), many companies are looking at barrel and vibratory tumbling with carbon steel instead of stainless. The BIG disadvantage of carbon steel is rust. Of course, the big ADVANTAGE is cost.

Keeping carbon steel clean and corrossion-free is critical to getting an acceptable surface finish on the parts. Using the proper chemical compounds is the answer to this problem. Even though acid compounds will return the rusted steel to near original condition, this should be avoided as this can actually make rusting problems worse.

Steel media should first be restored with a cleaner (like Kramco 750) containing sequestrants, detergents and be pH buffered to remove the corrossion and prevent flash rusting. The second step is to treat the shot with a rust inhibitor that will both prevent rust formation and not contaminate the parts {like oil based rust inhibitors}. Simply tumbling the steel media with a non-durable rust inhibitor (like Kramco 510) for a few minutes, draining the solution and then letting it air dry will keep the shot clean and bright even during longer term storage.