[wentyfalls]

My build is only in the planning stage but I would suggest aluminium extrusion bars.

Hi Joel,


Can you clarify a bit?

My design will be using t-slot aluminium for the gantry, do you think there is some value in haviong them on the Y-axis to support the 'supported-rail'

Rich

[wentyfalls]

And buy a new camera. LOL

taken with a phone... it gets the job done




lol

[joel0407]

Hi Joel,


Can you clarify a bit?

My design will be using t-slot aluminium for the gantry, do you think there is some value in haviong them on the Y-axis to support the 'supported-rail'

Rich

I'm tying to find a picture for you. Again I'm no expert since I haven't even started my build yet. I think if you use aluminium exrusion bars to support the rails you'll keep the run level. It's one thing to have a level bed but the rail need to be parralle with the bed. It's no good having a super level bed if the cutter (router, plasma cutter or what ever) goes up and down.

[wentyfalls]

I'm tying to find a picture for you. Again I'm no expert since I haven't even started my build yet. I think if you use aluminium exrusion bars to support the rails you'll keep the run level. It's one thing to have a level bed but the rails need to be parrallel with the bed. It's no good having a super level bed if the cutter (router, plasma cutter or what ever) goes up and down.

Joel,

Attached is a pic of what I am trying to achieve. It is mainly trying to get the rails as straight, parrallel to each other and as level to each other as I can. When I get the rails right I can machine the bed true.

The linear rails i'll mount on top are 20mm round supported rails -see pic

I am unsure if there is any advantage to adding another layer of extruded aluminium profile as it will still need to be leveled and parralleled etc.

All of this is basically why i thought id give the resin bed a go, based on the theory that it would self level and solve all the issues. I am still unsure why it did not work. But what I have at the moment is pretty wonky

There is abuild log on here by a bloke called MadVac and form what I have read he is basically held up as the model example of how to do a steel frame build.

I am way behind him in my skills and also do not have access to the gear he has so I hope to just get to a good final product that I am happy with as my first build. MadVac used a wire system to set and shim his linear rails I mat try that.

So I will continue to try it as I go and any suggestions are appreciated.

Richard

[joel0407]

Yeh I'm familier with those rails. Since you have a large thick layer of epoxy, can you sand it to level?

[wentyfalls]

Yeh I'm familier with those rails. Since you have a large thick layer of epoxy, can you sand it to level?

I could try - it'll be a lot of sanding

One thing is for sure I am going to consider every option before I make a move

[mhasting2004]

Sorry to hear that you've had some dramas.

Couple things...

Polyester resin is a very different beast to Epoxy resin (and yes Epoxy costs more).

I've not had any experience with the resin you used so not sure what its properties are like.... but if its from Bunnings I have my doubts on how good it would be. (not many boat builders buy stuff there)

Not sure if I understand what you mean about the curve but you will always get a meniscus curve at the edge of the form which needs to be filed down however if the epoxy is a fairly thin liquid type this is minimal.

You need something that pours like warm honey (or thinner) not cold treacle and sets slowly.

Another is to avoid mixing air into the epoxy as when it starts to react it heats up and these bubbles of air (if not able to float to the top... ie thicker epoxy) will expand as they are warmed... and you slurry expands resulting in a uneven surface.


Thin and slow is the go


Like always as they say your milage may vary... I may have had beginners luck as I didn't have such dramas and the level I use is an engineers type so very sensitive.

Up side is its easy to chip off if its a disaster and start fresh or try another approach.


I agree, MadVac's machine is definitely one of the benchmark builds on the zone.

Cheers

Mark

[wentyfalls]

Sorry to hear that you've had some dramas.

Couple things...

Polyester resin is a very different beast to Epoxy resin (and yes Epoxy costs more).

I've not had any experience with the resin you used so not sure what its properties are like.... but if its from Bunnings I have my doubts on how good it would be. (not many boat builders buy stuff there)

Not sure if I understand what you mean about the curve but you will always get a meniscus curve at the edge of the form which needs to be filed down however if the epoxy is a fairly thin liquid type this is minimal.

