Small rigid router - Design advise needed

[Boyan Silyavski]

Just saw your gantry. what size profile you use?

I don't like that back plate there, only adds weight and no gain at all against twist nor against bend in the middle.

Look how i do it on my build right now. Profile 100x100x4 up and down and in between 60x60x3 or 60x60x4 , 2 pieces soldered together, . The Z is 3mm from gantry. Just welded today my 1800mm gantry and confirm that is stiff as it could be. Will measure the bend tomorrow.

[mitchejc]

The top and bottom is 160x80x3 each with a 120x80x3 between them as per below picture. The main benefit is a very simple construction and less parts but the down side is those three sections are quite heavy. Because I'll have to buy 6m of each section the plan was to use the same for the sides that bolt to the table.

I agree the back plate does not offer much apart from completing the box instead of just a U so it might stiffen things a little but its probably not worth the weight and alu cost. Wow I like your gantry and ESPECIALLY the new Z design! Now you got me going back to the drawing board with mine :-) Will you please send me the link to the thread with your new design.

[Boyan Silyavski]

Post #56

Ignore the double ball screw, i will mount at least once a vibrating hammer so that's why. Same goes with the triple bearing blocks. 2 are enough. The 2 square bars on the Z plate can easily be substituted by structure of 20mm plate, but i don't have the time to fiddle with it so i will use solid alu bars.

Today just soldered many things. Still no time to update the thread, but one of the things i most like about this design are the gantry legs, save some money on plates, cutting and welding. Cheap profile i mean instead of laser cut plates. As i changed some bits of the design, the gantry legs will have a plate below slightly larger or access hole for mounting the bearing blocks. But i wanted it strong left right, that's the change from the initial plan. look below:

[mitchejc]

Thanks for taking the time to reply. I really like your design and I can see you put a lot of thinking into making the construction easier without compromising strength. The simplicity of the two solid bars on the top and bottom is a great plan. I'm going to keep a very keen eye on your build to see how you do things. Time for me to start changing my drawing to incorporate some of your new ideas. The only thing I will do different on mine is to not have the rotating ball nuts on the x. Not because I don't think its a good idea but its my first serious build and I'll rather avoid that bit of complexity and go for the stationary x motors on mine.
How are you mounting the spindle inside the z box? Are you making a custom mount or will you just be modifying those standard cast spindle mounts?

[Boyan Silyavski]

How are you mounting the spindle inside the z box? Are you making a custom mount or will you just be modifying those standard cast spindle mounts?

The simplicity of the two solid bars on the top and bottom is a great plan.

if speaking about the gantry, today while soldering changed the idea. As it was impossible to weld it well from all sides. So did not use the square tubing for support. Just made more ribs. Anyway i have bought 6m for the 2 plates, so i had enough of it. Instead used the square tube pieces/60x60/ to align the ribs. Its ridiculously strong. the gantry i mean. but the welding goes ridiculously slow. Great care should be taken. First spot weld, then short passes, then wait, then short passes... Still have to finish it tomorrow.

[JAZZCNC]

Has anybody tried to fill the steel sections of the gantry etc with high density polyurethane foam and would that make any difference with resonance? I'm referring to the two part stuff that can be pored thru relatively small holes and then it foams into a plastic like solid to fill the entire void.

No it doesn't work very well there's not enough density. The best success i've had is with kiln dried sand. Very cheap and simple with good results.

[mitchejc]

Thanks for the photo's Sylafski. VERY nice!! That gantry looks extremely solid.

[mitchejc]

@JazzCNC

Thanks Jazz, the sand makes sense. I'm bit worried about adding more weight to the gantry as I estimate it's already +- 80-90kg Z & spindle included but I guess a 20-30kg of sand is not going to hurt or will it? My plan is to run 8nm easyservos, will that work or do I need to back off a bit on the gantry weight?

[Tom J]

hi
Are you going to use servos or motors with encoders, if not, than you should change design for one motor on X but with two screw on each side. Loosing steps issue - big problem when you mill harder stuff like alloy.
I had the same problem - its complicate design, but for long term your gantry always run smoothly, without jamming on one side

[mitchejc]

Tom, thanks for the advise. Yep, I have EasyServos which are basically steppers with encoders but if I have any issues with racking I'll certainly go the single motor route.