Interesting Tech Projects
Archive for September, 2008
Introduction to End Mills
Sep 23rd
The best introduction I have found is from the Enco catalog. Fortunately you can view the catalog online. The introduction covers materials, types, number of flutes (including the trade offs), end cut type, shank type and surface treatments.
View the introduction at:
http://www.use-enco.com/CGI/INPDFF?PMPAGE=123
Note that this gives you page 123. Enco’s next release of the catalog may change the location of this introduction to another page. If you see this link is out of date please let me know the new page number.
CNC Cutting Speeds II
Sep 15th
Recently I wrote about the steps I took to reduce the cutting time of a particular part from 67 minutes down to 20 minutes. I have now purchased a couple of 1/8″ four flute endmills from Enco.
I can now cut the 1/8″ wide groove in the design, plus the outer profile with holding tabs much more quickly. In addition I can use the 1/8″ bit to perform a quick roughing pass on the pocket operation. Once complete I switch to the 0.0571″ endmill and make a finishing pass around the edges of the pocket, increasing the detail.
The new time, including the manual tool change, is about 10 minutes. Not bad. At the end of the cutting process the motors, stepper driver chips, transformer and dremel are all a lot cooler.
One small downside is that the 1/8″ bit make a lot of noise.
More On Inkscape and DXF Export
Sep 15th
Previously I wrote about a DXF exporter for Inkscape. Bob has updated his Better DXF Output exporter for Inkscape 0.46. All the files are now in one place and it is under the GPL v2 license. This is great news for CNC users and I hope it leads to more use for this handy Inkscape extension!
CNC Cutting Speeds
Sep 11th
I am working on a design that basically involves cutting out a 4″ diameter disk from 1/4″ thick wood, with some shapes pocketed into the surface of the disk. I have been using 10 inches per minute (IPM) to cut through the Poplar and I had no clue if this is average, fast or slow. What I do know is that it is painful to watch.
At 10 IPM cutting out the design took 67 minutes. That is probably split 60%/40% with the majority on the pocketing. Too long for my liking. I decided to try and reduce the cutting time. First I increased the speed to 30IPM, which is nearly the maximum that my PC can go. Next I reduced the depth of the pockets from 0.15″ to 0.10″. This saves an extra pass.
The new time to cut? 20 minutes. Less than 1/3 of the original time. But that’s no good if the result is a ragged mess. Tonight I found out – there are more burrs on the wood, but the vertical edges look just as good as the ones cut at 10 IPM. So I will likely continue to use 30 IPM in the future.
My next aim is to split the cutting into two parts. The pocketing with a 0.0571″ end mill and the rest with a 1/8″ end mill. This should reduce the time even further.
Importing DXF Files Into Inkscape
Sep 7th
If you search around for ideas on how to import DXF files into Inkscape or convert DXF files to SVG files, there are a lot of results. But they mostly seem to be shareware or orphaned applications that haven’t been updated for years. However there is a simple, obvious (once you see it) and free solution to converting DXF files to SVG files (which Inkscape can load).
It’s called Open Office Draw.
Yes, that’s right. Open Office Draw can load a DXF file and save an SVG file. I’ve tried it and it worked – I was able to take a DXF file, convert to SVG, load into Inkscape, edit, save as DXF (see my other posting from a couple of days ago on this) then load into CamBam for CAM processing.
Using Inkscape for CNC Designs and DXFs
Sep 4th
Update: see this later post before following the instructions below.
I don’t care for most of the DXF editors available. They seem a bit clunky and not too friendly. But I do like Inkscape. Unfortunately it doesn’t export DXF files.
Here is a way of getting Inkscape 0.46 to export DXF files which can then be processed in a CAM program to generate g-code for a CNC machine.
Firstly install Inkscape 0.46. It must be this version.
Next go to this post on BobandEileen.com, right click on the link to “dxf_templates.py” and save it in C:\Program Files\Inkscape\share\extensions.
Next step is to go to another post on BobandEileen.com, right click on the two .py files (“simpletransform.py” and “better_dxf_outlines.py”) and save in the same place. Then do the same for “better_dxf_outlines.inx”.
Restart Inkscape.
Create a drawing and then move it to the bottom left corner of the page. This corner ends up being the origin. If you want your drawing centered on the origin then center it on the corner of the page.
Go to File -> Save As…
From the list of file types in the save dialog window choose “Better DXF Output (*.dxf)” and save the file.
Now open the DXF file in your favourite CAM program, such as CamBam.
Note that you may need to scale the drawing in your CAM program. Even though I had my drawings correctly sized in Inkscape, they seemed to be quite a bit bigger. If anyone knows how to solve that please post a comment.
