If you have been following along at home, then you’ll know that last time I had a successful attempt at engraving a sign. With one main caveat. The backlash on the x-axis was still evident and ran to about 2mm.

During the week I tried rebuilding the x-axis captured nut setup to have 2 captured nuts which is common in ánti-backlash arrangements. I did the same on the y-axis and made an attempt to improve the overall alignment. Sadly this did not fix the backlash issue on the x-axis. I was just about to pack up for the day when I thought to just move the x-axis by hand to see the ‘play’ in it and look for signs as to what is moving. Once again I kind of kicked myself for overcomplicating things in the past and not just realising this was the simplest way to check for the problem in the first place.

This quickly revealed the real issue was the x-axis coupler. If you have really been following the whole series of posts, you may recall that early on I sheared off the first x-axis coupler when I had the alignment slightly off. In my haste to get things up and running again I didn’t really allow any time for the silicone to set, my impatience meant that the coupler didn’t wind up with a nice tough rubbery layer joining the two pieces in a firm connection. It wound up squidging out of place and left the couple with… you guessed it… 2 mm of extension/compression movement. Every time you changed directions it first had to compress or extend the coupler.

So after berating myself for the various failures that both caused the problem and took so long to diagnose it. I was happy that I had a spare coupler which I joined with silicone at the same time as the other. So this was now very much set and I could just switch it in.

It worked! I would now estimate that the backlash in all axis to be somewhat less than 1mm, certainly less than I can currently measure.

My first run with a fully armed and operational cnc rounter…

I was particularly pleased with this both due to the end result and due to having started from nothing on the same day. I designed the box in openSCAD over breakfast in the morning, Generated the tool path in PyCam over coffee. And finally spent an afternoon running the sequence and creating the real physical box. To be fair the design was just a copy of one I found on thingiverse and originally I was going to use that. However I needed to make adjustments to the part layout to fit the wood I wanted to use. I also had intended to use 5mm hardboard but the thingiverse design was for 3mm. After making adjustments in inkscape, I then had trouble getting pycam to successfully generate a toolpath and I didn’t really understand why. So I created my own parametric model in openSCAD. Same design, but with the ability to change a variable like material thickness and have the whole thing automatically adjust. (openSCAD is awesome) . I uploaded my derivative design here. I love that thingiverse has built into it the idea of expressing the lineage of a design, you can set links to show where inspiration came from or what parts you used.

Whilst I’m at it, I think its time to acknowledge that my own CNC creation was possible due to ‘standing on the shoulders of giants’. Lets list out those giants…

To control the motors you need motor driver boards, sure I could have tried to design my own, but I went for sparkfun easy drivers designed by Brian Schmalz

To send logic signals to these I needed something to interface with the computer. I came across GRBL which is an awesome open source gcode interpreter that runs on an arduino. The Arduino Uno itself is a cool piece of kit and pretty cheap, with lots of help and resources around it.

Then of course there is PyCam another amazing free program for generating the gcode from your models. it has some quirks, and can be very slow at 2.5D models, but for 2d stuff is generally very fast. And its FREE!

At the top of the chain, as I mentioned before is openSCAD Which lets me model what I want in a very ‘programmer’ sort of way which I find easy to work with.

Atop these giants building my CNC router was possible, and relatively cheap. Having done some research, gcode generators (CAD) programs alone can cost $250+ which is a steep ask for a personal project. So I am immensely grateful for the work of these other projects that made my own possible.

Woo hoo!, today I had what I’m categorising as my first full on successful run though a whole sign engrave program.
There are caveats, the backlash, particularly in the x axis is evident in a few places, however it was consistent and over 3 passes (1mm step down per pass) I got very consistent results.

After the first successful run, I upped the feed rate about 25% and upped the seek rate about 50% and ran again. I got another very consistent result. 3 full passes and very little deviation from the path each time. So I am very happy.

Here is the customary timelapse, you can tell that the second pass is running faster.

I did try to cut a piece for an anti-backlash block, however that failed when the bit slipped a little then bit into the wood and just pulled in. However it was also clear at that point that the model I downloaded wasn’t really scaled quite right for my needs. So the plan for this week is to design my own, and maybe hand craft the gcode a little to work around the backlash issue.

I’ve also been designing an openSCAD design for one of the rubber band guns I made a while ago, I think it would be cool to cnc out the parts for a second.

The CNC is no longer where it thinks it is relative to any previous move. Initially I had binding issues on all 3 axis. I had foolishly built the original structure with various ‘support’ points for the treaded rod, these were not responsible for any driving action, but they were drilled to be only barely larger than the threaded rod. That turned out to be a terrible idea, as short of absolutely perfect alignment each of these just provided a point for the rod to rub against and increase friction. So job one was to remove all of those, each axis really just needs to have the threaded rod connected at the motor, and ‘supported’ by the driving nut. That done the z-axis became pretty reliable, no more binding. The X axis still suffered some issues that I talked about previously, where my driving nut was enclosed in a block that was just a little too tall, at the far end of the workspace from the motor things seemed ok. But as the gantry was pulled back to the motor the height difference between the motor and the driving nut caused things to strain, and ultimately sheared the coupler in half. The Y-axis was a little more tricky, the brackets that hold it on the rails are metal, and the original design had tapped holes through the brackets that acted as the driving nut. one on each side. When this wasn’t working I elected to replace it with a block with a captured nut as I had in the x-axis. But that required me to totally dismantle the y-axis and open out the holes through the metal brackets. Sadly I already drilled the hole with the largest drill bit I own. So I had to go at it with a dremel and some cutting discs, and an abrasive but to work the hole open wider.

With the last adjustments made I finally found I could run my machine without binding. This has the effect that I can also run it faster, since less friction means the motor can operate with less concern over torque.

Home free? well no. As I wrote about previously, I was still seeing what seemed like odd behaviour which I eventually tracked down to the ‘sloppiness’ when changing direction, between the nut being pushed up hard against one side, and it become pushed up hard against the other.

This effect ( I now know) is called ‘backlash’ To a greater of lesser extent it is a very common issue in cnc systems. It turns out that most of the ‘real’ parts you might build an axis from are specifically designed to minimise/eliminate backlash. But of course it turns out that this is the yin to bindings yang. The closer you make the tolerances to avoid backlash, the more friction, the more friction the more binding. I took apart the x-axis and found there to be a small gap allowing movement. which I filled with a carefully cut piece of wood. Then clamped closed again. Excited to test out I rushed to repeat my test and found that I had reduced the backlash to 2mm. woohoo, 33% better… but still off. clearly I need to take more action in this area. But more on that later.

So it turns out that whilst it was binding I wasn’t really seeing these issues as clearly, since the very friction that was causing the problems was providing drive instantly after a direction change. But now I have mostly eliminated binding, I’m at the mercy of backlash. Now that is not a bad thing, I’ll take backlash over binding any day. And here is why…

Binding is an ostensibly random effect that drops ‘some’ moves and has a random impact on the resulting movements. Where as backlash is entirely predictable. It always has the same impact, and it always happens when you change direction. Also backlash is not additive. It cancels out when you turn back. This is how I came to realise the nature of the problem, by looking at the results of my cribbage board drill attempt, I realised that whilst I had apparently had an inaccurate move back to drill one hole, a little time later in the pattern everything lined up perfectly again. This hints at a way to work around backlash, at least for certain applications, until I can find the right balance in the hardware to eliminate the effect. If you always approach every cut/drill from the same direction, you’ll maintain perfect accuracy.

Let me give an example The machine starts having previously moved forwards into what we now consider 0. You then move forwards 10mm. which it does exactly. then you move right 10 and drill again. this is fine. a parallel hole. Now we move backwards 10mm, but we stop at 2, not 0. If you drill here then you are off and your pattern is ruined. It would be tempting to suggest that you tell the machine to go to -2 and drill there. since you know you will lose 2mm and it will actually be at 0. This is not such a great idea, it means that you end up drilling at places that are different in reality to where the machine thinks they are. It would be difficult to make this adjustment all over the place and keep things straight in your head. However. If you instead go back to -4, what you arrive at is -2. From there, you ask to go back to 0. The machine thinks its at -4 so attempts to move 4mm forwards, the first 2 mm is lost in backlash, and so it actually moves just 2mm. so There you are, back at 0. and importantly the machine thinks its zero as well. An issue here is that I have no control over the way pyCam generates Gcode. it uses an algorithm with the objective of minimising machine movements. and has no concept of backlash. and GRBL (0.8) also has no built in support for managing it, though it is on their future list. However for a simple program like my cribbage board drill program, I could simply edit the commands by hand. Which is what I did this week. I move the machine back behind the start point, then bring it forwards to the first hole. From there I drill every hole forwards of that point in that row. Then I move the machine over to the next row, and backwards to past 0 again, then forwards to the start of that row, then repeat. Here is the result

It worked! well, that part worked, I had a bunch of other issues. the zaxis was giving me grief and it stopped adjusting height correctly, on the first pass it wound up too high and stopped drilling, on the second pass it wound up too low and effectively crashed the drill bit through the wood. however for the purposes of this test it was successful, I got two parallel lines of drilled holes all correctly spaced.

Clearly this approach can’t work in all circumstances. and it would make most things very slow, as you ostensibly have to always move backwards past the point you want to drill then move forwards to it. However, for certain jobs, like my cribbage board, this provides a way to achieve the specific accurate result you want, despite the backlash. So the question becomes, can I use this approach to help me machine out parts that are accurate enough to help me actually fix the root problem?

What is required is an ‘anti-backlash’ setup, and the design I’ve found that seems the way to go is to have 2 nuts, separated by a compression spring. The spring acts to take the slack out of the nuts motion on the threaded rod. The question I have is whether I can put this together and maintain low enough friction to avoid binding. So now I have a two pronged attack on inaccuracy in my CNC machine, the first is software, by manipulating the sequence of commands, can I ensure I always cut in the positive direction and thus work around the problem. The second is hardware, can I build a setup for the xaxis that actually eliminates the backlash, or at least reduces it to levels low enough to not be a problem. I figured if I can get it down to less than 1mm it would likely be acceptable for most applications I’m likely to have.

Of course I could just buy a proper leadscrew and associated anti-backlash components… but where is the fun in that?

The image showed a few attempts at drilling out a cribbage board, but it kept not quite moving correctly, in particular when moving backwards.

On Sunday I spent a lot of time testing, I put a ruler on the bed, and moved back and forth. a lot. see:

I tried configuring everything, pulse lengths for the motor signals, steps per mm, acceleration rates, micro-stepping level. all based on the flawed reasoning that something was wrong with the electronics/motors/signals when the more sensible deduction should have been that my physical rig was the problem.

My big clue is shown in this picture:

2 separate tests, with two separate configs for various settings both yielded nearly identical layouts for the holes. the common factor? everytime the machine CHANGES direction it loses a few mm.

And behold:

the nut that drives the x-axis has a few mm slack inside its little house. everytime you change direction, it first travels across a few mm to the other side of its enclosure before driving back the  other way. I did a quick hack to reduce the slack here and got this result:

it’s not perfect but it showed that by reducing the movement of the nut I reduced the motion lost when changing direction.

I also had some issues on the y-axis in this test, but that I think is a slightly different reason, at this particular point on the travel of the y axis the threaded rod is rubbing against the metal bracket holding the x-axis. I think I just need to take it off again and widen the hole.

All in all whilst it was frustrating to spend ages trying to figure this out, I’m happy to have located the source of the problem, and I’m confident I can resolve it.

This weekend the first job was to replace this component, and see if I could fix whatever issue caused the break. I had my friend print me up another coupler on his makerbot this week (one day I really should get my own, but for now it is super helpful to know someone that has one). In fact he printed me two, so that next time I break one I have a reserve ready to go.

So i took apart the x-axis, removed the old coupler and started to put the new one in place. This time I realised that when fitting the couplers I really need the axis as close to the motor as possible, and this revealed the problem. there was a slight high difference between the motor shaft, and the mounted nut on the x-axis carriage. When the axis was pushed further away the height difference didn’t matter much. However, as it got closer and closer to the motor that difference caused binding, and general stress on the coupler joint. Eventually this just snapped all the lugs that held the coupler together.

Simple  fix, take the mounting block off, cut a few mm off the bottom and remount. No post would be complete without some timelapse video of me doing the deed…

At the end of that video you can see I started a router test. However a couple of things didn’t work so well, the main one being that the screws I used to hold the workpiece down didn’t bite properly and the piece lifted into the cutter. causing smoke, and general badness. Luckily limit switches are readily available to hit to stop the machine and then I could just turn off the rotary tool.

Worth mentioning at this point, I realised last week that starting, and stopping the rotary tool caused enough of an EM spike (I’m guessing) along its cable, that when the cable was next to the wires for one of the limit switches it caused a limit trigger. I since ran the cables a little differently to avoid that issue.

I was generally wondering whether the rotary tool, and in particular the cutter I was using was really appropriate to this task. I do want to setup a mount for my actual router, and at some point by a proper cnc router bit for it. However for the moment my range of cutters is limited. So I decided to move on to a drill test.

During the week I made up a model of a cribbage board. For those that have never played, its a card game, in which you score points. ostensibly you need to be the first to score 120 points, but this is normally measured out on a board with a few tracks of holes, 30 holes in a row, 2 rows make a track for each player. you go around the board twice. marking your score with pegs. Its not important, but my wife and I play occasionally and years ago I made a crib board ‘by hand’ with a printed template and my pillar drill. it came out ok, and we still use it. However, I did think that the cnc would do a much neater job of drilling the holes. or at least in theory it is capable of doing so.

I knocked up a model in openScad (my modelling program of choice) and came up with this simple model:

Then I imported it into pyCam and created a tool path. The trick here is that by default it will want to follow around the outside of the ‘holes’ rather than drill them. However it lets you set an offset from the lines. If you set this to the radius of the hole, and you have a cutter specified that is the diameter of the hole, then what you get is a tool path that just hits the centre of the hole. I also don’t want it dragging my drill bit around the perimeter of the shape,since it won’t be a routing bit, so I set my boundaries to be inside the shape, but outside the holes. the last thing is to set the ‘depth per pass’ to the depth of the holes you want. so the resulting program will move from hole to hole, then drop down the entire depth of the hole in one go, come all the way back up, then move to the next hole. The output looks like this:

So with a drill bit in the rotary tool, I manually job the machine to the 0,0 point, which i this case is above where I want the first hole to be. Then power up the tool, and hit go on the program…

and of course disaster. well, not disaster, but not good either. the drill bit I was using was too long, and had too much lateral vibration at the tip, this combined with some problems moving the axis reliably put some holes very close to each other and the bit tried to wander off into a previous hole…generally not good. so I hit the limit switch and thought about what went wrong.

The first point was the choice of bit, too long, too much vibration. fortunately I had another much shorter bit which seemed much more appropriate for the task. Second problem, was a combination. I originally screwed up my model, I had mixed up diameter and radius and set the holes twice the size I wanted them, and thus confused the spacing and it wound up smaller than I wanted. I fixed all this in the model. However it soon transpired that there was also the issue of the machine binding up again. I had been a little over optimistic, after refitting the x-axis I found I could set the seek speed way higher than previously used, and up at 200mm/min it moved smoothly (seemingly) however apparently this was not reliable enough, and certainly at some extremes of either the x or y axis this get a little less reliable.

So I reconfigued the model, reconfigured grbl and set off again….and again… and well again. in the video below you can see evey time I stop and reset. that is because it would get a certain way in then screw up. weirdly 3 times in a row is screwed up in exactly the same place despite having been perfect up to that point. I realised that the notable bit of the program was that it was the first time the x-axis moved backwards from a position. for the first several holes it was effectively doing ‘drill – right  -drill – forward – drill – left- drill- forward- drill-right’ etc. but then it did ‘drill-forward-drill-forward-drill-right-drill-back-drill’
but the backward move didn’t travel the same distance as the forward movement leaving a hole out of alignment.

You can see in this picture the various attempts and its easy to spot the first hole that goes off program. I take heart that the first several holes really are perfect.

The problem of the back move is a little perplexing. I manually tried entering the commands to go forward 20, back 20, forward/back repeat , and each time it did it perfectly. but for some reason in the program its not quite right. Later I will actually manually review the gcode, just to make sure something weird isn’t wrong in the instructions. However I think the reality is either the machine needs to be set to an even slower speed to try to make it stay reliable. Or I need to manually resequence the gcode so that it doesn’t take a backward step. it should be easy enough to drill all the wholes in a sweeping back and forth on the y axis, then stepping one row forward and repeating, so we never back off the x-axis. Obvioulsy that is a last resort. If I can’t get the program to work reliably today, then some evenings this week I will manually re-work the gcode to see if I can get better results next weekend.

With the last few minutes before I needed to stop for the day I decided to try the routing pass again on my logo. This time with the feed rates lowered back to the levels that worked so well on the plotting last week.
You can see this at the end of the video above. I don’t get all the way through before aborting.

It is clear that there is a big difference between dragging a pencil over paper, and pushing a cutter through wood. the axis struggled to move reliably and that pushed everything off position. Also I realised that I was just reusing the same gcode as I used with the pencil, but a pencil is a very fine point, and a cutter is 3mm wide. Following the same path was causing a mess. So I need to refine the program to account for the size of the cutter. probably there is a minimum size that I could reliably carve this into wood with a 3mm cutter without it cutting into the space between letters etc.

So this weeks test was …mixed.
Positives – I figured out how to make a drilling pattern which I’m sure will be really helpful in various applications. and for at least the first 9 holes or so, the machine seemed to stay accurate and capable of good precision.
Negatives – it really only takes one skip of a move, one revolution that stalls and doesn’t happen to screw up your whole program. once the machine is off position that is that.  For now at least, I haven’t hit on the right balance of settings/machine setup to give me complete reliability of movement even when not under the stress of a cut. And when it is under the stress of a cut things get worse.

Next steps…
Well obvious next step is to try the drill program with a really really conservative set of feed rates. This will take a long time to run, but if it works will be worth it. I also need to start making the support for my real router. I think some of my problems under cutting stress are due to using a bit which is really not suited to this use. its find for slowly grinding away on some metal, but it really isn’t a good choice for wood cutting. The sooner I can mount a real router spindle, the better.

So with that in mind I took my inkscape file of my website name ‘maker | geek’ not rendered in appropriate font, just typed in with regular font etc, just to get something quickly. I then imported it into pyCam, centered it around the 0,0 and offset negative z by the distance my rigged up pencil was above the bed.

Once I had homed the machine, then moved it back to somewhere near the centre, I stored the location by using the G28.1 code. In theory this means I can always return to this same point by homing, then entering g28.
Once there I reset grbl so that this became my 0,0,0 point.

Having duct-taped a pencil to the z-axis. I then positioned some paper on the bed, and kicked off  a simple stream of the gcode to the arduino. And everything started to spring to life!

I quickly realised that I’d rather messed up the scale of my model, and made it way too small. so I was just getting odd little squiggles. I was fairly sure this also indicated that not all was well, I could tell the Y-axis was binding up and stalling. but I went back to pyCam, doubled the size, reset and set off again.
After a few minutes I was rewarded with this output:

Impressive huh? The more observant reader may say ‘wasn’t that supposed to say maker | geek’ to which I respond…well yes it was, and if you squint and look at the right angle and use your imgaination that is indeed what it says. However it was very apparent that the Y axis was just not moving reliably. However the approximate spacing of the ‘letters’ on the x axis did seem about right. That was all I had time to try on that occasion since it was an evening mid week. However I resolved to return to the garage this weekend, strip down the Y-axis and rebuild it.

Cue timelapse of me fixing the Y-axis….

Sadly most of the work wound up at the bench, and so not really in shot….

Basically the original design (throughout the whole machine) I had attempted to get fairly tight tolerances and holes lined up across the length of the axis. This was a bad plan since I failed to get a precise alignment this just caused binding issues. To fix it I basically widened all the holes, leaving just the coupling to the motor and a single ‘captured nut’ in a block attached to the Y carriage. The captured nut was set so that it could slid up and down, but not back and forth. This means the rod is free to wobble a little laterally to the turn, but the nut/carriage has no slack in the direction of travel. This seems to have improved things.

I conducted another test which looked a little better,

but still suffered some binding and stalls. So I dropped the rate of feed/seek down to 80mm/minute. I then also jumped the text up to fill more of the page. And then at last… success!! it plotted perfectly (well as perfectly as I have any right to expect)

Ok, yes its back to front. But that is just a minor issue with flipping the Y-Axis, but the actual plot worked! including where it returned at the end to fill in the centre of the ‘e’s and the a.

Emboldened by success I attached the rotary tool which you can see at the end of the timelapse. My intentionw as to carve the same text into a length of wood. and perform my first actual cutting pass.

However, as I was setting up the position I was suffering more binding on the X-axis. I think the alignment is out such that the closer it gets to the motor end, the more out of line it is and the harder the binding. Just as I was thinking about this,…disaster. The x-axis coupling sheered completely in two.

And so the end of the plotting test was forced upon me. I now have to wait until I can replace the coupler before I can continue. However I think it will just require a little fettling of the x-axis to avoid it doing this again. (hopefully) However on the plus side this shows I’m not lacking for torque in the motors. When reduced to a slower rate of travel, they were able to develop enough to sheer straight through the plastic lugs that held the two halves of the coupler together.

At the end of the day this was my first properly successful test of a DIY cnc router that I built from scratch, for less than £250 and I’m very happy with how things are going. Excuse me whilst I go feel just a little pleased with myself…

Assuming I can overcome the stalling the next issue is the grbl config. I tested the homing cycle and it worked, however I don’t really understand it. The instructions seem to tally with what I’m seeing, I just don’t understand why it works that way. the homing cycle moves all the axis to their positive limit. for Z that means up and away from the workpiece which seems ok. Y pulls over to one side and X pushes to the front of the machine. All this is fine, but it leaves the machine at 0,0,0 with each access only able to move in the negative direction… but that is not how gcode comes out, it expects to move to positive points from 0,0,0 so I don’t really know why it doesn’t home to the negative limit. but I guess I’ll figure it out in time.

In all today was fun, I didn’t get as far as any real gcode test, I was just manually typing axis move commands enough to try and suss out what was working and how well. next time I will up the voltage and see if that stops the xaxis from stalling out. by then I’ll hopefully have figured out the homing thing, but failing that I can manually shift things to the right places to run some sample gcode.

So, I followed the instructions here  to flash the latest stable grbl version to my arduino, then followed the information here to wire up my stepper driver boards to the arduino.

That just left me needing to try sending some signals through. There is a very simply python script that is provided in the grbl source that can take a gcode file and stream it bit by bit over the usb/serial interface. Once setup the magic begins!

The next step on this adventure is to attempt to couple the motors to the various axis of my homemade cnc rig. I suspect this is where the real trouble will begin. its one thing to spin a motor with tape attached to it, and quite another to do so with an actual threaded rod and the weight of a cnc machine to move around.

One key component here is the pieces that actually couple the motor shaft to the threaded rod. Fortunately I have a friend with a 3d printer, and some ready made designs on thingiverse to use, so I have a coupler printed up and ready to try. However the shaft dimensions are not quite right, a combination of a slightly uncalibrated printer, and the fact that the model was designed for 8mm threaded rod, but I used 10mm. So I made a few adjustments on the pillar drill to make the holes the correct sizes. This worked well because it was a pretty solid print (obviously the part needs to be strong) so having adjusted the hole size I used some bathroom sealant to provide the silicone layer between the two halves of the coupler. This has set pretty hard so there is actually a little less flex than I expected. Hopefully I’ll be able to get a reasonable alignment and it won’t matter.

You can see it in the video above, at the moment it is not gripping the stepper shaft, for that I require some m3 bolts/machine screws to tighten up the coupling.

This are starting to look pretty real now, I have a few adjustments to make to my physical rig, and I’m still a little concerned about the sloppiness in the x-axis, I need to make sure I eliminate the side to side without making the friction bad. I have a few ideas about how to achieve that, we shall see how it goes. its quite exciting to finally be coming towards the stage of actually connecting motors and trying it all out for the first time.
I’m anticipating a considerable amount of fettling, and part of me suspects i may need to build a whole new rig with better materials, but I’m going to give it a damn good try.

The other thing I did was buy an arduino uno. This is kind of cheating. It makes everything much much easier. Part of that is being on a well trodden path. There are lots of people using arduino’s for lots of projects. and controlling a servo even has example code built right into the arduino ide. It was so absurdly simple to get a servo scanning back and forth that it does feel a little like cheating.

Today I moved on from servo, to stepper motor. I already had a sparkfun stepper driver (4.2) and I found a really helpful website that had a sample wiring and sample program to get things going.

Basically the boards mean I don’t have to worry too much about things at a resistor/capacitor level, and  just make sure I wire up the right stuff to the right pins of the boards, then worry about the code.

Even that might turn out to be , if anything, too easy. There is already an opensource project for interpreting G-Code on an arduino uno. What does that mean? It means with a couple more stepper motors, and some setup and I can have a 3 axis cnc electronics all ready to go. Just waiting for me to wire it to something.

Some time ago I built what I hopped would be the 3 axis physical cnc part. I have some concern that it may be altogether too heavy and too poorly made to get good results from. but I figure I should at least attempt to couple my stepper to the main axis and see if I can drive it. If not then I’ll just build something smaller/ligher/better designed. but if I can push enough torque to move the main caridge, then the other axis’ should be much easier.

I just need to figure out how to couple the shaft of the stepper to the threaded rod in a way that is secure and doesn’t have much/any play in it. Also I think I probably need to move a few things on the original cnc to make everything run smoothly without pushing/pulling the frame apart.

Anyway, here is my not very neat setup for running a single stepper motor:

oh, and here is the oscilloscope!

I am a man of many interests. I generally feel there is not enough time to do and learn all the things I would like. What with work and other commitments. Sometimes I do a good job of reigning in my sudden interest in something new, reminding myself that I already have lots of hobbies and not enough time spent on them. Sometimes I get involved in an idea or a project, only for it to fall by the wayside amongst many other priorities.
Normally my wife likes to remind me of the other projects I’ve started and yet to finish when I’m talking about yet another. I always protest that it isn’t that I’ve forgotten, or abandoned those projects,  just that they are on a back burner, for rather a long time. But I do intend to swing around to them in good time.
Sometimes this is due to monetary aspects of continuing a project. For instance my CNC router project. I started a long time ago, full of enthusiasm and built the physical gantry etc. But I didn’t get around to the electronics, mostly due to a lack of money to by the parts.

Some years ago I decided to build a pan and tilt webcam from scrap parts. as part of this I bought a bubnch of electronics bits and pieces and got briefly into playing. But basically I built my single project, using just barely enough knowledge to attach a parallel port to the logic pins of some darlington arrays, which in turn switched volatages around the input wires of a stepper motor (pan) and a worm drive (tilt). I cobbled it together, and for a while had fun remotely controlling the web cam in my lounge from the office.

Eventually the novelty wore off,the device got tidied away, and I had no other project in mind and so the electronics got packed away. I really didn’t learn that much, just a couple of simple things to make that specific project work. Since then I’ve done lots of workwork and woodturning projects, developed a mobile app, and I’m actually working on another now. But I always had it in mind to come back to electronics, maybe to meld together all these hobbies into some projects requiring a bit of everything.

But the problem is that if you don’t really know what you can do in an area, it is hard to envisage a project. When I watch stuff like the ben heck show, what is obvious is that he finds various projects easy, because he is just stitching together stuff he has lots of experience in. And so I decided that I should have some more directed learning and start playing with electronics to control motors/servos etc in some general ways. To build up a stock of components and experience so that I can open my mind to the possibilities of projects that would include these parts, just as I now have ideas that take turned components or need the bandsaw to make long straight cuts.

For christmas I asked for some components , a servo, a stepper motor, a stepper driver board etc, so now I have got the electronics out again. And so far what I’m realising is that I have no idea how electricity works in circuits. Well ok, that’s not strictly true. The problem is I’m pretty comfortable with a basic circuit, the kind that has a switch and a bulb, or a sensor and a buzzer. Where I get into trouble is with IC’s and servos, digital circuits that require pulse width modulation. I can go through some of the steps that I think *should* work. but when they don’t I lack the skills to figure out what is wrong. is the program totally wrong? is the circuit screwed up? Why do I get a voltage *here*? why does connecting +v *there* cause everything to stop? 

I’m pretty lucky in that I happen to have an old oscilloscope in the cupboard (now on the right side of my desk above), it has no probes but I’ve ordered some now. The next challenge will be to figure out how to work this machine, it looks somewhat more complicated than a multimeter…I hope I can figure it out and it becomes a useful tool in my arsenal. Not least because I’ve had the thing sat around for a long time since I was given it, and it has drawn the odd ‘why on earth..?’ comment. So it would be good to find it a useful place in my hobbies.

My biggest question right now, is where do I go to get the education I need? So far a lot of what I find is either so basic as to be trivial, or completely unexplained (just copy this circuit and don’t ask why this arrangement  of resistors/capacitors/diodes is the right one). On the one hand there is something to be said for just learning by copying and hopefully picking up experience. I certainly don’t want to drown in hard core physics. However I do want to get a much better understanding of how these things work together in a digital electronics circuit. It would be a start if my obvservations of a circuit matched up with my expectations. At the moment I am perfectly capable of building a circuit I think should work and see it do nothing, and similarly to build a circuit that I would never have guessed would work but none-the-less observe operating.

If anyone reading this happens to have any recommendations on books/on line resources etc,  I would love to hear them. I am going to build at least some basic cnc machine. and I would like to really understand it, rather than just plug together big components like lego.