A wise man once said "Failure is always an option".

Before I tell the full story, it is perhaps best to clarify, that although this post is about failing, it does not describe a failure… Riddle me this? OK here goes

Until recently I was the proud owner of a shed bound CNC3040. The CNC 3040 is a relatively inexpensive (and not the best quality) desktop CNC. Mine was sitting unloved in the garden shed far away from power supplies and therefore cutting action. At a previous address it had pride of place on a garage workbench cutting plywood components for model rockets and other projects. But after a house move it has been languishing waiting for a loft based workshop to be built.

Well recently that changed. My workshop was recently completed and the CNC3040 has come back out to play. Trouble is I have yet to build a dust/noise containing enclosure for the thing yet. So I got round to thinking, what else can I do with a desktop CNC? Vinyl cutting, that’s what. More importantly for me, I needed a project that will test and develop my making skills (I have been a year without a workshop now), as well as let me learn a new software package (Fusion 360). The mini-project was born, an attachment for a CNC machine that adds a vinyl cutter. It would be 3D printable and let me use the CNC while I design and build and enclosure for messy and noisy cutting. It would also let me use and learn Fusion 360. I was still using OpenScad for 3D design, and I have been wanting to use something more capable and modern for some time.

I found vinyl cutters straight away. My google searching for vinyl cutter blades brought me to many e-bay vendors and Chinese online stores selling spare parts. Being unaware really as to what makes a good vinyl cutter tool, I opted for the scientific approach as to “what was cheapest/most impressive looking for the money”. The one I settled on was described as “50mm Length Small Blade Holder for Liyu Vinyl Cutter”. It is fair to say, that I had no real appreciation for how a vinyl cutter worked having never used one, but how hard can it be, it’s just a knife that moves around surely?

Failure no 1

The first failure was not unexpected. With the cutting tool in my hand I decided to make a first prototype. The purpose of this prototype was to answer a few questions for me:

  • How was I going to mount the adaptor to the CNC machine?
  • How would I mount the cutting tool in the adaptor?
  • What other hardware would I need?
  • Would the aged roll of 3mm PLA that I discovered during the move be any good?

So a design was born, and of course did not work. The 2nd question on my list was the one that I failed on. I intended to place the tool holder in basically a tube, but the problem I had was it had a protruding collar. I thought I was being smart by shaping the holder in a certain way to allow me to insert the cutter then hold it tight with a tie wrap, but the tolerances were off, and the mount would not hold it tight… Oh well.

More successful was the mount to the CNC machine, a ring that tightened around the body of the spindle. I designed it with a complex tightening system that could be held in place by either bulldog clip, tie wrap or M4 nut and bolt. I ended up though settling for the nut and bolt, it was just easier and less wasteful.

As for the PLA. Well I got it working, even though my hand built 3D printer was designed (by me) to print ABS, by leaving the door open to the heated chamber I could squeeze good quality prints.

Failure no 2

Armed with my new found knowledge and more importantly rapidly improving Fusion 360 skills, I embarked on the next design… This design sported a new tool holder, no longer awkward to load, and much more able to hold the cutter securely in place. It clamped well to the CNC machine, it was even reasonably stiff (having used a denser infill when printing it) I printed it off in an evening, though needed to sleep before I got a chance to test it…

So where was the fail? My complete misunderstanding of how a vinyl cutter works. During my lunch hour at work I began an internet search on how to set up the cut. I figured that a good place to start was the operating instructions for the vinyl cutter the tool was designed to work in. I found a YouTube video that demonstrated the setting up of the machine and then the penny dropped.

You see when I designed the accessory I had looked at photos of the machine, and the cutting head looked to be pretty solid. I guessed that it simply moved the knife up and down when it wanted to cut. This was a mistake. In the setup video, as well as setting the cut height of the blade (I had worked out that bit for myself) the user also set the pressure in grams. This was when I realised my mistake. The photos of the machine did not make it clear that the head had vertical movement. It was being moved down to cut… That bit I guessed, but it was not solidly mounted, it was free to move up and down, held down with some pressure.

