Acrylic Duck Calls

Acrylic Duck Calls

Above is an other good example of the results that can be obtained with dry barrel tumbling using Hardwood Media and the Finishing Creams. The part directly out of the milling is on the left and the final result is on the right.

There are a number of other pictures with brief descriptions of the process used located at these links:

Polishing Molded Acrylic
Polishing Machined Acrylic
Polishing Colorless Acrylic
Acrylic Button Polishing
Acrylic Knife Handles

Wood Parts Tumbling vs Hand Sanding

Hand sanding wood parts can be a tedious and labor intensive process. The ability to smooth the surface, remove cutting marks and round edges on a large quantity of parts can same time and money.

The part pictured above needed to be sanded down prior to the application of a stain and coating. The part on the right shows the sharp edges and some flashing after the initial cutting of the part. A two step barrel tumbling  process was used to achieve the end result on the left.

Step 1 involved using a Hardwood Peg Media and relatively coarse White Aluminum Oxide Grit. This produced the edge rounding and major 'sanding' of the part.

Step 2 used a similar Peg Media along with a much finer grade of White Aluminum Oxide Grit to result in a smoother, sanded finish. If necessary, subsequent steps with even finer grades of Grit or a quick hand sanding to the final required surface finish can be used. Barrel tumbling the parts in this dry process can eliminate most if not all of the hand sanding often done.

Selecting Dry Tumbling Grit

Polishing or burnishing soft metal (brass, copper, aluminum, etc.) parts with Corn Cob Grit in either a barrel or vibratory tumbler is a popular process. Selecting the proper grit size for small parts or parts with complex geometry can be a real challenge.

The initial testing used for this part (only portion of part shown) used the same medium grit size as is used for larger, less complex parts also being tumbled by the customer. Due to the size of the many slots, holes and grooves in this part, this medium grit size media got stuck in many areas making the cleaning process timely and expensive. There are two options.

Using a larger grit size to prevent the media from getting stuck in the first place will address the problem and still provide the required burnishing action. Of course, as the media wears and breaks down, there is an increasing risk of media getting stuck.

Using a very fine grit will prevent the problem completely. Unfortunately, finer media sizes (i.e., lighter particles) can sometimes not provide the force/work necessary to achieve the desired surface finish. In addition, finer media can 'pack' into the interior areas of the part - like the inside diameter of the part pictured - making the media removal just as difficult.

There is no right answer to this problem. Balancing the required surface finish with the effort (time, labor, etc.) to achieve that finish will determine the appropriate process for each situation.

Dry Tumbling with Corn Cob Grit

Stamped, cut, machined and otherwise processed parts often contain cutting oils and lubricants and need to be cleaned. These parts also have burrs and sharp edges that may need to removed.

The steel parts pictured on the left are dirty and have light burrs that need to be removed. A typical process would simply demand a mass finishing, tumbling process with a Ceramic Media to degrease the parts and remove the burrs in a wet process. The challenge with these parts is the shape - long, flat parts. In a wet process these parts will stick together to form 'sandwiches' and will not be cleaned and will resist deburring.

The solution is to dry tumble the parts with Corn Cob Grit. The Corn Cob Grit media will remove and absorb the soils (note clean, brighter parts on right). In a barrel tumbler, with a high ratio of parts to media, the part-on-part tumbling action will remove the burrs. The Corn Cob Grit can be separated from the parts efficiently with a simple wire mesh screen. The dry tumbling process also eliminates the need to dry the parts so they are immediately ready for any further processing.

Fiberglass Deflashing - Alternative

Removing the flash off various types of molded parts (see last post) can be done in a wet or try process. Vibratory tumbling with a Plastic or Ceramic media in a wet process can be a quick and easy method to achieve the desired results. After the deflashing step, the parts will generally need to be rinsed and dried.

A traditional dry tumbling process involves the use of Hardwood media that have been treated with an appropriate cream compound. The selection of this compound depends on the needed aggressiveness and required surface finish. The challenge with these compounds isthat sometimes the cream can transfer from the media and become deposited in holes, slots or corners of the part. This then requires cleaning prior to further processing of the part.

An alternative to using creams is a similar previously described process for dry tumbling of wood parts. Depending on the type of part and the amount of flashing that needs to be removed, simply tumbling the parts with Hardwood media and an abrasive grit such as White Aluminum Oxide will provide excellent results with only a light dust on the parts. Because the abrasive material is not 'attached' to the media, a barrel tumbler is typically a much better process than vibratory tumbling.