You need something that pours like warm honey (or thinner) not cold treacle and sets slowly.

Another is to avoid mixing air into the epoxy as when it starts to react it heats up and these bubbles of air (if not able to float to the top... ie thicker epoxy) will expand as they are warmed... and you slurry expands resulting in a uneven surface.


Thin and slow is the go


Like always as they say your milage may vary... I may have had beginners luck as I didn't have such dramas and the level I use is an engineers type so very sensitive.

Up side is its easy to chip off if its a disaster and start fresh or try another approach.


I agree, MadVac's machine is definitely one of the benchmark builds on the zone.

Cheers

Mark

Thanks for the reply Mark

The curve is actually length wise which is the wierd thing. One of the pics shows a white line below the straight edge - that is sunlight! I reckon the gap is at least 2mm!

The stuff I used I contacted the manufacturer and its viscosity was as low as casting resin. It was nice and thin and seemed to flow easily.

It was cold up here yesterday and the resin had plenty of time to flow before it went off.

I got a meniscus around the edges as expected and was able to file it off fairly easily.

So the whole thing is a bit of a mystery. I wish mine worked as well as yours did

So far the best option I can think of an interpretation what of MadVac did:

1. Remove the epoxy and attach the linear rails directly to the steel

2. Set the linear rails parrallel to each other.

3. I have figured out a way that I can attach some temporary brackets to the ends of the frame that sit slightly higher than the top of the linear rail

4. level the top of the brackets to each other in all directions - front to back, left to right and diagonal.

5. Run a tensioned wire between the brackets above the linear rails

6. Taking into account wire sag (I think MadVac refers to a sag chart) ill shim each rail parrallel to the wire

7. Inject some resin into any gaps for extra support under the linear rail

and finally


Cross my fingers!

How does that sound?

Rich

PS: apologies for any typos, I looked at one of my earlier posts and it was woeful (i'll blame the cramped laptop keyboard)

[wentyfalls]

Well today I decided to go for the epoxy resin to level the rails.

I googled a bit and found a place near work in Blacktown that sells a range of Epoxy. I explained what I was trying to do and he recommended that I use an epoxy by Epirez. It is a general purpose epoxy that is often used to stick concrete together.

The guy who sold it to me said I should be able to thin it with up to 5% solvent, but I have contacted to manufacturer to double check. I may just run the heat gun up and down it to get it to flow. i have also done a little test patch with thinned resin.

So I removed all the old polyester resin that failed and sanded the top of the rails back to bare metal.

Then I built up the dam around the rails with 3mm mdf that is double sided (very thin) taped then gaffa taped, then clamped. The ends are taped on.

For a bridge I have used a piece of 25mm conduit with a pouring hole cut in the top.

When I was cleaning up I noticed that I had had a fair bit of the polyester resin leak at the ends. I think that too much leaked out and the resin went off before it could self level properly

So I am making sure there are no leaks this time by applying a small amount of the resin at the spots where there are gaps and corners and where the bridge connects.

To stop the resin from sticking to the MDF I have coated the MDF in a layer of wax.

We'll see how it goes.

Any thoughts would be appreciated.

One question - will the wax be an adequate release agent?


Rich

[mhasting2004]

Hi Rich

Couple points:

• Don't apply heat to the mixed resin asit will "kick" ie set faster
• Do preheat ( ie just warm it up abiwitha lamp or inside) the resin before putting the hardner in it to make it flow better
• pour around the full frame an even amount so as not to make the epoxy have to flow of its own accord the whole distance.
• pouring hole in conduit is a good idea but id still put a thin layer into the frame sides also.
• minimize the amount of leveling that the epoxy needs to do
• wax is a fine release agent
• avoid vigerous mixing that will introduce air bubbles
• leak check with a small amount of mixed epoxy like you said
• be aware that large amounts of epoxy give off alot of heat and will set faster than smaller amounts
• be sure everything is good to go before you start mixing as the clock is ticking as soon as you start.

