7mm Mickoo's Commercial Workbench

[mickoo]

Very impressive - do you think that the 3D print will be able to make the flange thin enough to match? It looks awfully thin to me. To match the fullsize proportions do you think a 3D print doors and lugs on a nickel-silver disc give a better representation?

Well there's a loaded question

Technically yes, in theory you can print as thin as 0.01 mm, in practice no, especially a large area like that.

The AWS/steam brake bracket on the B1 test was 0.5 mm thick and it's free standing so that thickness is certainly possible but again, give the large surface area the peel forces would distort such a thin edge.

The trick is to design the piece so that it can be printed and then post processed to give the desired result, in short, we make a sacrificial rim around the base of the door, in this case 1.0 mm thick, once printed and cured under UV we then sand that sacrificial edge back to the thickness we require, or as far as your cajones will let you.

It just requires some forward thinking into the design of the door so that you can achieve the final result.

You could have a metal disc and print as you suggest, but then the lugs would be very fragile spigots sticking out of the door, same for the hinges, there is a risk that these small fragile parts would distort during the print process, meaning you'd need to add a sacrificial edge to them which when removed would probably break them.

I tried that back last year with the gauge 1 Baureihe 50 smokebox door. The initial print had separate lugs and hinges, they did not fair well, even in gauge 1.



Further tests added the smokebox door flange sealing plate and eventually the whole smokebox front face, much stronger.



The parts failed for other reasons, lack of understanding of the material, supports and orientation in the printer, but most of all, lack of understanding how the print process actually works and how to design parts that will (on the whole) consistently print.

You only get that from doing it, again and again and again, over and over until you begin to understand what your doing. That's hard when something like the Br50 door in gauge 1 can take 4-5 hrs to print.

You also get it from reading forum after forum, post after post, trying this setting and that setting, it's not an easy process like CAD where you draw lines, join them up and then fill.

Really successful print gurus tend to be rather tight lipped about specific setups and tricks of the trade, I can understand why, it's like trying to build a 1000 piece jigsaw, but first you have to find all the pieces, as the box is empty.

Wargaming or mini/figurine forums are the best, what some of those guys are doing is mind blowing, but all of them are...for want of a better phrase....free style, what we're doing for models is engineering and SLA printers are not the best printer to achieve nice crisp engineered shapes. Excellent for middle earth Dwarfs and haunted forest Elves, crap at making a simple perfectly square dice.

I do need to go back to the Br50 project with the knowledge I have now, I think I'd get better results.

 

[adrian]

The AWS/steam brake bracket on the B1 test was 0.5 mm thick and it's free standing so that thickness is certainly possible but again, give the large surface area the peel forces would distort such a thin edge.

The trick is to design the piece so that it can be printed and then post processed to give the desired result, in short, we make a sacrificial rim around the base of the door, in this case 1.0 mm thick, once printed and cured under UV we then sand that sacrificial edge back to the thickness we require, or as far as your cajones will let you.

It just requires some forward thinking into the design of the door so that you can achieve the final result.

I can follow to challenges regarding thin unsupported lugs as opposed to the potential distortion on such a thin flange. So my final thoughts for this - actually having a precision cut (etched?) smokebox faceplate with an additional plate behind such that the 3D printed door and flange actually sits in a rebate on the faceplate. You retain the thickness to support the lugs but the rebate gives the appearance of a thin flange - once you get a lick of paint on it then I'm not sure you'd see any subterfuge.

 

[mickoo]

I kind of get it, but without some sort of flange on the print you end up with this.



My experience has found this does not work well, your sacrificial edge (you have to have one, it's almost impossible....I find....to print without one) is still the base, the overly large lugs on the first print might survive sanding the base smooth but I'm fairly confident that the hinge brackets would not.

It's not the final protection we're worried about, it's the post processing that's required to smooth the sacrificial edge or base that could cause the damage.

I have done something similar with Nick Dunhills Cambrian tank doors, in this case he has opened out the front to get some weight in the smokebox.



In this instance we are using that opening as a locator for the extended rim on the base of the door, it does leave the hinges and fixing posts exposed to damage and currently the rim is still a little thick at 0.75 mm, it really needs to be half of that, so, the next test print will push how thin we can get that rim and maintain print stability.

I also need to do another run with a different orientation but that will extend the print time from 2½ hours or so to near six so that'll be an overnight jobbie.

We may still have to get rid of that extended rim and go for a flat base which he will have to sand down to get a really thin edge whilst running the risk of the hinge posts getting damaged.

 

[adrian]

I kind of get it, but without some sort of flange on the print you end up with this.

