Box sash windows

[unravelled]

This is the result so far of an idea I had for modelling a box sash window. I wanted something which captured the fussiness of the frame without going overboard, and came up with a 5 or 6 layer sandwich to do that. You may have seen earlier samples on the Old Blue Last topic, but the pictures here are of a later batch, after some valuable input from Il Dottore.

While it would be possible to use this idea method with conventional cutting out, I've lasercut the parts for consistency.

 

 

This is a dry assembly of the parts. The overall size of the asembly is 25mmx40mm.

Note that there is an error in one of the layers, which will need recutting .

 

 

These are the individual components

The materials used are 40 thou(1mm) transparent acrylic sheet, and 10 thou(0.2ishmm) white plastic card . All pieces are the same outer dimensions

The first, inside layer is transparent acrylic, forming the lower glazing, with a cutout to represent the opening behind the upper sash.

The second layer (thin white) represents a combination of the frame and putty of the lower sash and the parting bead

The third layer is transparent representing the upper glazing with a cutout in front of the lower sash.

The fourth layer is again thin white, and represents the frame and putty of the upper sash.

The fifth is another thin white layer to represent the lip of the frame.

An optional sixth piece in the thick, or thicker, material can be added as the window reveal, depending on the basic thickness of the wall.

 

More to come

 

Thanks

 

Dave

[Blacque Jacque]

Very impressive, about 2.75mm thick when assembled ?

 

Do you have access to the laser cutter yourself or do you contract it out ?

[unravelled]

Actually the thickness has niggled me, and I've just ordered some 0.5mm acrylic sheet for the next version. This should make the assembled windows near to scale thickness, which could help with building interiors.

 

I bought myself an A4 capacity laser cutter as a retirement present about 18 months ago. It ended up last year producing a lot of items for a school D+T department, but now they have their own A2 sized machine (gauge 1 coach sides and baseboard parts come to mind).

 

 

Thanks

 

Dave

[Blacque Jacque]

Actually, from a scale perspective, 2.75mm ~ 210mm or 8" in real terms isn't far off for a sash window with a reveal. If you take a whole 1mm off that it should scale at around 5". I wonder if the thinner one might look a little too *flat* & lack depth ?

[unravelled]

I guess it depends on era. My1908 box sash windows are a shade over 5". After all they often had to fit into a half thickness recess (plus plaster) in a 9" brick wall. I'll tidy up some sketches I did to convince myself, and post them.

 

Thanks

 

Dave

[unravelled]

Below is a sketch comparison of the 5 layer model with the real thing, for both 1mm and 0.5mm clear acrylic. The 0.5 mm (lower) is a good match for the thickness of the real thing. I have been imagining that the assembled unit will be fitted in a recess behind the wall, (of scale thickness). While it would be nice to make the units the same width as the real thing, it is better to make them bigger all round, for easier handling and assembly.

 

 

 

 

In the current sample, a couple of holes have been provided in opposite corners to take alignment pins to assist accurate assembly.

 

Thanks

 

Dave

[unravelled]

The image below shows how I create the cutting files.The first step is to draw the elevation of the finished window unit, complete with outer border and alignment holes. This is at the left. It is then copied as many times as there are layers, and each one modified for the individual layers. This was the easiest way I could find to maintain accurate alignment.

 

 

The second outline is the inner clear layer providing the lower sash glazing, the rest are in order moving out. The last is an optional layer, intended for where a filling layer is needed between sash assembly and an existing wall.

 

One of the results of writing this up is that I've come up with some possible further options. One of my original intentions was to use paper for the thin layers, which could be coloured with stain or ink, to avoid a relatively thick paint layer. Of course this gave a problem with glueing to the plastic. An untested option is to make the frame components all out of paper and card, with just the panes made of acrylic. This will make a slightly more complex assembly, but keep the materials cost down. However, this is something for another day.

 

Another idea, which I hope I'll be able to create for the old blue last, is the reperesentation of part open windows, allowing a bit of variation on the model.

 

There's clearly still some development work left her, but I'll be carrying on with it.

 

Thanks

 

Dave

[hymek2]

I take it from this the laser cutter is ok with conventional plasticard?.

 

I have access to a laser cutter although I havent managed to get my hands on it properly yet. During the training from the supplier we were told that some plastics will catch fire if used with lasers and we should only use the material they supply, which is around 2.5mm thick for the thinnest sheets. This would be ok using off-cuts to produce walls for buildings which could be clad with embossed brick etc, I would like to use it eventually for making windows and more fiddly things as you have done here and using thin plasticard sheets would be really useful.

[unravelled]

I've been able to cleanly cut modelzone's generic white plasticard at under 5% power. Some of the thicker transparent equivalents have not cut that cleanly. Both as regards smoke, and ending up with a burr around the cut.

I think there's always a lot of play/testing needed to get the machine to behave as you want. It's often best to start with very low power, and work up to the lowest value which will reliably cut the material in question.

There may also be issues with materials which produce a lot of smoke clogging filters and dirtying the optics, resulting in a need for more frequent cleaning.

 

Check whether there's a user group for your make/model of lasercutter. There might be useful tips to be found.

 

Dave

[hymek2]

Thanks for the reply. Unfortunately i am going to be working away from home for the next 5 months or so, which means i wont be able to test it till i get back so will experiment then. I will have plenty of time to get used to using a cad package in the hotels though

[Rabs]

I thought that styrene was one of the no-no materials for laser cutters. Doesn't it release cyanide gas when cut (or is that PVC)? Also, I'm pretty sure that it will fog up your lenses and mirrors - making it very difficult to maintain focus.

You might be ok if you're only doing a little and have an air-assist nozzle to blow it away from the cutting head - best make sure that you also have very good fume extraction.

[hymek2]

Hi Rabs, thanks for your thoughts.

 

It is an industrial machine with air assist, and the extraction unit we fitted is well above the spec that the manufacturers recommend. I will still be careful though. It will be quite a while until I get to try it though as i start a secondment back to my old job for five months from next week.

[Rabs]

Ah, sorry - sounds like I'm providing you a lesson in egg-sucking! Might be of use to others though who are considering doing similar though. Best of luck with the project.

[hymek2]

Ah, sorry - sounds like I'm providing you a lesson in egg-sucking! Might be of use to others though who are considering doing similar though. Best of luck with the project.

 

Not at all. I have loads of experience of a traditional "cutting" engraver using very similar software (same supplying company) but have only had a demonstration and a short "play" with the new laser. Lots of learning to do, all advice and comments are always welcome.

[Rabs]

I've been reading up about them a fair bit recently (thinking of building a diy effort). The advice that I've read is that acrylic materials are by far the best to use, as the cut neatly and don't give off anything too nasty. I don;t know if you can get it thin enough for your windows though.