[ChipsBFlyin]

Pete,

I do plan to cast the base upside down. I have pallet jack and can have access to a forklift across the street that can flip it over for me. I am trying to figure out how to work out chip management, via auger or chip conveyor. So i have to figure that out before I can finalize the base casting.

I may have come across some free 1/2" (12mm) steel plate that I may be able use to build the gantry.

[mactec54]

Right so that the only 'connections' in the frame between the parts are rails and carriages then...

And they bolt to a machined surface, like a steel insert

[ChipsBFlyin]

Pete,

So I've been playing around with the model a bit. A big part and must of this CNC project is the ability to have large tool magazines. I have 30,50,70 on the ones I have access to and even 70 isn't enough, it seams like you can never have a big enough tool changer. haha.

Anyways, as you can see in the cutaway, to maintain my machine foot print small, I have to add the tool changers to the back. In order to have the tool changers in the back, I have to trim some of the base. Do you think this would compromise my base design? The last picture is of a top view of the base.

[peteeng]

Hi CBFlyin - Can only really tell if its modelled and FE'ed. But if the hole is not between the tool and the walls then maybe OK. This is a bit of a monster. How are you going to keep swarf out of the cassette? Commercial machines go to great lengths to keep swarf away from the tools. Only takes a bit of roughage in the wrong spot and it creates dramas. This is heading towards serious commercial grade machinery its getting more ambitious by the day. But you gotta aim high. Peter

[ardenum]

I'd go away with the disc toolholder and do a chain magazine toolholder instead, you wont need to do any cutouts because it will fit right in between the gantry and the bed. It can be as simple as 2 sprocket chain lines running parallel to each other and then you bolt in the tool socket onto them. One guy did just that on his youtube channel but it was in chinese so I couldn't find the link...

Also that gantry is flimsy compared to the bed. Especially that Z axis. I'd delete the side walls and cast a whole gantry 1:1 copy of DMU 200. If you want you can try to buy a cam model of it. Guys at 3D machine tools models sell cam models for cheap, you'd have to email them if they have DMU 200 (not the P version, that's a different machine). Make sure it has the full column geometry not just the front. Otherwise remaking it from videos and pictures is possible. Copy the whole assembly, gantry, carriage, Z axis.

[ChipsBFlyin]

Pete,

I'm trying to get the main components designed/placed, then I can tweak them slightly after to add way wipers and what not.

This is how I plan on attempting to build the machine,

1. Cast the Base and columns, They will have inserts installed for the sheet metal enclosure mounts locations, Y axis and ball screw mounts, etc
2. Mill/grind the top of the Y axis rail mounts, if I can't get a good parallel surface to my table ( surface plate) then, I would stop here and scrap the project.
3. Build gantry/X axis saddle, send out for heat treat, mill/grind.
4. Assemble and inspect the assembly so far. If I can't get good readings along the axis, and can't adjust further or can't resolve the issue. I would stop the project and scrap it here.

I feel like this would be the hardest part of the build and the rest can be tweaked without affecting the machine precision. My goal is to reduce the amount of coin I am going to gamble with. If I can't get the main frame and axis' aligned, then I won't proceed with the project.

I am going big with this project, because otherwise I would just buy a used VMC and call it a day. Also a VMC that has the travels I want, would have a footprint that is approximately x2-3 bigger than my current machine design. This may or may not work, all I am trying to do for now is reduce the risk of it no working. haha

Ardenum,

I originally thought about going that route with the tool changer, but for simplicity, cost and foot print, the round tool changer seems to the be the best bet.

Based on Pete's advice, I decided on going with a raised gantry design. I originally wanted to do a DMU 200 design.

From my research, I think my gantry has a better construction what is offered on some of the big dollar machines., I could be wrong though. Currently its 1/4" (6mm approx.) wall, but I may double that to 1/2" (12mm approx.). Its approximately 14" high (356mm) x 10 (254mm)" wide and 72" (1830mm)long. The biggest commercial big $$$ gantry I measured was a rectangle tube, 3/8" (10mm) wall 12' (304mm) X 6" (152mm) x 84" (2134mm) long.


What I like about the DMU design is that I can extend the X axis a bit to one side and have a tool changer on the side like this one pictured.

[ardenum]

You don't have enough space between the sides to make a rigid z axis and not loose some of the work area or making the bed wider.

[ChipsBFlyin]

Can you please explain, I don't understand what you mean.

[ChipsBFlyin]

Ardenum,

If you are refering to the X axis saddle, is 12" center center on the X axis and 7.5" center to center on the Z axis rails

[peteeng]

Hi CBF - Risk management and disposable income Hmmmm. You say you have access to large VMCs. If so why not build this machine Lego style? Build in steel or aluminium using as big as components the VMC can make. Use a mechanical connection (dowels, tapers, mortise, tenons, self locking tapers, ledge features, there's quite a few methods used by toolmakers.) between parts. These being made on a VMC will be made to a very good precision. This is called "self assembly". There are many machines made like this. car engines, swiss watches, press tooling. I've been involved in very large automotive press tools and they have been made this way and worked. I also have designed small ultrasound machines and I'm always surprised at how they fit together correctly and work.

So then you have little risk as the parts will be made to guarantee the final assembly precision. Production machines use the biggest parts possible to make them commercially efficiently but for a bespoke machine that may not be the pathway. The design does not need to be monolithic either, that's a function of casting. If you have generative design on your FE then you will be able to remove a lot of metal yet maintain stiffness. Its a BIG project each step has to be taken to ensure the next step works.... Do you have a big enough rubbish skip? Keep at it Peter

[ardenum]

Can you please explain, I don't understand what you mean.