Sorry I didn't explain it properly - I meant to retain the flange as you have already printed off, but instead of filing the back off the 3D print to thin it down I meant cut the hole in the smokebox face to the same diameter as the flange O/D. This will then sink into the front face of the smokebox face. A backing plate will stop it falling all the way through and leave a tiny lip proud as long as the flange is slightly thicker than the thickness of the smokebox face. - I really need to practice my 3D modelling as a picture will be a darn sight easier than trying to explain it.

 

[Peter Cross]

Mick
I'm one of those that still bash metal. I would love to be able to produce parts the way that you do. It is the drawing side that lets me down. Until such time as they can teach printers to read fag packet drawings, I'll just sit here and drool over your inspirational work.

 

[mickoo]

Sorry I didn't explain it properly - I meant to retain the flange as you have already printed off, but instead of filing the back off the 3D print to thin it down I meant cut the hole in the smokebox face to the same diameter as the flange O/D. This will then sink into the front face of the smokebox face. A backing plate will stop it falling all the way through and leave a tiny lip proud as long as the flange is slightly thicker than the thickness of the smokebox face. - I really need to practice my 3D modelling as a picture will be a darn sight easier than trying to explain it.

Yes, I understand now, but I think I can get there with just a resin front and thin rim. Your method would work well on a green field site, sadly I've already built a new front riveted face, not keen to rip it off and make a big hole in it

 

[mickoo]

So, we now have smoke box door MkII, I wish it were as easy as writing those eight words.

The change to domed front means that you have to change the print orientation, that means a layer change and by virtue new settings, it took six test doors to work out the new settings and we now have the below. It's not without fault, nothing that cannot be sorted in the post processing stage and to be fair, not spotted until paint was applied.

Therefore a MkIII is now in the printer to see if it can be fine tuned. For the record, MkI prints took about 2 hours, MkII was near six and MkIII is now topping just over eight.

Cruel close up, not so good with the paint this time but if needed it could be made right, the handrail and knobs were added to try and get some sort of spacial feel for the door, they are not printed



On the engine, overall I'm how happy with the size, the lugs might be a tad small so I might scale them up a fraction on the final render. The hinges came out well on the MkII, it even managed to render the small gaps between the straps and posts, I do need to drill them out and insert the pins as per the real engine.







Currently the rim is 0.48 mm thick, it can go thinner with some more elbow effort, I also think I need to compress the height of the hinges, I.E thin the flared strap section a little top to bottom.

I found a very high angle shot of the front deck, it confirms the rear edge is flat against the smoke box front, with a small opening for the lug nut.

Other than that, I think we now have a good base to work forward with.

 

[mickoo]

Right, back to the elephant in the room, the Peppercorn A2.

The base coat was smoothed off and a layer of green added, it went on much easier and smoother than the black, having said that I did decant it from a rattle can and dilute again 50/50. The rattle can comes from the same supplier that the painter uses and I've just ordered some green in a tin and some of their black. Hopefully their black will go on better than the lot I have here.

The green is a problem, new legislation recently has seen all the lead taken out of paints so my new paint will almost as likely not match Warrens tin for several years ago, even then, mixing in small doses in rattle cans can lead to differences in hue. I never expected to match Warrens hue exactly, amazed it's this close actually.







The hue is slightly darker, that could be down to the finish which has not been lacquered as yet, oddly it matches the lower sides of the firebox and cab front/sides much better; It still needs some more work for a perfect blend mind.

On the fire mans side there's still a little bit of speckling to smooth out around the washout plugs from a touch of over spray; I'm going to let the paint fully harden before I tackle that part though.

I'll ask Warren to send a strip of his lining to replace that which got damaged and once I've finally finished smoothing the paint will attach the safety valve clothing plates and finally fit the valves, they're only placed for photos at the moment.

I do have an ace in the hole in that it is going for light weathering later, that way any hue change in the colour will hopefully be blended in with the dirt.

 

[oldravendale]

I'll ask Warren to send a strip of his lining

Warren does his lining with pen, doesn't he? How can he send a strip of lining? And if he does how can you be certain that it'll be precisely the same width? If it's on a backing, as in a transfer, how can you apply that without showing a line for the backing?

Sorry, Mick. That sounds aggressive! It's not, but my own experience with lining says that getting the width correct across a model is difficult enough without trying to do it at a distance. And we use the thickness of the transfer to give the thickness of the boiler bands. Which may just be the answer to the question.

Brian

 

[mickoo]

Warren does his lining by pen = true.

Warren applies his lining to transfer material = true.

Warrens transfer paper is VERY thin = true.

Cutting very very close to the thin black line hides the backing sheet = true.

Warren will send me a couple of his lining strips, I will cut and apply, it will look like all the others because Warrens strips are almost all identical, such is the quality.

Besides it doesn't have to be precisely the same width as you cannot compare it directly with anything, once fitted the only way to measure it will be with the one on the next ring with a spectrum microscope. The width is irrelevant as it is only going on one band all by it's self, the one joint will be hidden under the ejector pipe, if not, I'll peel back that last vestige of the original lining strip as well and make it all new.

 

[Yorkshire Dave]

The green is a problem, new legislation recently has seen all the lead taken out of paints so my new paint will almost as likely not match Warrens tin for several years ago, even then, mixing in small doses in rattle cans can lead to differences in hue. I never expected to match Warrens hue exactly, amazed it's this close actually.

Recent legislation? Lead was removed from the majority of paints during the 1960's. A 1992 EU directive banned it completely except for paints intended for historic buildings and artwork restoration.

On a technical and scientific note paint will never match unless it's from the same batch. Even if it's not discernible to the mk.1 eyeball.

Very good job on the repair and finish though - some weathering will hide it....

 

[richard carr]

Mick

I'm impressed that is pretty darn good on the A2, you will do very well to get anything better. A bit a of dirt will go a long way to improving the look.

Richard

 

[oldravendale]

Warren does his lining by pen = true.

Warren applies his lining to transfer material = true.

Warrens transfer paper is VERY thin = true.

Cutting very very close to the thin black line hides the backing sheet = true.

Warren will send me a couple of his lining strips, I will cut and apply, it will look like all the others because Warrens strips are almost all identical, such is the quality.

Besides it doesn't have to be precisely the same width as you cannot compare it directly with anything, once fitted the only way to measure it will be with the one on the next ring with a spectrum microscope. The width is irrelevant as it is only going on one band all by it's self, the one joint will be hidden under the ejector pipe, if not, I'll peel back that last vestige of the original lining strip as well and make it all new.

Thanks Mick.

I thought you might say that.......

Those are very difficult things to achieve for us mere humans which is my stuff now goes away for painting.

The covering of the seam is a masterful recovery indeed!

Brian

 

[mickoo]

Recent legislation? Lead was removed from the majority of paints during the 1960's. A 1992 EU directive banned it completely except for paints intended for historic buildings and artwork restoration.

On a technical and scientific note paint will never match unless it's from the same batch. Even if it's not discernible to the mk.1 eyeball.

Very good job on the repair and finish though - some weathering will hide it....

Well, apparently it's changed again in the last couple of years. The new formula for BS224 looses some of the yellow aspect so they have to factor it back in with a slightly different mix, it also doesn't cover as well....they say.

You're right about paint, even the same colour will have minor variations, especially if it's a mixture of other colours (which it nearly always is). There is little assurance every single time they mix a new batch up that it will be the same. There's even little assurance it'll be the same through out a batch, or after storage once produced.

 

[mickoo]

Thanks Mick.

I thought you might say that.......

Those are very difficult things to achieve for us mere humans which is my stuff now goes away for painting.

The covering of the seam is a masterful recovery indeed!

Brian

You have a sharp knife and rule?

Simply cut very close to the painted line and remove the carrier film, something most mere humans can do surely

To be honest, the lining is/was the least of my worries.

 

[Max M]

Well, apparently it's changed again in the last couple of years. The new formula for BS224 looses some of the yellow aspect so they have to factor it back in with a slightly different mix, it also doesn't cover as well....they say.

You are probably referring to the banning of cadmium based pigments which is used in yellow and therefore would have an effect on green.

 

[Eastsidepilot]

You are probably referring to the banning of cadmium based pigments which is used in yellow and therefore would have an effect on green.

Ahh.....Sir Percy...



Col.

 

[mickoo]

The Garratt progresses slowly, new etches went off last week for the current replacement parts (I'm sure there will be more) and I'm kind of stalled until they arrive, but I'll post up a progress report over the weekend.

In the mean time I've fallen back onto a back logged project this week. A Collett H38 Composite Restaurant car as rebuilt after the war.

Most of the chassis and shell is complete and laid out, just some brackets, trusses, bow ends plus interior to work up on a second sheet, small it isn't.

Also need to work out how to fit the roof, glaze once constructed and be able to drop the interior in at the end.

Never designed a coach or even built one before so kind of making it up as I go along; it's going to be, how shall we say? Fun



Hopefully I'll get all the art work done and away be end of next week which is when the Garratt etches return.

 

[dibateg]

Nice work Mick on all fronts.. I do like the way you print out parts you need.

I'm missing loco building - still only 10 out of the 30 odd points to go.....

Tony

 

[mickoo]

I love it when Mr Pat and his black and white cat turn up with intact goods



Garratt cab, ash pan and frame bracket replacements/upgrades, Nick Dunhills detail parts and some foot bridge supports for another customer.