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Member postings for Donald MacDonald 1

Here is a list of all the postings Donald MacDonald 1 has made in our forums. Click on a thread name to jump to the thread.

Thread: Looking for a non-magnetic, strong, easily glued material
30/04/2022 11:18:37
Posted by Jouke van der Veen on 30/04/2022 08:39:07:

Interesting topic!

I would like to see a reference to software used to compare relative permeabilities of the different materials and as a result a list of these values. I assume it must have been rather a search on the Internet than a theoretical calculation.

Nice to read about a book of Frans de Waal about chimpanzee politics in this topic. Remember he is a Dutchman from origin! 😉

"Finite Element Method Magnetics"

You guys have WAY too much time on your hands. No offence but you'd make excellent Chimps!

D

30/04/2022 02:46:16
Posted by Samsaranda on 29/04/2022 19:10:00:

I used to work for a seal-less pump manufacturer we manufactured our own magnetic drives, they used stainless steels of varying specifications to meet the product conditions, some of which were highly abrasive or corrosive, the magnetic drive operated through the stainless steels with no problems, my choice for this application would be the appropriate stainless steel. Dave W

Dave W - yes, this is an excellent call.

I have now run some tests on magnetic prototyping software and it seems that the key metric is (magnetic) Relative Permeability and it turns out that "non-magnetic" stainless steel (e.g. 316L), 1050 Aluminium and Nylon all have a magnetic Relative Permeability of very close 1. And for this reason magnetically speaking when in 'permanent' magnetic fields there is little to choose between them.

Meanwhile I have already now got my hands on both some 1050 Aluminium and some 316L Stainless Steel, but not the Nylon 6. Given how much physically stronger the 316L is compared to 1050, I have started experimenting with the 316L first.

And so far the 316L is working... beautifully. I think we have a winner!

So bad luck to the pedants & detractors... and a big thank you to those of you how have been helpful. 

I think we're done here.

Cheers

Don

PS Once it arrives, I shall also experiment with the Nylon 6 as that may prove to be useful too.

Edited By Donald MacDonald 1 on 30/04/2022 02:56:51

29/04/2022 16:01:39
Posted by Jon Lawes on 29/04/2022 14:07:51:

It's all got a bit silly. I think we need to remember we are all here because we support an enjoyable, inclusive hobby.

The voice of sanity.

HONESTLY!

Don

29/04/2022 12:59:20
Posted by Baz on 29/04/2022 11:36:10:

PS: A copy of my Ph.D. is available for reading in the Cambridge University library, where is yours?

Edited By Andrew Johnston on 28/04/2022 21:06:35

Mr McDonald seems to have forgotten to answer Andrews question, just a gentle reminder for him.

Baz, I can't see any genuinely relevant questions, and I'm not going to get into a war of words. Sorry.

Tim, I am on mainland UK. Given that I am not very mobile, I don't intend to leave the house if I can avoid it in any case but deliveries work well.

29/04/2022 11:18:39

@Andrew Johnston
Good. So I think can both agree that we both have better things to do than boost our Egos by reading anybody's entirely unrelated PhD theses just to prove some point on a forum.

Yes, we also agree that although cheap and widely available that 1050 Aluminium is a broadly horrible engineering material. Knowledge of the point was precisely the reason for my starting this thread. Only because time was against me did I buy some more 1mm thick sheet.

@Bill Pudney Yes, assuming that the 1050 works adequately magnetically, I shall keep searching for a small piece of Grade "2024 T3" "7075 T651". But first I also have the Nylon 6 to experiment with, which should arrive shortly.

If anyone happens to know of a model-making friendly supplier of such grades of Aluminium [1mm sheet, small samples, fast delivery] please let me know

And if I find a good supplier myself I shall let you folks know.

Don

28/04/2022 12:59:46

Thank you for all your thoughts, folks. [Albeit what a strange reaction from some of you!]

I was hoping that you might be able to furnish me the names of model-making suppliers because as we all know sourcing small amounts of industrial materials can be difficult to locate, slow to arrive and suffer from large minimum order quantities.
I just wanted some suggestions as to what materials that I hadn't thought of, and which might also be swiftly available.

