El Beast - Initial design phase, comments and critique welcomed!

[Zeeflyboy]

Thought we already mentioned that the rails would be aligned to the ecocast ground bed plate?

I'll be using Thorlabs precision corner brackets for frame squareness (combined with the ecocast end plates and milled extrusion).

Does that not cover the alignment issues, especially given the relatively small size of the machine?

[Boyan Silyavski]

They will be aligned left-right, not up-down , plus have to be straight up down, not wavy, same for left right, but as you said that will not be a problem as eco cast plate. 3d, means there are 3 directions that things have to be on plane

[Zeeflyboy]

No, they would be aligned in the vertical plane too... ecocast bed plate could be fastened to the top and then I would insert a shim of 2.5mm between carriage and bed with the carriage at one end, clamp it in place and tighten end screw. Move carriage to other end, insert same shim again and clamp. Tighten that end screw... If required you could repeat that at several points along the length.

Repeat on the other side and both rails are aligned vertically using the eco cast bed plate as a reference.

The parallelism and squareness of the Y-rails would be taken care of to acceptable tolerances by the captive ecocast end plates, milled extrusions and thorlabs corner brackets, while the vertical alignment (both in X axis rotation and Z plane height) would be done in reference to an ecocast bed plate.

What am I missing? In my head that ends up with the rails fully aligned in all axis to within the tolerance of the milled surfaces which should be sufficient for a pretty accurate machine all said and done.

[Boyan Silyavski]

Seems 100% ok what you are saying. Thats very similar to the way i thought it could be done.

[Zeeflyboy]

Ok great, thanks - glad you agree with my thinking then!

I've just done a mass analysis on the finished machine and its coming in at just shy of 190kg... I know mass is but one suggestion of rigidity but that's not far off 3 times the mass of my current machine.

I've also taken the opportunity to change to a HGR25 rail and HGR25HA carriages on the Y-axis since there is more space now.

Had a quote back for all motion parts, it was pretty reasonable for ground screws and HIWIN rails. Think I'm good to pull the trigger on those parts?

[fifa]

Few comments:
- I do not understand why you are using AL profiles and AL plates, check stiffness...
- design of lower (x) rails is .... You need to grind both surfaces to get perfect parallelism, otherwise will linear bearings feel the load caused by angular displacement of both rails , put them on the top of the table, in same plane - much easier for DIY,
- design of gantry (y) - it must be closed beam - it has no sense to do a "nice look" without functionality,
- side brackets, what is the method for setting the "true" right angles? Do you expect that everything will be machined within few microns? , y length tolerance stack is problematic anyway
- foots: do you expect that desktop is planar?, machine must be stable, it looks nice, but

Before design set the requirements i.e.
- max work space
- max space for machine
- max tooling dia
- material of machining
- define what you wish to do ( mirror surfaces, engraving...)

and the start with design.

regards

[Zeeflyboy]

Few comments:
- I do not understand why you are using AL profiles and AL plates, check stiffness...

Why alu profile, because it is available cut to length at sizes larger than I can handle myself with decent precision and also with ground surfaces from misumi. GFS (high rigidity) profiles are being used, they have substantially more mass than normal profiles.

Why alu plate, because I can process aluminium plate myself and I can buy it in ecocast form with a high flatness tolerance, again readily available. If I pay for every part of this machine to be made up in steel to high tolerances by someone else then I will not be able to afford it, even if the material itself is cheaper... which i'm not sure it is when you start talking about milled tooling plate.

- design of lower (x) rails is .... You need to grind both surfaces to get perfect parallelism, otherwise will linear bearings feel the load caused by angular displacement of both rails , put them on the top of the table, in same plane - much easier for DIY,

Both surfaces are ground...

- design of gantry (y) - it must be closed beam - it has no sense to do a "nice look" without functionality,

I don't understand what you mean here.

- side brackets, what is the method for setting the "true" right angles? Do you expect that everything will be machined within few microns? , y length tolerance stack is problematic anyway

That little mounting plate at the bottom of each side has an eccentric nut on one end and a DIN shoulder bolt at the other, which will allow the entire gantry to be trammed fore/aft, while the side arms and mount plates are both made from eco-cast plate which will have to sit flat to each other when bolted together. Further adjustment is available on the spindle mount for tramming left/right.

- foots: do you expect that desktop is planar?, machine must be stable,

On a machine this small I think adjustable feet are more trouble than it's worth. Better just to make sure you have a flat level surface for it to sit on... depending on what I can find I will either sit it on a granite block or pour a self levelling base block for it which will form the bottom of my enclosure.

Before design set the requirements i.e.
- max work space
- max space for machine
- max tooling dia
- material of machining
- define what you wish to do ( mirror surfaces, engraving...)

and the start with design.

regards

My design requirements were of course set out before I started to design it... the majority of what you list there was mentioned in the very first post. I'm not sure how you can even start designing a machine without knowing what you want it to do...


