Use of epoxy for levelling

Have you considered whether the fault lies with poorly mixed resin? The cure is a polymerisation. If the relevant components aren't available in sufficient quantities, the density of the film may change, leading to variation in final thickness?

Epoxy resin tends to be quite sensitive and there's little mention of preparation in this thread.

Using a good set of scales will ensure the right amount of resin and hardener is used. Really important if you want to resin to perform per manufacturers specifications e.g. hardness

Mixing. Spend at least five minutes mixing before use. Hand mixing is fine, an electric mixer is easier, but a slow speed. Avoid mixing in air. Once you have mixed for a minute, use a pop stick to ensure the resin sitting on the side and in the crease of the cup is integrated properly. Mix for the remaining four minutes. Once the batch is mixed, poor into a separate cup - leaving a little behind, so as to avoid any un-mixed resin transferring across.

The surface to be coated needs to be clean and dry.

The video was helpful in some respects. Personally, I wouldn't put a heat gun near epoxy without wearing a mask - air bubbles or no. But he's right epoxy loves heat and it does affect the viscosity of the poured resin. Personally, I'd lift the temperature of the resin prior to mixing using a water bath, especially here in the UK. I'd also be more interested in ensuring the ambient temperature of the room remained constant - especially in a hot climate.

I understand the target thickness for the film is 3-5mm. There's no reason why this need to be done is one pour: http://www.westsystem.com/ss/epoxy-chemistry/ A second layer can be applied once the first layer has started to gel, sufficiently. This might well be the best approach, assuming the underlying cause is human error

I'm not entirely certain what steps are taken after the film has been applied, but if the variation remains say 0.3mm i.e. human error is not a factor, could a high viscosity resin/compound then not be used to seat the rail? I believe that what is taking place here? http://www.moglice.com/ . You'd need to wait around a week before seating the rail. Ambient cure epoxies take a while to reach a state of final cure, which could be a problem, as you don't want an ultra thin layer of epoxy being exposed to pressure, when not chemically bonded to the layer below .... all my epoxies are heat cure, so I'm not in a position to run any tests. So lets hope its human error and applying two layers to create the desired thickness produces a lower error rate.

Oh yes. Vinegar is a good solvent for any split epoxy.

Personally, for this job, I'd been thinking about urethanes - but I'm not any way near needing to do this yet.

Mixing definitely is not the error if you mix the epoxy 10 minutes. Though i agree that it could be if not careful.

I believe i showed all already how to arrange and pour epoxy properly on even very big table, + saving 1 liter mixture at least on doing it with one bridge only. i hope my experiments and waste of money was not a waste, so people repeat the same mistakes over and over again, just because they want to do it their way or reinvent the hot water.

We could speak and speak, but - the errors are the following below. Only one of them or a mixture of them. Nothing more, nothing less.

1. Epoxy:
-poor choice / epoxy not fit for casting/
-shrinkage /not pure epoxy, cheap epoxy/
-cast thickness -ideal 5mm, no less than 3mm


2. Temperature:
-less than 15C or max 35C, ideal 22C
-differential between material temperature / heating the room shortly before, bringing the epoxy from other room/

2.Mixing:
-not weighting precisely the mix parts
-too much air in mix
-mixing less than 7-10 minutes
-not changing the mixing bowl with new, just before pouring

3. Surface preparation
-not cleaning the surface with acetone prior to pouring
-dust on the surface or hidden at the corners

4. Dams
-varying distance between dams on same rail
-too flexible dams
-dams from different material at different places
-hidden leaks between dam and material that don't show outside leak -not impregnating and check beforehand with thin epoxy layer for leaks
-dam leaking or absorption due to wrong dam material


5.Bridge
-not positioning it right so when it shrinks it sucks from channel
-not making extra long dam structure at the long rails
-not making bridge and dam extensions strong enough
-wrong bridge and extensions material,

6. Heating/degassing
-heating too much/too slow pass with the torch/
-making more than 2 separate passes /leads to orange peel/
-heating from different angle,not trying to be 90 degree with the torch
-heating too much the dams if they are from plastic
-accidentally heating the bridge more than the epoxy mixture

7. Drying
-dust when drying
-checking with finger if the epoxy is dry, during the first 24h
-laying the rails on top during the first 3 days to check how it looks
-mounting before a week has passed from pour

8.More
-not checking for dust particles that integrated during drying and scraping them with the straight edge
-not cleaning properly the rails and epoxy from dust before mounting, seat with the edges and scrape when laying down so no dust gets trapped
-heating the epoxy during drilling
-not chamfering the holes properly to clean the raised epoxy
-knocking the epoxy when dropping something or checking with the rails, and so making invisible raised points

9.later
Exposing the machine to >50C/ direct sun when outside temp is >25C/ will lead to problems.


Thats all folks. Do it properly and you will have 0.01 precision. Do it right and you will have great machine. Miss one point and you will have woodworking machine. Miss 2 and you will have a problem. Though of course people could lie to themselves and believe they have done it ok.

Quote:

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Originally Posted by silyavski

Thats all folks. Do it properly and you will have 0.01 precision. Though of course people could lie to themselves and believe they have done it ok.

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Sorry Boyan but who's lieing to them self's if they believe they can measure to 0.01mm accurecy over 3000mm length.!!! . . . . . Yes Epoxy method works OK and easy when done correctly but anyone is fooling them selfs if they think there going to get accurecy down to the Hundreth's MM's over such length and width.!!

Thou as they say in Yorkshire " Proof is in eating the pudding" so when your machine is finished let us know if your machine can surface two faces parallel to each other across it's full length & Width then surfaces hold ONE hundreth millimeter parallelism over the whole length.? . . . Then I'll be impressed and Don my Flat Cap to epoxy and You Sir.!

Its relatively speaking. I did not mean to brag or mislead, just to encourage and lay down the points that should be followed to the letter, if one wants to achieve what could be achieved at home.

Yes Dean, its more like a wishful thinking. Of course it could not be measured, especially at home. I agree its not real 0.01mm. Maybe even not real 0.05mm at some places. But may be it is between 0.01 and 0.05mm if lucky and done right/. I was able to discover bigger than 0.05mm gaps using the edge and strong led torch.

Lets say i am happy when with the straight edge i could not find a spot where it did not look perfect and tight fit to the edge. Thats my criteria for straightness for my machine. Obviously on a 3000mm travel, that's something, when done right and at home.

Having in mind that the straight edge itself is not so straight over 3000mm , table below, that on paper it should be supported/handled at a special length for the measurement to be right i would say there is no way that something could be proven right or not.

That means though that there is still a small chance in a million that in fact is that straight. :joker:. Who knows, when its not measurable. :hysterical:


So i say, better do things right with the idea that all must be perfect. Yeah the result may not be. But what would happen if one even does not even strive to do it right.



http://www.mycncuk.com/attachment.ph...id=14886&stc=1

Thanks Silyavski, its good to have all the detail laid out like that.

When thinking about the issue last night, I had in mind UK conditions and the tendency, recorded within various logs, to complete this task at below 25oC i.e. circa 10oC. This is relevant because as a general rule of thumb, a 5 degree F increase in cure temperature will half the time taken to cure, which is a thought I'd like to carry forward.

Per Jonathan's data, the suggestion must be that even with careful construction and preparation, the process retains a relatively high error rate, when compared to the required outcome. My addition is to suggest that the impact of the error rate, regardless of cause, could be halved by taking a two pour approach. I think that's relatively sound logic. But that not good enough.

However, as per the original posts #1, it took 72 hours to reach a state whereby it was possible to mark the epoxy using a finger nail i.e. the epoxy was still in a very plastic state at this time. So I am thinking, is this not the time to be thinking about mounting the rail?

The sort of procedure I have in mind is detailed below, but then I don't know how long it takes to mount the rail accurately? How much tinker time is needed?

Broad brush, the process would be as follows:

- Set up a bench test for the epoxy you are using. Dam an off-cut from the material used to make the supporting axis, circa 30cm in length?

- Before testing the epoxy, measure the ambient temperature, it needs to be below the manufacturers recommended cure temp, let say 15oC instead of 25oC. This provides for a much long gel and cure time.

- Mix and pour. One layer or two, depending on your view.

- Measure the hardness of the epoxy at regular intervals during the cure. A cure schedule can be drawn up based on the manufacturer specs in any event. Once it becomes evident that a thumb print can be made, start measuring the hardness of the cure by dropping a ball bearing from the same height and recording the difference in the diameter of the depression made.

- At a point to be determined by the dropping of the ball bearing i.e. while the epoxy is still relatively plastic, seat the rail using pre-drilled placement holes.

- There is where there is a balance to be struck, or not, depending on tinker time and ambient temperature. The rail needs to be seated on epoxy that is able to resist the the weight of the rail, but unable to resist seating of the rail when lightly bolted into place i.e. such that there is insufficient upward force to cause a deflection in the rail at the mid-point, between the two bolts.

Clearly it would help to run this experiment a few times. Removing a test sample isn't an issue.

Silyavski,
Like you clearly suggest, the right epoxy system is key. I would be concerned about using the West System if the ambient temperature is above 25 degrees C. Mixing - don't just stir the components together, mix the top into the bottom. Acetone will affect the chemistry of the resin system, so clean the frame well before the dam is constructed. Personally, I would do any final wipe using IPA. Heating/Degassing ... don't mix bubbles in. I wouldn't put a heat gun near epoxy, random application of heat? Use a brush and wet out the steel - like they did in the video. If you must, use a hair dryer set at min heat until you have a level. Heat the resin as a whole should you need to lower its viscosity prior to pouring. A water bath is the safest method - just be sure to dry the cup, as water and liquid epoxy need to be kept apart. Has anyone used a syringe to transfer the epoxy into the dam - 100ml every 40 cm or so?

Rich,

its proven that's its better to drill when epoxy is dry, not before pouring it and then messing with masking the holes.

The epoxy should be same temperature as the table to avoid shrinkage. yes you de-gass it by slightly heating it, but you pass with the torch very fast and as i said if you heat it further here by mistake, you will end with orange peel surface .

i dont insist on that, but its my feeling that the epoxy should be same temp. I took care of that and it worked. Why waste 100euro pour, just to see if it can be done as you say. :listening_headphone

Quote:

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Originally Posted by silyavski

Yes Dean, its more like a wishful thinking. Of course it could not be measured, especially at home. I agree its not real 0.01mm. Maybe even not real 0.05mm at some places. But may be it is between 0.01 and 0.05mm if lucky and done right/. I was able to discover bigger than 0.05mm gaps using the edge and strong led torch.

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Boyan I agree that in all aspects of building that 100% should be put into every aspect of building but one of my pet hates is seeing boast's or claims regards accurecy or torque/power etc like Some calculators offer that can't or haven't been proven. I feel it's misleading and while possible to achieve it's Very very difficult in reality to achieve and even harder to verify. This can and does cause the less equiped or able to over expect results leading to dissapointment.

IMO it's much better to give the details of how it's done and leave out any claims of accurecy unless can be verified to avoid dissapointment and instead show results of your labour with work produced.

Don't take me wrong here i'm not taking anything anyway from your build and I'm quite sure your machine will give very good accurecy and results. But to me the whole point is what gets spit out the other end, so IMO build to the best of ones abilty and be happy in the knowledge that what comes off the cutter is the best it can be given each persons Skills/equipment.! . . . . THE POINT. . . . Don't get hung up on pointless details that can't be proven or seen.!!!

Quote:

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Originally Posted by Rich

Thanks Silyavski, its good to have all the detail laid out like that.

When thinking about the issue last night, I had in mind UK conditions and the tendency, recorded within various logs, to complete this task at below 25oC i.e. circa 10oC. This is relevant because as a general rule of thumb, a 5 degree F increase in cure temperature will half the time taken to cure, which is a thought I'd like to carry forward.

Per Jonathan's data, the suggestion must be that even with careful construction and preparation, the process retains a relatively high error rate, when compared to the required outcome. My addition is to suggest that the impact of the error rate, regardless of cause, could be halved by taking a two pour approach. I think that's relatively sound logic. But that not good enough.

However, as per the original posts #1, it took 72 hours to reach a state whereby it was possible to mark the epoxy using a finger nail i.e. the epoxy was still in a very plastic state at this time. So I am thinking, is this not the time to be thinking about mounting the rail?

The sort of procedure I have in mind is detailed below, but then I don't know how long it takes to mount the rail accurately? How much tinker time is needed?

Broad brush, the process would be as follows:

- Set up a bench test for the epoxy you are using. Dam an off-cut from the material used to make the supporting axis, circa 30cm in length?

- Before testing the epoxy, measure the ambient temperature, it needs to be below the manufacturers recommended cure temp, let say 15oC instead of 25oC. This provides for a much long gel and cure time.

- Mix and pour. One layer or two, depending on your view.

- Measure the hardness of the epoxy at regular intervals during the cure. A cure schedule can be drawn up based on the manufacturer specs in any event. Once it becomes evident that a thunb print can be made, start measuring the hardness of the cure by dropping a ball bearing from the same height and recording the difference in the diameter of the depression made.

- At a point to be determined by the dropping of the ball bearing i.e. while the epoxy is still relatively plastic, seat the rail using pre-drilled placement holes.

- There is where there is a balance to be struck, or not, depending on tinker time and ambient temperature. The rail needs to be seated on epoxy that is able to resist the the weight of the rail, but unable to resist seating of the rail when lightly bolted into place i.e. such that there is insufficient upward force to cause a deflection in the rail at the mid-point, between the two bolts.

Clearly it would help to run this experiment a few times. Removing a test sample isn't an issue.

Silyavski,
Like you clearly suggest, the right epoxy system is key. I would be concerned about using the West System if the ambient temperature is above 25 degrees C. Mixing - don't just stir the components together, mix the top into the bottom. Acetone will affect the chemistry of the resin system, so clean the frame well before the dam is constructed. Personally, I would do any final wipe using IPA. Heating/Degassing ... don't mix bubbles in. I wouldn't put a heat gun near epoxy, random application of heat? Use a brush and wet out the steel - like they did in the video. If you must, use a hair dryer set at min heat until you have a level. Heat the resin as a whole should you need to lower its viscosity prior to pouring. A water bath is the safest method - just be sure to dry the cup, as water and liquid epoxy need to be kept apart. Has anyone used a syringe to transfer the epoxy into the dam - 100ml every 40 cm or so?

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Rich, you need to leave the epoxy until it is totally set. If you bolt the rails to it before its totally set they'll sink into it. Eddycurrent had just this thing happen to him, he corrected it by filling the marks/dents with more epoxy.

I'm advocating a bench test in advance of pouring! Surely that saves money Sil?

I would leave the bolts in and if they were a little resistant, I'd heat gently using a soldering iron to release them. That's if I hadn't applied mold release.

Shrinkage is a post cure issue ... you might be seeing a change in viscosity due to temperature disparity between the resin and the table, which is affecting flow. The resin will quickly adopt the temperature of the table in any event, hence the suggest to paint on a thin film in advance of a pour - but in reality the impact on flow will be negligible.

Syringes, reminds me of these: http://uk.rs-online.com/web/p/epoxy-...zzles/0503385/ If you want belt and braces on the mix.

The resins I use are heat cure epoxies, so I don't have anything suitable for running a test. Once I've sold a few more things on Ebay, I look at finding a suitable resin system for the job.

Neil,
Hence the need to run a bench test in advance and track the behaviour of the epoxy you have chosen.

I would be hesitant of leaving the bolts in as you will get miscues around the bolts like you will get at the edges of the moat. I used West System very slow cure 10 - 20 hours. After I had a long conversation with them on the phone they suggested that I flash the surface with a hot air gun (just a very quick flash) 5mm one pour. ..Clive

Hi Guys
Have been following the progress of this thread and think there might some advantage in using trace heating cable on the bed to provide a stable temperature prior to resin pour, bed can be uniformly heated then knock off the power and let the bed cool to the desire temperature and do the pour.
Regards
Mike

Well I'll be watching with interest to see the results of all this...

Clive - a soldering iron to the head of the bolt should stop that. Apply just enough heat to let it dissipate from the thread.

Cheers Mike, like you suggest, if you are going to apply heat to lower the viscosity of the resin, it needs to be applied uniformly. A heat gun is a little too intense and random IMHO. Adding an aluminium plate to the nozzle would certainly help the situation - a more consistent heat over a wider area.

Heating the frame with trace heating ... that's a lot of metal? Have you seen this thread: http://www.mycncuk.com/threads/6565-...dy-Eddy/page18 , photograph 6, you'll see a piece of flat bar below the film. There's no reason why this bar couldn't be used as a heat shield - held at a prescribed height above the dam (pre-drilled holes and placed back below, once the film had set). Ideally, it would be a little wider, but this approach would put the heat gun back on the menu, switch to full power with little risk of over-heating the surface ) I'd be inclined to test that last comment, especially as the thread of the bolt holding the bar is sitting in epoxy. If you are happy to keep waving the heat gun around in a consistent fashion, it would have the desired effect - reducing the viscosity of the resin and if you are patient and consistent i.e feet per second, you'd be well on you way towards curing the epoxy within specs. This assumes a thermometer, temperature gauge or such like between the flat bar and dam and the bolts don't become the focus of any heat build up.

Anyway - thanks for entertaining these ideas. If someone could let me know how much tinker time should be allowed for setting up the rail, it would help.

Quote:

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Originally Posted by Clive S

I would be hesitant of leaving the bolts in as you will get miscues around the bolts like you will get at the edges of the moat. I used West System very slow cure 10 - 20 hours. After I had a long conversation with them on the phone they suggested that I flash the surface with a hot air gun (just a very quick flash) 5mm one pour. ..Clive

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Clive I have some West systems slow cure coming on Monday, after the pour when should I flash the surface? Straight away? Is a hair dryer hot enough or do I need a proper industrial hot gun?

Cheers

Quote:

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Originally Posted by gavztheouch

Clive I have some West systems slow cure coming on Monday, after the pour when should I flash the surface? Straight away? Is a hair dryer hot enough or do I need a proper industrial hot gun?

Cheers

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Gav, a hair dryer will just blow the epoxy and splash it everywhere....i believe (I didn't do it myself as I didn't have many bubbles) the time to do it is when you're happy that you've got the epoxy evenly spread out and are just about to leave it to cure but I'm sure Clive will tell you when he did it.

http://www.mycncuk.com/attachment.ph...id=14890&stc=1Ok This has all been said before. The system I used is this http://www.westsystem.com/ss/209-extra-slow-hardener/ this is the pdf. http://www.westsystem.com/ss/assets/...%20105_209.pdf
.
It is very important to measure and mix well. it is important to make the moat water tight as any small leaks will spoil the job. I used a thin bead of silicone all round the inside edge. Just make sure that the frame is least at about 18C .
.
Mix the epoxy with a flat paddle ie not a round dowel and mix well slowly so as not to introduce air into the mix then let it settle for a couple of minutes. If you have another prepared container with a hole near the bottom about 6-8mm with some tape over it you can then pour the epoxy into the prepared container.
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Then take the tape off the hole and let the epoxy pour from the hole into the moat. (this will get rid of most of the air as bubbles rise and you are pouring from the bottom)
http://www.mycncuk.com/attachment.ph...id=14888&stc=1http://www.mycncuk.com/attachment.ph...id=14889&stc=1
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Don't just pour all the epoxy in one place but try and get it even all the way round. Then if you see any big bubbles you can just flash them with the hot air gun they instantly disappear. (you are not trying to heat the epoxy up it is a quick flash)
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The epoxy is almost like water and will flow very easy.
.
Rich There is no way a soldering iron will stop the surface tension miscues thing from happening all around the edges of the moat AND around any bolts you have put in.
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When the epoxy has cured at least a week then remove the moat sides etc and with a rasp bastard file carefully remove the miscues. If you are using 20mm rails you want the moat at least 40mm wide (mine was 55mm)

I used two dams from one rail to the other and was more than happy with the result.
.
This has all been done to death and is not rocket science I think in a hot country you may have to be a bit more careful. The epoxy may feel hard to touch but DON'T play with it until at least 7 Days have past and has been said already make sure that the base is clean and oil free. You can rub some oil around the inside of the moat edges to stop the epoxy sticking to the sides (make sure it is sealed first though). ..Clive

Clives spot on and speaks from experience so anyone going to do this would be advised to listen. Esp about the time to leave and longer the better I find.
It's very easy to get caught out thinking it's cured fully when it's not and then get sinkage, I've had it happen to me recently after leaving nearly a week and should have known better but was rushing. so don't think it's a rookie mistake because you will get caught out if you try to rush.!

