CNC miller instead of laser cutter?

Martin Wynne

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@AndyB

A laser cutter is large, expensive, and not very home-friendly.

A CNC-miller/router is much more affordable, for example this one is £240

https://www.amazon.co.uk/dp/B08K95J434/

3.3mm and 4mm wide plywood strip is readily available.

Use a miller to cut the sockets in it? 1.5mm slot-drills appear to be readily available. A holder/jig for plywood strip could be FDM printed.

Templot could generate the G-code directly for the sockets, and cutting the strip to length. No need for DXF or CAD.

So now we need an option for the Plug Track sockets and chair plugs to have semicircular ends. I'm on the case. :)

I think AndyB suggested something similar, and I was a bit dismissive. Sorry Andy.

Martin.
 
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Martin Wynne

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For Scalefour Society members, an A4 sheet of laser-cut 4mm wide timbering strips costs £10

BSS12.jpg


Thickness not quoted, but given that it is labelled for Brook Smith (riveted) construction, it will be 1/32" (0.8mm).

Other suppliers are available. Anyone?

Martin.
 
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AndyB

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My experience with one called Woodpecker at this link:


I've never tried it with plywood. It seems to like hard materials like MDF and FR4. Doesn't do well on brass and I think that's because brass tends to be a bit "sticky" meaning the chips don't clear easily. Plywood might be a bit sticky too if it's softwood but I'm just guessing.
 
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Martin Wynne

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Thickness not quoted, but given that it is labelled for Brook Smith (riveted) construction, it will be 1/32" (0.8mm).

Or for something thicker than 1/32" plywood, a wide range of limewood strip sizes is available from model boat suppliers. See for example:

https://www.cornwallmodelboats.co.uk/acatalog/lime_strip.html

Including 4mm x 1.5mm, 4mm x 2mm, etc., for 4mm/ft scale crossing timbers:

limestripprofile.jpg

In fact 4mm x 2mm is exactly to scale for both width and thickness.

Other model boatbuilding suppliers may be worth a google.

Limewood is a soft easily worked wood (similar/same wood as Basswood). Strips are planed rather than laser-cut, so the dimensions might not be spot-on. But an FDM timbering fret could be adjusted to fit.

Martin.
 
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Martin Wynne

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Doesn't do well on brass
@AndyB

Hi Andy,

Those engraving burrs and cutters I can see on Amazon wouldn't be very good on metals. For brass you need a proper slot-drill, end-mill, or D-bit. And preferably some "suds" (cutting fluid/coolant/lubricant). For easier milling use aluminium alloy instead (unless you need to solder it).

But we are not looking for metal timbers for track. :)

cheers,

Martin.
 
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Martin Wynne

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I should not encourage you Martin, but here you go:-

But by the time you have bought the CNC Mill (unless you want it for other purposes) it will probably be more cost effective to get a laser cutting service to produce your socketed timbers, especially if Templot can provide the "bunch" option.

Steve
@Steve_Cornford

Hi Steve,

Thanks for the link.

Yes, a laser-cutting service would be fine -- eventually. But I want something that I can use myself because in the initial stages of Plug Track there is going to be endless trial and error. Sending experimental bits to someone else, explaining exactly what you want, and waiting for the results is just too frustrating (and expensive).

I think you are jumping ahead and don't realise just how much road is still in front of me for Plug Track. The stuff in 228a is not ready to be used for any actual model making, I didn't release it for that purpose. :)

I'm still regarding FDM timbers as the default option for Plug Track, but I can see the attraction of real wood timbers with sharp corners. For someone without an FDM printer, a little CNC miller might be a more attractive buy.

cheers,

Martin.
 
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Hi Martin,
You were enquiring about laser cut strip. Yes the Scalefour strip is 0.8mm. I believe that Tim Horn cuts the plywood for them and he will (if you ask him nicely, (he's a busy man) do 1.5mm if you wish. There is lots more that he can do of course and he might be persuaded to cut the sockets too. (I have no idea on this possibility though). Intentio is a possible alternative. Brian Lewis probably could too but I understand he is trying to retire and has been for a while.
 
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Martin Wynne

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I'm always amazed at Amazon. You order a CNC milling machine at breakfast time, and it's delivered in time for tea. :)

It's the 3018PRO miller available from several sources and brandings:

https://www.amazon.co.uk/dp/B08K95J434/

Beautifully packed -- unlike some of the unboxing videos I've seen of machines ordered direct from China, which appear to arrive in battered boxes all tied up with string and sticky tape.

I went for the Mostics version because it seems to be the only one having external knobs on the feed screws. Which makes it much easier to set up, but also means the machine could be used as a manual miller at a pinch. I can see the knobs being replaced with proper calibrated handwheels made on the BIBO printer. I watched a video on some other 3018PRO machine in which the only way the guy could move the slides manually was by twisting the screws in his fingers, which struck me as crazy.

Now the fun begins of putting it all together, and then seeing what it is capable of. After the disappointment of the Cameo cutter I'm not too hopeful, but we shall see. As ever, the only way to find out is to get one.

I'm feeling a bit sheepish about admitting I've obtained a CNC miller, after rubbishing the idea of using one, and then getting all grumpy about the Plug Track topic being distracted with too many confusing options. :)

Martin.
 
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Martin Wynne

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A possibility with a CNC miller might be to have thin timbers milled in relief on a thick trackbed base:

thin_milled_timbers.png


Timbers just thick enough to allow a thin layer of ballast (which might be applied before adding the rails -- cover the sockets while doing it). This would require milling time only for a single pass, and retain maximum rigidity of the track base, while allowing a good depth for the chair sockets. The milling cutter would be changed to a smaller size for the sockets. If milled of course the sockets can't have the square corners shown, they would need to be radiused corners. But the sockets can be wider without weakening the timbers, for easier milling.

