Pantograph Milling Coach Panelling For G3

jamiepage

Western Thunderer
These frets were cut out this afternoon using a window/door/window plasticard pattern on the pantograph miller. The pattern had originally been used to produce some 10mm (sorry, not 1/32) panels and I played around with the ratios to produce these 13.5mm (/foot for G3) frets. Both the original 10mm panels and these larger ones were produced by sliding the blank coach side between two parallel runners on the pantograph table to pre- marked datums at which point the panels were cut out. Pleased to say that some initial experimentation with arm lengths produced nicely rectangular sides with no bowing and accumulated length was held within 1mm overall (c.0.03%). The master was cobbled together with plasticard shapes at twice the G1 requirement and has now worn out due to so much use.
The next burst of enthusiasm may see these frets mounted on the inner outers, bolections fitted and window blanks cut through.
I guess it just shows how a pantograph miller and a simple pattern can be used to produce coach side frets with repetitive detail. Mind you, I do prefer the idea of programming a machine to do it and wish I knew how. And wish I had one.
Actually, I am also building up door, pair of window, and window end panels with the idea of having them resin cast for assembly that way. Not sure which route would ultimately be quicker.
Eiher way, have also just received some beautiful strip Jelutong, 1/2 inch x 3/16, pretty well perfect for the 11 inches x 4.5 inch underframe solebars, headstocks etc.
The last photo also shows a G1 version, slightly more advanced in construction but also awaiting another burst of enthusiasm.
 

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JimG

Western Thunderer
These frets were cut out this afternoon using a window/door/window plasticard pattern on the pantograph miller. The pattern had originally been used to produce some 10mm (sorry, not 1/32) panels and I played around with the ratios to produce these 13.5mm (/foot for G3) frets. Both the original 10mm panels and these larger ones were produced by sliding the blank coach side between two parallel runners on the pantograph table to pre- marked datums at which point the panels were cut out. Pleased to say that some initial experimentation with arm lengths produced nicely rectangular sides with no bowing and accumulated length was held within 1mm overall (c.0.03%). The master was cobbled together with plasticard shapes at twice the G1 requirement and has now worn out due to so much use.

Jamie,

How did you do the (what look like) square corners on the bottom of the quarterlight openings? I could only get close to doing that on my mill if I used a very small radius cutter to finish off the corners.

Jim.
 

Steve Cook

Flying Squad
Nice work Jamie, they look very clean and accurate :thumbs:
I look forward to seeing the results of the next bout of enthusiasm :)

Steve
 

28ten

Guv'nor
Seems to work pretty well to me :) I'd love to have either a cnc mill or pantograph mill as I could cut brass then. There are pros and cons to both machines and you just have to adapt accordingly, I do know a very easy of producing the templates for the pantograph miller......
 

Dikitriki

Flying Squad
So with a known good drawing, you could vectorywotsit the doohickey, laser it in MDF, and I could cut it out on the pantograph miller. Bingo :cool:
 

28ten

Guv'nor
So with a known good drawing, you could vectorywotsit the doohickey, laser it in MDF, and I could cut it out on the pantograph miller. Bingo :cool:
Exactly :cool: all that valve gear would be a doddle and it is easy to produce templates double, triple, quadruple size
 

Steph Dale

Western Thunderer
I can laser the template in mdf, much easier than trying to cut tricky shapes in plasticard, or keep boiler formers symmetrical :)

Cynric,
Surely in G3 you'd just cut out the parts on the Laser wouldn't you? I wouldn't have thought you'd need the intermediate stage.

Jamie,
Interesting stuff - I never had much luck cutting out plastic parts on my engraver when I had it. Added to which it was in pretty much full-time use with brass for patterns, I wouldn't have had the time to build coaches then ;). Nice assembly job on the finished parts too.

What sort of material thicknesses are you using in G3?

Steph
 

jamiepage

Western Thunderer
'How did you do the (what look like) square corners on the bottom of the quarterlight openings? I could only get close to doing that on my mill if I used a very small radius cutter to finish off the corners.'

I think that's just a trick of the scale, Jim. I used a 2mm dia D bit type cutter which has left the expected radius in those corners. They will need to be filed squre. The large radii at the window tops (actually radiused corners and a slightly curved tangent between) and the eaves panels were of course formed by following the patterns.

A controlled cutting out of the master patterns, rather than the hand made ones I managed, would lend themselves to producing all the other required layers of the body sides with a good chance of consistent register layer to layer.

Photos here are of the potential alternative. Blanks all cut for patterns for door (singular), single window end panels (handed and two different sizes), then the whole sequence of window - window panels to allow for various compartment dimensions/ juxtapositions.
An All- Third could be produced using the four panels shown in one of the photos ; I will probably finish those four (tumblehome, layers of panelling, hinges etc) then take them to a resin caster for their opinon- and quotes.
The idea would be to apply a .040 main panel, then beading layers on top. The .040 panel when applied to an end section would produce a rebate to take the coach end proper. Hmmm, a pattern would be needed for that as well.
 

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28ten

Guv'nor
Cynric,
Surely in G3 you'd just cut out the parts on the Laser wouldn't you? I wouldn't have thought you'd need the intermediate stage.
Yes, but if you want to cut brass parts, it is quicker and more accurate way of making the template. If I was doing G3 I would need a bigger laser :D
 

jamiepage

Western Thunderer
Steph,
The fret was cut from .020 sheet although .015 would have been better. The idea will be to mount it on a .040 layer, to produce a total bolection scale thickness close to the required 1.25 inches.
The sheets were mounted with double sided tape onto a backing piece and cut quite well with the cutter running at a slow speed.
The G1 frets were cut from .010 with beading thicknesses of 1mm and likewise cut well enough.
Too fast a cutter speed and they would melt, pull, or rip. Back off from that a bit and it was fine.
The degree of 'grab' from the tape was important- too fierce and it was difficult to separate the fretted panel, too weak and the workpiece would shift and spoil. Two rubs along the exposed sticky tape with non stick paper before laying down the workpiece did the trick!
All the best
Jamie
 

JimG

Western Thunderer
Steph,
The fret was cut from .020 sheet although .015 would have been better. The idea will be to mount it on a .040 layer, to produce a total bolection scale thickness close to the required 1.25 inches.
The sheets were mounted with double sided tape onto a backing piece and cut quite well with the cutter running at a slow speed.
The G1 frets were cut from .010 with beading thicknesses of 1mm and likewise cut well enough.
Too fast a cutter speed and they would melt, pull, or rip. Back off from that a bit and it was fine.
The degree of 'grab' from the tape was important- too fierce and it was difficult to separate the fretted panel, too weak and the workpiece would shift and spoil. Two rubs along the exposed sticky tape with non stick paper before laying down the workpiece did the trick!

Jamie,

I am using Letraset Low Tack double sided tape to give a "gentle" hold on delicate parts. If I need a stronger hold, I use low tack carpet tape which is low tack on one side. As I reported a while ago, Seklema Multimatt would be the dog's doodahs for the job but it costs a lot and its variation in thickness doesn't suit my working with a traditional mill.

On the melting of the material, can you get carbide cutters for your machine? Carbide cutters machine plastics with no melting problems at all. I run my carbide cutters at up to 5000rpm in styrene and acrylic and have not had any heat problems - except once when I started getting what looked like melting of styrene. I thought it might be a blunt cutter and changed it for a new one, to find the same problem still occuring. It took a while for the penny to drop that the spindle was running in reverse - a problem with the KX1 setup. I now find myself regularly checking spindle rotation with my finger. :)

Jim.
 

Eastsidepilot

Western Thunderer
Guys'
With regards to double sided tape I too use it for mounting brass or steel on a plastic base for cutting and I release it by using a hair dryer, this softens the tape enough to release it, not sure if this would work with styrene though:)

Col.
 

jamiepage

Western Thunderer
Col,
Thank you. I would worry about using it with plastic because I seem able to melt the stuff without trying, but have definitely stored the tip for brass work.

Jim,
Thank you. I hadn't thought to look for better alternative tapes, so will track those down to play with. I wish I had re- read your comments properly.
Have you had any problems cutting down into the tapes? Every so often, the cutter picks up some tenacious goo from the tape I've been using, which then attracts plastic waste and generally mucks things up a bit.
The collet is compatible with my conventional mills so I could use carbide mills- I'll give it a go.
Interesting you use up to iro 5000rpm; the casting pattern blanks ( 2 x .100 plasticard) were cut on a conventional mill with a 3mm dia. HSS slot drill at about 900rpm. (Pure stab in the dark and very slow for such a small diameter but I was spooked by the melting business). Fortunately, it proceeded to cut like butter and would cut the full 5mm depth with no sign of distress. It did however, leave some slight ridging to the cut surface so a higher rotational speed (or an interminably slow feed rate) would definitely be beneficial.

Jamie

Last picture showing the multi- layered panelling on these coaches which may be of interest.
 

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JimG

Western Thunderer
Jamie,

Thank you. I hadn't thought to look for better alternative tapes, so will track those down to play with. I wish I had re- read your comments properly.
Have you had any problems cutting down into the tapes? Every so often, the cutter picks up some tenacious goo from the tape I've been using, which then attracts plastic waste and generally mucks things up a bit.

I try to cut exactly to the bottom of the plastic, but I do pick up glue if my zero is a tad too deep. I don't get much pickup with the Letraset tape, but do get noticeable pickup from the carpet tape, but the carbide mills seem to be able to cut through the accumulation and I don't get many problems because of it. One thing I do do if I am getting build up because of glue is to brush it off using a stiff bristled artist's brush to get rid of as much as I can while cutting - maybe not so easy to do on a pantograph mill when you are using at least one hand for the job. But cleaning the flutes of the cutters off afterwards can be a bit difficult and I usually use a fair bit of meths to get them completely clean

The collet is compatible with my conventional mills so I could use carbide mills- I'll give it a go.

I use Drill Service for my cutters, They have a very wide range and they have a cut price range with a "Y" suffix that are comparatively inexpensive and seem to work fine for me cutting plastics. Here's their carbide slot cutter page

http://www.drill-service.co.uk/Product.asp?Parent=100040020000&Tool=76

but you can use the menu at the top to see their whole range of cutters and drills.

Interesting you use up to iro 5000rpm; the casting pattern blanks ( 2 x .100 plasticard) were cut on a conventional mill with a 3mm dia. HSS slot drill at about 900rpm. (Pure stab in the dark and very slow for such a small diameter but I was spooked by the melting business). Fortunately, it proceeded to cut like butter and would cut the full 5mm depth with no sign of distress. It did however, leave some slight ridging to the cut surface so a higher rotational speed (or an interminably slow feed rate) would definitely be beneficial.

I tend to take light cuts - between .15mm and .5mm - and would take several cuts round a part to get the complete depth of cut required. I realise that doing a cut in one pass might be preferable on a pantograph miller but I would have thought that you would be able to cut quite deeply and at a good spindle speed (in the thousands) with no problems.

Jim.
 

JimG

Western Thunderer
Wouldn't a compressor and air tube help keep the work clear of swarf?

Better suck than blow:) - I have got a cheap, bagless vacuum cleaner from Tesco Online which is excellent for cleaning chips from the milling table but the glue and gunge that Jamie refers to won't move under suction so the stiff brush bristles help to get it off the cutter flutes while cutting.

Jim.
 
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