How I Got Lean by Eating Twenty Pounds of Sawdust

I was recently talking with a friend who is a fellow lean practitioner. He is in need of a new Hijunka box for the pull system at his facility. We built his current one out of corrugated plastic and duct tape. Is there anything duct tape can’t do?

A Hijunka box is a production leveling tool used in lean companies. The box is divided into rows for part numbers, and columns for pitch times. Kanban cards are placed in each slot and provide the mix of parts to be produced each time pitch. The Kanban cards are distributed evenly across the pitches as to smooth or level the work load on the production cell.

After 6 months of use it's starting to loose its shape and luster. The quote to have a new Hijunka box built was two thousand dollars! I thought, "Hey I can make that!" My wood shop in the garage has not been in use lately. My friend emailed me the drawings and I asked my daughter if she'd like to spend time in the shop with me. There is no greater gift a father can provide to his daughter than teaching her how to build Lean tools.

We chose 4X8 sheets of MDF. They don't fit in the back of my Avalanche without cracking the mid gate open. The boards are heavy so I decided to cut them using the box of the truck as my saw horse. Using a skill saw and guide fence, my daughter, and friend James helped me move the fence after every cut. I sliced the boards in the 7.5” strips that we needed. They were much lighter to handle(PDCA #1). I thought I was smart. Then I got in the truck to pull it forward out of the garage at the end of the first night. There was dust everywhere, and this stuff sticks to any surface it lands on.

The next morning I got up and went to the shop and started more cutting. I cut all the strips to width and length. I now have 207 little dividers 4” by 7.5”, 6 boards that needed 23 ¼” detos to be cut into both sides and 6 more that needed detos on one side. All the detos on all the parts need to line up so that the dividers line up during assembly.

I set up a jig to start cutting. The first board comes out and... none of the cuts lined up!! My jig has to much play and is not accurate enough to keep the tolerance stack from messing this process up. (PDCA #2). I needed a new plan.

Standing staring at my saw, I see my wife Donna coming around the corner of the garage on her way to the store. She breaks out in laughter. I looked down and realized I am covered in dust from head to toe. My daughter, hearing the laughter, sticks her head in to the garage from the door to the kitchen. "Wow that is a lot of dust!" she said as she closed the door and returned to watching her tablet. Teenagers.

My next plan was to mark each board were the dedo cuts were to be. Then I'd make a guide that lined up with the blade edges. I cut the first board on both sides and the cuts line up (PDCA #3). I cut the second board and they line up (PDCA#4). I started getting excited! I start cutting the rest of the boards. The dust covered me from head to toe. It was inches deep under the saw and all over the shop.

It was time to clean up. I started at the top of the equipment and worked my way down. I swept the dust into a pile using a small snow shovel to pick up the pile and put it in the trash bag. The bag was heavy, probably close to twenty pounds. I've never enjoyed creating dust so much.

It was time to assembly my labour of love. It was time to check how well my cutting and layout skills worked (PDCA #5). I went away on business for a few days and the shop needed to be swept up again as all the dust had resettled. I started the assembly and only needed to recut one board (PDCA#6).

The dry test fitting went well so I got out the glue (PDCA#7). I let the glue set over night and this morning I realized that it is backwards. Too late to fix it. I glued the back on and flipped it over. Then started fitting in the dividers.

Got finished and loaded it into the truck, and off to my friends factory to deliver.

The guys were thrilled to see the Hijunka box. The General Manager came out of his meeting to inspect my creation. He asked for a second one! I have learned so much making this one. I am sure the next will be better because continuous improvement is the name of the game.

I am so happy when I think about building this Hijunka box for the team. It's a pleasure to be a part of their journey. I can't wait to help them get their Pull System in place and running well. They are the only one of my teams using this system. I'm so proud of them.

Paul Hill

The Lean Geek

#LeanManufacturing #LoiadLeveling #Woodworking #Hijunka #Kanban