Laser Cutting

Hand-bent curved acrylic housing for Sherline

Posted by Josef

IMG_0216.JPGI was recently working with our Sherline desktop CNC mill and got fed up with the ancient PC Sherline provided with the unit. I decided to upgrade the rig myself and quickly located a usable and fairly modern PC. Using the linuxCNC live image, I was able to get the system up and running fairly quickly, but now needed to deal with how to drive the mill’s stepper motors. Sherline provides a stepper motor driver assembly that is housed within the decaying PC tower I so desperately wanted to upgrade from, so I gutted the tower and excised the driver board with the 24V power supply they were using to power it. The stepper motor driver uses a parallel port and since those can’t be found on a modern PC, I had to locate a PCI card that would work. Luckily, a local vendor had one in stock. I installed that bad boy and it worked like a charm under Linux. A quick test with the powered driver board showed this was going to work, so I turned my attention to housing the driver assembly in a new case.

I’ve been working with our laser cutter for a while now and felt confident I could design and fabricate a chassis that would bolt together using some kind of joinery technique. I sketched a couple designs on paper, but I wasn’t loving the look. Wanting to make it more of a challenge, I wondered if I could make a curved surface design of some sort. I hadn’t worked with shaping acrylic yet, but knew it was a thermoplastic and figured I should give it a try. I grabbed my trusty heat gun, some scrap metal and a vise or two and gave it a go. After a couple test runs, I was confident it could work. The hardest thing about bending acrylic is controlling exactly where the bend occurs and not stretching the material so much as to throw off your dimensions.

The images below show my final attempt. I was able to house the driver assembly inside a curved acrylic chassis. Though the dimensions aren’t perfect and there are some alignment issues, it is a completely usable housing. What I learned after this project is that bending against a form yields far more accurate results than the rig I was using to get these bends. I look forward to trying this again soon.

 

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Making a custom iPhone stand… WITH LASERS!

Posted by Josef
PRO LF CO2 Laser from Full Spectrum Laser
PRO LF CO2 Laser from Full Spectrum Laser

Recently, my access to a laser cutter has gone from hopeful, to occasional, to every (laser filled) day! We picked up a brand new Pro LF Series 36×24 CO2 Laser from Full Spectrum Laser here in Las Vegas. The build quality is solid and installation and calibration was a breeze.

After some initial requisite etching of Einstein’s face onto acrylic blocks, I decided to turn my attention to something more practical. I fired up Solidworks and used the specs provided by Apple for the iPhone 4S. I wanted to be able to prop up my phone while using Facetime, but not obstruct the screen. Using clear acrylic, I cut out a shape that allowed me to slide my iPhone through a precisely measured slot… Almost.

Laser-cut iPhone stand
iPhone 4S stand made of Acrylic. Designed in Solidworks and laser cut using the Pro LF Series CO2 laser from Full Spectrum Laser.

 

As it turns out, this was my first lesson in the challenges of laser cutting. Namely, the problem of the laser kerf, or the width of the beam as it cuts. This is directly analogous to the kerf width of a saw blade when cutting wood. Basically, you need to determine this width for you laser and the media your cutting, then adjust your vector paths accordingly. For internal, closed paths, you want to reduce (subtracting the kerf from the radius of a circle, for example) and for perimeter paths, you want to expand your design by the kerf width.

After some fairly simple adjustments, I was able to get a perfectly fitting iPhone 4S stand made of clear acrylic that can be adjusted to any position along the iPhone body and stays put using friction alone. Not a bad way to spend 30 mins to create something useful.

Oh, and here’s Einstein!

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