Small rigid router - Design advise needed

[mitchejc]

@ silyavski
Thank very much for the reply, I was hoping you would have a look at my design. Your build really inspired me to go the metal route!

Point 1: Agree 100%. After calculating the cost for that brute of a table I realized I have to scale it down a bit so I'll do that
Point 2: The belt length is also bothering me. I really like the way you did yours but I have a bit of a problem because I already have a 350mm long ball skrew for my z and also my steppers which are very long so there's just no way I can do it the same as you did yours. My compromise at this stage is to make the gantry top narrower to move the stepper closer to the ballskrew or go with the long 650mm belt. Which one do you think is the better option? I think my wife will poison me if one more parcel with cnc parts gets delivered here so getting a longer ballskrew is not an option

IMHO:

- no need for such a beast table.

Use 100x100x4 or 100x100x3 and make something similar like i did, worked quite well. Its simpler, cheaper and easier to make. At the back you can see the same design but with legs. See post #53



-Z belt length bothers me. See how i did it. post #109

[Boyan Silyavski]

@ silyavski

oint 2: The belt length is also bothering me. I really like the way you did yours but I have a bit of a problem because I already have a 350mm long ball skrew for my z and also my steppers which are very long so there's just no way I can do it the same as you did yours. My compromise at this stage is to make the gantry top narrower to move the stepper closer to the ballskrew or go with the long 650mm belt. Which one do you think is the better option? I think my wife will poison me if one more parcel with cnc parts gets delivered here so getting a longer ballskrew is not an option

Then flip the motor. Look at the z i am doing right now.
Note that:
-the plate is reinforced against vibration with the small triangular pieces
-longer towards the front plate - to provide dust protection
-longer towards the back - to mount the cable chain there

I wish I could hear silyaski machine take an aggressive cut into a piece of alu then maybe I can put my mind at rest about the steel structure resonance :-) 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.

Dont worry about that. It does not vibrate at all. I see your design ok. Not quite the expert though. use common sense and reinforce with 10mm steel rib plates where necessary against bend and twist

Important part of my design are the stair like pieces which reinforce in all directions and don't transmit resonance. To understand better what i am saying, this design is better than just sticking two profiles together.

Split and conquer! That's how you fight resonance.

Soon will make some aluminum pieces for my machine i am building right now, so will show a video about the aluminum, though my friends machine/ the yellow one from the build / has only 0.8kw spindle so it could not be appreciated very much, but there is no resonance, glass like finish.

[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.