I have worked with an Epilog laser engraver for the last couple years at work and recently purchased a manual rotary engraver for home use. As powerful and versatile as the Epilog is, it cannot engrave into metal objects like challenge coins.
Once I got proficient at the New Hermes manual engraver, I started working on projects like door signs, hallway signs, and house numbers for neighbors, my wife's office, and local businesses. I am planning on starting my own engraving business.
I was asked if I could engrave a friend's name into a copper pipe he was using for a project. Normally, the curved surface of a cylinder is not possible to engrave due to a plate that sets the depth of the cut. The plate would prevent the cutter from reaching over the curve and only engrave on the middle surface, cutting off the top and bottom of the letters.
Step 1: Research
I took to the web trying to find a solution without spending the $4000 on a machine lathe with rotary attachment. I only found 1 prospective idea and no one had actually made the device in the above picture, just a concept picture and paragraph describing how it should function on practicalmachinist.com.
Step 2: Design
I started this like all other things I work on. Using a stubby pencil and trying to envision the finished item and how the parts work together. I was not enthused about the use of strap to wrap around the object to be engraved and originally drew my plan to have a gear mechanism to turn the cylinder. I soon realized that the gear would need to be the same size as the cylinder to not distort the engraving. My solution is to have removable wheels with sized inner wheels to match the cylinder diameter and turn the cylinder at a 1:1 ratio and not distort.
Step 3: Design for Laser Cutting
Since I am used to working in Corel Draw, I used that for the design. all the similar parts are identical so they can be interchanged and rotated.
The size markings are raster engraved at speed 65, 85% power and the outlines are hairline sized, vector cut at speed 40, 100% power, 2500 Mhz.
included are My Corel File and PDF export. The PDF can be imported and converted to any Laser cutter software.
Step 4: Parts List
1/8th inch Plywood 12X24 inches- 2 each
1/4x20 1 inch bolts with nuts - 8 each
garden twine - 1 roll
1/4x20 4 inch bolt - 2 each
Spring, 1/4 inch ID x 1 1/2 inch long - 2 each
rubber stopper 1 inch long - 2 each
locking ring, 1/4 inch ID - 2 each
epoxy, 5 minute - 3 tubes
drawer slides, 16 inch - 1 set
Basic Hand tools
Patience - lots
Step 5: Vector Cut
After measuring the New Hermes machine, I finalized my design in Corel Draw and vector cut the outlines on the Epilog at work.
Step 6: Base Plate
The cylinder adapter will be held in the machine by the normal clamps as seen in the first picture above. base plate has four towers to hold the cord between the two pieces of wood screwed together. I cut an extra piece with 7/16th hexagons to hold the nuts securely and not need three hands for assembly. the final pieces on the base plate were two drawers slides from Lowes, cut to match the length of the plate.
Step 7: Moving Platform
The main moving platform is assembled and the cylinder holding pieces added.
To hold the cylinder, I have a 1/4 by 4 inch bolt with a locking ring through the side walls( 2 spaced 1 inch apart to assist with keeping bolts straight) then a spring and rubber stopper drilled and screwed onto the bolt threads. The locking ring helps adjust the offset to the cord and adjust for the length of the cylinder.
The springs apply pressure to the cylinder and hold it in place with the rubber stoppers.
Step 8: Sized Wheels
I raster engraved the size of the inner wheel onto the outside so they were easy to identify and glued the wheels together. The hex on the inside fits the end of the bolts and turns the cylinder by the cord attached to the towers on the base plate.
I only made sized wheels from 1/2 to 1 inch, but a cylinder up to 3 inch diameter is able to fit, I just need to make more sized pulleys.
Step 9: Fully Assembled
I started to drill and bolt the base plate, drawer slides and platform, but many alignment issues kept coming up. I reverted to 5 minute epoxy, aligned and clamped until it dried.
The second and third pictures show the full range of motion from front to rear.
Step 10: Attach the Cord
I used garden string for the wheel to turn the cylinder. It is knotted and bolted at one end, then wound around the sized wheel and knotted and bolted at the other end.
The cord must go over the top of the sized wheel first or the cylinder will turn backwards and your image will be engraved upside down.
Step 11: Installed in Machine
Lay the base plate on the machine and tighten the clamp to hold tightly. the oval in the top of the moving platform fits the depth adjustment ring.
The oval allows the cutter head to travel left and right, forward and back movement pulls against the cord on each side, turn the sized wheel and ultimately rotating the cylinder under the cutter head.
Step 12: Ready to Try!!
I placed a piece of copper tubing into the device and set the lettering and font for my friend that inspired this project.
Step 13: Results
OK, its not up to the quality I would like.
I have identified several issues to fix and work on before I start engraving expensive items:
1. The bolts need locked in on one side and only be adjustable on one side.
2. The two cords either need to be combined to work together or be very meticulous about pulling tight equal pressure on both of them.
3. The rubber stoppers need to be concave to hold the piece centered, if I pushed too hard, the cylinder slid out of the bottom.
4. I will need to make more sized pulleys for cylinders up to 3 inches.
I think this is a pretty good result for a weekend project and the first run of a device I could not find ever being built before.