Time is short and I don't need a perfect solution. And I am assuming that you lot have better things to do than to read my PhD. But to save time I have carefully given you the broad constraints which should suffice.

I couldn't locate any higher performance Aluminium last night, so to keep things moving I have ordered some Grade 1050 Aluminium plus some 316L Stainless Steel in 1mm sheet from Amazon. I suspect that the 1050 is probably a bit soft and I am suspicious that the 316L will be under 1mm (as well as the paramagnetic concerns), however one or other may do the job well enough for now, and both of which should arrive within 24 hours.

I spoke to direct-plastics.co.uk, (good suggestion, thank you Andrew!) about Tufnol of which there are various sub-types. However they said that a) it can chip on impact and b) it's not black. Instead Direct Plastics suggested black Nylon 6 so I ordered a small 1mm thick sheet. Nylon 6 it can be hard to bond with standard epoxy resins, but they suggested Permabond TA4246 (a "2-part, no-mix, room temperature curing structural adhesive"  ), which I have also ordered from GlueOnline.co.uk who offer a next day delivery. The Permabond TA4264 should like it will be useful for other stuff I am working on.

If the 1050, 316L and Nylon 6 all fail, then fibreglass (FR4) will be next on my list.

I think most woods are will be softer and less good a resisting abrasion than each of 1050 Aluminium and 316L stainless. Any normal paints will presumably abrade off as well as require a really good bond so I'm not going that direction for now.

Don

Edited By Donald MacDonald 1 on 28/04/2022 13:01:04

28/04/2022 00:05:16
Posted by not done it yet on 27/04/2022 23:53:23:

Aluminium is paramagnetic. Depends on what the application involves.

The application involves high strength permanent magnets. The main thing is that it is important that material does not "short circuit" the magnetic flux between two plates.

D

27/04/2022 23:43:20
Posted by Bill Pudney on 27/04/2022 23:10:19:

Epoxy glass material has been used for PCBs (printed circuit boards) and are used in a few thickness's. It can be cut but not really accurate.

Any of the SRBP/SRPL (synthetic resin bonded paper, and synthetic resin bonded linen, if I remember rightly the SRPL has better properties) machine moderately well. Look at Tufnol, they make it, they market it in all sorts of special trade names (Carp, Whale etc)

Acetal resin could be quite interesting. The sheet panels are probably not adequately flat for your purpose, so they would need to be machined. It can be a challenge.

Personally I would suggest that you use 7075 T651, its very strong, i.e. better than steel, machines beautifully, relatively cheap. Probably to easy.

cheers

Bill

Hello Bill

Any idea where I can get a small piece of 1mm thick "7075 T651" Aluminium sheet, at short notice?

I'm not having much luck on either ​​​​​Amazon or eBay...

Cheers

Don



PS You might find this link interesting. It compares your "7075 T651" to 1050 aluminium.

https://www.makeitfrom.com/compare/1050-A91050-Aluminum/7075-T651-Aluminum
**LINK**

27/04/2022 22:53:23

What about Stainless Steel - "Grade 316L"
e.g. on Amazon:
https://www.amazon.co.uk/gp/product/B074SWM4S5/
**LINK**
Although it is available "tomorrow" however this product is isn't very well reviewed on Amazon... :^/

Don

27/04/2022 22:25:37
Posted by Brian G on 27/04/2022 22:16:28:

Tufnol Kite is available in black.

Brian G

I've never used Tufnol Kite. It sounds interesting. Can you recommend where could I buy a small piece?

TBH, I'm having doubts now. Maybe I should settle for Aluminium or a non-magnetic stainless steel?

Thanks

Don


PS TBH, I've never used Acetal (POM – Polyoxymethylene) either.  How would it compare to any of the other materials in terms of impact resistance/strength/abrasion resistance...?

Edited By Donald MacDonald 1 on 27/04/2022 22:28:18

27/04/2022 22:16:44

Carbon fibre laminate is an interesting suggestion, however it sounds like carbon fibres do have a slight impact on a magnetic field.
"Carbon fibers are finite conductors with a weak diamagnetic response in a static magnetic field. "

**LINK**

I don't know anything about "epoxy glass". Is it a sheet of epoxy resin with "fibre glass" embedded in it?
If so I think it might be too brittle and/or not very good at resisting abrasion.


Meanwhile I found this on "1mm Aluminium Sheet Plate - 1050 Grade" on Amazon
**LINK**

However is grade "1050" relatively soft? (I understand that aluminium alloys do vary in strength pretty dramatically..)

Don


27/04/2022 21:27:05

Hello

I am looking for a material that is:

A. Completely non-magnetic

B. Strength: As strong & abrasion resistant as reasonably possible

C. Size: Available at as a sheet of at least 10x10cm and thickness of 'exactly' 1.0mm (at least 0.97mm, less then 1.1mm)

D. Bonding: Must be reasonably easy to bond with adhesive (e.g. general purpose epoxy resin, or E6000 or CA/superglue)

E. Colour: Must be either black or 'silver' colour

F. Must be machinable. (i.e. I need to be able to sand/machine it.)

G. Needs to be available... fast!
(ideally within 24 hours)


APPLICATION
For indoor use. And normal room temperature. The exact application details are complicated. It is for some scientific testing instrumentation that I am ​​​​making. It will need endure quite a lot of repeating mechanical impacts & a bit of abrasion...

DISCUSSION
I was thinking about various metals:

- Aluminium?
I was thinking of aluminium but the stuff that I have is rather soft. What would be a strong grade & where could I get it from?

- Copper & Brass
I also have some copper & brass but of course neither of them are silver in colour.

Lead is too soft. Titanium is weakly magnetic. Chromium/Platinum - too expensive

Stainless steel - from memory if it is 'Austenitic' then it should be completely non-magnetic. From my notes, the following grades of stainless steel are Austenitic: 201, 205, 301, 302, 303, 304, 316.

But which grade would be best & where can I get it super-fast?!

I was also thinking about some kind of strong black plastic (e.g. Nylon?) but that's quite hard to glue.

Any suggestions?

Thanks

Donnie

 

Edited By Donald MacDonald 1 on 27/04/2022 21:42:15

Thread: Any tips for working at higher precision? e.g. Do you do this?
20/04/2022 20:30:59

> Is this marking out paper to cut it accurately, or drawing accurately?

I was talking about marking materials including card, paper & plastic for cutting. And also when cutting metal  material roughly.

When cutting out metal more precisely I would try to use Dykem Steel Blue layout fluid, and then mark it with a scriber... but it isn't always possible/practicable particularly for larger objects.

Personally my drawings I always do digitally (2D illustration package or 3D CAD), although I may wish to annotate/correct the printouts by hand, before the design is added back to the 2D/3D CAD. Although of course before any of that happens I will often do sketching by hand, before turning it digital, but - by definition - no accuracy would be required for that.

But my above technique of marking with Ls with one long leg/line and one short leg/line has greatly helped me avoid errors, although on has to make sure that one leg/line is significantly longer than the other. The down-side is that it's slightly more time consuming, than making a single short blob and then (presumably) aiming to cut down the centre of the line.

Edited By Donald MacDonald 1 on 20/04/2022 20:32:57

19/04/2022 13:35:51

Hello

I thought I would share this technique. I am wondering if it is a standard way of working.

Simply put, if my pen is really too fat for the job in hand, I draw a long thin L shape and work from the 'far' edge of the L.

e.g. In this photo I am trying to measure exactly 10mm. To mark it I have drawn a rather fat blue line with my 0.5mm Frixion pen (which has the advantage of be erasable cleanly, without any rubbings). The red dotted line is the line I will need to cut the (white) material which I am marking.



NOTE: "For good measure", in this case I have used a steel block to butt up against the white material, so that I can use my engineering rules (i.e. rulers which have no lead-in and start at zero), to make 100% sure that my measurement is starting precisely at the edge of the white material.

Discussion
It seems to me that the only down-side of drawing from the edge of an "L", (rather than from the centre of a short line - that is hopefully drawn with a thinner line), is that it's a bit more time consuming to remember which side of any given marking one is supposed to be working from!

