Here we go again . . . MK4

[Davek0974]

Amazing build, has to be the heaviest Z axis I've seen yet.

[routercnc]

Thanks Dave. Yes, glad I managed to squeeze two steppers on the Z axis. It is too heavy for my scales so I need to find a way to weight it. Certainly picking it up is a challenge (and there is no spindle yet).

The whole machine will run initially off 3 Nm steppers at about 70V, through some fairly old analogue drivers (DQ860MA) and a DB25 breakout board through the parallel port. Not massively high spec so it will be interesting to see how it copes with the weight of everything . . .

By the way, thank you for the grub screw insert idea. You might have seen your name mentioned in the video (faintly on the 'Grub Screw Insert' title page) ! I tried to get much larger inserts in there but there was no space on the upper part to go much bigger. I would have needed to counter sink them into the lower part (manually, no CNC!) but even there the space between other fixing holes was tight. The surface area of the 8 mm discs is much bigger than the 'ring' contact area on the base of the hollow cone on the end of the grub screw so will be better. I could always make new plates with steel pad inserts if the head keeps moving out of alignment.

[routercnc]

Episode 15 is now ready for viewing: Setting out the epoxy leveling for the X rails. This was my first time using epoxy like this and I certainly learnt some things along the way - especially those bubbles !

[Electroconducive]

Beautiful work as always.

What did you learn about the bubbles?

I saw in the video you used a heat gun to try and get rid of them.

Were you successful?

[routercnc]

Beautiful work as always.

What did you learn about the bubbles?

I saw in the video you used a heat gun to try and get rid of them.

Were you successful?

Answer is quite a lot! Although I had read lots about epoxy levelling on this site it is not until you do it yourself that you get a feel for it all. In short I made some mistakes.
It will all be in the next video but that will be some time away.

I checked the flatness and it was all over the place because of the bubbles. Where I had used the heat gun the most started to cure quicker which probably didn't help.
I tried to lap the surface back but it was taking forever and it was going to be tricky to ensure I kept both sides parallel to each other.
I think the epoxy should have been mixed slowly to avoid too many bubbles and then left in the warm bath to help some of them escape. Then pour slowly and use a stick to pop any remaining bubbles. The heat gun should be used sparingly if at all.
I had a long think about it all then took a chisel to it and took it all off. New epoxy on order plus some redesign of the channeling. I may even lay in multiple stages just waiting for it to skin over between coats. Not sure yet . . .

In short I'm back to square one but this needs to be right!

[Electroconducive]

I noticed you were rather vigorous with the mixing. You also poured the epoxy with some kind of measuring jug from the spout.

I am sure I read somewhere that poking a hole in the bottom of a container and using that to pour is a handy way to do it. It allows any bubbles that have formed in the 'gentle' blending of the two part epoxy to rise to the top. Stopping an aerated mixture being applied to the frame.

Also, it might be worth a try with the extra slow tropical hardener?

My thinking being the longer cure time would allow not only the bubbles to rise for the bottom pouring method, but the heat gun to work to release bubbles as the epoxy remains less viscous for longer.

I've never poured either. I am just repeating what I've seen other people have success with on this very forum.

Hope your next pour goes better.

[Desertboy]

You definitely did the right thing, if it was was me I'd be bitching about it for years to come but it's got to be right.

It reassuring to see I'm not the only one that can make a mistake although we call it learning ;)

[mekanik]

routercnc
if you have access to a vacuum pump you could degas the resin prior to installation, have seen old pressure cookers used with a perspex lid, then you could place the resin in a container that can be pressurised. poly pipe going to the bottom of the container, LOW pressure air on top of resin to initiate your pour, after bleeding you resin supply pipe place that in direct contact with the pour surface and this should prevent any entrainment. initial mixing might be better done with flat stirrer figure of 8, softly softly.
Regards
Mike

[routercnc]

I think it was Clive who mentioned pouring into another container with a hole in the bottom. It crossed my mind but I had decided on the water bath to decrease viscosity and was concerned that water may get in and ruin the mix.
Sylavski had also posted lots on epoxy as well as Neal plus many others.
Thing is I'm not ignoring what others have written and it all goes in, and you have a plan, but you need to do it for real yourself to appreciate all the subtle aspects.
As for the tropical hardener I was using the 206 not the 205 hardener as this takes longer to set. I actually emailed West systems about what I wanted to do and was advised to use the 206. Thing is that a skin forms after 30 mins or so anyway and any bubbles will then be trapped so I don't think the long set time helps on the bubbles side. Good for self levelling though.
West said laying in one session was best rather than layers but I got the impression from the overall reply that they had not used it for 5mm beds for CNC rails. It is usually for boat repairs etc.

Whilst I wait for supplies to arrive plus some other parts I am rethinking my approach. Looked into vacuum pumps to degas but this is £200 for a small kit. I think next time I will :

Mix gently
Then place in water bath to help bubbles escape
Pop any remaining bubbles
Slowly poor but start in the 2 channels as bubbles come out first (and these are waste area)
Make sure surface is all wetted and coax with cocktail stick into all areas on first layer
Then maybe leave to just skin over (so still tacky) and repeat or may just go in one long session?
Pop any bubbles with cocktail stick or gently blow

Intuitively feels like this should be gently poured and touched as little as possible ( I think any prodding and touching will show on the finished surface)

Also thinking even with a perfect pour the last tiny deviations (once cured) will need shimming or epoxy putty to get the last 0.05 or so dialled in?

[driftspin]

I think it was Clive who mentioned pouring into another container with a hole in the bottom. It crossed my mind but I had decided on the water bath to decrease viscosity and was concerned that water may get in and ruin the mix.
Sylavski had also posted lots on epoxy as well as Neal plus many others.
Thing is I'm not ignoring what others have written and it all goes in, and you have a plan, but you need to do it for real yourself to appreciate all the subtle aspects.
As for the tropical hardener I was using the 206 not the 205 hardener as this takes longer to set. I actually emailed West systems about what I wanted to do and was advised to use the 206. Thing is that a skin forms after 30 mins or so anyway and any bubbles will then be trapped so I don't think the long set time helps on the bubbles side. Good for self levelling though.
West said laying in one session was best rather than layers but I got the impression from the overall reply that they had not used it for 5mm beds for CNC rails. It is usually for boat repairs etc.

Whilst I wait for supplies to arrive plus some other parts I am rethinking my approach. Looked into vacuum pumps to degas but this is £200 for a small kit. I think next time I will :

Mix gently
Then place in water bath to help bubbles escape
Pop any remaining bubbles
Slowly poor but start in the 2 channels as bubbles come out first (and these are waste area)
Make sure surface is all wetted and coax with cocktail stick into all areas on first layer
Then maybe leave to just skin over (so still tacky) and repeat or may just go in one long session?
Pop any bubbles with cocktail stick or gently blow

Intuitively feels like this should be gently poured and touched as little as possible ( I think any prodding and touching will show on the finished surface)

Also thinking even with a perfect pour the last tiny deviations (once cured) will need shimming or epoxy putty to get the last 0.05 or so dialled in?

Hi guys,


I must say by the sound of it West is harder with the bubble issue then the resin i used.


I did not use west systems resin, 209 was unavailable in NL.... had to look for a alternative but found a usable resin else where. 5hr of pot life so plenty of levelling time. Get the slow hardner


I weighed out (kitchen type 1gram scale) and mixed the resin+/- 1kg at a time in a 1.5 liter kitchen type container with a bend wire on the batterydrill.

The whole mix turned greyish from air getting trapped in the fluid. This worried me at first.


After mixing i left it to de-bubble for at least 30min or so, some bubbles at the surface of the container remained and where wiped away with a paint brush.

Then poured only in the bridge channel, in between the x rails. no bubbles remained after flowing out evenly.


Hope this helps.

Grtz Bert.



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