CNC – What’s the Problem?

[IanTParticipant @iant]

This is a subject which has been discussed recently on the G3 forum and we are probably a mini-representation of the views I've read here – with one or two members making very extensive (and impressive) use of CNC to produce their models and others seeing it akin to learning Black Magic.

I've been a late convert to 3D Print but certainly don't see it as a 'do-all'. I see people printing things that would be more easily & quickly made in other materials for instance. I've looked at the gantry 'router' type machines but a G3 friend has advised they are simply "not rigid enough" – which I think also raises the question of "for what"

To my mind CNC is particularly useful to a Hobbyist in two areas. The first is to machine parts which have complex geometries. My current approach to this problem would often involve fabrication. The second is the area of 'mass production'

As someone has already commented – most hobbyists don't make multiple parts – although they do in fact often use them, in the form of commercially produced parts and fixtures. Using purchased components is usually the most sensible method to pursue, assuming that the parts you require are actually available and are affordable in the quantity you require. Has anyone tried to purchase 16BA nuts or bolts recently?

There are also some operations where it's all too easy to make mistakes if your mind wanders for a second (my mind does this frequently). Drilling multiple holes in small parts has been already mentioned but there are other things where it's very easy to make mistakes when doing repetitive actions .

I don't really need CNC for largish 'flat' parts in steel – laser cutting is a viable option for this and even smallish flat parts can be assembled (and brazed) to produce useful fabrications.

So within my specialist area (Gauge 3 Railway Modelling) I see several uses for (inexpensive) automation.

1/ A 'Micro' CNC machine – a kind of automated mini capstan lathe & mill – not removing huge amounts of material but capable of producing multiple small parts. It wouldn't need to be ultra quick (like its commercial counterparts) – simply fast enough to do a few dozen parts over a day or so. Not waiting for a commercial solution but hoping for a public domain one to pop up.

2/ An automated drilling table (probably already available in the form of the 3020/6040 type routers) – the issue being mainly cost for something that might only have limited uses.

So I think that 'capable of machining most things' CNC may be overkill in terms of price and technology for my uses – but smaller, cheaper, probably more specialist machines might be a better solution (for me). I certainly do use my 3D Printer but for things (I consider) best suited for it – e.g. not everything.

Just my thinking on CNC currently – but as things evolve so quickly these days, who knows what we will have available in another year or two.

Regards,

IanT

[Another JohnSParticipant @anotherjohns]

I use CNC extensively in my workshop. (when I get in there, that is!)

I figure that it is like the change from making parts to fit, to making parts that fit. No longer any need to stamp mating parts for assembly, the parts just fit.

Look at the Sherline CNC products, although they have gone now to an expensive CNC controller. I do have a CNC-ready Sherline lathe and 5400 mill, but have only used them for manual machining at this point. (have 2 cnc mills, a KX1 and a larger one, both LinuxCNC driven, that work well)

I am a real fan of LinuxCNC; each mill has a small computer with monitor and one of those track-ball mice things (no keyboard) so they are self-contained. When I turn power on to the electrical socket for the mill, the computer boots in a few seconds, and bobs' your uncle – ready to go.

[Martin KyteParticipant @martinkyte99762]

It would be interesting to get some feel for how people got going in CNC. I suspect there are more gradual processes than all at once leaps. Sticking a stepper on a rotary table or dividing head gets a toe in the wtaer. Starting to use draughting software especially 3D versions really breaks down a lot of barriers. As soon as a person can generate a 3D version of an object there is always the notion in the back of the mind that there is not much further to go to a CNC manufactured part.

Maybe some responses of what path you took would encourage others.

I have a CNC mill part built and a fully operational dividing system. The stalling point for me is a settling on a reasonable draughting package and sorting out a computer for home. I have over relied on work equipment to do whatever I needed in the past so never really got set up at home, so that is my next barrier to cross.

regards Martin

[Ex contributorParticipant @mgnbuk]

How I would love to go back to using SolidWorks if only there was a cheaper 'lite' version

How cheap is cheap ?

Solidworks Education Premium is a membership benefit at the Experimental Aircraft Association – membership is from $40 year. Personal, not-for-profit, use only though, if that is a consideration.

Nigel B.

[IanTParticipant @iant]

Anyone know how different Solid Edge is from SolidWorks?

I ask because I recall reading that the (underlying) 3D CAD 'engine' that SolidWorks originally used was licensed by them from Siemens. So I wonder if there may be some product commonality lingering on from that previous association?

Either way – Solid Edge 2020 Community Edition is free to download and seems to be a very capable 3D CAD system – more than enough for most peoples needs I'd think.

Regards,

IanT

[Martin ConnellyParticipant @martinconnelly55370]

Want to create a nameplate? F-engrave is free. I've also just downloaded Estlcam 11 (another free program) to have a play with. It loads a DXF file (available from plenty of CAD programs) and creates the Gcode program for the part and also simulates the program running. Just an few examples of the useful free programs available.

I use Mach3 on old laptops running XP that were going into the WEEE waste at work if I didn't salvage them. I have external motion controllers so an old computer works fine. On the lathe I use a wireless mini keyboard as a pendant control. I have a wireless pendant with MPG (manual pulse generator) for use on the mill because it has two more axes than the lathe.

You can download and run Mach3, F-engrave and Estlcam onto a windows 10 computer and play with them to see what can be done without knowing any Gcode and without buying any hardware.

Martin C

[Nigel KParticipant @nigelk]

Thanks again to all for this information – all very useful.

As I type I am downloading Solid Edge 2020 Community Edition so I'll take a look at that.

mgnbuk – great tip – thanks – and JasonB I will take a look at that Webeco website – I hadn't seen it before.

[Anonymous]

Posted by Martin Kyte on 01/04/2021 13:38:54:

It would be interesting to get some feel for how people got going in CNC.

I suspect my path was somewhat different to the norm.

Over the years I'd seen small CNC mills pocketing out clock wheels and similar at exhibitions. But that really didn't interest me. Similarly I have the skills to convert my own CNC, but not the interest. I'm lazy and want to make parts, not faff about with machine projects.

The impetus to go CNC came from work, where I was doing the mechanical and electronics design for a high power bi-directional AC to DC power converter. Clearly the case and liquid cooled heatsink was going to need to be CNC milled. I looked at a number of options from new, or secondhand, professional to high end hobby. In the end I settled on Tormach. The criteria were a minimum envelope of 6" cubed (which in restrospect would have been far too small) and 4-axis. Of course I could see that the CNC mill would be useful for my traction engines as well.

I was already conversant with 3D CAD, so it was simply a matter of learning CAM. Suffice to say I ended up with VisualMill, although looking back I'm not sure that was the right decision. OneCNC might have been better. These are commercial packages, but remember I want to make parts in a sensible time so multiple tools, automatic tool length measurement and tool tables, plus 2.5D, 3D and 4th axis capability were essential. Re-machining capability is essential for me.

Learning CAM and CNC was a very steep learning curve done under extreme time pressure from the client. Within a few weeks (full time) I was comfortable making fairly complex 2.5D and 3D parts. I can't show many of the larger parts, but here are some of the simple parts I made while feeling my way:

Subsequently I've made many parts for work and for my engines. The engine parts range from simple but where multiple parts are needed like wheel spokes to parts that would be difficult to make in the workshop by other means:

or impossible:

Like everything else the CNC mill is a tool to be used when appropriate. I don't have a CNC lathe, but my repetition lathe is probably quicker at turning out the multiple parts I need such as nuts, bolts and studs.

Andrew

[John HaineParticipant @johnhaine32865]

I started thinking about an ELS system for my lathe and looked at the online project that was going on. After a bit I realised that if you were going to go to all that trouble just to cut a thread you might as well add full CNC, so after a small amount of cogitation (and inspired by Tony Jeffree's articles on his ML7 conversion) I converted my S7, using Mach 3 to drive it. This was back in 2010.

Once I'd discovered how easy it was I realised it would be much easier to avoid twiddling handles on the mill and thought about adding CNC to my VMB, but I didn't fancy doing major violence to it to add ballscrews, plus would need a mill anyway to do the work! I flirted with the idea of converting an X1 and actually bought one, but realised after a short while that it needed a lot of work just to make it an adequate mill (like machining the mating face for the column flat!) let alone converting it, so I sold it on.

I was keeping an eye on eBay and scored a Denford Novamill mechanics for a modest sum without the electronics. But who wanted an old DOS PC anyway? Since I'd already built the drive box for my lathe I did the same for the mill.

