Category Archives: laser cut case

Re: Treat your machine/pcb/acrylic/laser shop professionally

Update: 9/25/2010 to http://openpcr.org/2010/07/treat-your-machine-shop-professionally/

Good comment from mo – spread the love around. I want to point out that the relationship with your machine/PCB/acrylic/wood shop can be challenging! It’s important but not necessarily easy!

If you can’t meet in person it’s tougher to build repertoire over email or telephone, no matter how charismatic you are. And though I’m usually close to my email, people in shops are on tools and machines most of the time. A phone call is a lot quicker and more personal, but conversations on the phone often lead to miscommunications and frustration. What’s worked for me is talking on the phone, and then summarizing in a follow-up email immediately afterwards. Other points of friction I’ve found are in file formats (I was in Bangalore, India, bouncing between coffee shops and I just couldn’t get the right program in order) and computer use  (for instance a shop that insists on printed 2D drawings of a nice 3D CAD file you struggled to put together…), and one guy that always returned calls around a week later.

Experience says: lavishly praise shops you come across when everything goes smoothly.

Right now: I’m working with a shop called OharaRP (out of Dayton, Ohio) on a PCB board and they kick ass!

Tito

I hate glue (feat. Nodes)

New cases arrived this week, acrylic and wood!

Nodes rock!

That is, when you design them correctly. Working with birch wood, I added 1 simple node on each of the notches for the lid parts. The parts “snap” together, and glue doesn’t even seem necessary.

With 1/4″ acrylic, I used the exact same sized node as with the birch which didn’t work out so well. Acrylic is a lot less flexible than wood. I ended up just sanding off the nodes on the acrylic parts to get them to fit together correctly. (I’ll read up on what size nodes to use with acrylic, or comments are appreciated!)

This was my first time designing a case and immediately having it made with 2 different materials. The design was for birch, and I attempted to change the design for acrylic which is a good bit thicker. I made the holes for the notches wider which was a good first step. What I skipped was making the parts themselves a bit shorter to accommodate for the thicker material.

One other revision to make is 4 sets of holes/T slots don’t line up perfectly. I’m not sure why they got a bit off (Update: the tooth on the bottom edge was a few mm off, which pushed the holes off), but it’s definitely something to fix. I hacked the birch case to get everything to fit.

Down to business, the T-slot design is sturdy, and assembly is straightforward. With the T-slow and notched teeth, glue will no longer be necessary! I also found that rounded corners on laser cut wood make a big difference in durability. In my experience, sharp corners easily chip, wear down, and start to look less than best. Rounded corners are more durable and can take a bit more wear and tear.

Next up is the important step — when the flat aluminum parts arrive from Ponoko NZ we’ll test out the heated lid.

Both the acrylic and birch look great! Thanks Pololu and Ponoko :)

Inspired by: http://blog.ponoko.com/2008/11/03/how-to-create-better-nodes/

Laser cutting – Acrylic and Wood

This week I designed and sent off requests for new laser cut cases — one wood sheet from Ponoko, and an acrylic sheet from Pololu.

Material: One surprise for me — I made a slightly bigger case, and adding on 1″ to each dimension roughly doubles the material. For instance, take a 4″ square, that’s 16 square inches of material. A 5″ square is 25 inches of material. This can get out of hand pretty quickly!

Speed: On the recommendation of a friend, I browsed onto Pololu.com, which offers custom laser cutting services. Pololu doesn’t have plywood or bamboo in stock, but they do have 1/4″ acrylic and promise a 3 day turnaround time vs Ponoko’s 11-15 day turn time. Of course, I pay extra for the speed but for prototyping it’s well worth it. I placed my Pololu order on Thursday afternoon and it shipped Friday!

Prototyping: Designing laser cut cases sure can be a pain in the butt. I spent all day on July 4th simply designing a bigger OpenPCR case with bolted edges rather than teethed edges. My workflow goes from the overall design in Google Sketchup, adding features like teeth, bolt holes, nodes, and radii. Then importing that into Illustrator, adding additional teeth, and the submitting it to be cut.

This is fine if you’re putting together a one-off design, but for prototyping, changing, and updating designs I certainly could use some better tools. A good friend of mine has the same issues. If you have any suggestions or experience in converting Sketchup designs to Illustrator for Ponoko/laser cutting, let us know!