The base could be plywood, or a composite board such as MDF, or solid wood (made by gluing together strips of wood), or something else. No need to fiddle about with individual timbers, plug locators, templates, or anything else. Just one solid piece of trackbed ready to have the rails plugged in.

In theory the same thing could be done in FDM printing, but a large flat sheet of polymer is a bit impractical, being difficult to remove from the build plate, and liable to shrinkage and warping.

Just thinking aloud. :)

Martin.
 
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AndyB

Member
A possibility with a CNC miller might be to have thin timbers milled in relief on a thick trackbed base:

View attachment 2198

Timbers just thick enough to allow a thin layer of ballast (which might be applied before adding the rails). This would require milling time only for a single pass, and retain maximum rigidity of the track base, while allowing a good depth for the chair sockets. The milling cutter would be changed to a smaller size for the sockets. If milled of course the sockets can't have the square corners shown, they would need to be radiused corners. But the sockets can be wider without weakening the timbers, for easier milling.

The base could be plywood, or a composite board such as MDF, or solid wood (made by gluing together strips of wood), or something else. No need to fiddle about with individual timbers, plug locators, templates, or anything else. Just one solid piece of trackbed ready to have the rails plugged in.

In theory the same thing could be done in FDM printing, but a large flat sheet of polymer is a bit impractical, being difficult to remove from the build plate, and liable to shrinkage and warping.

Just thinking aloud. :)

Martin.

Oddly enough I just had exactly the same idea :) That would solve quite a few problems. I'd give MDF a shot first.
 
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Martin Wynne

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A snag with any milling operation in wood is that it will raise a burr on the surface. For the timber tops this could be dealt with by sanding and a stiff brush, but ideally the sockets need something cleaner. Fortunately the machine comes with a pack of ten 20-degree v-cutter D-bits, intended for wood carving. Which could be run round the sockets to chamfer the top:

socket_chamfers.png


(The FDM 3-D printing already includes a socket chamfer, but the above would be done on the machine using the cutter size and depth adjustments.)

p.s. the blurb for the machine suggests that it can be assembled in 20 minutes. That seems a bit optimistic to me -- it would be wise to allow a fortnight. :)

Martin.
 
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timbersgalore

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England
Martin
Vinal may be a better option. The splinters would be a big issue. If using traditional method PCB is a good option. In my junk pile I just dug out and photographed this attempt at making a 2mm slip using a CNC mill/router. The base is all one bit as you describe.
from the discards pile.JPG

Excuse the cobwebs. A little bit of the vynal colour can be seen on the switch operating slider. The crossing makes use of a drop in bass milled plate.

I may be able to find some pictures on the job on the router.

Timbers
 
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Martin Wynne

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@timbersgalore

Hi Timbers,

That's interesting. Not many folks would chuck that in the scrap bin!

What is Vinal/Vynal? Do you mean PVC? As in floor tiles perhaps?

Can you post a link to the material you mean and a supplier? Thanks.

cheers,

Martin.
 
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timbersgalore

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Location
England
Yes 1.6 mm ABS. I went and found the packet in the workshop. I should warn you that it was not easy, it can be an uphill struggle to get the CNC tamed. You have to be carefull not to melt the plastic - this usually ends with a broken cutter. As the cutter get smaller so does the feed rate. Don't be supprised if you end up maching at a snails pace.

g1.JPG


Paxolin is another material to consider. I use it for jigs etc.
 
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Martin Wynne

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I'd give MDF a shot first.
@AndyB

Hi Andy,

Yes, I was thinking in terms of MDF to try first. Plywood is very likely to warp with most of one skin removed, and being softwood is likely to splinter from the milling cutter. But MDF dust is regarded as a health hazard, so I would need to make a dust-extractor attachment for the spindle housing (FDM?), to connect to Henry the vacuum cleaner.

And then this stuff appeared on my screen:

cherry-real-wood-edging-50mm-15303067655_400x.jpg


Various sizes and hardwoods:

https://www.veneersonline.co.uk/col...any-pine-ash-cherry-wenge?variant=27855505735

https://www.veneersonline.co.uk/collections/50mm-iron-on-wood-edging

It's 0.6mm thick, which is the depth I had in mind for the timbers. If stuck all over the MDF, it could be machined away to leave the timber tops (with some grain). That still leaves the MDF dust from the sockets, but a lot less than milling out the timber outlines all over it. And being hardwood, it should mill more cleanly and make more precise socket locations -- cherry and beech are favourites of woodturners for clean-cutting:

https://craftgecko.com/what-is-the-easiest-wood-to-turn/

Hardwood dust can also be harmful, but it's not the very small particle size as MDF, so not so easily breathed in.

The 50mm strip is wide enough side-by-side for multiple tracks at roughly one track per strip (4mm scale). The cost would be around 60p per metre from a full 50-metre roll. The big unknown is whether the hot-melt adhesive will hold a small sleeper-sized piece firmly enough for milling, and/or be affected by friction heat from the cutter. The vacuum air-flow should help to keep it cool.

It's possible to buy ready-veneered MDF, but not as far as I can find in the 2mm thickness I was thinking of using. And it's double-sided, so half the extra cost of the veneer would be wasted.

milled_timber_tops.png


Always some idea waiting to be tried -- and usually failing. :)

cheers,

Martin.
 
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