Small rigid router - Design advise needed

[mitchejc]

I'll try and get the drawings done, but the picture I have in mind is basically a 4 legged steel tube structure made from 80x80 tubing with lots of support under the table and space inside where I can sandbag the whole thing to add lots of weight to the base. I then epoxy level the top of the steel base to get that flat, bolt 2 layers of good quality birch ply + a 5mm steel sheet on top. Then bolt the gantry sides to that surface and epoxy level them before the rails go on. Does it sound practical or are there an easier way to build a sturdy base. I started off with the idea to do a concrete slab on top of a steel structure but there's just to many issues with that approach.

thats not going to work

no ways you gonna bolt it together so that the rails come out within a decent tolerance ....
have a read about epoxy leveling a frame if you havnt already ?

[mitchejc]

Ok this is roughly what I have in mind for the base. Idea is epoxy level the top of the base just to get it +- flat and level. Then put 2 layers of 16mm sealed birch ply on top and then a 5mm steel plate and secure that to the base with bolts. Apart from using bolts I really don't see another option of how to secure the machine to the table? I'm referring to the red parts in the second picture. I really don't want that to be the weak point so I'm open to suggestions. Am I approaching this the wrong way to wanting to build the router and base separately? Any advice would be greatly appreciated!

[Boyan Silyavski]

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

[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.