John's Alu Profile build

[Evengravy]

Planning is in the works for the base, I've been collecting materials here and there as I can source them in the current climate. I've decided against the wall mounted option, when I drew it up in CAD it wasn't really saving me a massive amount of floor space (due to the relatively small footprint of my machine) and I really want to make use of high flow flood coolant so felt a regular horizontal setup would be best.

I've decided to be a bit unconventional with this design as outlined in the images.



The main sides of the structure will be made from concrete based blocks, each measures 140mm(H) x 212mm(W) x 442 (L) and are very strong. These blocks are common here in Ireland and are largely made from a high proportion of granite aggregate along with a minimal amount of concrete as a binder (I'd estimate 15 - 20% concrete/cement) and I hope in this case, given the ratio of granite to cement, that shrinkage will be quite low and vibrations can be minimised too. I've had these blocks for over 12 months now so they should be relatively stable, but time will tell I suppose.

The intention for the main table surface is to cast this from home made glass fibre reinforced ultra high performance concrete. The intention is to cast this as a 75-100mm thick section in one pass by supporting the open section with ply braced from underneath (pre cut in the middle and siliconed at the joint for easy removal). I have sourced and received the glass fibre strands and the superplasticiser which I'll use to minimise the water content required in the concrete mix. I also intend to embed typical steel reinforcements (rebar or mesh or a combination of) I have yet to source those aspects as local steel outlets are closed for the next week or two. Time wise it's likely to be around the second week of June before construction can start, I'm looking forward to it.

For wiring/routing I intend to cast some 30-40mm plastic conduit (sink drainage pipe) into the front section, to allow motor and limit switch wiring to be routed cleanly from the left side to right. Controls box for the steppers and spindle VFD will mount to the exterior of the right hand wall.

I've been experimenting with some cast concrete of late and some alterations in mixes and proportions, likely I'll keep it fairly simple but I'll make some test samples soon to test those out.

The top of the table will be certainly quite rough post concrete casting, so the intention I have is to allow the concrete some time to settle and after that period level the entire table top with a 3mm layer of epoxy to give a nice flat surface to measure from and secondly, to provide some waterproofing. Part of the idea of designing the base this way is to allow sufficient space for a flood coolant capture tank to be housed in the underside of the 'table' and further design some fluid direction system once a tank has been sourced.

I could obviously go the tried and tested route and build the base from steel or aluminium, but I'd like to try this out to see how it goes. It's relatively cheap and if it all goes tits up, well I'm sure I can get a sledge hammer handy enough.

[Mister Mills]

Good stuff John. I would have never thought of a concrete base but now that I see you mock up it makes perfect sense. It will also be much easier to surround the upper part of the walls with a side/back etc to catch coolant. Flood coolant it a really good thing to have on any machine cutting aluminum. It will save toy a ton of cutters! Good luck with the build.

[Evengravy]

Good stuff John. I would have never thought of a concrete base but now that I see you mock up it makes perfect sense. It will also be much easier to surround the upper part of the walls with a side/back etc to catch coolant. Flood coolant it a really good thing to have on any machine cutting aluminum. It will save toy a ton of cutters! Good luck with the build.

Thanks, yes I think it should work out okay. I'm doing some calculations for mixtures at the moment in the hope to test the mix out this weekend in a very small batch. The only unknown is the shrinkage of the mortar for the walls/block but I'm hoping with a solid UHPC top any shrinkage should even out each side or be small. I'll try to get away with as little mortar thickness as possible but may test the Glass Fibre Reinforced mix as a mortar first to see if it bonds okay.

I'll upload sources etc when I get the initial test done.

[Kitwn]

That's a really interesting base design, I've been wondering about a concrete or block base myself in the future as a cost-effective and very rigid structure. I'll be interested to follow your progress.

If you plan to drain the coolant to a tank underneath then it may help to cast a short length or two of plastic drainpipe through the base to act as conduits for the fluid hoses.

[Evengravy]

That's a really interesting base design, I've been wondering about a concrete or block base myself in the future as a cost-effective and very rigid structure. I'll be interested to follow your progress.

If you plan to drain the coolant to a tank underneath then it may help to cast a short length or two of plastic drainpipe through the base to act as conduits for the fluid hoses.

We'll see how it works, I can't see why it will be a major issue unless shrinkage is significant over time, but I'll give it a bash. That's a good point on the drainage, I'll have to reiterate the CAD some more. The general idea was to have the coolant flood over both front and back and design a fibreglass chute to direct fluid back to the tank but that could also work, I'll have to have a think.

[Kitwn]

Just thinking out loud here John, but once you have the base epoxied up for leveling the rails you might as well use that surface as the base of your coolant-catching tray with a drain down to a storage tank below. Maybe build up the surface to direct the fluid to the drain. Rather like an Australian bathroom where the entire floor is built up round the outside to direct any spilled water into a central drain.

[Evengravy]

Just thinking out loud here John, but once you have the base epoxied up for leveling the rails you might as well use that surface as the base of your coolant-catching tray with a drain down to a storage tank below. Maybe build up the surface to direct the fluid to the drain. Rather like an Australian bathroom where the entire floor is built up round the outside to direct any spilled water into a central drain.

Hey, I think I'm following what you mean, that's not a bad idea actually, thanks. What I could do is run channels at the sides down into pipework and into the catchment tank from there, rather than fluid running over the front and back, and build a lip at the front and back for liquid catchment. That might make things a bit difficult loading and unloading stock though, particularly if stock is to overhand the Y (I do that sometimes).

The spindle only gets within 150mm or so of the alu sections which holds the rails left and right so there's plenty of space there for a liquid channel. I must draw up some options to gauge the simplest approach before starting.

[Evengravy]

Initial test mix is done, the testing here is designed to judge bonding strength when using a simple UHPGRFC mix as a replacement for mortar. This might be unnecessary but mixes like this are said to be good for 12,000psi or so, so I'd like to try it.


UHPGFRC mixes (in my very limited experience) are approached differently than regular cement type mixes, insofar as the cement to aggregate (sand) proportions are quite different. With regualar cement mixes you would generally be 1:3 cement to sand ration, here we are 1:1 roughly.

I have a simple mix and a more exotic one, the simple mix is approached here as I'll need to source some other part for the latter which I'll detail later.

Here we have:




+200g Sharp Sand (quartz I believe) I live near several quarries and this stuff costs me roughly 25 euro per tonne, give or take, and makes great concrete.

+200g Portland Cement (regular cement). Generally this will be mixed with other elements such as 20% CSA or Silica Fume, I'll fill you in on that later, those can be hard to source.

+6g of Glass Fiber (From mbfg.co.uk added to the mix last, strand length is 13mm in this case, probably too long but it'll do the job)

+0.6g of Plasticiser (FLUP PCE 104 from moertelshop.de) I went with the manufacturers recommendation in this case of 3g/kg, it probably needs to be doubled in reality though, so I'll have to order another 1kg tub for the table to be sure.

Don't take anything I say as gospel, this is what works for me so far, I'm very new to this so take everything with a pinch of salt and as 'in testing'.
The mixing procedure used was pretty straightforward, mix sand and cement together dry first, add a small amount of water to make an overly dry mixture that is just starting to clump a little. Add super plasticiser, continue to mix for a minute or two (vigorously) and add more water to bring it to field capacity being careful not to overdo it. When the consistency was where I wanted it, I mixed in the glass fibers last.

I ended up using a little more water than I would have liked or predicted from my calculations (65g), but I think I'll double the plasticiser next time and test again to see if I can further reduce the water input.



I used some small 'soap bar' bricks which are almost identical in nature to the larger versions to test it out, at the moment I'm mainly concerned with bonding strength if I use it as a mortar between the blocks. If it fails to bond, I plan to make another custom mortar mix using standard mortar mix with sand, cement lime and mortar plasticiser with some added glass fiber reinforcement to beef it up as I know that will stick well to the blocks.

One thing I've noted is that the mixture consistency becomes noticeably more 'dry' when adding the Glass Fiber, so I'll have to balance that out. Also the working time is short, around 20 minutes, so I'm going to have to be on the ball when doing this but I have a cement mixer so it should be doable.

The mixture is curing very fast, so in a day or two I should have an idea how the bonding is.

[Evengravy]

Some small progress.

After letting the GRFC mortar test cure for a week in situ in my workshop I inspected it for bonding, the very scientific method of slapping it with a hammer was employed. I was mostly concerned initially with whether it would bond significantly to each brick but I'm confident now that it will be perfectly fine in that regard. It's clearly much stronger than regular mortar and I'd expect it to shrink less and be stronger in compression. That's good enough for me to move on.

One thing I realised after purchasing the glass fibre and mixing up this test is that AR glass fibre is recommended as it is suitable for the extreme environment of usage in concrete (general E glass is not as it is attacked by the alkalinity). After reviewing the technical documents from the supplier though it seems that this isn't a major issue for me, luckily. The glass fibre I have purchased, whilst not AR glass, the type I have (E6-CR from Jushi Tech http://en.jushi.com/res/excel88fcd3bf87268a79.pdf) is tested and recommended in both high acid and highly alkaline situations so it should be fine. I note it here for others though, be careful, glass fibre is not all suitable here and go for something that is specified for concrete usage.

Here's a picture of the GFRC mortared test, being reused as a weight. This mortar is tough stuff. I'd like to do some more scientific tests before casting the main bed, I'll get the walls up firstly.



I'm pretty slammed at work but had some time to layout the basic structural outline on my newly concreted floor. Nothing too complex, four bricks, some string and some careful corner to corner measurements to make sure it was square. One of the issues I was having with the concrete floor was it was endlessly dusty, no matter how much it was swept it kept producing more and more dust. I treated it once with a PVA based sealer and water and this has cut this down. I will aim to treat it once more before moving on with the block work next week. This should also help ease my mind around bonding to the floor, I was more than a little concerned that it wouldn't bond correctly due to the dust but I'm told this is a commonly used solution to aid bonding.



Next step for me is to get my workload tied off and begin on this around the 10th.

I've ordered some new motor to ballscrew connectors some months back but they have yet to arrive, if anyone knows of a reliable UK source I'd appreciate it. I'm looking for something to handle 480oz/inch with minimal backlash. 8mm to 12mm. Without a lathe in situ I can't really modify what I have accurately and haven't as yet been able to fully test the new ballscrew install.

Anyway, that's it from me for now, more soon.

[Clive S]

[QUOTE]I treated it once with a PVC based sealer and water and this has cut this down. I will aim to treat it once more before moving on with the block work next week. This should also help ease my mind around bonding to the floor, I was more than a little concerned that it wouldn't bond correctly due to the dust but I'm told this is a commonly used solution to aid bonding.
[/QUOTE

Looking good, I take you meant PVA or even better is SBR