Also when marking out more complex shapes it quickly becomes confused if one is working on the EDGE of a line rather than the CENTRE of a line.

Which is why I started this thread:
"Need a pen to draw the 'finest possible' lines?"
https://www.model-engineer.co.uk/forums/postings.asp?th=179283

So when you folks are needing to work with great precision:

- Do you folks tend to draw Ls or short lines?
- What other tips & techniques can you share that help with your accuracy?

Cheers

Don


 

Edited By Donald MacDonald 1 on 19/04/2022 13:36:23

Thread: Need a pen to draw the "finest possible" lines?
19/04/2022 12:02:20


@Jann west

> the rapidographs on drafting film required special edges on their
> drawing tools (rulers, set squares, etc.) which had a step ...
> essentially so that the ink wouldn't smudge underneath the ruler edge
> - which occurred if the pen nib was against a flush ruler edge.
Excellent point.
Another reason to avoid Rotring Isograph/Rapidographs.
And no, I am not about to buy some more rulers & set squares just for my new pens!
[Although if I end up with a Rotring/Rapidograph buying I might put a layer of adhesive tape on the rear, 1mm away from the drawing surface, in order to lift the tool off the paper.]


@Dave

I don't want to get into a war of words. However nor do I wish to ignore you.

In the nicest possible way, I would simply encourage you to carefully re-read my original question. Because TBH, I don't believe that I have changed to the goalpost by a single inch. There in my original question, I carefully laid out my core priorities, which have not changed.

There I specified what papers I intend to use. So why is anyone telling me to use different types of paper?

There I say that top of my list of important factors was "low maintenance". So why is anyone telling me to use dip pens or (old fashioned Isograph/Rapidograph) Rotring pens?

But IF no one can suggest anything that seem able to reliably draws a finer line than the "0.05mm" Uni-Pin pens that I already use, then yes I shall simply buy a Rotring Isograph or Rapidograph (what we used to call "indian ink" pens). But I know that they like to be used every day and that they are hatefully high maintenance if they are NOT used every day.

Did I mention that the purpose of my question was to try to avoid high maintenance pens?

But technology rumbles on and it is notable that in the last decade or two that manufacturers have increasing move towards fibre tipped pens (AKA "fineliners", and even the likes of Rotring & Staedtler have their own versions.


@Michale G
> Your supposedly 0.05mm Unipin does look a bit of a joke...
> Is that a new one, or “well-used” ?
Good question. Well, I have three of them. They are about 6 months old but the one I drew with is barely used. It is possible that they may all be fractionally dry on ink, I'm not sure.


UPDATE:

Feather-weight use of Fineliners
What I have noticed that if one doesn't mind a line being a bit faint, it is possible to get a very much finer line with a Fineliner pen if when it is absolutely new if you only ever use the lightest possible weight (i.e. barely more than the weight of the pen itself!)

More later after I have tested my new pens...

Don

18/04/2022 12:54:13

@Bill Pudney - Er, to repeat, yes I am already using an excellent CAD system. As before, in the nicest possible way please, confine yourself to my answering my question, not questioning my processes.

My question is about pens. Because I need a pen.

Nope I want to write on my CAD printouts.
> If you are seriously hoping to use some sort of felt pin, look for Unicorns
Depends what you mean by "Rotring". Your views not withstanding, your beloved Rotring clearly do believe in fibre pens. They don't actually call them Unicorns, but they make do 'em.

This is their finest. "0.1mm"

[And TBH, I am still trying to work out whether it lines would be finer than other fibre pens that claim to have "0.05mm" or even "0.03mm" nibs. ]


@Speedy
> Uni Pin Fineliner do a 0.1mm pen
As before, yes, I do have them. And a smaller "0.05mm"version. And as I have said, I am already using their smaller version "0.05m".

@JasonB
> Now you have moved the goalpost from wanting the pens to draw on paper
> and tracing paper to wanting to write on all manner of surfaces,
Incorrect. Writing on other surfaces is a bonus not a requirement.

> This is a quick freehand drawn line on photo copy paper using a 0.1mm Pilot DR pen.
JasonB, when you say "0.1mm"... I am assuming that you mean Pilot's "Drawing Pen 01" (which has a "Tip Size: 0.5mm", and a "Writing Width: 0.28mm", yes? Or do you means their "Drawing Pen 05" which has an actual "Tip Size" of "1.00mm"?

Source: **LINK**
https://drpen.co.uk/products/pilot-drawing-pen?_pos=1&_sid=937715b6f&_ss=r&variant=34775728193

[See how confusing all this is!]


     *     *     *

OK, I don't want to spend too much more time on this. I have now ordered a (reassuringly expensive) fine liner / fibre-tipped pen ("Copic Multiliner SP-0.03mm"  ) which has a "0.03mm" nib. I suspect that they really mean 0.3mm, but time will tell!





Meanwhile here is a photo of my lines drawn by my current pens (on a reasonable quality injet paper which I use to do CAD printout paper - Avery "Papier 90 Art 2563" )

Note that the start of each line (i.e. at the left) I have done, a single pass... and the next few mm is a triple pass which is much darker but is also significantly fatter.

I don't know how obvious this will be from the photo, but my ruler lines are thinner than that of any my pens.

Did I mention that, yes I already use a CAD system?
And that my printer can very get much finer lines when I do my CAD printouts than any of my pens?
And that one of the things that I am wanting to do is annotate my CAD printouts?

[sigh]

OK I'll let you folks know how I get on with the "0.03mm" Copic Multiliner SP when it comes.

Don

 

Edited By Donald MacDonald 1 on 18/04/2022 12:58:23

18/04/2022 00:52:39


Speedy Builder
1. > Draw 2 x size and photo reduce to size.
Yes, I already do that where I can, but in this case I can't.

2.
Link
> DÉSOLÉ
> cette page n’existe pas (plus).

Are you suggesting search for "mapping pens" on Amazon?
If so can you recommend anything specific that is finer than my "0.05mm" pens


Dave - To be fair some, the injet papers I am using seem to only barely blot - if at all. Ideally I need a paper that I can print (using inkjet) on as well as write on, which is why I specified ordinary paper/tracing paper.


Re "Mapping Pen"
Frome what I can see this is a generic term for a type of "dip pens"/"dipping pens", yes?
If so, like I say I'm trying to avoid the hassle & maintence & potential for spillage of dipping pens.


Hmmm... I don't know anything about ultrasonic cleaners. It seems a little excessive just to get a pen that works. What other stuff do you use your ultrasonic cleaners for?


In terms of "Technical Drawing Pens" it depends what you mean. Different websites seem to mean different things!

Re Rotring/refillable Technical Drawing Pens (what we used to call Indian ink), about 20 years ago I used to own some Staelder Marsmatic Technical Pens, which I think we found to be slightly less scratchy than Rotring but both types clogged up quite quickly if not used and I also found they had to be used very vertically to the paper. So I threw mine out many years ago.

That said, I see Rotring also make a "Rotring Tikky Graphic 0.10mm Black Fibre Tip Pen". However the thinnest one they make is that "0.1mm", whereas other manufacturers seem to much thinner (?).


e.g. It turns out that Uni Pin (Mitsubishi Pencil Co) now make a "0.03mm" version. Sound tempting although it does not seem particularly well reviewed.

But I'm extremely confused about "0.05" Uni Pin Fine Line pen that I have.
The official website has the "pen nib size" as "0.05mm"
(see **LINK**)
However I just measured mine, and metal jacket/pointy bit seems to be 0.78mm and the actual felt measures 0.5mm and not "0.05mm"!

Maybe they mean the line thickness...(??)

However IME, if you are pressing hard enough to get a reasonably consistent black line, I still seriously doubt it is "0.05mm" thick. I mean 0.05mm is thinner than the nominal thickness of human hair which is 0.075mm (75 microns).


Mike: Yes, I use Pilot Frixxion pens too whenever I will need to erase the lines. If you try hard enough you can find them with "0.38mm" nibs. The immediate problem is that - esp with those finest nibs - they don't lay down a very dark line. "0.5mm" nibs are very much darker. Either way I am really hoping for a much finer line, if possible.


JasonB - Thank you, but I am asking for suggestions for a pen, not a re-think of my process.

(And for the record, yes I am using CAD etc etc, but there are times such as marking up card/bookcloth/certain plastics/other materials and/or annotating printouts... including ones that are required to be life size... when one needs an actual pen. And please don't anyone start telling me about Dykcem Steel Blue Layout Fluid, because I am already using that on steel too!)


Have any of you tried the Copic Multiliner SP-0.03mm?
Not cheap for what I think is a fibre tipped pen, but looks tempting. Nibs can be replaced.
**LINK**

 

Or what about the "Art-n-Fly FineLine Drawing Pens" which have an "Ultra Fine Tip 003" - and claim to draw a "0.15mm" line, which claims to use Archival Japanese Ink, which they claim work well on non-porous surface and "won't feather or bleed through most papers"
**LINK**




As ever, thank you for all your suggestions. 

Don

Edited By Donald MacDonald 1 on 18/04/2022 00:54:38

17/04/2022 15:35:19

Hello

What type of pen do you recommend to draw the finest possible lines on ordinary paper & tracing paper?

Important factors:
- Low maintenance
- Must reliably draw dark/black lines, of constant width
- Must dry fairly quickly

Major bonus factors:
- Being erasable
- Should not smudge easily (e.g. once dry)

Minor bonus factors:
- A nice smooth action ==> easy to write as well as draw with
- The darker the better ==> easy to read
- Different colours of ink

Doesn't matter:
- Fade proof
- Waterproof

Use:
- High precision "life size" drawings of extremely small objects.
- The precision required is hard to quantify, but to give you an idea, I am using +5 reading glasses.


THINGS I'VE TRIED

A) Indian ink pens

When they work they are great at drawing jet-black ultra-fine lines.
BUT
- They are massively high maintenance. i.e. The block up easily
- They can be messy & ink can easily leak out & get everywhere

B) Unipin Fine Line pens (e.g. "0.05mm" )
Low maintenance, fairly smooth action, fadeproof, waterproof
BUT:
- I am hoping to get finer lines!
- Also not erasable

C) Propelling pencils
Erasable
BUT:
- I have a 0.3mm propelling pencil but the leads break easily
- I hoping for a finer line than 0.3mm
- Pencil lines are not very dark.

Thanks

Donald

PS This is what I currently use: (0.05mm Uni Pin Fineliner drawing pens)


 

 

Edited By Donald MacDonald 1 on 17/04/2022 15:35:48

Thread: What adhesive - that shrinks when it sets - do you recommend for melamine laminate sheets?
06/04/2022 01:06:39


Jason - Yes, like I said, I would definitely use strips.

Yes, the idea of using convex-to-convex to make camping easier, is brilliant thinking. Thank you. And how lucky that I have yet to apply any glue! The only weakness is that I will need to apply multiple clamps all around the edges, but I can probably find some strips of timber/thicker MDF to help spread the load at least a little.

You raise an important worry about CA swelling if it gets too much moisture. TBH, I had slightly forgotten just how much CA adhesive DOES swell over time if moisture ever manages creeps in... e.g. over the years.

How would you recommend I seal the edges? Using some kind of varnish? It slightly worries me just how thin the Melamine layer on MDF sheets is. Maybe moisture will get through it over a few months and my nice strips of CA would eventually product bumps no matter what?

So where did we get to with using a contact adhesive? (e.g. my All Purpose Welder). Thinking it though I guess one problem with contact adhesive is that it's difficult to get on nice and flat in the first place. So lumps & bumps may appear.

With all due respect I really don't want to buy any more panels. If glue fails then yes, but like I say, in the first instance I want to see how far I can get using some sort of adhesive.

Thought: Given how thin the MDF layers are... what about using a thin, solvent-based glue like Collall? (acetone/ethanol solvent) Or E6000 (perchloroethylene I think). Again applied in bead strips. It occurs to me that the melamine layers really are incredibly thin. So maybe after a few hours the enough solvent would work its way through the melamine to cause the glue to set? Particularly if I don't apply too much AND apply it in strips?

Dave - again thank you for your thoughts but I really don't want to spend the time & money to go out buying planks or screws etc. And I definitely don't want the boards to become significantly thicker, as the table top is already slightly too high. And I don't want to lower the table buy cutting the bottom of the legs off (for several reasons).

But you raise a good question as to where to lay the board down WHILE IT SETS. I very much doubt that any of my floors are flat enough. TBH, I had also thought about lying it on a soft bed, while it sets, but obviously I would need to measure what is going on in situ before applying any adhesive. If clamping around the outsides I had thought that I would just have it point vertically upwards...

[General comment: TBH, I am now deeply regretting the fact that I EVER described my application. The problem is that you helpful nice people have come up with all manner of wonderfully creative ideas, but each of which cause unwanted side effects, such significant extra cost (which I can't afford), losing the use one side of melamine to craters & fillings, adding unwanted weight (A0 boards are already hard enough to lift), extra thickness (my table is already slightly too high), paying to buy a different table (but which probably wouldn't fit into my house...)
==> And then everyone gets cross with me for either: not following their personal advice, or for failing to go into the details of exactly why their suggestion wouldn't be suitable for me or for not wanting to engage into a detailed discussion when they challenge my constraints or for not telling them at the start exactly what all my constraints were... or - if all else fails - folks get cross for my not taking action immediately.
So next time, remind me to NOT describe my application.

As that way, we can have a much simpler conversation that just focuses on my question, and do with less opportunity for frustrations & general crossness.]

Donald

Edited By Donald MacDonald 1 on 06/04/2022 01:07:25

04/04/2022 12:52:46

To get clear, I'm sorry if offends anyone that I still have not actually done the bonding, but my 2 sheets are deply buried under projects.

MichaelG - Noted. My main problem is that I would need to go and buy some A0 material and get it cut to size. It would also add unwanted weight onto 2 already slightly heavy boards. I'm assumging honeybomb wont offer enough tentile strength to resist any pre-existing warping. What do you think is the thinnest material (e.g. MDF/plywood) that I could get away with that would absorb enough moisture to allow a wood glue to set?

MichaelR - Magnets won't bond over nice large surface area (to help flatting any warping), will require the melamine to be drilled into. Ultimate flatness is the primary goal here not ease of shifting the A0 MDF sheets.

MichaelR - No, the problem with adhesive tape is that never sets. Over time, any bowing of the material would re-establish itself. Ultimately, I just want to bond melamine to melamine.

So back to my question ideally I really I just want a glue that sets to bond Melamine to melamine.

It would be nice if the glue shrank at least slightly as this would help pull the 2 surfaces together. (In fact best of all would be if the glue shrank to zero thickness and just bondind the two sides together!). But I am happy to drop the shrinking requirement if necessary.

Jason - Much though I hate CA, I concede that CA may well be the best way forward. It would certainly save me the bother of finding and cutting third sheet to fit between other two, that would be required for say wood glue.
Good to see you got a good bond. And hopefully one could still get a good bond right in the middle of a square metre or so (?)

How importantd do you think using thin strips are? And how far apart do you think that they should be?

Thin strips will of course let help let the air out, help get an extremely thin layer of glue... plus in theory even let the additional moisture in the air diffuse back in (eventually).

That said, the problem with strips is that the melamine is such a thin/fragile layer it will need all the help that it can get to fight any bowing after the clamps have been removed. But I think if one ended up with strips of glue over c. 50% of the bonding surface area, that would be fine.

In your model I see that for much of the areas in question you seem to have acheived nice wide bonding strips... but that ends the bonding strips are very narrow. [And FWIW, this is exactly that sort of problem I personally always seem to get with CA!]

Nonetheless, CA may well be the way forwards. But I'll have a think. My boards won't be free to be bonded for at least another week in ay case.

I'm also still tempted by mixing up a load of Epoxy resin - at least I could guarantee it will set! On the down side even though it's so viscous that it would difficult to get it properly thin. So I guess that I would definitely still use strips though to let the air out and minimise the distance the the viscous glue would need to flow to... in order to overcome accidental lumps & bump in the application of the adhesive.

As well as applying the adhesive in strips, I would of also use a serated glue applicator to help apply the adhesive evenly, as well as to create micro-escape channels for the air to escape locally.

Don

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