At some point I converted a Myford dividing head with a stepper to use as a 4th axis and built a "Ward" controller as well, and actually I've not yet used it as a 4th axis only straight dividing.

For software I use Mach 3 which was the obvious choice in 2010. I got a reconditioned Dell desktop to run it using the parallel port. I suspect the time is coming to change from M3 to something else before the PC disc drive crashes on me. At the time I didn't fancy the Linux learning curve as well. I have some special purpose macros I've written for Mach3 and it's harder to do these things in LinuxCNC I think, and the choice of motion control boards seems more limited – so not sure where to go next.

I don't yet use CAD/CAM but ought to learn. The Mach 3 wizards are very useful and do loads of common tasks for both turn and mill. I use a free CAM program called G-Simple which is good for shapes beyond the wizards (but no longer supported and hard to find a copy). F-Engrave is great for nameplates – have a look at my album called Nameplates. Also it's free. I also make G code for specialist things like cams, ratchets, and pallets, and wheel crossing-out. That's done in Excel (or could use Open Office Sheet). I've got some special purpose stuff like a program for thread milling that someone kindly supplied.

When you get into CNC technology you can use it for other things. When I wanted an X power feed for my VMB I used a stepper controlled by GRBL on an Arduino, just because it was easy – my phone provides the user interface. The controller will support 3 axes, so currently I'm building a CNC coil winder that will use the same box with an extra axis enabled. I will be able to use the same box to also drive the dividing head on the VMB so I'm thinking about whether I can do some helical gear cutting…

You might gather from this that I find the CNC technology as interesting as what I make, and you wouldn't be wrong…

[jaCK HobsonParticipant @jackhobson50760]

I feel (maybe just hope) that a cheap CNC metal cutting market will appear. With 3D printing, people are learning CAD so CAM should be an easy step for them. I'm amazed by what you can get in 3D printing for the money but I guess it is rigidity that really costs.

I got a real urge for a 5 axis Pocket NC https://www.solidprint3d.co.uk/pocket-nc-store/ but I need to win the lottery tonight before I can get that toy.

I'm sure the future is going to include a combination of additive and subtractive machining on one device.

[Peter Cook 6Participant @petercook6]

Posted by jaCK Hobson on 02/04/2021 11:23:40:

I feel (maybe just hope) that a cheap CNC metal cutting market will appear. With 3D printing, people are learning CAD so CAM should be an easy step for them.

I'm not sure. I suspect an awful lot of the 3D printers bought are being used to print things from the internet (Thingverse, Yeggi, Instructibles etc.). The learning curve for 3D design is steep, and the risks inherent in metal cutting are also far higher than for 3D printers.

Be careful what you wish for. If 3D metal cutting tools become "cheap" and mass market – watch out for the H&S brigade to be close behind.

The other issue that I suspect will get in the way is tool changing. Commercial CNC setups have some very sophisticated tool changing capabilities, difficult to replicate at any reasonable cost. what proportion of hobby lathes have a capstan turret? How may of them could be automated?

[John HaineParticipant @johnhaine32865]

The vast majority of my CNC work uses the same tool throughout the job, unless for example there are a few holes to drill as well as some profiling/pocketing etc. Toolchange is manual.

[JasonBModerator @jasonb]

I probably average 2 or 3 cutters per job plush any drills and manually change them which works fine for me as most parts are one offs or maybe pairs and I tend to watch the first cut a bit more than I would subsequent ones so am by the machine when a tool needs changing. Also the free F360 no longer allows you to output multitool code so need to load the next bit of code anyway and I don't have any quick change tooling so set each tool as needed.

regarding the earlier comment about gantry type machines not being rigid enough, that will also depend on the machine. The very basic 3020 type machines from the likes of BangExpress are a bit lightweight but if you pay you can certainly get more capable machines in those sizes. However when I said that a gantry machine may suit a lot of "makers" more than a mill I was thinking more along the lines of the ones somebody else linked to from CNC4you or Sorotec. which are certainly more capable. Or you can build your own, this one is made from JB Welded together bits of granite but is more than capable of taking a decent size cut. ( colourful language alert)

[Nigel KParticipant @nigelk]

A braver man than me in that video!

To Jack Hobson's comment, yes, the Pocket NC does look attractive and may be useful for some applications but it's very limited on the size of things that it can cut and very expensive. I have to say also that a training video that I saw online didn't give me the confidence that I was a 5-axis sort of guy!

In my search for a suitable CNC mill my favourite wavers – and I clearly need to do more research – but my gut feeling is that the Tormach is a good bet. Yes, it's expensive, but the company gives the impression of being 'sorted'. Detailed product information is available, lots of videos and there is clearly a large amateur/SMB user base (which is a good sign). The other manufacturers of CNC equipment could learn a lot from their marketing. If I have any criticism it's that when you google 'Tormach' from this country (the UK) you are taken to a static page which, on the one hand, claims "United Kingdom Wide Coverage; Our delivery and customer support services are available to customers across the UK" but doesn't give any clue what this means or any addresses – just a web form. Anyway, I'll contact them and see what they say.

Turning to CAM software, I may have mentioned that I have been using FreeCAD for some time. This most definitely has its faults but I like the no-strings-attached nature of this open source application. I decided to find out whether there was a good CAM package to go with it and after a short browse on the Internet I realised that my very small brain had missed the fact that FreeCAD contains a tool path generation facility. For anyone who's interested, you might be interested in the following video because it shows, in very short order (about 17 minutes) how to both draw a part in FreeCAD and then to create the G-code to cut it on a CNC mill:
 

Edited By Nigel K on 02/04/2021 14:56:03

Edited By Nigel K on 02/04/2021 14:56:43

[Bob RodgersonParticipant @bobrodgerson97362]

As a Tormach owner I can vouch for their excellent after sales service. I have had, since 2013/14, two occasions on which I have had to contact them with problems. On both occasions, even though I have zero electronics background they were able to trace a fault, determine what spares were necessary and get them to me in a short space of time. They do not have agents in the UK because Electrical regulations prevent them selling their products within the UK but you c an import theme direct.

[Nigel KParticipant @nigelk]

Very helpful Bob, many thanks!

I can feel a bullet-biting moment approaching

As a matter of interest, do you know what electrical regulations they don't conform to? Perhaps not CE marked?

Edited By Nigel K on 02/04/2021 16:02:51

[Bob RodgersonParticipant @bobrodgerson97362]

They are not CE marked and they have held discussions about importing them to the EU and having dealerships but there is too much red tape as far as I know. On the occasions that I had to call them they described exactly where to place the probes on my Multi-Meter (Bought specifically for any problem solving required while installing various attachments to my mill). The wiring within the cabinet is very clearly marked and numbered so that it is fairly easy to trace things.

[Ex contributorParticipant @mgnbuk]

Commercial CNC setups have some very sophisticated tool changing capabilities, difficult to replicate at any reasonable cost. what proportion of hobby lathes have a capstan turret? How may of them could be automated?

Toolchangers are not compulsory on CNC machines – 3 of the lathes at work have manual toolposts ( 2 x Multifix & one Capto). When a toolchange is required, the program halts & a lamp flashes to alert the operator. Pressing a "tool change complete" button restarts the program. Obviously requires the operator to fit the correct tool ( a comment in the program can be added as a prompt) , but that hasn't been a problem so far. 4 of the CNC milling machines don't have ATCs either – lack of an ATC really isn't the end of the world !

They are not CE marked

As we are no longer a member the EU, CE marking is no longer required – but UKCA marking is. Whether or not there is any practical difference yet (other than the required marking being attached) is another matter !

Nigel B.

[hang rexParticipant @hangrex53765]

In close imitation to the entire science and research landscape in the country, the marking technologies were largely imported, but the Chinese manufacturers are gradually upping their game and making their own high precision marking and engraving equipment.

[Nigel KParticipant @nigelk]

Toolchangers are not compulsory on CNC machines

mgnbuk I would say that you are absolutely correct. However, with model engineering (and sometimes when you own your own company) there is also the element of fun and the enjoyment of learning to be considered. I admit to feeling a bit of a fraud ordering an ATC with my CNC milling machine – I am quite certain I could get on without it – but I'm not only interested in economic efficiency, I want to learn how to use it and enjoy the fact that the machine is running by itself. If you're paying someone to operate a milling machine then perhaps in certain circumstances an ATC is counter-productive in the sense that you probably want that person to be keeping an eye on everything.

[Author]

Posts