Name and Number Plates

[753]

I would think most of the people that offer an etched name and number plate service are aimed at the smaller scales so they tend to use thin brass such as 24, 26 gauge brass which works well, but when you get to our scale I have thought they lack the depth of the prototype.
I was just about to order a set of plates for the River loco I am building when it occurred to me why not have a go at making the plates myself. As with the etching process good artwork is the key to a successful plate. I started with drawing the numbers at 1in cap height which is manageable to get into those small corners, when complete I scaled them down to the required size. The smallest corner was 0.025in dia so I ground up a spade cutter 0.020in dia.
I set up the mill to cut 0.020in deep and ran the file, and to my delight it worked.   The plates have depth just like a real loco.
When it comes to the smaller plates like builders and shed plates the only way is to go with etching.

Mike.

[Alan_H]

Superb job!! I was wondering if one of the small CNC engravers might be useful for making parts, (I'm thinking of the frames for my Rover loco which I would normally fretsaw). As a computer duffer, and having served my time 40 odd years ago when things were rather more manual, how easy is it to programme CNC machines?

Alan

[IanT]

A very simple answer Alan, not quite as simple as 3D print.

Also "programme CNC machines" covers a great deal of ground.

You mentioned small CNC engravers - of which the 3018 is probably the cheapest. They normally come with a simple arduino-based controller running GRBL that understands G-Code and which can also have a manual jog/control handset. It's quite possible to code simple actions in G-Code directly once you have understood a few basics

https://cncphilosophy.com/g-code-programming-for-dummies/#:~:text=%20G%20codes%20%201%20G42%20%3D%20cutter,programming%209%20G91%20%3D%20incremental%20programming%20More%20

But generally, you will need more software to sit between your drawing, design or image and your engraver.

This can be characterised as being 2D, 2.5D and 3D but perhaps it's easier to think in terms of routing or machining. Generally in routing you are cutting in one plane and just adjusting the depth of cut as you make sufficient passes to do the work. The 2.5D aspect is where there are a number of 'levels' of cut required in the same part. There are lot of 2D/2.5D programmes that can take a DXF or image file and do this work.

For 3D 'machining' we are moving into the area of CAM (computer aided manufacturing) which are programmes that can convert a 3D CAD design into tool movements in 3, 4 or 5 axis. There are CAM packages included in Fusion 360 and FreeCAD. Their correct use needs a good deal of expertise I understand.

I have also thought about experimenting with a simple 3018 type 'router' which could be fun (and instructive) but it's important to realise that it's going to be very limited in it's cutting capability and pretty noisy too I believe. Might be a toe in the water though...?

Regards,

IanT 

[Nick]

Alan,

I can't tell you how easy it is because that is a personal decision, but if you know the steps involved maybe that will help. First you must acquire or make a drawing of the frames, much as if you were cuttting them by hand. Then you have to translate that drawing into instructions for the CNC machine, commonly called "G code". If your drawing is done the traditional way, on paper with dimensions indicated, you have two choices.

One is to learn enough G code to translate the dimensions by hand and type them into the computer or the CNC controller. That is quite doable for a frame that is a relatively simple two dimensional (flat) object, though much more complicated for something like a chimney or dome.

The other option is to draw the frame on the computer using a CAD program and then post-process it into G code. Many CAD programs have in-built post processors, but if not it is necessary to export the frame as a CAD file and run that through a separate post processor. On that route you don't have to learn G code, but you do have to learn CAD.

A necessary step in created the G code is making decisions about the machining process, particularly the size and shape of cutter, the feed rate and the stepover (the step size from one cutter pass to the next. It is necessary to understand the machining setup.

That's a very high-level view of the processes. All routes involve some learning, and whether and how you do it depends on your inclination and determination to undertake it.

A final thought - if your interest is in frames and you don't want to cut them out by hand, consider laser cutting. There are many individuals and companies around that will cut based on your CAD file, or in some cases from a hand sketch. A web search will give you plenty to choose from. Model Engineeers Laser is highly regarded in our hobby (usual disclaimer).

