3D Printed Mallet Project : Printed in PLA

3D printing is developing many important tools for home and industrial use. Along with specialty tools and attachments, I wanted to see if a home 3D printer could produce one of the simplest and most universal of tools, a working dead blow mallet.

3D printed Mallet
Source: Author

3D Printed Mallet Design

Dead blow mallets are a staple of woodworking shops and garages everywhere. The simple construction and utilitarian use makes it an ideal tool to experiment with 3D printing plastics.  While I could 3D print it in exotic carbon fiber or 3Doms glassfill I realized that many 3D printers do not carry these expensive and exotic filament blends.

So I challenged myself to 3D print a mallet that could be printed with common PLA’s and easily assembled with other tools.

Inspiration

I was inspired to do this project by this from a YouTube video by Jeremy Schmidt , and the mallet he produced in plywood on a CNC mill.

 

Jeremy Schmidt did release the .svg files, which I used to help me draw a 3D printable version of the mallet in AutoCAD 2014. I designed it to be printed in 2 solid pieces instead of the 4 pieces in his version.

In designing my version I did beef up the handle, modeling it after the grip of the geologist rock pick that has taken tons of abuse in the past.

When I was designing the mallet, I incorporated a construction method I learned from my 3D printed spinner fidgets. Some of my early prototype marble fidgets popped apart when they were dropped due to the shear force breaking the glue bond I made between the two halves of the design. To fix this I used some scrap 3 mm filament as a rivet to provide reinforcements across the two parts.

In this design I’ll glue and rivet the two printed halves together.

 

In a  second video on the CNC produced mallet, Jeremy Schmidt points out an issue with gluing multiple layers of plywood together. The BB’s that he used for weight shattered and blew out of the mallet head. In the video Jeremy created a capsule for BB’s with square steel tube stock, and then encapsulated that tube within the mallet head.

I was going to do the same, putting BB’s inside a recycled pill jar I had on hand. But looking at the video I noticed what may have caused the BB blowout.

I saw that when the BB’s hit the bottom of the mallet they

Fender washers inside the mallet to provide weight. Source: Author

placed pressure on all the interior sides, including the weaker glue layers. It seemed like the BB’s were producing a water hammer effect, putting pressure on the inside of the mallet and causing a BB blowout. To avoid this water hammer effect I designed a cavity inside the head to hold a stack of heavy steel fender washers. Using the washers would avoid the lateral movement caused by the BB’s, and create less mess if the mallet fails.

 

Printing this mallet took a couple of tries. I drastically changed the settings for this in Cura 19.12 from any print I have done before. I set it to 4 shells and 25 % infill with a 0.4 mm layer thickness. These large heavy-duty settings produced a print that took 118 g of ColorFabb PLA/PHA and almost 8 hrs of print time. This was a great way to use up a lot of old ugly PLA / PHA filament that was taking up space on my shelf. It may have produced a mallet that looks like a bad cosplay prop, but feels as solid as a real hammer.

When the mallet was finished, it weighed in at 1.2 lbs or 529 g.

I was also worried about nails penetrating between the vertical layers of the mallet. Looking at other dead blows, they tend to have a hard rubber cap over the striking faces. So I knocked out a couple of end caps in NinjaFlex and SemiFlex to cap the face of the mallet.

Instructions

After a quick hardware store run for more 1 ¼ inch fender washers, I started assembling the mallet.

1. Sand and prep the surfaces for super glue. I used a sanding sponge.

   Assembling the 3D printed mallet. Source: Author

2. Ream out the rivet holes and put the 3 mm filament pins in to align the two halves of the mallet.
3. Put in the washers in the cavity, leaving about 2 cm of head space for the washers to move.
4. Glue and clamp shut with bench vise and C-Clamps. Let the assembly cure overnight.
5. Using flat-iron or soldering iron, smooth and fill the seam between the hammer sections. Solder the 3 mm filament pins in place as well.

   Seam between two halves ironed smooth in mallet. Source: Author

6. Sand down or trim any rough edges with a sanding sponge.
7. Glue on the flexible face caps with super glue or contact cement. Let cure.

Testing the Mallet

To test the mallet I wanted to see if it could start a nail. So I tested it by pounding various nails into a dry and seasoned 2 x 4 pine board.

All 3 nails tested sunk into the wood just fine.

There was no damage to the mallet, and expected surface scuffing to the SemiFlex pad. I

Overall I consider the mallet a success. It printed well and is sturdy enough to drive nails into seasoned pine 2 x 4’s.

I will hold off on releasing the .stl file until I do some more field testing. Stay tuned to 3Dprinterchat.com for the files.