Tableless CNC router

[DaRy]

Hi

I'm in the planning state of building a simple small/medium sized cnc router and my head just hurts by all the thinking.

I must make it dead simple and cheap or else it will never be finished. I've started with the electronica (since I'm that kind of guy) and made a simple test drive circuit (http://http://www.cnczone.com/forums/showthread.php?t=31384) with constant current drive. I have this on a experiment board to drive two unipolar stepper recoverd from discarded 5.25" diskette drives. Will make a circuit board later on... I need to find one more stepper, or preferably three slightly bigger ones. (constantly scanning for discarded Laserjet II/III, to my great annoyment everything gets recycled or sent back to the manufacturer here in sweden).

In my eager I started build some hardware but discarded it... Found that it might be useful to have some sort of plan beforehand.

Ok, whats up with the "tableless"? Well, I want the main table to be the table... or the door, wall, window or anything else I place the router on. So it needs to be hanging in the top with legs down to the working surface. Kind of like the pipedream router but not permanently mounted to the table. I have some ideas but not compleatley satisfied with them... Se the pictures/sketchup files. The Z travel is a bit limited unless I make the legs really high. I might tilt the X rails to vertical position (if you understand) to open up the top (thats what I started to build but later scrapped).

Brainstorming is needed badly.

I do like the angle iron rails. It seems simpler than a pipe mounting, and the bearings have a larger contact with the rail surface. What do you think?


Have a good day!

[joecnc2006]

Not exactly sure why the upside down, but why would you want to fight gravity, cut material falling into router, and if used as a table, having the possibility of the machine getting miss-aligned all the time. if space is what you are after the try to do a wall mount or vertical cnc mill.

Joe

[DaRy]

Ok, maybe the title was a bit missleading. The router-bit will be faced down as usual. It's just that it will hang from the upper rails. This will even make the chips stay away from the rails. I've not marked the router in the drawing yet, only planning XYZ supports and rails.

Having an open bottom will let me mill big things the router stands on, or normal small things if I just place it on a aligned workbench.

This maybe a nutty idea, but I can think of numerus occations where that would be really useful. For example milling wooden inlines in a big kitchen-table. Ither you could build a jumbo cnc router the size of my garage where the whole table would fit, or a small one that can be placed on the table in question. That way I can even mill smileys in my wooden floor... Yeah, I told you this was going to be useful...

Well, I hope I clarified some bits...

[CurtisU]

I like the design. Clamping the thing onto the work may prove challenging, but I think you've conquered the "simple" part. Keeping the rails and screws above the work, very good.

I assume you've seen the Solsylva design?

Hope you get to start on it soon and treat us to a build log.

Curtis

[DaRy]

Yes, I've picked ideas from three desings:
Solsylva: can be tableless, hanging above. But can have alignment issues, require more ballbearings and two leadscrews for X travel (complicated).
Pipedream: simple hanging above, with modofication can be made tableless. But has bad rigidity.
Joe's: the rails is supported by mdf that will let slider squeze tight without bending the rails. But way too complicated for me, and not tableless (well, you might hang it upside down thou... ).

[BMG]

Originally Posted by DaRy Joe's: the rails is supported by mdf that will let slider squeze tight without bending the rails. But way too complicated for me, and not tableless (well, you might hang it upside down thou... ).

Actually your thought of hanging joes design upsidedown has merit. For one, depending upon the dimensional area you wish to cover, you can scale his design up or down quite nicely. You could move the torsion box that normally runs below the table and have it skim just beneath the "roof" Since your not using the X axis as a cutting plane, you don't need to offset it to allow for Z travel. You would have to come up woith stands for the X. A sketch below shows generally what I mean.

I drew it as a single pipe rail (like Lionclaws design) but it could be a dual rail as well.

As for complicated, I don't think Joe's or lionclaws are all that complicated, There are alot of part yes, but they go togehter fast and offer tremendous rigidity.

Just my two cents.

Brian G.

[txcowdog]

Excellent design. You can bring the router to the item to be routed.

[DaRy]

Originally Posted by BMG You could move the torsion box that normally runs below the table and have it skim just beneath the "roof" Since your not using the X axis as a cutting plane, you don't need to offset it to allow for Z travel.

Mmm... Just imagining a BIG router filling up an entire room hanging in the ceiling. That would be impressive...

Ok, there is one thing with Joe's router, and it is the mounting of the Y-rail. Unless all parts fits prefect (I'm using handtools so mine would definately never fit), I will need to align this in all three planes relative the X-rails and that mounting makes it complicated. The X and Y motion is the most important here, and by placing these two flat onto each other will make them almost self align in two planes out of three. Now the alignment problem is moved to the Z motion instead, and that is not so important IMO.

As for complicated, I don't think Joe's or lionclaws are all that complicated, There are alot of part yes, but they go togehter fast and offer tremendous rigidity.

Yes, true, and I think that similar strengthening technique could be applied to this one too.

Originally Posted by txcowdog Excellent design. You can bring the router to the item to be routed.

Thanks! Since this is a rather small router I think that would be really useful.



Now, I've skeched some more details such as steppers, leadscrews, leadnuts, router and more... Here you have.

[datacop]

Interesting concept indeed. The only thing I would be worried about with your design is the lateral stress on the skate bearings riding on the angle iron like that.

I know you said earlier that you didn't want to go with pipe, but if it were me, I think I would want my contact area at a 90 degree angle to the cutting area.

[Madclicker]

I know you call this "tableless", but to use it you'll have to fix it securely to some kind of working surface and also fix your workpiece to this surface in order to cut it. Wouldn't this "surface" be defined as the missing table?

[DaRy]

Originally Posted by datacop Interesting concept indeed. The only thing I would be worried about with your design is the lateral stress on the skate bearings riding on the angle iron like that.

I'm not sure since the bearing mounting makes the contact angle flat on the rail. Would'nt that reduce the stress instead? It you mean the 45 deg angle compared to gravity, then maybe. But other design are using this alignment witout problem (Joe's for example). It's not like these bearing is stressd by high rotation speed.

Originally Posted by Madclicker I know you call this "tableless", but to use it you'll have to fix it securely to some kind of working surface and also fix your workpiece to this surface in order to cut it. Wouldn't this "surface" be defined as the missing table?

Yes, sort of. I might make some dedicated workbench to put it on for small work. But I have the ability to move it to larger workpieces that would otherwise not fit inside the router area. To secure it I might use some clamps. Maybe even the total weight will be enough to make it stay still... I guess that depends on the gantry acceleration rater than the pressure on the routerbit.

[srstol]

I like the potential for a portable machine like this.

If you rotate the top axis (not sure whether that is X or Y) 90 degrees from its current state you would gain beam strength between the angles. That might not be an issue with a machine this size. By the way, what travels are you looking for?

Rob