One way good way to test if fully hardened is to make separate test piece same width about 12" and pour to same depth. (the moat will work for testing) Then pour at same time and leave.
Then when you think it's cured check the test piece by bending, if it just bends and doesn't snap then your not cured enough, if it snaps then your ready.

Quote:

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Then when you think it's cured check the test piece by bending, if it just bends and doesn't snap then your not cured enough, if it snaps then your ready.

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Yes I forgot that bit:yahoo: .. Clive

I wonder if anyone has tried polyurethane casting resins instead of epoxy for levelling?

The stuff i have used in the past ( for casting not machine levelling) has the viscosity of milk and is designed to run and fill all the voids in a casting, i would imagine it would be better than most of the epoxy resins i have come across.

Its tough too and will take fillers and reinforcements if you want to use them.

http://www.benam.co.uk/products/plastic/

just a thought...

Thanks Clive, I will go back and edit, so it's clear that I am talking about the threaded bolts. The residual meniscus would be of a nominal thickness using this method and subject to removal once the drilled hole was opened out.

These guys might be worth a shout: epoxies start at page 58: http://www.swiss-composite.ch/scs4/h....shtml?lang=en (selling on behalf of: http://www.r-g.de/en/ ) I've never had cause to deal with them directly, but they are known to have a good reputation. Supplier to light aircraft industry, so quality is a priority.

Using the west system 105/209 as a point of reference, viscosity of the mixed resin @ 22oC is 650mPas. This figure will increase as the temperature decreases, so the resin will become more viscous, the lower the temperature gets. Minimum recommended temperature for the 209 is 18oC. Physical properties once cured are really important, so its good to have this datasheet as a reference point.

Possible alternatives:

- low viscosity resin system 100 mPas @25oC, cures at 10oC
- low viscosity resin system 250 mPas @25oC, cures at 15oC

There are some other low viscosity resin systems in there, if your ambient is higher.

Jazz, you're waiting 7 days? You're not adding any heat, not even ensuring a consistent 15oC?

Quote:

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Originally Posted by Rich

Jazz, you're waiting 7 days? You're not adding any heat, not even ensuring a consistent 15oC?

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How do you get that I never added any heat or kept a consistant Temp just from me saying waited nearly a week before fitting rails.?? . . You know what they say about Assumption.!!
My workshop is fully heated and Temp controlled with a Thermostat. The frame was slowly brought to room temp of approx 17deg over 3 or 4 days before applying epoxy and then workshop was kept at this temp for constant 3 days 24/7 afterwards then rails fitted after 6 days of curing.
This was using West systems 206 Slow hardener not 209 but still it caught me out, which I should have known better after doing several machines with epoxy.

From experience I know my elevated cure resin will harden in cold well, just add time. Excluding the 205 hardener, a workable cure should be achieved within 2.5 days (72oF cure is 15 hours max, 67oF equates to 30 hours, 62oF should be 60 hours). They quote 'thin film'. It tends to be 1mm or so. Thicker films, shorter time periods. I guess you must have been unlucky, or the hardener is getting old.

Matthewb,
I agree, polyurethane has potential with some additional benefits, including vibration dampening. I had a quick look at the website you posted. There were some reasonable numbers, attractive numbers on shrinkage, however, they tend to require elevated post cure. Quite expensive in my opinion. Have you thought of looking to the industrial floor coating industry - they might entertain a few free samples. Help you get your eye in before you pour.

Just noticed this website: http://www.resins-online.com/ I'd contact the underlying manufacturer for clarifications.

