Ken Nicholas Photography Astronomy & DIY CNC

Hi all,

After a long cold winter and then a very busy few months at work I have finally resumed some work with the CNC.
As the old sacrificial base board was getting a bit tired I decided to do what I had originally wanted to do and that was to fit a series of blind nuts under the board in a grid spaced at 75mm allowing clamping over the entire base making it a lot more usable than before.

The original blind nuts ordered were 6 mm but I received 2 lots of 4 mm as previously noted in this blog so I decided to use them anyway. If the bolts are too short I have threaded rod that I can cut to length to suit.

I had also shimmed the table to level it to within +/- 0.07 mm and that should be level enough for my work although some of the engraving I want to do on the Perspex templates might require a little more accuracy. If that is the case then I may need to invest in a spring mounted engraving tool to soak up any imperfections in the table top.

The new optical limit switches are here and look to be ok for the job at hand although it's yet to be decided if a NO or NC setup is to be adopted. I purchased ten of the them so I would have a couple of spare for other purposes such as homing switches but that's something to think about later.

I've not been to the shed much as it's been very cold this winter and I still have to figure out what voltage these run at and then where to power them from, I may need another small power supply just for the switches. I'll Google the data sheet on the switches and go from there I guess, it shouldn't be too much of an issue.

There is no rush to do this as I'm mostly working with Perspex/Acrylic sheeting or wood so this little mod is only to improve the robustness of the machines operating envelope and that of high frequency vibrations when cutting metal causing the micro switches contacts to bounce and thereby causing the machine to go into an Emergency stop.

If I set these up as normally closed I will only need one switch per axis as it will need a rail in the switch at all times during normal operation with a gap at either end of travel to allow the switch to go open circuit, at least that's how I think they work, it may be the other way around. I'll take them to work with me tonight and test their operation along with the info from the Google search.

Hi all,

Its been a little while since I posted but there’s a bit going on.

The dust hood hasn’t been as big a success as I would have hoped for due to the router fan pushing more air into the hood than the vacuum can pull out so it winds up blowing out from under the brushes, so I need to look at redirecting the air from the router somehow. A work in progress.

Next on the list was to level the bed and I had done this to the main bed, a 25mm thick piece of MDF with some brass shims to within about 0.006” and that’s not bad for a piece of manufactured wood over an area 450mm by 650mm but as I have a need to do some 0.005” deep engraving into Perspex sheet over a reasonably large area I needed it to be perfectly flat so I ran a 16mm end Mill “Router Bit” as a fly cutter over the sacrificial bed a 19 mm thick MDF panel and now it is perfectly flat as needed.

The weather here has been horrendous so I’m not spending as much time in the shed as I would like, went out there today and it was 4º C, that’s fridge temperature.

I had tried a couple of different tools for doing the engraving from a 90 and a 60 deg V bit both running and stopped like a diamond drag and neither was very good as the finish was rough and not desirable at all.

So looked at what was available on the net and saw that there was a tungsten drag bit with a 120º point

and a YouTube demonstration that showed it to work quite well on Perspex as I need.

So as I like to make what I can and I just happened to have a nice piece of tungsten handy, “a broken ¼” straight router bit from an earlier post”, I set about putting a an approximate 120º point on it.

As it was only very short it was difficult to hold while grinding so I put it into my cordless drill and that allowed me to not only hold it but rotate it at a very steady slow speed at my Greenstone wheel, this the special grind stone for tungsten.
I am very happy with the result, not quite 120º, more like about 85º I think but the test I ran on another template for my wife’s quilt making it worked quite well with a finish that is quite acceptable.

So now with the bed leveled and my custom engraving tool all I need to do is put it to the test.

This is the Quilt templates piece that I will be engraving and cutting, it’s the same as the ten and five inch I’ve done before but it's a smaller set for an 8.5 inch pattern as can be seen and this will be cut all at once, this is approximately 18 inches in the X axis and by 10 inches in the Y axis. This will be the next job on the bed and with the new engraving tool a better finish will be achieved.

The improvements have gone well so it now it's time to tidy things up a bit.

Mounting of the electronics under the side of the desk had to be rearranged to accommodate the extra break out of Port 2 from the Smoothstepper.
I have rewired the Y and Z limits to to Port 2 and also the emergency stop along with the Z probing for the Auto Z Zero function testing function of all as I went. All this has allowed the wiring to be finally tidied up and now it's looking fairly neat I don't mind saying so myself.
This only leaves the X axis limits to go, I still haven't decided on the mounting of the switches but will have to look at it now as it's the last of that to be done.

I've been having a bit of fun playing with the Auto Z Zero it's a very neat feature to have but as you see from the rather large touch plate in the pictures that's one of the other jobs to take care of, something a little smaller I think.