Nick

[753]

Alan

Ian and Nicks description of CNC are correct, but like all unknown processes they seem daunting at first. When I first got involved with CNC my knowledge was zero, also I have no knowledge of programming.

I would advise you to bite the bullet, Free CAD is what it says, start by drawing simple shapes such as a square go to the CAM section choose a tool dia, depth and speed of cut and run the file on the simulator. If you can get that far then buy a small machine and away you go, you will not regret it.

Mike

[John Candy]

The plates look superb .... I hadn't previously really thought about the depth of the commercial etches and had accepted them for what they are.

Concerning the 3018 engravers ...... looking at them, the "blurb" seems to suggest they are NOT suitable for engraving metals only soft materials (plastics, wood and the like). The ones I have just Googled seem to be a combined CNC mill and laser cutter.

Has anyone here used one of these?
Reason I ask is that it is a "bit of a fiddle" switching the Snapmaker 2 between 3D print / laser cutting / CNC milling modes (I have only used the 3D print mode as yet) and the 3018 seems to be so cheap that it may be a better solution than fiddling about with the Snapmaker changeover routine.

John.

[IanT]

I've been watching this 'CNC Engrave' tech developing for little while now John - and it's definitely coming along apace.

My personal thinking was that (whatever I eventually do wrt CNC) I needed to have a decent 3D CAD 'engineering' capability and decided that Solid Edge was the right CAD, at least for me. It works well for both my current engineering work and my 3D print needs. It doesn't have a CAM capability but there are both free & 'paid-for' CAM-type programmes available (and there's nothing to stop me using Fusion or FreeCAD just for CAM for instance).

As Nick also mentions, I can already export my 2D 'parts' for laser (or water cutting) without any need for an in-house CNC capability - the costs are quite reasonable and the quality very good.

The cost of transitioning from 'manual' machining to 'CNC' in-house would be significant, as you need a pretty robust set-up to cut (harder) metals at sensible rates (e.g. a CNC equipped mill or lathe). My short term (and perhaps final) solution has been to purchase a DRO set-up for my existing small mill. This obviously doesn't automate my machine processes but hopefully will make them more accurate and possibly faster.

Going back to the 'Engraver' tech, they come in many flavours with varying (e.g. increasing) price tags. This includes table size, spindle type, guide type etc. Whilst it's possible to start with a very cheap 3018 and upgrade it, I'm not sure 'upgrading' is a very cost effective idea. Might be better to just use it, learn it (and it's limitations), then sell it for what you can get and move up to a better machine.

Another option is to custom build a machine. All the essential parts are available and pretty much standardised now (2020/2040 extrusion, round or linear guides, threaded or ball screws, stepper size/power, electronics & PSUs etc. A kind of CNC 'Meccano' really. This probably wouldn't be the cheapest option but is certainly possible and may give a machine that better meets personal requirements.

What would I use an engraver for?  Well I like working wood, so simple routing to start with but also possibly smaller/thinner parts in metal where I either need repeatable accuracy or volume parts.

I haven't completely ruled out a very cheap machine to play with but I'm not in a hurry. The Chinese are a clever lot and they keep tweeking and improving things to sell us more, so I may well be tempted eventually. I didn't think I'd get into 3D print - but it is certainly a useful tool for some things (although not a cure-all).

Regards,

IanT

[AshleyW]

if you don't have the tackle to make em , though, here's who i use, they come out very well. ash
https://www.lightrailwaystores.co.uk/products/npp-416?variant=11354164801

[cabbage]

I do have a 3018 CNC machine... But I don't use it that often. Given a solid TC cutter in a ER6 collet it can (slowly) cut Aluminium to about 2mm thickness. Its real working material though is MDF. Although I bought it to produce things for the railway - its main use is making things for  Barbie...

Regards

Ralph

[John Candy]

Ian and Ralph,
Thanks for the comments and info on the 3018.
I would mainly be wanting to laser cut / mill plastics and soft metals which my Snapmaker can do, so there would appear little point in adding a 3018, other than to avoid the hassle of switching the beds and cutting head units.
I think Ian's "wait and see what develops" philosophy is a good one : There is bound to be an improved version "just around the corner".

Regards,
John.