The z axis will collide with the side walls if you make it big and rigid. So you will either have to make the bed wider or have a smaller work area or have a weak z axis

[ChipsBFlyin]

Ardenum,

What size box are you thinking of for being "big and rigid"?

Pete,

I would not say I have a lot of disposable, I would like to be able to see a return on my investment down the road, but like all investments, it comes with a risk.

The problem with VMCs is that they usually have a poor Y axis travel. The biggest VMC I have access to is 50" on X and only 20" on Y, so it's still too small to use for the big parts. There is another VMC that I could use that is bigger, but that one is always in high demand and rarely has any down time. Looks like my best bet is to send out the big parts.

I was doing some maintenance on my bandsaw and I just noticed that it has a UHPC base for the motor/drive.

[peteeng]

HI CBF - Too small is relative. Its about making parts at the required accuracy so they mate together to make what you want. Doesn't matter if it takes 50 parts to get there. Just another thought bubble. In regards to getting a return on machines that's interesting, Some of the machines I make sell fast, some sit there for years, then sell, some are still sitting . Can't pick it... You can't compete against commercial machines. If its a commercial enterprise they get a loan and pay off the machine with the work. Your circumstances will be different... Peter

[ChipsBFlyin]

Pete,

I thinking making it from more than 3 components (base, 2 columns) would not be a good idea, as I would be tolerance stacking. Every milled flat joint surface would have some error and I would end up adding some stress to the structure, no? unless I scrape it? I should be getting some of that precision grout next week to play with.

The way I plan on getting a return, is making parts from it, I don't think I would try to sell this boat anchor, unless I really had to.

- - - Updated - - -

Pete,

I thinking making it from more than 3 components (base, 2 columns) would not be a good idea, as I would be tolerance stacking. Every milled flat joint surface would have some error and I would end up adding some stress to the structure, no? unless I scrape it? I should be getting some of that precision grout next week to play with.

The way I plan on getting a return, is making parts from it, I don't think I would try to sell this boat anchor, unless I really had to.

[peteeng]

Hi CBF - I think it comes down to what accuracy, precision & repeatability you are aiming at for the machine in total. if you made the parts on toolmaking grade machines then have them suitable checked via CMM then you could achieve 0.001mm accuracy. This occurs on one the ultrasound machines I used to be involved with...

If on std commercial machines then 0.01mm say. I have been looking at geometric alignment equipment for machines and they start at $20,000USD. Way outside my budget. But machines need to be aligned correctly. You will have to jump that issue when you get there. Peter

[ChipsBFlyin]

Pete,

I own a CMM, although some of the components for this build will exceed the capabilities of my CMM. I may be going back to the drawing board with this machine. I agree, some of those tools are very pricy, but I may have access to some Renishaw aligning equipment, but I have to check.

I've been playing around with some configurations for the tool changer and I think I am going to stick it on the side, I may change the way I do the casting as well. I think I may try making a simple casting and making a steel base like the one pictured on this Datron. If it functions and I get decent results I may keep it that way or I'll end up building a more complex casting. I think I am going backwards with this build. haha

What are your thoughts on the raised wall on the left and lower one on the right. I lowered the wall on the right for tool changer clearance. Everything will be protected from chips with way covers eventually.

[peteeng]

Hi CBF - I don't think there is any in principle issues with being asymmetric. If its stiff enough its cool. I've re read a couple of my threads and the journey is often convoluted and circular.... But better to spend CAD time and sort it then spend real $$$ and obtain objects to find its not good.... I recon at least 500 hrs from clean sheet to a reasonable design. Peter

[ChipsBFlyin]

Pete,

Thanks for the input. I agree, on the CAD time. I'd hate to try and dispose of one of these castings if I made a design error.

Speaking of going in circles. I came up with another design. I really wanted to stay with raised walls, but tool changer and floor space limitations made it difficult. So here is what I came up with. I am concerned with the gantry sticking out 12" to the side. Should I be concerned with how this extension may vibrate or am I overthinking it? Its only used for tool change purposes. I still plan on having covers over the tool changer and the linear rails. The chips drain down the sides and fall into the chip pan/coolant tank. The design is still in progress.

[ardenum]

I like the removal of side walls and the gantry is going in the right direction, keep at it. I'm confused why you want to enclose your granite plate inside a uhpc cast. Is it a replacement for a t slot table for example?

Don't just try to pour uhpc around the plate, uhpc shrinks, glue it in after curing or put thin foam around the granite (but not under it) when casting.

The legs you can do like this: machined inserts and uhpc sits on it (with anchors going up into the legs). You can reverse the bolt cutouts to the outside since you're not mounting rack&pinion like in the example below. If you want to take a closer look you can download the model from my thread.

[ChipsBFlyin]

Ardenum,


Its hard to see from the picture of the model, but the plate would be installed after the UHPC was cast. I am planning on casting 3 threaded inserts into the surface plate cavity, this would allow me to adjust the plate from underneath. The next part is were I am stuck. I would like to pour something, not sure what material would be appropriate for this yet, to increase the surface area contact between the UHPC and the bottom of the granite plate. My thought is the main load bearing would be done by the 3 screw.

Note: the model does not include the inserts, sizes or the exact location of the inserts yet.