S4 Code75 BH Rail Dims/Settings

[Terry Downes]

Although I have successfully resin printed many S4 chairs to suit Code75 BH rail I sometimes need to twist the resin chair on the rail to overcome an angled or non-perpendicular fit. This is generally okay when printing in a tough ABS type resin but, When I recently ran out and was trying to use a standard resin it became quite frustrating and resulted in many broken chairs.
So, I began investigating this with CAD as follows. I created the measured rail and exported Templot chair into CAD and discovered that there is potentially a tiny interference (0.1mm / .004" max at underside of rail head, upper circle as shown below). I suspect the offset interference is the cause of the occasional rail tilt.

I have created a custom code75BH rail setting within Templot as shown below and the results seem much better as the rail fit is smoother and appears to be consistently perpendicular/vertical.

Here are the custom settings I used and will be using going forward but, it would be interesting to know if anyone has experienced similar fit/alignment 'opportunities' or felt the need to adjust/tweek the current default code75BH settings within Templot?

 

[Steve_Cornford]

Hi Terry,

Ditto for code 75, use the [save custom data] button
see your code 125 question.

Steve

 

[Phil G]

@Steve_Cornford
Hi Steve,
Just a general question and I did not want to bother Martin, so I am going to the trusty I2C
If my memory serves me right, which alas is not always the case any longer. I seem to recall in earlier versions of Templot when it came to model rail sections you could assess all the paraments IE if you clicked onto the C&L/EMGS/S4Soc code 75 radio it opened up the same dialog box as you now get when opening up the custom dialog box. screenshot attched. Was that the case? .
If so does it now also mean the std C&L/EMGS/S4Soc code 75 values are now only hard coded?
If that's the case could you just check what the C&L/EMGS/S4Soc code 75 value is for the rail web dimension "E". in Terrys drawing. above.
It also goes back direct to this post
message ref: 15340
where Martin added some dimension's to my drawing, most notably the rail web thickness of 0.35mm (also the same dimension he gave earlier in the dialog, which I think is an extract from the hard coding.)
Both of which do not agree with the next imagine in that post of the same message where a value of 0.25 mm is stated as the web thickness. Which incidentally is the same value you get from the default web thickness when you open up the custom screen.

The primary reason for all these questions is I like Terry have noticed recently printed batch's of S1 chairs (noting I printed over a 2000 back in April/May. which I have been working my way though) Suddenly seem to have a much higher breakage rate, especially with the solid jaw version much more of an issue then the loose jaw version but both seem to have got a lot more noticeable in terms of broken chairs..

To be honest I am wondering if some how the web value has changed from 0.35 mm to 0.25 mm If that is not the cause then I will start looking into other possibility's. of which there could be many to be honest. not least the different batch's of resin.
Cheers
Phil

 

[Steve_Cornford]

Hi Phil,
quick reply

I seem to recall in earlier versions of Templot when it came to model rail sections you could assess all the paraments IE if you clicked onto the C&L/EMGS/S4Soc code 75 radio it opened up the same dialog box as you now get when opening up the custom dialog box. screenshot attched. Was that the case? .

I dont think so.
As far as I am aware it is only the custom option that actually shows you the settings and allows you to amend them.
Steve

 

[Terry Downes]

Hi Phil,
I can confirm that the jaw gap being generated by the default code 75 BH rail settings is 0.35mm. I don't believe it has ever changed. I suspect you may have encountered different resin shrinkages or batch materials properties.

I would STRONGLY advise anyone to only print chairs as You need them and avoid printing off large batch quantities unless You are going to fit/install a lot in one go!

Remember the 'Experimental Project' and 'on-going Development' Mantra's at the top of every Templot Forum page!

 

[Phil G]

Hi Phil,
quick reply

I dont think so.
As far as I am aware it is only the custom option that actually shows you the settings and allows you to amend them.
Steve

Hi Steve,
Ok I will take your word for that, it does then open up the most important question, which is what are the current Code 75 non adjustable settings?
cheers
Phil,

 

[Steve_Cornford]

If so does it now also mean the std C&L/EMGS/S4Soc code 75 values are now only hard coded?

Always have been I think.

Here is the hard coded values (rail section = 1)

   if dxf_form.emgs_75_rail_radiobutton.Checked=True
       then begin

              rail_section_option:=1;

                 // convert to full-size at 4mm/ft and back to current scale   (4mm/ft = *3" per mm)

              rail_depth_mm:=1.90*3*inscale;   // code 75 // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.rail_height_pi - inclined rail calcs - in inches)

              rail_head_width_mm:=0.90*3*inscale;   // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.railtop_pi - in mm)

              rail_corner_rad_mm:=0.15*3*inscale;

              rail_foot_width_mm:=0.90*3*inscale;

              rail_fish_angle:=1.5;          // 1:n   arbitrary

              rail_web_top_mm:=0.80*3*inscale;        //  from rail top to intersection fish angle on rail centre-line
              rail_web_bottom_mm:=1.25*3*inscale;     //  from rail top to intersection fish angle on rail centre-line

              rail_web_thick_mm:=0.35*3*inscale;

The above from the first Delphi open source published by Martin.

Steve

 

[Steve_Cornford]

Hi Phil,
The current version 556a source

    if dxf_form.emgs_75_rail_radiobutton.Checked=True
       then begin

              rail_section_option:=1;

                 // convert to full-size at 4mm/ft and back to current scale   (4mm/ft = *3" per mm)

              rail_depth_mm:=1.90*3*inscale;   // code 75 // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.rail_height_pi - inclined rail calcs - in inches)

              rail_head_width_mm:=0.90*3*inscale;   // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.railtop_pi - in mm)

              rail_corner_rad_mm:=0.15*3*inscale;

              rail_foot_width_mm:=0.90*3*inscale;

              rail_fish_angle:=1.5;          // 1:n   arbitrary

              rail_web_top_mm:=0.80*3*inscale;        //  from rail top to intersection fish angle on rail centre-line
              rail_web_bottom_mm:=1.25*3*inscale;     //  from rail top to intersection fish angle on rail centre-line

              rail_web_thick_mm:=0.35*3*inscale*(100+chair_web_adjustment)/100;
            end;

note that this now includes an extra parameter chair_web_adjustment which by default is zero, thus giving no change.

Hope this helps

Steve

 

[Phil G]

Hi Phil,
I can confirm that the jaw gap being generated by the default code 75 BH rail settings is 0.35mm. I don't believe it has ever changed. I suspect you may have encountered different resin shrinkages or batch materials properties.

I would STRONGLY advise anyone to only print chairs as You need them and avoid printing off large batch quantities unless You are going to fit/install a lot in one go!

Remember the 'Experimental Project' and 'on-going Development' Mantra's at the top of every Templot Forum page!
View attachment 13038

Hi Terry,
Thanks for the confirmation good to know the 0.025 is not actually being used.
Thanks for the head up on the old chairs, fully understand why your saying that, just clarify there stored in tin cans. Similar to the old tobacco tins, so zero UV penetration, there not even painted and there are all good for at least 6 months. As long as the tins are not opened until your ready to use them. I do agree if left out and not used the UV can get to them, you do have a very serious brittle issue.

Also just to confirm I am get about 1% breakage with these "old" chairs the newly printed once last say in the last week or so are far closer to 10% or could in fact be even worst. Something is clearly different, if its not the generation of the chairs, which it does not look to be. Then I must start to look at other causes.

In a very strange way, although I fully understand why you are making your recommendations the current evidence is suggesting the opposite is actually working out to be better.
cheers
Phil

 

[Phil G]

Hi Phil,
The current version 556a source

    if dxf_form.emgs_75_rail_radiobutton.Checked=True
       then begin

              rail_section_option:=1;

                 // convert to full-size at 4mm/ft and back to current scale   (4mm/ft = *3" per mm)

              rail_depth_mm:=1.90*3*inscale;   // code 75 // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.rail_height_pi - inclined rail calcs - in inches)

              rail_head_width_mm:=0.90*3*inscale;   // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.railtop_pi - in mm)

              rail_corner_rad_mm:=0.15*3*inscale;

              rail_foot_width_mm:=0.90*3*inscale;

              rail_fish_angle:=1.5;          // 1:n   arbitrary

              rail_web_top_mm:=0.80*3*inscale;        //  from rail top to intersection fish angle on rail centre-line
              rail_web_bottom_mm:=1.25*3*inscale;     //  from rail top to intersection fish angle on rail centre-line

              rail_web_thick_mm:=0.35*3*inscale*(100+chair_web_adjustment)/100;
            end;

note that this now includes an extra parameter chair_web_adjustment which by default is zero, thus giving no change.

Hope this helps

Steve

Thanks Steve,
Also good to know what the Chair web adjustment does.
cheers
Phil,

 

[Phil G]

Hi Steve,
Is chair web adjustment getting its value from the rail fit fine adjustment, if any values is different to zero
cheers
phil,?

 

[Steve_Cornford]

yes

have you also checked your resin shrinkage parameters?
also have you changed the resin?

 

[Steve_Cornford]

Have you upgraded chitubox?
Make sure you have anti-aliasing switched OFF

 

[Phil G]

yes

have you also checked your resin shrinkage parameters?
also have you changed the resin?

