With regard to the base, you need to post some drawings I think. With anything, you need good solid foundations to build from.
Printable View
With regard to the base, you need to post some drawings I think. With anything, you need good solid foundations to build from.
thats not going to workQuote:
Originally Posted by mitchejc
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 ?
Yep, you are right, I'll do the drawing for the base and post it as its obviously an integral part of the design.
Quote:
Originally Posted by EddyCurrent
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.
Quote:
Originally Posted by Blackrat
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!
Attachment 13218Attachment 13219
Depends how it's done. Epoxy leveling isn't the be all and end all solution. I've said this many many times but for a good DIY machine you need to build in as many oppertunity's for adjustment as possible and bolting allows plenty of scope for shimming etc to get machine accurate.Quote:
Originally Posted by Blackrat
If done correctly then it's actually better than epoxy because you can fine tune to very high tolerence.! Only thing is it takes much more time and patience.
Actually can make a huge difference esp on all steel machine that's running analog drives with limited resonance handling. This is actually the main reason to use Belts and the ratio option and flexabilty is just a bonus.Quote:
Originally Posted by Blackrat
Often folks running direct drive don't realise they have resonance problems and just accept that the speeds and performance they are getting is just the max level they can tune to or achive from there motor/drive setup. When often the reality is that the same motors/drives when run on belts and unaffected by resonance will achieve much higher and smoother performance.
@ 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 :friendly_wink:
Quote:
Originally Posted by silyavski
@JAZZCNC
Thanks for the great input. I'm going for the belt option. I think I got decent steppers and drivers but I'll do anything that might deduce resonance and I like the possibilities that the belts give e.g. change the ratio if I needed. Not sure with a ballskrew system but I know from first hand experience with rack an pinion that belts also offer little bit of safety margin with strong steppers and would jump teeth or snap when things go horribly wrong.
I've thought long about Blackrat's suggestion not to bolt the sides down but there's much weaker points in the design so I'm pretty sure that not the weakest link. The other thing is I'm really a novice welder so I'm not very confident I'll be able to build the base and gantry sides as one unit to any reasonable tolerances. With the bolt on plan I do limit that factor a little as I have the opportunity to shim an adjust a little like you suggested.
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.
Quote:
Originally Posted by mitchejc
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
Attachment 13290Attachment 13291Attachment 13292
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 twistQuote:
Originally Posted by mitchejc
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.