The start of this holiday was a little bit hectic, as half way down to my parents house Joey realised that her passport had expired. This meant we had to get up super early and drive into London to get her passport renewed. We only just made it to the airport in time for a really late check in. The 18 hours flight gave us a chance to relax and reflect in relief.
Here is a quick and easy way to get 2D DXF drawings extracted from 3D STL shapes using OpenSCAD. Launch OpenSCAD and enter the following:
projection(cut=false) import_stl("/full/path/to/stl");
Replace “/full/path/to/stl” with the path to your stl file, and hit F6 to compile and render using CGAL.
From the Design pull down menu choose Export as DXF.
The resulting DXF file as viewed in QCad is basic (circles are made from several straight line segments), but its good for making measurements or printing out templates.
You might find that you have to rotate the STL if you want to get a projection from a different side. You can also set cut=true if you want to cut the object using the XY-plane instead of projecting onto the XY-plane, if you do you will need to translate your object by a negative Z value. e.g:
projection(cut=true) translate([0,0,-10]) rotate([0,90,0]) import_stl("file.stl");
See the projection function in the OpenSCAD manual for more details.
I decided to “upgrade” my generation 3 electronics to use a real stepper motor driver instead of the PWM hack non-sense.
For those who don’t already know, the Makerbot electronics are not really designed for Mendel, and specifically the extruder controller is designed to run a gearmotor instead of Mendel’s stepper motor. The Mendel firmware was “hacked” to make the gearmotor controller push 12v through a 2.3v stepper motor but, by making the gearmotor controllers simulate PWM output (which reduces the output power) it doesn’t blow the stepper. From the perspective of re-purposing existing electronics, the idea is a “really neat hack”, and in theory it should just work. Needless to say that in practice, in my experience, the extruder controller makes the stepper run hot, and with a high pitched squeak coming out of it at all times.
Re-wiring the motherboard to use a separate extruder is quite a simple task, just connect the SCL output of the motherboard to the Dir pin of the stepper driver, and the SDA output to the Step pin. However when I came to do this myself I didn’t have and couldn’t find this vital bit of information. So using a multimeter connected to the powered up motherboard I tried to determine which output should be connected to which. Well in the process of probing around I managed to short +5v to GND. I heard a fssssszt noise and saw a flash come from the motherboard….oh no!
Well I think I managed a lucky escape, one of the tracks on the Motherboard had acted as a fuse and blew, so with the bit of repair shown above circled in green, the motherboard was working again.
Well for some of the bigger parts I have been trying to print, I have tried using Polylactic Acid.
The first part I printed with the PLA, belt-split-jig-universal-20ff.stl, was a great success. But the second copy wasn’t so good. I have no idea why, but perhaps the ambient air temperature of the room was different.
The second copy is on the right in the first image, and on the top in the second image. You can see that a corner lifted quite substantially during the print.
I recently had someone round to fit a new Aerial to the exterior of my house (previously I had a makeshift Aerial propped up in the loft) Just after he left I noticed that he had left an empty coaxial cable reel next to my dustbin.
Great I thought I shall use it a a filament dispenser. Now all I have to do it attach a spindle so that it can rotate freely. I was lucky to get hold of one for free, I guess the only way someone else could get one is to buy some coaxial cable
I haven’t posted for a while because I have been too busy tinkering and printing things 😉 But I thought I would post an update because I have finally managed to print some usable pulley’s.
I am finding Repsnapper, much easier to use than anything else and I am getting good results because it keeps the gcode simple. Removing the shield and homing gcodes, saves a lot of time and headaches. Thanks to Trish for that who timed my printer while it was returning home, and calculated that I could save about 1hr 30mins on the overall print!
Giles Bathgate 