[mrendu43]

hello people.

i building myself cnc for wood, acrilic, and some soft metal.
i have most parts, 2x20mm linear barings for x-axis, 16 mm trapezoidal screw, and for the y and z i have raxroth 35 mm linear barings and 12 mm trapezoidal screw. steppers for all axis are 280 Oin 3 A.
Costruction will be made from aluminum plates and profiles. dimension will be 900x700x200mm

[crane550]

Looks like a worthy project! Be sure to keep us updated with the progress, I look forward to seeing it come together.

[FannBlade]

May I ask what the small linear rail is for?
Keep the pics coming!

[mrendu43]

smal rail 200mm is for z axis.

[mrendu43]

i need to buy 2 more 20mm linear baerings ( round ones) for x axis
because I realized that the two will not be enough. so that x will be on 4x20mm Barings

[mrendu43]

this is how should look like

[Phife]

Just a suggestion based on experience.. Unsupported rails are going to give you trouble.. I recommend going to supported round rail or profile rail.

[DeadTom]

I concur with Phife, if you are supporting all of the weight on those round rails they will definetly flex. You will end up with light cuts at the extreme travel limits on the long axis and deep cuts in the middle...I speak from experience.
Tom

[mrendu43]

I know that and am aware that there will be a deflection. But unfortunately I have no other tracks. I have very limited budgets so i can not afford new ones
but thanks on suggestions

[Phife]

After reading the post again.. IMO I would do a lot more research into what works and what doesnt on CNC.

I can see several issues with your design that will greatly affect the performance of the machine.

First off 20mm unsupported rails on your X are going to be spagetti noodles, well maybe not that bad, but they Will flex, even under their own weight.

Next, the single rails for your Y and Z, while quite beefy, will probably not be enough to keep those axis's from twisting. On your Z axis, I looks like you will have the motor on the moving Z plate, you dont want that extra weight on the Z carriage, your already going to have some considerable weight from your spindle, adding more weight will make things worse.

With your current design, you will be hard pressed to machine acrylic or any metal, its just not ridged enough.. You maybe able to do some wood, but you will probably have an unacceptable finish, and your tolerance will be low, especially from the unsupported rails.

If you are building a machine to learn on, then dont spend the money on aluminum, just use MDF and see how well it performs, but I would spend more time reading before I spent anymore money.

You mention you have a limited budget, I wouldnt waste my money on something that will not work for what I need it to do.

[mrendu43]

thank you again for noticing and remarks. I don' worry for Y and Z. I looked for rexroth specifications and I won't get near their capacity. And for X I'll make one simple upgrade on the current state to get rid of deflection.
i will remove one bottom aluminum profile and put another one in the middle.
then i will put two Vgroove barings on the mile point and glide them on stell Vprfile to remove flex. do you thint taht this will work well?

[mrendu43]

Ofc steel profile will be suported by groung and conested to construction

[DeadTom]

thank you again for noticing and remarks. I don' worry for Y and Z. I looked for rexroth specifications and I won't get near their capacity. And for X I'll make one simple upgrade on the current state to get rid of deflection.
i will remove one bottom aluminum profile and put another one in the middle.
then i will put two Vgroove barings on the mile point and glide them on stell Vprfile to remove flex. do you thint taht this will work well?

I am not following what your are saying here my Croatian brother, if you can make a simple drawing of your fix I am sure that anyone reading this thread will comment on it for a better machine for you.

[mrendu43]

a šta recimo da ove ležajeve koje imam izrežem kučište kako bi napravio od njih otvorene i zamjenim postoječe u kučištu sa otvorenima ležajevima i kupim potporu za šinju te je zašarafim na nju? I izmjenim malo dizajn? bilo bi puno jeftinije nego kupovati nove i šinje još

[mrendu43]

evo nacrto sam na brzinu glupo izgleda al nadam se da čete shvatiti

[DeadTom]

That might work, but in cutting that bearing truck you might damage or loose the bearings encased inside the truck.
What is the length of the long axis?
You might want to consider a stationary gantry with a movable table along the long axis.
Keep the ideas coming as I am sure that with all of the knowledge on this site someone has an answer.

[mrendu43]

BTW anyone know whare can i buy this rail supporter

[DeadTom]

PBXbearing.com has the full rail and round stock but you might be able to email them and ask about just the rail.
Did you see my last response? If you redesign your machine to have a moving table instead a moving gantry you can still use the rail and trucks that you have already and still keep to your original budget.
Tom

[mrendu43]

thnx but i found realy cheap 20 mm open baerings on ebay, so i will buy new one s. i only need that suport for rails so i can put round shaft i allredy have on them

[DeadTom]

Very cool, keep the faith