Quote:

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Originally Posted by JAZZCNC

How do you get that I never added any heat or kept a consistant Temp just from me saying waited nearly a week before fitting rails.?? . . You know what they say about Assumption.!!
My workshop is fully heated and Temp controlled with a Thermostat. The frame was slowly brought to room temp of approx 17deg over 3 or 4 days before applying epoxy and then workshop was kept at this temp for constant 3 days 24/7 afterwards then rails fitted after 6 days of curing.
This was using West systems 206 Slow hardener not 209 but still it caught me out, which I should have known better after doing several machines with epoxy.

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Thats what i meant before, but could not explain it better. Machine,epoxy and room should be same temperature from the moment of pouring to the moment ready to mounting.

I have done some experiments and epoxy will even cure at 5C though not advisable.

Lets be getting real here.? Epoxy method isn't rocket science and doesn't need to be made so.!! . . .It's just a matter of using correct Resin/hardner mixing it correctly and applying in clean enviroment at sensible tempreture with-in Manufacturers recommendations. . . THEN . . . Leaving alone until it cures FULLY.

By far the Hardest part for most is being patient enough to leave for couple of weeks but it really is best if your unsure because if rails are bolted on and they Sink it's all been for nothing and correcting is hassle.!

Silyavski as highlighted some good points and made sensible suggestions which for anyone building a Large machine with lots oof expensive epoxy would do well to follow but for smaller machines where Epoxy settles quicker and easier to handle then it really is quite simple if some common sense is applied.!

Clean, Warm, Dry with leak free dams and it's a doddle. .:cower:

Jazz, so you're saying the epoxy method, as described by Clive and Silyavski is the best way to go because it achieves what level of accuracy?

Quote:

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Originally Posted by Rich

Jazz, so you're saying the epoxy method, as described by Clive and Silyavski is the best way to go because it achieves what level of accuracy?

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Let me respond instead.

It achieves the level of accuracy of your straight edge + your intention of accuracy.

You need a straight edge that should be at least as long as your machine is wide, to check the result and later square the gantry. Your intention of accuracy will help you see small mistakes if any and using shimming and checking against the edge will help the desired accuracy. Anyway you will need the edge to mount the rails straight in the other direction. The more accurate you want it to be, the more you will check and adjust and generally the more time it would take you.

For an example i did 3 separate pours of epoxy on my 3m long rails, when happy with the epoxy i mounted and dismounted 2 times the left rail and 4 -5 times the right one until i was happy. It took a week with helper, only adjusting the rails. The only reason to do that was because i will use that machine to surface other smaller machines and gantries in it and not mess in the future with epoxy :black_eyed: if not building something huge. If this machines purpose was not meant for that, i would have shimmed the first unsuccessful pour and finish with that stage.

So if you mean all day doing precision aluminum milling is one thing, other thing is if you do all day wood.

Even so, the bigger the machine the difficulty to achieve precision multiplies. It not only the epoxy, it how many times you check all and if you take your time to repair all that you have found.

Its difficult to explain but at the end the precision of the machine depends how precise are you or how precise you want it to be. All else is means and ability to achieve it.

Quote:

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Originally Posted by Rich

Per Jonathan's data, the suggestion must be that even with careful construction and preparation, the process retains a relatively high error rate, when compared to the required outcome. My addition is to suggest that the impact of the error rate, regardless of cause, could be halved by taking a two pour approach. I think that's relatively sound logic. But that not good enough.

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At risk of repeating myself, the error I got with the epoxy was exceedingly small (according to my surface plate) - the large deviation you see at the end of the graph was caused by the bearing seal/lower surface rubbing on the aluminium epoxy boundary. That error went once the rubbing problem was alleviated. The other graphs with large errors were false readings caused by accidentally measuring roll not height. I'm not mentioning values here lest they taken out of context - see the original post for a proper explanation.

I heated the resin in a water bath before pouring. It clearly lowered the viscosity, but I can't comment on what effect this had overall as I have nothing to compare with.

Thank you Jonathan. What a mistake. I couldn't understand why everyone was so relaxed.