Cheers

[wentyfalls]

Well I poured the resin last night and it was a success, hardly any bubbles

The main thing i learnt was- make sure there are no leaks in the dam.

My prep this time was to hold the dam (3mm mdf) on with thin double sided tape, lots of gaffa tape and then timber and clamps

I drizzled small amounts of epoxy into the corners and any other spots that can leak over two nights prior to the main pour so it would harden and seal the holes.

The pouring/bridge conduit was sealed at the dam junction with KneadIT epoxy. It is an epoxy dough that you knead to mix the two parts and then can form into any shape. It was great for pressing into corners etc and when I poured I found another leak that I also sealed with the KneadIt

I heated the resin in a bucket of hot water and did the pour on a cold night so it had plenty of time to run and level before it set.

I ran ovver it with a heat gun and that seemd to pull out the bubbles.

Also I cut the lid off the resin tin to remove the rim. I did this with the good can opener from the kitchen (don't tell the wife). This gave me a clean edge to pour with, which is much better than trying to pour straight from the can with its "paint tin lip"

I have to wait a few days for the resin to fully harden before I clean the edges up with a file.

Next stage rails.

Rich

[mhasting2004]

:banana: Glad to hear it worked out this time around.


Not a big deal but looking at the photos I had a "but first.." moment. When I did mine I had already drilled all the mounting holes for the 8020 extrusion onto which I mounted the rails (these were taped over from underneath so I didn't have a bunch of leaks . This made it easier to drill as I could use the dril press to drill the steel and then after assembly and the epoxy pour it was easy to use a hand drill to clear out the epoxy.

Minor detail but might be worth pointing out is anyone else follows this route.

Looking good though.

Cheers
Mark

[wentyfalls]

:banana: Glad to hear it worked out this time around.


Not a big deal but looking at the photos I had a "but first.." moment. When I did mine I had already drilled all the mounting holes for the 8020 extrusion onto which I mounted the rails (these were taped over from underneath so I didn't have a bunch of leaks . This made it easier to drill as I could use the dril press to drill the steel and then after assembly and the epoxy pour it was easy to use a hand drill to clear out the epoxy.

Minor detail but might be worth pointing out is anyone else follows this route.

Looking good though.

Cheers
Mark

Oops pre drilling may have been a good idea. Although taping from underneath may have been difficult with the RHS tubing. Mark you used 'I' beam yeah?

Mark your build used THK/HIWIN square rails and I can see why you'd want the 80/20 extrusion to support the narrow rail. I am hoping to keep the cost down a bit by mounting my wider rail (20mm round supported) directly to the Epoxy.

The plan is to clamp the rail in position and pilot drill straight through the rail support, epoxy and steel. Remove the rail and tap the holes and then mount.

Fine adjustment on the second rail may require elongating the holes in the rail (last resort)

The next challenge!


I was going to use 80/20 extrusion on the gantry axis but need t-slots with 30mm centres. The place I was planing to get it from (Australis Engineering ) do not stock it in Australia and other places I have tried are either really expensive or shipped from interstate (I don't want to risk getting them bent)

So if the Epoxy is successful I thought I might try a steel gantry that has been 'faced' with epoxy to mount my supported rails.

If the steel gantry is sucessful i'll be hundreds of dollars in front compared to an 80/20 frame

So considering I started off planning to buy a chinese machine then build an all 80/20 extruded frame it may end up all steel handmade

And I'll add that the build process is a challenge but great fun


Won't get much done this weekend but ill keep plodding
Rich

[RomanLini]

Nice thread Rich.

Polyester is not suitable for levelling. It sets to a "soft gel" as a solid, then continues to harden and shrink in that solid state so it can warp as it set and even set bumpy etc.

The epoxy if it's a topcoat type should remain liquid (and gravity level) throughout the shrinkage until it sets solid and give you a good level surface apart from the meniscus at the outer edges.