Thank you for the feedback but I do think there is a danger sometimes of losing sight of reality on this forum. For what is ultimately a small hobby desktop machine the rigidity of a 50x100mm GFS extrusion and 20/25mm alu plate is hardly going to be the limiting factor... This machine will be an order of magnitude more rigid and precise than my current one while expanding the work area, which is really all I'm after.

[A_Camera]

Ok great, thanks - glad you agree with my thinking then!

I've just done a mass analysis on the finished machine and its coming in at just shy of 190kg... I know mass is but one suggestion of rigidity but that's not far off 3 times the mass of my current machine.

I've also taken the opportunity to change to a HGR25 rail and HGR25HA carriages on the Y-axis since there is more space now.

Had a quote back for all motion parts, it was pretty reasonable for ground screws and HIWIN rails. Think I'm good to pull the trigger on those parts?

This is certainly going to be one of the most beautiful and best machines I have seen. Seeing and following your posts I am sure that the quality will match the beauty and it will not just be a "beautiful blond" with only good looks and sexy appearance, but it will also have massive quality and accuracy attributes.

I also like the idea of protective side covers, I think this is important because of several reasons, apart from the most obvious that it keeps most of the chips inside the working table area, it also works pretty efficiently when the cutter is broken and comes flying at you like a deadly projectile at high speed. I also have side walls around mine and that have stopped two such projectiles already from hitting me, so it is definitely a good idea to design that protection from the start. I actually don't understand how other people dare to run these machines without any protection at all, some not even using protective goggles. Perhaps they never make mistakes and never break a mill bit, I don't know, but that's their business.

The only thing I'd do differently in your design regarding the walls is that I'd make them easily removable, preferably without the need of unscrewing. This is because it helps placing the work piece/vice/measuring instruments and so on on the table more easily. It also allows working on longer than the table work pieces if you would need it some day.

The other thing you should consider is the mass. 190kg is a very heavy thing, which is very good for a machine, but it sets some requirements for the table also. No point building such heavy machine if the table it is on is not stable enough, which I am sure you know very well also.

The other thing about the mass you have to consider is the ability to move it around. Perhaps it is a non-issue, but anyway, if you one day have to move it just a little bit, it is going to be a very difficult task if you haven't thought about that during the design. My machine is only about 90kg but to move that around on my own is not possible, so I have to lower the machine on wheels to do that, and even so it is not something which is done in a minute or two, first I have to lift the machine then remove the wooden blocks it is standing on then lower down on two wheels and do the same for the back, or the front part, depending on where I start. Mine is standing on it's own feet, so it is a bit easier than it would be for yours.

Perhaps you have these questions covered/solved already, but before starting the machine build, I'd build the table to build it on and made sure the table is extremely easy to rotate and move around during the work. It is going to be necessary to have easy access to all sides, that's for sure.

Anyway, it is very interesting to follow up on your work and see the progress. Good luck with the rest of the work as well, and don't forget too keep us updated, both here and on the Zone.

[Zeeflyboy]

Boyan, you are clearly a man of high standards which I respect, and I thank you for your advice. I just hope that when I start building it doesn't become painful for you to watch ;)

The only thing I'd do differently in your design regarding the walls is that I'd make them easily removable

It would be nice to have them removable, but they need to be water tight for underwater cutting of carbon fibre. I think making them rapidly removable may be tricky whilst also being sure I'm not going to flood my work bench. I get on okay with the current version which is quite similar, but I will have a think about whether I can do anything to make at least one side removable.

The other thing you should consider is the mass. 190kg is a very heavy thing, which is very good for a machine, but it sets some requirements for the table also.

The table is crazy strong and rigid... In fact I think the table is probably 100kg or more itself! It's constructed from some very beefy pine struts, big slabs of 18mm moisture resistant MDF and topped with 40mm solid oak.... here are some pics from when I was building it with one of my friends just out of interest (not that you asked):

Main frame:




Skinned and being massaged to perfection





Controller mount and utility draw:




Finished table:

The other thing about the mass you have to consider is the ability to move it around. Perhaps it is a non-issue, but anyway, if you one day have to move it just a little bit, it is going to be a very difficult task if you haven't thought about that during the design. My machine is only about 90kg but to move that around on my own is not possible, so I have to lower the machine on wheels to do that, and even so it is not something which is done in a minute or two, first I have to lift the machine then remove the wooden blocks it is standing on then lower down on two wheels and do the same for the back, or the front part, depending on where I start. Mine is standing on it's own feet, so it is a bit easier than it would be for yours.

It won't need to move very often, but when it does it will probably be a case of having to separate the gantry and the main bed... unless I just pick up an old engine hoist perhaps. Actually that's not a bad idea - perhaps I should built in some hoist points?

Moving heavy things is ultimately just an engineering challenge!


Just in case any one is interested, this is the Man Cave I built last year, which is the home for this future machine.... I also have to try and find space for a Wabceo D4000 lathe: