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  • Author Author: ralphjy
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CNC - First Try at Engraving

ralphjy

I'm starting to get some experience with my CNC router and quickly learning that there are so many variables due to material, cutting tools, and individual machine capability that there will be quite a lot of trial and error.   As with most tools,  the only real way to get more proficient with them is to use the tool for an actual project.

 

I'm still looking for a tool flow that will work well for me.  I recently got an RPi4 and I 'm going to try to use that as my workshop computer.  I currently use a mishmash of different computers to support my 3D printer, the CNC router, and my development boards and digital oscilloscope.  I use a Mac Mini with my 3D printer, a Win10 box with the CNC and another Win10 box for application development and the oscilloscope.  An RPi4 with dual monitors seems like just the ticket to consolidating all this stuff.

 

As for a fabrication workflow, almost everything that I currently use or am considering has a Linux version.  The one notable exception is Fusion 360.  I haven't invested time learning Fusion 360 yet, so I'm going to postpone that until later.  I'll see how well I can do with FreeCad.  I'm sure I'll get back to Fusion 360 when my designs get more complex.  But even FreeCad has quite a learning curve and for a beginner it would be nice to separate hardware issues from software issues.  So, I've decided to start with some simpler programs to get a feel for different cutting tools and material with different machining operations.

 

I thought I'd start with some simple engraving to get a feel for spindle speed and feed rate for different tools and materials.  I found a program called F-Engrave by Scorchworks https://www.scorchworks.com/Fengrave/fengrave.html .   It's a pretty basic tool.  It does text engraving and v-carving with text and images.  I bought 1/4" birch veneer plywood slats from a local crafts store to practice.  For simple text I find that I like the look of solid line stick fonts rather than the two line silhouette fonts.  I downloaded a set of CAMBam stick fonts to use (the program uses true type fonts).  For engraving you need to manage the character spacing and depth based on the tool (cutting bit) that you are using, the program doesn't do any auto-adjusting but it does preview the effect of the settings.

 

This was a simple exercise but it surfaced a few issues.  The most significant one is the surface flatness of what I was engraving.  Part of it is the dimensional variation of the plywood, some of it is the flatness of my extruded bed, and a lot of it is due to the warp from clamping soft wood.  Secondly, I really don't have any feel for these cutting bits (also that I don't have a great selection to choose from).  You can see from the program setup that I'm using a very slow feed rate of 127 mm/min.  I'm using a 20 degree v-bit that came with the kit.  The 775 spindle motor that I have is rated at 3000-9000 RPM (12V-36V).   I'm running it at around 7000 rpm.

 

Here is my setup in F-Engrave (the spindle speed is set manually in the G-Code header).

image

 

Rather than watching the CNC router cutting, I found it more interesting to watch the controller executing the toolpath.  For engraving the solid stick font the cutter makes precisely two passes for each segment.  The sequencing of the toolpath is pretty neat.  The F-Engrave program is written in Python.  It would be interesting to look at how it is implemented.

 

Here is the G-Code running in Candle (GRBL controller):

 

 

And the finished output.  The cut is rough around the edges.  Next try will be to use an endmill instead of the v-bit.

image

 

I can see that it is going to take me a few months and a lot of scrap to get somewhat proficient at this.

Parents

  • Hi Ralph,

     

    That's a great start, it is already looking nice! Looking forward to seeing the enhancements as you progress. It will take time to be familiar with the capabilities and settings with different materials too.

     

    My work is progressing slowly : ( Yesterday I purchased a couple of lasers, a small laser-pointer type module, to use it to see the area where the future tool will do its work, and a basic (cheap) diode laser to maybe try laser engraving first, since I don't have the mechanics for any spindle system experimentation yet. For that initial test I'm trying to keep costs low, so I don't mind if it doesn't perform very well or for very long, just hopefully enough to help me work on the interface board.

  • in reply to shabaz

    Hi Shabaz,

     

    I've been thinking about adding a laser module also, but probably shouldn't try too many things at once.  There is a 5.5W laser module that Sainsmart sells for the 3018-Pro.  Most of these low power lasers seem to be 12V @ 2-3A, which should work with my control board but I'd like to get one that would fit my spindle holder so that I don't have to do too much mechanical work.  My spindle diameter is 42mm so I'll need to stay at 32x32mm or lower for the module size.  I'm not sure what the dimension on the Sainsmart unit is but the picture shows a tight fit.  I've seen some units on Amazon that are 40x40mm so those won't fit.

     

    I'll be following your progress and will be interested to see which laser module you end up using.  Be nice to get the benefit of your experience image.

     

    Ralph

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  • in reply to shabaz

    Hi Shabaz,

     

    I've been thinking about adding a laser module also, but probably shouldn't try too many things at once.  There is a 5.5W laser module that Sainsmart sells for the 3018-Pro.  Most of these low power lasers seem to be 12V @ 2-3A, which should work with my control board but I'd like to get one that would fit my spindle holder so that I don't have to do too much mechanical work.  My spindle diameter is 42mm so I'll need to stay at 32x32mm or lower for the module size.  I'm not sure what the dimension on the Sainsmart unit is but the picture shows a tight fit.  I've seen some units on Amazon that are 40x40mm so those won't fit.

     

    I'll be following your progress and will be interested to see which laser module you end up using.  Be nice to get the benefit of your experience image.

     

    Ralph

Children
  • in reply to ralphjy

    Hi Ralph,

     

    For the laser, I went with this NEJE 6000mW laser,  it's probably not very good, but it is small (30mm square by 60mm length) so I figured that may give some flexibility on mounting, and hopefully it is light, for simpler mechanics. I'll definitely report back once it arrives, if it is any good. Due to its small size I'm going to initially monitor its temperature (it has a thermistor) to see if there's a risk of premature destruction of it. It also showed me that I ought to design in a few temp sensor connections for the interface board!

  • in reply to shabaz

    Shabaz,

     

    Thanks for the link.  That laser would fit in my spindle holder and it certainly is inexpensive (half the price of the Sainsmart unit).  I hope that it works well for you.  NEJE has quite a few different models on AliExpress.  Must be a large market for these devices.  Amazing how inexpensive they are.

     

    Ralph