[ihavenofish]

Not sure what this diagram is showing


Normally you make some surfaces (like a steel bar machined for a linear rail) that you precisely mount to the mold frame, and then they get cast in with anchoring devices. No post machining of any kind is involved.

[mactec54]

An alternative to machining cast parts after casting. The 'template' surface has to be machined though. Much easier in my eyes since you don't have to transport the cast part in and out of a machine shop. Should also end up cheaper since you can produce more castings with one template.

https://www.rampf-group.com/en/news/...-top-accolade/

Yes this is normal what a lot of the manufactures that do EG type casting do, the steel required is fabricated or cast, stress relived, blasted clean, machined and Ground where needed some may add some coatings on the steel before machining

So all the casting is doing is adding damp and weight to the steel or cast iron structure

[ihavenofish]

Yes this is normal what a lot of the manufactures that do EG type casting do, the steel required is fabricated or cast, stress relived, blasted clean, machined and Ground where needed some may add some coatings on the steel before machining

So all the casting is doing is adding damp and weight to the steel or cast iron structure

I don't think you looked at the pictures close enough.

There's a precast EG base - no steel necessarily involved, with no precision surface for the rails and ball screw mounting. Then they seem to "recast" a new precision surface on top - probably with a fine AlO3 aggregate. I have seen people do this in the EG thread here.
This is actually similar what is done when reconditioning dovetail machines - recasting with moglice (similar to turcite B) using a form.

My only thought is as I said above, I think the general wisdom is to not directly mount rails and screws onto the EG. You also need to remember with an aluminium oxide surface, you have zero ability to correct anything without sending it to a diamond grinding facility.

[spumco]

you have zero ability to correct anything without sending it to a diamond grinding facility.

Speaking of the point of no return...

[peteeng]

Thanks Ard - Yes a guage or countermould can be used to create the reference surfaces post casting. The registers can be cast in directly as well. Once the concept is firmer manufacturing issues & costings will be brought into the design. Well done Ralph...

Studer cast their bases then recast the ways

https://www.youtube.com/watch?v=RwbY...ature=emb_logo

Peter

[mactec54]

I don't think you looked at the pictures close enough.

There's a precast EG base - no steel necessarily involved, with no precision surface for the rails and ball screw mounting. Then they seem to "recast" a new precision surface on top - probably with a fine AlO3 aggregate. I have seen people do this in the EG thread here.
This is actually similar what is done when reconditioning dovetail machines - recasting with moglice (similar to turcite B) using a form.

My only thought is as I said above, I think the general wisdom is to not directly mount rails and screws onto the EG. You also need to remember with an aluminium oxide surface, you have zero ability to correct anything without sending it to a diamond grinding facility.

Don't have to I have been in some of these factory's that cast there machine bases / parts, any of the good one's are doing pre machined parts which are precisely placed into the molds

They insert the red part in there drawings, which is normally all machined Steel or Cast Iron, no finishing to do after casting, they are completely ready for assembly

The pictures are only a rendered drawing they are not going to show you all the details

[ihavenofish]

That's not at all what those pictures show.

[ihavenofish]

Thanks Ard - Yes a guage or countermould can be used to create the reference surfaces post casting. The registers can be cast in directly as well. Once the concept is firmer manufacturing issues & costings will be brought into the design. Well done Ralph...

Studer cast their bases then recast the ways

https://www.youtube.com/watch?v=RwbY...ature=emb_logo

Peter

Those are hydrostatic ways. The "granite" is the linear way itself. So, very different usage than bolting the steel rails down onto.

Datron uses real solid granite for their bases, and bolt things to it, but i think EG is prone to movement and creep when you bolt the rails on directly.

Should look up to see if any commercial EG machines have the ways bolted directly to the surface, without a steel plate insert. The tech has progressed over the last few years, so maybe its ok now on a light machine like yours.

[ardenum]

Should look up to see if any commercial EG machines have the ways bolted directly to the surface, without a steel plate insert. The tech has progressed over the last few years, so maybe its ok now on a light machine like yours.

They do but those surfaces are ground instead.

