We now have a working 3D router built up from a set of 3 Velmex positioners from the 1990′s. The built in limit switches are also connected. With Sonny Jeon’s excellent work on Grbl over the past year this is now a fabulous combination.
A short video of the first real cut. There is still some packaging work to do and it needs a control panel, esp. an E-Stop panic button. Router bits are on order from Richon Tools. These are inexpensive, a factor because I expect to break a few while figuring out the optimum cutting speeds, esp. for aluminum.
Grbl runs on an Arduino Uno but has no user interface. Instead you need to use a sender program. I tested out a bunch of different ones but the best for our purposes is Universal Code Sender. This program runs on various Windows, Mac and Linux. It provides various controls such as jogging and a file loader to send the actual Gcode cut program to Grbl. And it provides a cut visualizer.
The Grbl site has a copy of UCS but it is out of sync with the .9G version. So I installed NetBeans, , replaced the out-of-date RXTX library that is in the git source and compiled UCS 1.0.8. It is rock solid when run by double clicking the .jar file, no communication errors as before. (I do not use the start-windows.bat file, an open Command window seems to affect behaviour.) All testing is done on 64 bit Windows 8.1
I am presently blocked on the Glass 2 Cylinder project while I decide what grinder tool rest I am going to build. Boring the cylinder head, which is brass, is showing me that my hand grinding of cutting tools is not adequate. This requires a trip to a metal supplier and so need to fill up the hobby cash pile first.
In the meantime, I decided to revisit my previous CNC efforts. For the Unimat I used Mach3 (free edition) on a dedicated small PC. This worked well enough but it seemed overkill plus the learning curve for Mach3 is steep. After a bunch of browsing I came across Grbl and SmoothieBoard. SmoothieBoard requires a processor that I don’t have (it is partly based on Grbl though). For Grbl I only need an Arduino Uno, which I already have. It took some investigating to see if the 2.5D milling/routing that we want to do is supported by the limited G Code subset of Grbl. There are enough free tools to generate the code we need. Even helical threading is possible!
Posted in CNC
Tagged cnc, grbl, nema17
Now that I have 2 cylinders, it is time to make the pistons. These are supposed be graphite, which is easily obtained. But that only works if the cylinders are perfectly round inside. And regular borosilicate glass isn’t perfectly round. Close but not close enough. Option B is to make pistons out of brass and add a groove for an o-ring.
I’m a big fan of Plan B anything. First up, cut some hex brass to just over the final length of 2 pistons plus room for finishing the ends and the .05 wide cutoff blade. My 4×6 band-saw takes no time at all. Some time spent aligning its blade means that cuts are close to perpendicular. Less post processing that way. At same time I also cut the cylinder block. It amazes me sometimes just how much scrap material my dad collected from various places he worked. The waste was incredible. After 40 years I am still using the scrap leftovers.
After a month or so of building more add-ons for the Taig lathe and going over the drawings that Jan provided, the build has begun.
Jan Ridders designs and builds fascinating engines. Stirling, gas, steam, doesn’t matter. His designs are imaginative and buildable. Drawings are free for the asking, as is advice on building and further modifying them. The specific engine I am building has glass cylinders. This provides a lovely view of the engine firing. (The whole site is available in Dutch and English so you don’t need my ‘I speak Dutch’ super power.)
Really, really almost done for now with my ‘must make’ tool list. My DW wanted to avoid looking at dark brass marks on my fingers at dinner. Since I will be turning knobs a lot while making my engine, it was time to retire the original brass handles on the carriage, cross slide and vertical milling slide. The handle design came from Keith Brooke’s excellent article on making zero-resettable dials for the Taig.
Making 1 of something is a simple task, making 3 identical units is something else. I marked out the dimensions on the first spindle, and then used that as a pattern for the other 3. Each was almost complete before moving on to the next one. The cross slide DRO was most useful. Touch the cutting tool to the material, zero the DRO, calculate diff between original and target diameter, divide diff by 2 and you get the desired reading for the DRO. (It always measures radius, not diameter). Wind the cross slide to the desired number, press zero again and now all you need to do is cut until you get to zero!