Week 16 Assignments - Wildcard Week

Prototype Aluminum Clock Hand Cut on OMAX Waterjet

Waterjet Cut Clock Hand on Prefab Clock Kit

Assignment

The task for this week was to:

Design and produce something with a digital process (incorporating computer aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it. Possibilities include but are not limited to wildcard week examples.

Machine - Waterjet Cutter

For the wildcard week assignment, I chose to explore a new machine, the waterjet cutter. This is a machine taken as an option from the wildcard week examples. In our cohort, Jeremy is experienced with waterjet cutting, and I worked with Jeremy for training and introduction to using the machine. This involved:

Safety training for the waterjet
Basic operational training for the waterjet
Testing design rules for the waterjet
Cutting aluminum on the waterjet

Waterjet Machine Information

The Charlotte Super Fab Lab has a Waterjet Cutter. The specific model is an OMAX GlobalMax 1508 waterjet cutter.

OMAX GlobalMax 1508 Waterjet Cutter at Charlotte Super Fab Lab

The OMAX uses an ultra-high-pressure pump (30K PSI) to generate a stream of water that is then forced through a nozzle to create a cutting stream. The OMAX uses a garnet abrasive material that is mixed into the water stream at the cutting head in order to cut harder materials such as metals.

Garnet abrasive material supply for OMAX Waterjet

Safety Training

I went through ough our OMAX safety training with Jeremy for using the waterjet cutter. The primary safety elements included:

Eye Protection - safety goggles are required for operators and bystanders when the machine is being operated, in order to protect against agregate or material being discarged from the perimeter of the tank.
Safety Panels - clear, removable guard panels must be in place to protect from aggregate / material discharge
Machine Safety Stops - we covered where the emergency stops were on the machine, as well as where the pause buttons are in the operating software

Waterjet Introduction - Setup

As an introduction to waterjet setup and operation, we cut a basic shape (2" x 1" rectangle with a .75" diameter interior hole) out of 1/8" thick aluminum. This also served as a test to characterize waterjet accuracy by comparing the final cut piece to the design dimensions.

Jeremy covered the fundamentals of operating the waterjet with me. In general, Jeremy first went through the operations to demonstrate, and I then followed suit to gain the experience. This included:

Turing on/off all of the subsystems, including machine, computer control, water supply, high pressure pump, and aggregate supply
OMAX Make software basics for machine configuration and operation
Waterjet calibration - moving the head of the machine, homing and zeroing x/y/z axes
OMAX Layout software basics for CAD design / revision and toolpath creation

Once the OMAX systems are turned on, the OMAX Make software on the podium computer provides a control panel for machine settings and operation. This enables manual control of the waterjet gantry and z-axis from the keyboard. Arrow keys are used to control the axes for X (left/right) and Y (up/down). Baseline movement is in gradual movement - holding the shift key enables more rapid movement. For the Z axis, the Page Up /Page Down keys move the axis up/down with gradual movement. The keypad 7 / 1 keys move the z-axis up/down with more rapid movement.

Moving OMAX X,Y,Z Axes with the OMAX Make Keyboard Control

For the introduction / testing activity, the first step was to place the stock material on the cutting table in the water tank. The nozzle was manually moved out of the way, and we positioned a piece of 1/8" aluminium stock in the waterjet, and secured the piece with a clamp.

The next step was to zero the waterjet axes in relation to the stock piece, and we began with the Z axis. The Z axis needs to be positioned at a specific height from the stock material, in order to ensure smooth cutting and to avoid clogging. To position the Z axis, we used a height gauge in order to ensure the correct distance between the nozzle and the material. The nozzle was positioned with reasonable Z axis clearance above the material, and we manually X/Y positioned the waterjet nozzle into the center of the target area of the material for cutting.

The Z axis was lowered until the nozzle was relatively close to the material, but with reasonable clearance for positioning the height gauge. The height gauge was then placed under the nozzle, and the nozzle was slowly lowered until it touched the gauge. The nozzle was then lowered with fine adjustment steps until there was just enough clearance for the height gauge to slide freely underneath.

Zeroing Z Axis Height to Material with Height Gauge

With the nozzle height positioned using the height gauge, the Z axis setting was zeroed in OMAX Make.

Zeroing Z Axis Height in OMAX Make Software

In order to ensure cutting happens in the correct place on the material, the X and Y axes were zeroed. The X and Y axes were positioned so that the design would fit on the stock piece while maximizing the remaining usable material for other use. The gantry was moved to the lower edge of the stock material.

Moving Nozzle X and Y Axes to Edge of the Stock Material

With the nozzle positioned, the X and Y axes were zeroed in OMAX Make.

Zeroing X and Y Axes in OMAX Make Software

Waterjet Introduction - Basic Cut and Testing

With the material in place and the axes set, we created a basic design, both as an introductory metal cut and to test the cutting characteristics of the OMAX.

We used the OMAX Layout software to create a basic rectangular design (2" x 1") with a central hole (.75" diameter). An important design consideration for the waterjet is when parts are smaller than the cutting table grid openings in the OMAX tank. Jeremy had demonstrated an initial design with just the rectangle + hole. As soon as the waterjet had completed the recangle outline cut, the piece fell to the bottom of the tank. OMAX Layout provides a straightforward way to add "tabs" to a design that can hold a part in place during cutting. Once the cut is complete, the part can be bent out of the stock material, and the tab area can be finished / smoothed as part of post processing.

Calibrated Test Piece Design with added Tab on Top

With the tabbed design ready, we generated the toolpath. We then set up set up a cutting job with a quality setting of 1, which is the fastest speed. We ran the cutting job, and the OMAX cut the piece in the aluminum stock. When complete, we removed the piece at the tab, and deburred the edges with the disc sander.

We observed and measured the completed part. We first noted the taper. As the cutting stream passes through the part, it loses energy. This can cause the bottom of the part to be marginally wider than the top of the part. We used calipers to measure the sides of the finished part, noting that the dimensions of the sides were slightly larger than the design (1" side measured at 1.005", 2" side measured at 2.010"). The differences may be due in part to tapering, but important to note as a consideration for future designs.

Waterjet Design & Production - Metal Clock Hand

Having gone through the basics of using the OMAX waterjet, I decided to try creating a prototype design of a clock hand toward the final project. I designed and produced a prototype clock hand in 1/8" aluminum using the OMAX.

The 2D design of the clock hand was created in the Cuttle 2D design tool. It includes a pointed hand shape with internal cutout. I had sourced a typical prefab clock mechanism kit, in order to better understand clockwork design. The clock hand design includes a hole at the base of the hand that is sized to fit the clock mechanism kit.

I exported the design from Cuttle and imported it into the OMAX Layout software for setup.

I added a tab to the bottom of the hand, in order to prevent the piece from falling into the tank during cutting. In that position, the tab actually seemed to be a natural addition to the design, so I kept the tab on the finished piece.

In preparation for cutting, I followed the basic process for positioning the stock material and zeroing the machine axes. I generated the toolpath for the design and set up a cutting job at the fastest speed (quality setting 1). I ran the cutting job, and the OMAX cut the clock hand piece in the aluminum stock.

In-Process Waterjet Cutting Design

When complete, I removed the piece at the tab (keeping the tab), and deburred the edges with the disc sander. The clock hand was attached to the clock mechanism kit alongside standard hands from the kit, in order to get a sense for the design in context.

Waterjet Design & Production - Ceramic Material

As part of our lab learning experience with the waterjet, Jeremy explored the potential for using the OMAX to cut drainage holes in the bottoms of abandoned ceramic mugs for more sustainable use as small planters. To learn more about waterjet use, I followed along with Jeremy in the exercise, and more detail can be found on Jeremy's Wildcard Week page.

Waterjet Drainage Hole Cut in Ceramic Mug

Project Design Files

Application design files for the assignment are: