Retrofitting 1983 Shizuoka AN-SB CNC milling machine, Bridgeport mill, Colchester Bantam lathe and 1982 Tree UP-1000 CNC lathe with modern controls - and other workshop stuff
Most knurling tools in use in home workshops rely on forcing a hardened, knurled wheel into the workpiece as it rotates in the lathe. This causes the workpiece to deform plastically and equally it requires a hell of a lot of force. This process is called "form knurling":
There are "tangential" holders that hold 2 knurling wheels at opposite sides of the workpiece. This can help to reduce the load on the tool, the lathe and the workpiece but still requires a lot of force on the wheels and they still have to be either forced into the work or tightened into the workpiece.
The other type of knurling tool uses a sharp edged knurling wheel that is fed sideways along the workpiece from one end, cutting the grooves as it goes.
This is a single wheel version:
And they also come with two wheels:
One key difference between the single and dual wheel versions is that it is possible to cut cross hatched knurls in one pass. The single wheel tool would need to cut one set of grooves in one pass, then have its head angled so that a second set is cut at an angle to the first set.
And usually you'd be wanting a toolholder to be using them with. But make sure you are sitting down before looking closely:
So you can see why you might not see so many of these in the average home workshop.
Anyway, I managed to win a similar tool through the homeworkshop.org site not so long ago. I haven't got round to trying it yet and TBH I don't make a lot of hand tools that would benefit from it - but that's not really the point.
But it came with a user manual that has a wonderful smell of cutting oil. It would be rude not to refer to that.
How to use it:
And a parts list / section view:
One thing I noticed fairly early on is that the "arms" are fitted the wrong way round (see the first photos above). I suppose this allows the knurls to be used on smaller diameter workpieces than the specified 20-65mm. However, when fitted this way, the graduation marks for the adjusting screw aren't visible from above. No big deal but it had me puzzled when I was reading the instructions.
The wheels run in needle bearings, although there's no thrust washer as such. The wheel thrust is taken directly by the face of the needle race, which seemed strange. But the parts list confirms this is correct and indeed there's a note telling you that "only the engraved side of the needle bearings is hardened" so you must fit the bearing with the part number visible and against the knurl wheels. The bearings are INA (German!) HK1015.
The adjustment wheel has opposing left and right handed threads, so turning it brings the wheels together symmetrically about the workpiece. The thread has a pitch of 1mm, so each turn moves them 2mm closer.
In the mini tool set that comes with it, there's a quaint little plastic collar that fits on the hex key with graduations. So you can actually set the depth of cut with some accuracy if you are that kind of person.
The toolholder shank has been machined. They come in either 20mm or 25mm square.
We can see that the end of the shank was originally faced off in a lathe during manufacture and thus we can be fairly certain that it was originally a 25mm shank.
And now it's 3/4" (19mm). No problem - in fact that's handy, as most of my Multifix toolholders (for the Bantam) are for 20mm tools and the toolholder turret on the Tree expects 3/4" tooling for it to be on centre, being of US origin.
There are a few wheels with it, including a pair on the tool itself. They are all "straight" ie the teeth are parallel to the lathe axis. The tooth pitch is 1.2mm or 1.6mm although others are available, down to 0.5mm. Most are fairly sharp and of course they are double sided. FWIW, it appears compatible replacements are available from Chinesium outlets.
The tool presents them to the work at a fixed angle - which is 30 degrees on this example which is fitted with the BG2065 "holder set". This means that the knurls from one wheel are at 30 degrees to the axis and 30 degrees the other way from the other wheel. The result is "diamond" knurling with the grooves at 60 degrees to each other. Other angles of 0 and 45 degrees are available apparently.
The angle referred to in the knurl descriptions seems to refer to the angle of the crest of the teeth - either 90 or 105 degrees here.
So, after some gloating and "researching", I may be forced to actually try the thing out. That will come next....
The "Centauri Carbon" version incorporates a glass door and top and metal side panels ie it is fully enclosed and better for maintaining temperature.
The "Canvas" is the "4-colour printing" feature.
The "Combo" models have the Canvas option fitted but you can also buy the kit to convert your basic Centauri of either flavour to 4-colour.
The guidance on which materials the various models are capable of is a bit inconsistent but I think we can conclude that you don't stand much of a chance with the more "difficult" filaments if you don't have a hood if you've got the Carbon option fitted, due to the fact that having an open top will allow all the heat to escape and you'll struggle to keep the base of the part from warping.
So this sort of justifies fitting a hood if you fit the Canvas upgrade.
There was a big hoohah last year after many customers had prepaid for their Centauri Carbon printer with the "Canvas" multi colour option. This allows 4 different coloured filaments to be loaded in the machine and for those to be automatically switched during the print, the end result being a single part with multiple colours. The uproar was due to Elegoo announcing that in fact they would only be shipping the base model without the multi colour option due to development problems. Result - lots of pissed off customers.
I bought my Carbon printer, happy without the option to print multi coloured parts. It may be early days and/or I've been lucky but so far I've been very impressed with the printer. It's been faultless and the preset filament settings have been largely spot-on.
There was never a clear promise that the Canvas option would become available as a retro fit for the non-Canvas Carbon but recently Elegoo has made exactly that available. It appears the accessory is priced at only £38 as a way of making up for the disappointment. In contrast, the conversion kit for the later Carbon 2 is priced at £98 for the equivalent kit. I'm guessing £38 is the cost price.
This comes with all the parts you need for the conversion of a mono colour carbon to a multi colour Carbon Canvas:
Even at cost price, it's remarkable that they can make and ship this lot for £38 but I'm not about to complain. I ordered it on Thursday and it should be with me early next week, shipping from local UK warehouse.
One item that isn't included is a hood for the top of the machine. The single filament Centauri Carbon machine has a glass window at the top surface but this has to be removed to allow the 4 PTFE tubes to emerge above the machine.
What's rather annoying is that the Canvas kit doesn't come with a hood and they don't sell it as a standalone accessory.
Without the option to buy a top cover, it seems to me that I need to knock one up. Obvs I'm not the first user to have figured that out and there are a few models available on the likes of Printables.
I like this one, as it retains the original glass top cover and also the vented riser that I have already installed.
There are 21 pieces to this, plus a couple of acrylic panels. Looks as if it will require several lengthy sessions to get them all done but I have several days before the kit arrives.
The 3MF files contains all of the parts, so I can import it and delete out the parts I don't want each time I start a printing session. Looks like 4 or possibly 5 sessions will be needed, each of around 12 hours. They can run overnight.
Ooof. Something's not quite right here;
While the parts are printing, I thought I'd assemble them in Fusion and see what they look like, check for issues etc. Nothing against the author of these parts but some of the uploaded content can be "rather mixed" in terms of quality.
This is the underside of the assembly. Those pillar things are intended to mate with the existing "vented riser" - but the one on the left here has an angled face that seems to have been flipped so it results in a narrower face where it mates with that riser.
And this is the uppermost of the 2 rear panels. The top one should have a groove at the base and a flat top. Instead, it seems that it is simply a duplicate of the bottom panel. That's not right.
Here's what it looks like with those features corrected:
But while I'm at it, I can't be arsed to source the acrylic panels that are supposed to be fitted in those 2 windows on the front and left sides. So I'll fill them in - after all, there's a glass panel at the top and I can't even see the left side of the machine.
And here's the final, modified (windowless) assembly.
There are a few minor misalignments but they are neither here nor there and I couldn't go back over the guy's original design even if I wanted to, as the 3MF assembly file is a set of mesh bodies, not parametric models.
It looks a bit shit TBH but that's partly because it uses the original glass top (hence parallel sides) and it's made in multiple parts due to the limited print volume in the machine. Also, The Stupid Fat Bloke made the executive decision to use ABS rather than PETG and Any Fule Kno that ABS doesn't like sticking to the plate without large rafts and good temperature control. Ah well.
Here we are then:
Here's the original vented top. I'm going to retain that.
I may glue this together using pipe weld solvent if it looks like a goer.
Fitting the Canvas upgrade kit:
But first, time to do the actual upgrade on the machine. If that all goes West, there's no point having buggered about with the hood beforehand.
It comes very well packaged. I've never seen such neat tapework - perhaps mechanised?
Little manual tells you everything you need to do, step by step
Replacement board for the head. This has one of the STM32s on it.
The STM32F402 seems to be a China-only variant that doesn't appear in "Western" listings but nonetheless:
Processor Core: ARM Cortex-M4 32-bit RISC with Floating Point Unit (FPU).
Memory: Typically equipped with 256 kB of Flash Memory and 64 kB of RAM.
Clock Speed: Standard internal operation up to 168 MHz (utilizing an external 16 MHz crystal baseline).
Peripherals: Features a single 12-bit ADC, full-speed USB 2.0 OTG interface, multiple timers, and standard communication rails (I2C, SPI, I2S, and USART).
Once the board, motor/gearbox and fan have been replaced, there's a little change required under the base.
I was expecting a Meanwell PSU - but not this time it seems....
The wiring actually looks pretty good.
This little board seems to be the heater controller for the heated print plate. There's an optoisolator, a triac on a heatsink and some basic EMC filtering.
The base and chassis are actually diecast.
Elegoo seem to like the STM32 microcontroller, as it's also present on the print head and the Canvas module.
This is a Samsung eMMC flash memory KLM8G1GETF-B041 (64GB).
Although this short cable is described as an extension, it's actually a crossover patch cable thing if you look carefully. Presumably the Canvas has a different connection scheme to the original Centauri pinout.
Then these spool holders are slapped on the side of the cabinet. They have a rather neat friction clutch that provides a small preload torque to prevent the spools from unwinding.
Each spool now has its own motor and PTFE tube.
Here's the PCBA inside the Canvas module. Yes, that's another STM32 (the 3rd!).
And here's the contraption perched on top of the machine. Looks shit but here we are.
After relevelling (first time in months), upgrading to the latest firmware that supports the Canvas features and loading up some PLA, here's Benchy:
It seems to be working well, despite suffering my attentions over the previous hour or so. We will call that a result for now.