So this design I never even tried.

Failure no 3

Back to the drawing board, by now I was becoming half competent in using Fusion 360. I needed to come up with a new design that would allow constant pressure to be applied to the cutting tool. I discovered through more googling and some Facebook advice from someone who had actually used a vinyl cutter that machines were using springs to exert the pressure. This caused me a problem. Where to buy springs, and what spec would I need. The answers were online and no idea! This project was supposed to a cheap and simple diversion. Purchasing springs and testing (and perhaps failing) them was going to take time and money. I had no doubt the manufacturers of commercially available vinyl cutters would have spent time and money developing their products. I needed something cheap and adjustable.

What I opted for was a design that used gravity to apply the cutting pressure. Best of all, it used some parts that I had in my spares box… 8mm stainless steel sooth rod and LM8UU bearings. Users of 3D printers would recognise these, they are widely used in many designs.

In my design I calculated that the weight of the smooth rods (cut to a set length) plus the weight of the rest of the moving assembly would exert 90gm of pressure on the cutting knife tip… No springs would be required, and if necessary I could either shorten the rods lower the pressure or add weights to make it more… Awesome!

For the first cut I simply lowered the cutting knife onto the vinyl and using the jog controls of the CNC machine manually cut a crude shape. It worked! I got clean cuts and perfect depth adjustment. So where is the failure? One word… Bearings!

I put together some g-code using Fusion 360 (yet something else I had not done before with this software) and attempted to cut the openhardware logo. The machine did its thing, but the cut was far from perfect. Why? LM8UU bearings have allow the smooth rod to twist and move laterally in this design. And I don’t know if it is something that can be fixed. If you watch the video you can see the cutting tool moving around. This mal-forms the shapes and makes it impossible to cut detail….

So far I have considered adding a second set of bearings to constrain the movement of the rods. But to do this I need to lengthen the steel rods. I do that and the carefully designed in cutting pressure is increased. Not sure that I am going to pursue this design any further. Instead I have ordered a linear bearing that should be more accurate (I hope)

So you failed right?

All but Edison would have to consider the design a failure. My lack of knowledge, coupled with lack of research and lack of engineering prowess have led me to spend hours designing and printing a pretty useless attachment. But I do not consider this a failure… here is why:

  • I got back in the making saddle. After a year away from the workshop. I both got my 3D printer back up and running and the CNC machine turning its lead screws. It’s good to be back, hell yeah!
  • I cut some vinyl. Sure not well, but I made a functioning vinyl cutter.
  • I know more than the average person about how vinyl cutters function. My new design will use that knowledge I am sure
  • Most importantly, I am now a reasonably competent at designing parts in Fusion 360. A powerful software package that I will be using to create 3D designs and cutting paths for the CNC machine. This is a good place to grow from and I have no doubt I have increased my “Making” capability by a decent margin here. Yay me!

You can see some of my older projects at

www.justblair.co.uk

I also document projects at

https://www.youtube.com/channel/UC8ajSC8WbXpzvrN5W0Z2fwg

Blair Thompson.

People are Buzzing about Pollinator.

Hello everyone, Glasgow is getting a Mini Maker Faire! How exciting is that? To celebrate, the team thought it’d be great to invite local makers to write a few words about their builds and motivations for making and since i’d never ask anyone to do anything I wouldn’t do myself, introducing “Pollinator”, my latest build.

So I’m building a machine. I’m always building something. I suppose people have all kinds of reasons to build. They may want to change the world with some amazing innovation. Maybe it’s a living or a hobby. For some of us it’s a creative impulse, it’s how we express ourselves, how we present ourselves to the world. I’m no writer. I’m not terribly comfortable in the company of other people but I do have that extrovert streak, making things is how I show off. I think a lot of artists are showoffs at heart.

Pollinator framed but missing front playfield.

Pollinator framed but missing front playfield.

I think you can spot makers like us early. It starts with breaking things. It grows into taking things apart to see how they work. I’m sure it’s really annoying when it’s your things. I’m really sorry I pulled the hands off grannies clock, Mum. But the cogs and gears made the best unofficial upgrade to my lego set. I’m sorry I broke the TV too Dad. I chipped the screen of our black and white set with a stray marble. The tube slowly gassed out and the picture grew smaller and fainter over the space of a week or two. Yes I got in so much trouble but once the picture faded to oblivion, my dad and I spent a day in the garage taking it to bits and making electromagnets from the salvaged wires. This is one of the fondest childhood memories I have of my dad, so yes, making things is an extremely positive thing for me. Oh and we rented a COLOUR tv after that. So it was a double win.

 

The tiny cathode ray tube from a camcorder viewfinder.

The tiny cathode ray tube from a camcorder viewfinder.

Yes I’m still taking black and white TV sets apart because .. you say as a joke “wouldn’t it be cool to have a smart watch with a cathode ray tube screen” .. then you think.. Actually I really want that to exist, and you realize, you have a new maker goal.

I should probably point out that large coiled springs and tv tubes can both be dangerous so don’t give ’em to your kids to take apart…. this was the 70s after all. We didn’t know any better.

Anyway the cathode ray tube wrist watch isn’t the subject if this blog, it’s a distraction. I never make one thing at a time, I’ve always got several pieces of nonsense on the go at once. No, this blog is about “POLLINATOR” my Christmas project (yes I know it’s March).

I love old arcade machines, both videogames and the earlier electromechanical marvels. I had the idea of using arduinos and similar programmable microcontrollers to create some electromechanical like arcade game sculptures but using the electronics to take some of the work out of building the incredibly complex and cunning mechanical brains these machines depended on.

I was also inspired by Tim Hunkin’s wonderful and whimsical amusement machines.

I’d played a game called Ice Cold Beer at a few game shows and discovered it was based on a traditional pub game where a ball is dragged up a playfield, covered in holes, with 2 strings. It’s actually pretty simple compared to some arcade games but it’s very addictive and fun so it was a good prospect for my first project on the theme.

The design actually sat in a sketch book for a couple of years but at the end of last year I was messing around with 3D printers a lot and I realised I was looking, not only at the tool to build ‘pollinator’ but I was also looking at the mechanics I required too.

some of the 3D printed components

some of the 3D printed components.

I bought a bunch of 3d printer parts and fired up my own 3d printer to do all the difficult bits… but the majority of the material came from B&Q and scraps from the garage.

Plywood from the hardware store.

Plywood from the hardware store.

Pollinator is basically a box with some holes drilled in it, a bunch of switches and 2 linear actuators , a lot like those you find on the 3d printers mentioned earlier.
Also a suspended bar with a ballbearing balanced on it.

Little switches.

Little switches.

I really enjoy collaborating on projects like this too, so when a friend suggested ‘flowers’ as a theme for the game, it quickly became a game about a bee, moving from flower to flower (Pollinator, get it?) and avoiding the carnivorous plants (holes). Expanding on the idea, it was obvious we had to including the frantic “flight of the bumblebee” music and this gave me an excuse to rope in another pal who does amazing things with microprocessors and music. Sound effects covered.

I have one more collaborator. So my mum’s a maker also. She paints. I had a blank playfield. She likes painting flowers … how could I say no? One Van Gogh sunflower number for the play field, thank you very much.

My Mum's sketch for the playfield art.

My Mum’s sketch for the playfield art.

Pollinator is still a work in progress. I’ve got some interesting plans for the controls and the code still needs a lot of finessing but it’s playing and It’s been a great deal of fun to put together with my fellow makers. It’s going to appear at the Edinburgh Mini Makers Faire and maybe at the Newcastle Maker Faire also. After that it’s form may change, mutate, pupate? But it shall emerge in its final guise at the Glasgow Mini Maker Faire in July along with all the other amazing makes (assuming there’s room for it).
So the Glasgow Maker Faire adventure begins. I hope you enjoyed this inaugural ramble. We’d like to bring you regular blogs from Glasgow makers so if you’ve got an interesting project or story you’d like to share, please give us a shout and we’ll post it up.

Jams G Watt can be contacted at jim@artronix.co.uk