Good luck with wax as a mold release.

[wentyfalls]

Nice thread Rich.

Polyester is not suitable for levelling. It sets to a "soft gel" as a solid, then continues to harden and shrink in that solid state so it can warp as it set and even set bumpy etc.

The epoxy if it's a topcoat type should remain liquid (and gravity level) throughout the shrinkage until it sets solid and give you a good level surface apart from the meniscus at the outer edges.

Good luck with wax as a mold release.

Thanks for the encouragement Roman

the epoxy resin has worked well and was definately worth the hassles fuss to set up right
the wax also worked perfectly

rich

[wentyfalls]

Hi all

I have spent a bit of time out of the cold garage fiddling with my gecko G540 controller.

It was as close to plug and play as i think you'll get.

All I had to do was

1. set my resistors to 3k on the DB5 plugs

2. Solder the motor connections - I first identified the coils on my steppers and then soldered every one the same

3. As per the Gecko instructions set the parrallel port in my PC BIOS.

4. plug it all in and add an E-stop

5. in Mach 3 I set the 4th axis to be a slave to my X-axis as I have two ball screws on my X axis

6. at first nothing happened so I downloaded the MACH3 config file and then away it went

7. Tune the motors.


The Gecko instructions were clear and it all worked - I am pretty impressed and know that at least the electronics are largely sorted. For $280 it is money well spent

[wentyfalls]

Well now that the X axis rails are mounted i have moved onto the Gantry.

I was originally planning to have an alluminium T slot gantry but could not get the size that I wanted for a reasonable price, so I have switched to a steel one.

It is 150mm x 50mm x 3mm blue primed steel and boy does it bulk things up.

It is however just the right size to fit the 20mm supported rails with the ball screw running up the centre.

I have mounted the rails directly to the gantry and then shimmed them to match.

I hope that even though the RHS is slightly concave as long as the rails are level and co-planer etc it should be ok. (correct me if im wrong)

So to check this I clamped some alluminium angle to each end and ran a tight fishing line along the centre of each rail.

Then I placed a piece of 10mm ally flat bar under the line and checked that the distance between the line and the bar was the same

I needed to shim one rail approx 0.15mm and did so with some folded over allumimun foil.


So I have a couple of questions

1. Is my gantry now too heavy - it is being driven by dual ballscrews and 640oz steppers?

2. Is my shimming method likely to be accurate enough - I plan to machine mostly timber and plastic but would like to do some alluminium?

I know that both these questions are a bit open and there are lots of variables to consider, other peoples thoughts would be appreciated.

[JohnZ]

I think that will make an excellent gantry beam. I see no problems using aluminum foil as a shim for thin spacers as you needed. I believe you will have zero problems with your steppers and the weight of that beam. I have a moving table with a single stepper motor that weighs over 300 lbs when I have a machinist vice installed. Just tune your acceleration as needed.

Sent from my DROID4 using Tapatalk 2

[wentyfalls]

I think that will make an excellent gantry beam. I see no problems using aluminum foil as a shim for thin spacers as you needed. I believe you will have zero problems with your steppers and the weight of that beam. I have a moving table with a single stepper motor that weighs over 300 lbs when I have a machinist vice installed. Just tune your acceleration as needed.

Sent from my DROID4 using Tapatalk 2

Thanks John

So as long as I am mindful of the accelleration and decelleration of a fairly heavy gantry I should be ok.

I can still pick up the gantry so it is well under 300lbs - probably less than a 100.

Rich

[LN-JET]

I am really starting to like your build:-)
The gantry on top eliminates a lot of flex. Those rails are not near as stiff as profiled rails with preloaded trucks, but I think you make the best of it.
I am wondering about the length of your y-axis, and screw. Will you be using all that travel, when the sides of the table limits where your z-axis and spindle can go? The length of the screw should be kept to a minimum to avoid whipping.

Lars