Apologies if degassing has already been mentioned.
Although I haven't got to the epoxy levelling stage on my build yet, I have had a bit of experience of some resins and silicones used for mouldmaking- After mixing and before pouring resins should be degassed thoroughly. It is very surprising how much air is trapped in the liquid even after careful mixing. I don't think you can achieve the figures on the data sheets without this process. Pouring/flow and shrinkage qualities are much improved.

https://www.youtube.com/watch?v=9sN0KT-tRsY

Not done it myself but the 3 processes usually mentioned to reduce bubbles are:

1. Pouring the final mixture into another pot with a sealed hole near the bottom (e.g. duct tape), then opening the hole and pouring from the lowest part of the mixture, leaving the bubbles near the surface.

2. Once poured into the moat on the frame, flashing over any remaining bubbles with a hot air gun.

3. Not stressing over the odd bubble or two which gets trapped unnoticed.

I agree, those methods are the usual processes but in the pursuit of more accuracy and better working methods degassing removes the micro non visible bubbles trapped within the liquid. The video above shows just how much air comes out of a small amount of carefully mixed resin. Without degassing you are basically pouring foam.
I haven't used west systems 105 epoxy and 209 hardener yet so I might be talking rubbish but I will try to video the degassing and levelling process when I get to that stage to see if it makes a difference or not.

It works without degassing but a tiny mistake like being in a hurry could mess the whole process. last time i was pouring WS epoxy i wanted to be able to degass it. And as i said somewhere earlier in the thread, passing one time with heat gun degassing is okeish but second time is asking for trouble, third time for sure will result in orange peel surface. So yes, degassing will be great.

some really great guides here and has helped me feel more relaxed trying the epoxy method so thanks guys :)

just a couple of questions though...

1. how much weight can 5mm thick resin take before cracking ect.
2. if 90% of the time all ill be doing is engraving 3d designs in wood soft or hardwood such as oak and say the other 10% will be acrylic/thin aluminium, will the epoxy resin still be advisable?

cheers

ash

Quote:

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Originally Posted by reefy86

some really great guides here and has helped me feel more relaxed trying the epoxy method so thanks guys :)

just a couple of questions though...

1. how much weight can 5mm thick resin take before cracking ect.
2. if 90% of the time all ill be doing is engraving 3d designs in wood soft or hardwood such as oak and say the other 10% will be acrylic/thin aluminium, will the epoxy resin still be advisable?

cheers

ash

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You won't have any problems with the weight of the gantry on the epoxy check out my post #56 here http://www.mycncuk.com/threads/8197-...evelling/page2
.
If you are using steel it is a great way to get your rails on the same plane. ..Clive

+1 ,on the above.

thanks clive really helped alot :) so the best epoxy to use is the westsystem 209?

cheers

ash

so in theory i should get the frame as level as a human can by hand using adjustment castors on the feet, then once thats as level as you can get it i then place the dam ontop of the frame (im using 25mm rails so my dam will be 65mm wide) then pour epoxy into the dam and let it level out then wait for about 2 weeks (to be safe) and then i can now bolt my rails ontop of the epoxy assuming its flat level?

cheers

ash

http://www.mycncuk.com/attachment.ph...id=15938&stc=1http://www.mycncuk.com/attachment.ph...id=15937&stc=1http://www.mycncuk.com/attachment.ph...id=15936&stc=1http://www.mycncuk.com/attachment.ph...id=15934&stc=1http://www.mycncuk.com/attachment.ph...id=15935&stc=1

I doesn't really matter if the machine is not level on the floor as the epoxy will level out like pouring water into a channel it will find it's own level. What is important is that you do not have any leeks in the moat I put a very thin bead of silicone all around the inside.
You will need it about 5mm thick. If you use MDF for the moat after the silicone you could put some Vaseline on the insides of the moat to stop the epoxy from sticking.

thanks clive, do you mean the silicone has to be 5mm thick or the epoxy? i was going to use about 5mm anyways for the epoxy if so.

cheers

ash

Quote:

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Originally Posted by reefy86

thanks clive, do you mean the silicone has to be 5mm thick or the epoxy? i was going to use about 5mm anyways for the epoxy if so.

cheers

ash

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The silicone is only to stop any leeks so a very fine bead between the MDF and box section. Iff you have any leeks the job will fail:devilish: