Introduction: Plane Light
The Plane Light is a lamp celebrating simple materials designed for small batch production.
Blocks of walnut or maple are split in matched halves, with light occupying the space between them. All the parts were designed using Autodesk Inventor HSM and created on computer controlled machines in small batches using Pier 9 Workshop's DMS 5-axis router and their Haas lathe and mill.
This Instructable will briefly cover the entire process of this design, which was first conceived for Christmas presents for my family last holiday season. The challenge was to deliver multiples of a beautiful object - meaning the design had to be simple and efficient - in terms of design time, materials, fabrication, and cost.
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Step 1: The (quick) Concept
This idea here was pretty simple. To use matched pieces of wood with a crack of light shining through the center to make something so simple as a wood box give a magical, warm feeling.
Quickly, I identified design concerns that drove the refinement of the design.
I needed to allow heat to escape the lamp, so I offset the panels of wood and acrylic by 1/16". I needed to fit a lightbulb, light fixture, switch, and wiring... So I went to the hardware store post-haste and purchased all the parts I needed to make six lamps. Fortune favors the bold. Right.
I designed the outer pieces of the lamp to be symmetrical in length and width, proportional to the height by an appealing scale - roughly the golden ratio, of course. The width was determined by stock acrylic that I had left from my first project as an Artist in Residence at Pier 9, which was 4" - so I made it 1/8" small than that on both sides. I tried to maximize the internal space (thinking of heat) without making the walls too thin (0.5") - although I did briefly consider machining the walls so thin that they became translucent - but opted for a simpler, less risky design. I thinned out the walls near the base, to make a larger glow coming from the bottom.
I quickly made a model of the parts in Inventor to mock up the concept.
Step 2: The Complete Design
Once the concept was validated, I took out my trusty calipers and started making measurements. This let me really quickly develop parts around the materials and purchased parts that I was not planning on machining. Giving myself such clear constraints from the beginning helped make the design very fast.
For each part, I imagined the stock material that I would use to make the part, and the minimum number of cuts and part flips that I'd need to make each piece for the lamp. I was cycling quickly through stock available through McMaster-Carr (everyone's favorite), the necessary dimensions for the parts I had purchased, and what tools I would be using to make the cuts. By integrating all these factors into the details of the design, I was able to do the complete design in one pass.
I had to be careful to take into account assembly, heat effects, wiring, bulb replacement, stability, weight, center of gravity, cord entry, and some other random details. One simply does their best to think of everything.
With the design mostly finished, I powered up HSM and started to make toolpaths.
Step 3: CAM
With the parts modeled and dimensioned, I moved into the HSM portion of Inventor to create toolpaths for the various machines.
The brass base and the acrylic center portion were made on the Haas mill.
The base was made in two steps. First I would machine two sides on edge to create a flat edge, and then machine the other sides to the proper dimension. The next step was to mount this square piece in the vice to create the pockets for the light fixture and fixture housing, along with holes for the bolts to fasten it to the light housing and acrylic.
The acrylic portion was also made in two steps (more than two starts to get pretty complicated!). First, it was stood upside down on edge to make a circular pocket to capture the round fixture housing with the appropriate pre-drills for threading, to receive bolts from the base of the lamp. Then it was put face down and the main cavity of the light was hollowed out, along with reference holes to mate onto the wood pieces. **(Change: when I did this a second time, I made the reference holes on the DMS in the same sequence and fixturing setup as the wood block to guarantee that the outside was totally flush after joining. On the first set I made, there were small offset issues that made the outside not totally flush).
The wood pieces were made on the DMS 5-axis router.
The wood was tricky. Since it is a non-homogenous material with grain the behaves in unusual ways, I had to modify my toolpaths. What I ended up doing was drilling holes, then using an endmill to make a very shallow cut of the interior profile, just to create a clean edge to help prevent tear out. This is called a knife-wall in traditional woodworking, and is usually made with a box-cutter before using chisels to shape a joint. Then I hogged out the meat of the area with a larger endmill, leaving a little bit of buffer material to clean up later (about 0.020"). A ball end mill followed this up to leave a nice clean finish in the rounded corners. There was also a slight difference between the front and the back of the lamp, with the backside having a small feature to capture cords, and holes for the cord and switch. These were additional paths made with a long 1/8" flat end mill.
Finally, the fixture housing was made on the Haas lathe, although in fairness it would have been just as easy (just a little more wasteful) to make on the mill. However, to program toolpaths for the lathe (at the time of the project) I had to use Solidworks. This is another modelling program similar to Inventor that HSM was originally designed for. The Autodesk HSM team was still working on the lathe CAM software for Inventor when I made my parts.
The Haas lathe is an awesome machine that can turn parts like a lathe, and also do live axial and radial milling, indexing or rotating as necessary. I used a variety of axial endmills and drills, as well as lathe tools to turn down the outer diameter, bore the inside out, mill the pockets for cord outlets, and drill the holes for threading to the base and allowing the acrylic screws to pass through.
Next I'll walk through setting up each part in a little more detail.
Step 4: Milling the Base
What you're looking at in the photos...
1. Cut the stock to rough dimension on the bandsaw.
2. Reference the machine to the bottom of the vice.
3. Make a reference work coordinate system on the top of the part on the computer.
4. Move to this point in the machine.
5. Call this point G54 origin (user home).
6. Mill face flat, oversized.
7. Use a parallel to square the second edge relative to the first, positioning it against the bottom of the vice and the vice stop, to maintain coordinate systems.
8. Repeat this process for all parts.
9. Repeat on the second faces of all parts on the second pair of rough sides, this time to dimension. Now, a square is not necessary, since there are reference surfaces to sit in the vice.
10. With parts milled square, mount in vice with a parallel (new Z home height) and perform the milling and drilling operations from CAM.
The next couple steps will detail the other parts. I'll just be plugging in the same kinds of info...
Step 5: Milling the Acrylic
1. Cut stock to proper outer dimensions.
2. Put into vice at user home position, bottom facing up.
3. Machine the contours for the fixture housing, and pre-drill for tapping later (the CNC roll-taps can't reach).
4. Repeat for all parts.
5. Mill a reference notch on a piece of scrap material to use as the user home for the next operations.
6. Position the piece on the user home position.
7. Mill the main pockets.
8. Repeat for all parts.
**I will do this differently next time... It would be smarter to do all operations in the vise - strap clamps are hard to use! But of course, you can't clamp down on the part from the side once it is finished, so I need to change the order of operations.
Next time, I would mill out the area in the center for the light, and then flip it onto the edge so the bottom was showing to cut the contour for the fixture housing and drill. Seems so obvious in retrospect!
Step 6: Prepping Wood for DMS
I bought wood that was large enough to match the two halves of the lamp across the end grain. But I also wanted to match the set to each other, since I was giving the original set to my family for Christmas.
First I jointed two edges of the wood, before planing it to clean up another face. This left just one rough edge, which I cleaned on the tablesaw. Everything was oversize at this point. I used the tablesaw at max height to divide the two halves of the lamp, and then used the bandsaw to finish the cut. This is a little cheat compared to resawing a large board on the bandsaw, but our tends to have a pretty gnarly tilt to it, so I opted for the wider kerf (cut width) of the tablesaw in exchange for ease. I then planed the two halves down to my target dimension for thickness that I wanted on the DMS.
Once this was set, I marked the place I wanted to cut the other lamps from, and ripped two lengths of the board equal. Then I cross cut the dimensions I needed for the width of the main piece for the DMS.
To match widths perfectly, I cut the acrylic for the previous step without changing the saw settings as I was cutting the wood.
Step 7: Cutting the Wood on the DMS
With the wood properly matched, marked, and cut size:
1. Reference part on vise stop at user home.
2. Use light cuts to create an edge to prevent tear out.
3. Clear out the major volume with a large, flat end mill, leaving a little extra material to clean later for a nice finish.
4. Finish the part with a ball end mill to leave nice corners.
5. Drill the reference holes.
Step 8: Turning Parts on the CNC Lathe
The Haas lathe is quite a little monster. It was axial and radial milling/drilling turrets, which make it in some ways like a 4-axis milling machine. I didn't take full advantage of these capabilities with the parts I made for this project (check out my rocking chair to see that!). These parts were a fun project for the lathe, even though they could have been made just as easily on the Haas mill. But using the lathe minimized wasted material, which is nice.
You can see some process photos of the stages I took on the first pass, but I quickly modified my order of operations to ease strain on the 1/8" endmill that is cutting the slots in the face (for the cords for the light). By using a big endmill to pocket the center out, I cleared the way for the endmill to release chips on each side of its path. This reduces heat and load by a lot!
The operations are mostly vertical milling steps turned on their sides, until the last two where I used a lathe tool to simply clean up the outside edge, and a parting tool to cut my piece to dimension, with no flip required (like I would have needed on the mill).
1. Bore out center.
2. Drill holes.
3. Machine grooves for cords.
4. Turn down outside diamater.
5. Face part.
6. Use a parting tool to remove the part from the stock material.
7.Repeat! Yay CNC.
Step 9: Putting the Pieces Together
With all the parts complete, I tapped the last holes that need threads and set to work.
First, I wanted to assemble one lamp complete to make sure everything was working right. This started with the base, fixture, and fixture housing. Note the tiny 6-32 machine screw that's holding the fixture to the base. Then I wired it up, and pressed the lamp together. I needed to use 1/16" sheet metal to space the parts appropriately away from one another, which is a feature I'm changing in the next version of the design - making it so the parts press full to the bottom.
With everything wired up, it worked like a charm, so I set after the others to repeat the assembly.
Step 10: Fini!
Thanks to the awesome tools at Pier 9 and some aggressive design constraints, this project took 38 hours from start to finish for all six lamps. It's pretty amazing to see how CNC can be used to make simple things - let alone all the crazy complexity it can support as well.
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