Hi Steve,
Yes same shrink values and same batch of resin, which does of Course make it at least 6 months older now.
cheer
phil,

 

[Phil G]

thats a good point, I had have to update Chitubox I will check the anti-aliasing setting latter today.
cheers
Phil,

 

[Steve_Cornford]

Please tell us what version of chitubox you are now on.
Steve

 

[Martin Wynne]

Both of which do not agree with the next imagine in that post of the same message where a value of 0.25 mm

@Phil G @Terry Downes @Steve_Cornford

Hi Phil,

I've explained 3 times that the 0.25mm web thickness figure is the exact scale conversion from the prototype. I posted it simply for comparison with actual model rail. No actual model rail matches it, and no plug track settings do so, or have done.

Unless that is, you select the custom rail section option but without actually setting any custom dimensions.

• I have noticed that resin chairs made 6 months ago have become more brittle with age and break more easily. They can be restored to their previous resilience by putting them in boiling water, drying them warm and letting them cool naturally. Whether they then get brittle again with age I don't know, but I suspect probably not. Whether they would have got brittle in the first place if I had kept them in the dark and/or painted them, I don't know. These are chairs made with Anycubic water-wash ABS-Like resin.

I will start looking into other possibility's. of which there could be many to be honest. not least the different batch's of resin.

Old resin nearing or past its shelf life needs a lower exposure setting than fresh resin. This is presumably because it starts to polymerise in the bottle. It becomes noticeably more gloopy and less fluid with age. This probably depends on storage temperature (keep it in the fridge?)

Likewise resin temperature for printing makes a big difference. It's best to arrange some sort of heater and always print at the same temperature. Over-exposed chairs won't fit on the rail.

There is a lot still to learn.

cheers,

Martin.

 

[Phil G]

Please tell us what version of chitubox you are now on.
Steve

Hi Steve,
to answer your question Chitubox V2.2 Beta and the anti aliasing is switched off.
cheers
Phil,

 

[Martin Wynne]

@Terry Downes

Here are your settings for code 75 Option B:

    if dxf_form.emgs_75_rail_B_radiobutton.Checked=True     // option B TD 2024
       then begin

              rail_section_option:=6;

                 // convert to full-size at 4mm/ft and back to current scale   (4mm/ft = *3" per mm, sf 12/4)

              rail_depth_mm:=1.90*3*inscale;   // code 75 // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.rail_height_pi - inclined rail calcs - in inches)

              rail_head_width_mm:=0.92*3*inscale;   // - 2D TEMPLATE SETTING MAY DIFFER  (cpi.railtop_pi - in mm)

              rail_corner_rad_mm:=0.17*3*inscale;

              rail_foot_width_mm:=0.92*3*inscale;

              rail_fish_angle:=2.0;          // 1:n   arbitrary

              rail_web_top_mm:=0.85*3*inscale;        //  from rail top to intersection fish angle on rail centre-line
              rail_web_bottom_mm:=1.25*3*inscale;     //  from rail top to intersection fish angle on rail centre-line

              rail_web_thick_mm:=0.35*3*inscale*(100+chair_web_adjustment)/100;
            end;

Will be in 556b.

cheers,

Martin.

 

[Phil O]

Martin/Terry,

I don't know if it will make much difference, but wooden keys are symmetrical, looking on end.

 

[Martin Wynne]

Martin/Terry,

I don't know if it will make much difference, but wooden keys are symmetrical, looking on end.

@Phil O

Hi Phil,

Yes, I know.

However, they can't be symmetrical in the model for 3 reasons:

1. if you want the chair jaw to be in the prototypical place on the chair base, the distance to the rail is more than the depth into the overscale thickness of the model rail web.

2. the fishing angle on the model rail is steeper than the 1:2.75 prototype angle. So the angles on the top of the key are not symmetrical.

3. if you had an angle on the underside of the key, it couldn't be 3D-printed because you would create an island at the middle of the key when sliced into layers.

So we have to make do as best we can.

There is another change which I made for practical reasons -- on the web face of the key on the solid slide-on chairs there is a taper at each end, so that the rail can slide in more easily. This also creates a centre pad area, ensuring that the pressure on the rail is always opposite the inner jaw and not offset at one end of the key. This is the top view:

All this and a lot else was decided way back in 2018 when I first started experimenting with my first 3D printer, the BIBO. Mostly it hasn't changed since, and one day I will need to explain every detail.

The taper isn't done on the keys on the loose jaws. By then I had decided that it wasn't really needed, as the rail doesn't slide through them. It could be made an option with yet another tick-box. Which I would then have to explain several times over.

cheers,

Martin.

 

[Phil O]

Martin,

I did wonder if there had to be compromises for 3d printing to work and as ever you have thought through the processes and come up with a logical solution.