[peteeng]

Hi Martec et al - If the EG is correctly post cured I'd expect no creep to occur. In a prior role I engineered composite parts for elevated work platforms. These fibreglass parts replaced steel parts for EWP's that where used on high tension power lines and formed part of the insulation for the workers. One of the concerns was losing tension on the bolts due to creep or relaxation of the laminate under long term bolt compression loads. So I set up a dummy part and kept track of the bolt tension over a period of a year. No loss of tension occurred. The epoxies the DIY EGers use with very low activity hardeners maybe a different matter. To be able to cast thick sections with no runaway exotherm low activity hardeners have to be used. To fully cure the epoxy post curing is required and DIY generally don't do this. So the epoxy will not achieve full hardness or cure at ambient conditions. I'm sure the processes used by commercial EG people would be able to produce parts where rails etc could be bolted to the part directly with no concern of relaxation. I say relaxation as creep is unlikely in this situation. There is a slight difference between creep and relaxation mechanics in plastics. Peter

[peteeng]

Hi Ralph - Are the bolts at the back of the arm hard to do up? Are the cars snug in the gutter and this gutter is the prime alignment for the rails? I don't like the arrangement but it maybe a solution to make the arm stiffer...Peter

[spumco]

Peter,

I didn't model it, but the outboard flange side of the right side head gutter has four grub screws to tighten the cars against the opposite (inboard) edge. The cars are a close fit, but not tight. Perhaps 0.005" sideways clearance.

The inboard side has been scraped slightly, presumably to get the head aligned with the Z-axis rails when the grub screws are snugged up. This is what I used for a reference surface while indicating the head for boring out the spindle hole.

The inboard car mounting screws are accessed through the column from the back. There are two holes which permit a long hex wrench or extension to line up with the car holes. You have to raise and lower the head to get to all four... see the two pipes I cast in place on the column? Those are so I can access the car bolt holes.

If you look closely at the first photo below, you can see at the left side a couple of holes in the head casting on the outboard edge/flange. Those are for the lower car, and there are two more for the upper.

All of the other car mounting points on the saddle have similar grub screws to force the trucks up against a reference surface. Second photo is of the saddle Y-axis, and you can see the (loosened) grub screw which bears against the left-front car.

-Ralph

[peteeng]

Hi Ralph - Thks for extra photos. This design area is always a fiddle...I think in Millis case rear holes thru saddle and column would mean really really long extension for wrenches etc... so rear access is out at the mo... I was looking for some materials for the arm and came across some Plutonium but its the same stiffness as titanium lots of depleted uranium around E=175GPa... Currently steel is 18kg Al is 6.3kg... CSA is 7kg... Tomorrow businesses start opening up so I can go get some CSA to play with... Peter

[peteeng]

Hi All - New ER version details:

1) Shall be able to take ER16 standard and BT-30 optional power head. 750W and 1kw servo drive options.
2) X 450 Y 200 and Z 300mm
3) nose down ht from bed approx 75-100mm nose top ht from bed 400mm
4) prefer max part weight to be 50kgs currently base is 100kg and the column is 75kg

model stiffness X 19 Y 16 and Z 13 N/um this is achieved with the arm and saddle in steel. (Target actual stiffness >10N/um all axes ) Steel not ideal still thinking about the arm geometry and material. The crux geometry is not ideal for torsion or bending.

The column and base is CSA at E=40GPa Hopefully testing shows I can get higher then that. Will make the base deeper.

The struggle continues. Peter

[mactec54]

That's not at all what those pictures show.

Here is a better look at what some manufactures do there castings, it can be done in more that one way some Grind and lap the castings that just have inserts in for all the mounting points

Studer is one of the companies I have had a tour of there manufacturing, there surfaces that do not have pre machined inserts are Ground and lapped

China has many manufacturers doing Mineral Casting some also machining straight from solid Granite and add inserts so there are may ways it can be done

[ihavenofish]

I was talking about THAT picture as it was brought up as a method to do it.

[peteeng]

Hi Guys - We are discussing the proverbial cat problem and there are many solutions. Lets move along to the next hurdle... Peter

[peteeng]

Hi Guys - We are discussing the proverbial cat problem and there are many solutions. Lets move along to the next hurdle... Peter

https://www.bnd.com/living/liv-colum...20inside%20out.

[ihavenofish]

You haven't even passed the first hurdle, which is what your machine is. Every post is entirely different.

[peteeng]

Evening All - have used a sub plate for the column. This is currently steel but will be aluminium I hope. It can be used to square the rails then the column is bolted on top and set square. The big hole needs to be removed with a central ligament. The static stiffness is well balanced at X 15 Y 18 and Z 15 N/um. I have a hollow aluminium arm but will use the same subplate philosophy on the arm next time around. The front face is 25mm thick but you can see it flexes too much.

The subplate also allows MACHINING of features for the cars (will keep a few onlookers happy)

I prefer Al is it lighter and can be anodised. The machinist I use makes tonnes of aluminium parts and gets most of it anodised so he gets Al and finishing at good rates... I changed the base thickness from 150mm to 200mm and it made a big difference but now its quite heavy may have to be two pieces. Peter