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TWEAKIE my CNC machine under construction. |
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CNC is only limited by our imagination. |
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Making stuff - Routing and Profile cutting. |
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(31) The old favourite Harley Davidson. Everybody seems to do this one, I think it is obligatory amongst CNC builders, and I am certainly no exception.
(32) Routing wood smells nice and looks good. Lynne is fine but Gary, well he gets a little mixed up sometimes. Although the Z axis has been made to take a 27,000 rpm (and extremely noisy) Bosch router I have found this unnecessary for working on pine and mdf and instead, I have opted for a 3,000 rpm perfectly silent 3 phase motor to which I have fitted a 6mm Jacobs chuck. The lower RPM is ideal for cutting and profiling plastic parts.
(33) There are many shapes of identical parts which interlock to form a structure. Six of these make a cube. If you wish to profile cut your own then the Mach3 G-Code file for this cube can be downloaded here CNC Cube.nc. It has been dimensioned for 2mm thick material and to be cut with a 2mm dia endmill. The X axis & Y axis zero is bottom left corner and Z axis zero is with the cutter touching the work.
(34) The CNC cube. Curious but of no practical use.
(35) Difficult to see at this resolution but this is the vinyl cutting blade and holder which I made. The knife blade itself is made from a 3mm drill bit which has been sharpened to the requisite angles for drag cutting. The bearings are ex-model aircraft parts and the housing is alloy. There is also an adjuster screw and locknut to set the cutting depth. More details are given on the Simple Vinyl Cutter page.
(36) The cutter is mounted in an adjustable spring loaded bracket fitted to the Z axis. |
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A late addition is an adjustable stop for the Z axis.
When profile cutting, setting this stop to the point when the cutter just does not quite touch the table saves a lot of grief should unforeseen software issues arise.
As with all things, compromise is essential and provided the stepper drive torque is not excessive (as is the case with Tweakie) this type of mechanical stop does no harm to the Z axis components should it be invoked. Had the Z axis drive had a high torque the adjustable stop could just as easily have been fitted in a position to operate the end of travel limit switch. |
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Because there are so many Company Logos available for download on the net, they are a wonderful source for practice of engraving, routing and vinyl cutting. Here are but a few of the practice pieces I have made.
The MG sign was made, by using two G-Code routines - the first to route the letters and the second to profile cut the perimeter (using the same size 1 mm dia endmill). These two routines were cut and pasted together to form one file which was then fed to Mach3.
You can never have too much vinyl and traffolyte but be careful you dont fill up your house with signs and notices. |
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There are a number of different web sites devoted to making wooden clocks and perhaps I will make one, one day. Their gear wheels are usually cut by sticking a printed DXF template onto a piece of plywood and then profiling with a fret saw. With CNC we can of course do better than this.
A brilliant piece of software, related to spur gear profiles, is GearDXF from Forest Moon Productions and this is available to download from here GearDXF.exe. This simple yet sophisticated program allows selection of the diametral pitch, pressure angle, number of teeth and precision before creating a DXF file, which can then be saved to a location of your choice.
Mach3 can convert DXF files to G-Code and using the tool radius offset function, I profiled these little gearwheels in hardly any time at all. They are not perfect in so far as a tool lead in must be programmed when using tool dia offset or else the cutter can start (and finish) at a position within the work, as indicated by the arrow. I will try to get this right next time. |
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The G-Code for these little gears was generated using CamBam, its 2.5D profile routine takes care of the tool radius offset perfectly and these were cut without a tool lead in / out.
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I found the G-Code for this plaque of Neptune posted on a popular CNC forum and I could not resist running it to see how it would turn out. The size here is 220mm x 80mm with a maximum depth of 8mm and it was cut with a 3mm single flute slot drill. Single flute cutters really do cut wood well, with very little furriness at the ends of the grain and no clogging. The big question here is - How long will it be before my wife discovers that the cheese board is missing. |
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This picture shows two typical cutting tools. The cutter on the right is a single flute type and it is ideal for wood routing and profile cutting. However, when profile cutting certain laminated materials, at a high feed rate, the helix angle is such that it tends to lift the material and cause some chipping and slight de-lamination in the top surface of the work. A possible solution here is to fix the work face down and cut from the back, where any chipping will not be visible in the finished product or to reduce the feed rate until satisfactory results are obtained and accept an increased time to complete the project.
An alternative approach altogether is to use a cutter such as the one shown here on the left. It will be seen that the helix angle is reversed. This tends to push the material down when profile cutting, leaving very nice sharp edges on the top surface of the work whilst still allowing high feed rates to be used. The swarf / tailings clearance is not as good with a reversed helix and to prevent bind up problems a vacuum extractor almost certainly has to be used. |
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This relief has been routed in oak. It is approx. 350 mm x 80 mm and is cut 2.5 mm deep. Appropriately it is the nameplate for a Beec |