[RotarySMP]

Thanks for your suggestion with covering the mould with tape. I used it on a test piece, and it demoulded perfectly, even without waxing the entire surface.

[LeeWay]

CNC Milling machine in a bag. I love it.

[Fenza CNC]

LET'S DO THIS!

[skippy]

Interesting thread. Good luck with the pour. I'm looking forward to seeing the results.

[RotarySMP]

I did the same, buying the aggregates in the gradings which the local hardware store has, with the finest sand also being 0.1-0.3mm like yours. The only thing you might like to consider is some super fine quartz flour, fly ash, or alumina. All the academic articles I have read point to about a 30% increase in strength and rigidity if your aggregate is graded done into a fine powder. I got some Alumina from a pottery supplier. In making cement concrete they stop the grading at fine sand, because the portland cement is the fine powder. Since we don't have that, it makes sense to add a replacement. Using Thomas Zietz XLS, I ended up with 12% alumina in my mix.

[RCaffin]

Just a thought, and maybe too late.
The Z axis bearing blocks come in two sets: upper and lower. The two sets look a bit to close together to me (picture, page 1). I would prefer to have another 4-6" between uper and lower sets, as the distance from the blocks out to the spindle axis is largish.

Cheers
Roger

[nateman_doo]

Why are there no pictures yet? Its been days.

[LeeWay]

He's up to his elbows in wet epoxy.

[petruscad]

Why are there no pictures yet? Its been days.

Patience, all good things come in their own time!

[Jan Rune]

Cant wait to see the result. Great job Petrus!

[gt40]

Thanks for posting this- the pics and work flow descriptions are great.

I am curious how much epoxy you mixed and for how long before adding it to the aggregate? I saw you have US composite 636 with the slow hardener. I have to mix 6.5 gallons worth for my build and am a little wary about exotherme and running out of time mixing it- Any suggestions or observations are much appreciated...

I can't wait to see when you take off the mold!

[petruscad]

I have to mix 6.5 gallons worth for my build and am a little wary about exotherme and running out of time mixing it-

The polymerization reaction is exothermic but very, very barely so. I have not noticed any temperature rise at all, either while mixing or in the mold. As to how much time you have, US Composites lists the pot life at 35-40min after mixing. However, I would say you have at least one hour and maybe even 1.5 hours before any solidification begins. So you can mix the epoxy for 5 minutes, mix the aggregate for 10min, fill the mold in 30min and you still have time left. US Composites lists the set time at 5-6h which is about the amount of time after which the EG seems to gel a little. 2-3 days is the minimum time you need to keep the part in the mold.

[petruscad]

I like the attitude in the last comment by louieatienza. All material have shortcomings and we design around their limitations. This stand is just that: something for the mill to sit on so it doesn't sit on the floor with me bent over it. If it changes shape and the six contact points are no longer co-planar I will shim them. If it does not stay level in the beginning I will add shims under the legs until it does. After a while wood dries and stabilizes and California is not exactly a wet environment. The base is so think that it will probably not deform even if the contact points move. Ad far as stability and precision are concerned there are much more consequential issues to worry about...

[nateman_doo]

The week just won't go by fast enough will it?? can not wait to see this thing.

[petruscad]

Moving on with the infamous and controversial wood base!

Here are the pieces being fitted to the mill base to see if everything lines up.
Attachment 273730

And here is the box structure completely glued and the casters installed on each foot.
Attachment 273732

This is a closeup of the anatomy of a foot. The plate is glued and screwed to the foot (note that this also effectively seals the end of the leg!). The casters are simply screwed through the plate and into the leg itself.
Attachment 273734

Each caster is rated for 110lb so I have 440lb per foot. When fully loaded it may not be very easy to roll the whole mill around at will, but that's not the purpose. The purpose is only to be able to move the mill from the middle of the garage where it will be assembled to against one of the walls where its final place will be (~10 feet) without the use of a forklift or any other contraption of that sort.

[RCaffin]

Hi petrus

I have (bigger) hard rubber wheel casters on my wood base, but my 'concrete' floor is close to 100 years old and not what you would call 'flat' any more. Not real good concrete either. Oh well.

I was concerned that the hard rubber wheels might deform over the years, so once I got it into position I jacked it up with a crowbar and slipped wide wood blocks under the timber frame at the corners. Now the wheels are free. And I shimmed each block so the top was pretty level and very stable. Works for me.

Cheers
Roger

[nateman_doo]

Hi petrus

I have (bigger) hard rubber wheel casters on my wood base, but my 'concrete' floor is close to 100 years old and not what you would call 'flat' any more. Not real good concrete either. Oh well.

I was concerned that the hard rubber wheels might deform over the years, so once I got it into position I jacked it up with a crowbar and slipped wide wood blocks under the timber frame at the corners. Now the wheels are free. And I shimmed each block so the top was pretty level and very stable. Works for me.

Cheers
Roger

I was going to suggest that to him, and anchor it to the floor.

[RCaffin]

> anchor it to the floor.

Ah well, there must be 500 kg there, trolley plus CNC. Gravity seems to do a fine job of anchoring it down for me. And the wood is not very slippery.

Cheers
Rogr

[RotarySMP]

Looks excellent.

[gt40]

Looks great- following your progress with great interest. You cast in steel feet for the bottom, how are you attaching the rails for the top?