Post your Tips/trick on how to align/calibrate Linear bearing X,Y,Z ?

[Calico]

How do you guys align say Moving table linear bearing and Y land X ?
I havent' build CNC yet, not done yet. but from your experience when designing CNC Mill, what's your Tips to add so the alignment will be perfectly square xy and Z axis ?

for example should I use adjustable Y not weld it, so it wiuld be esier for adjungting ?

or what design should be simple to be use for adjusting on every axis?
Need the comment from the pro who built CNC many times.

I'm building CNC Mill for Wood cutting with 2meter (Y) travel moving table and 70cm (Z) travel and 1meter Y travel and 1 meter (X) travel. I'm trying to make as accurate as possible, specially easy to be calibrated/adjust between all axis and perfect.

how do you square/calibrate Yaxis to X axis ? i know the basic but sure how to do it correctly.

regards
ruddy

[andy_ck87028]

Hi Ruddy

I have not yet faced this task myself but I have had some great guidance from a friend who is a retired experimental scientist. I will basically be following his advice when it gets to the point of aligning and locking down the axes. When fully aligned I will be welding anything that shouldn't be allowed to move!

The guidance is obviously specific to my machine. I will attempt to summarize his observations for you. You would be best to transpose these comments to a hand drawing for them to make sense.

My machine made from mild steel framing with stainless tubing.

The principle revolves around using a starting reference point which is one end of one side of the x axes. Let's assume the two x axes are x1 and x2. Both x1 and x2 have two ends being x11 and x12, x21 and x22. As a starting point it is essential that the base frame is completely rigid and has zero flex achieved through welding and bracing.

Make sure x11 is rigid to the base frame. Ensure longitudinal expansion is possible at x12 (relevant for me as I have stainless tube and mild steel frame and temperature differential of 40 degrees in the workshop (low winter - high summer). Ensure x12 cannot move up or down or sideways. When that is done, x1 will then be suitable to use as a reference for x2.

Ensure x2 can move sideways but not up or down. Sideways movement allows for thermal expansion of the y axes. Allow for thermal expansion of x2 but do not make it a rigid connection to the base frame. Rigidity is only allowable for up and down. My x2 has anchor points underneath the stainless tube at regular intervals along the full length of x2 connecting x2 to the base frame. Those anchor points are able to flex sideways only thus allowng for y axes expansion.

Fyi, pillow blocks (I think that is the right term) will be under and above x12, x21 and x22 to ensure no up or down movemnt are allowed.

When x2 is assembled, y axes can be aligned.

Repeat y in exactly the same way as x by nominating y11 as the reference point axcept that rigidity to frame is meaningless. Instead rigidity is established to the truck that sits on x1.

I hope that helps.

Cheers

Andy

[Calico]

Andy, thank for the advice.
X2 is new forme if you said it can be move side ways not up and down to handle the temp. difference. how you design that x2 to be move sideway not up dand down ? any sample photo's ?

in my country there is no winter, summer all year, indonesia.
I don;t thing I bother that ? right ?

so far that's the first question

regards
ruddy

[Graham S]

Andy, one warning. Welding is a guaranteed way to ensure things move. I had a frame welded up recently, it was done on a flat bed and consisted of 3" square 1/4" wall box section. It warped when welded. Anything but the smallest tacks and things warp.

Graham

[space_case]

Then how do we make true frames???!!!!

What about an overbraced, overbolted structure??

I will be getting started soon and I was about to buy as welder!

Help!

[hobotek]

Originally Posted by space_case Then how do we make true frames???!!!! What about an overbraced, overbolted structure?? I will be getting started soon and I was about to buy as welder! Help!

Anything welded requires machining/grinding to make it true. I'm curious
as to how those guys using weldments are making accurate cuts on
bases that are warped from the welding.

[andy_ck87028]

Very interesting your comments about warping after welding! Will definitely tack weld and to be honest I reckoned that tack welding would be adequate but I was going to go the whole hog............ Maybe not now!

I have taken a picture but cannot get it down to a loadable size. Jpeg at 25% resolution and it was still too big..........sorry.

Point taken re. lack of thermal expansion in Indonesia but I am sure principle remains same. I.e. use one end of an axis as first reference point then use whole side of axis as reference for other side. Lock one side in on both vertical and horizontal axis and as long as the other side cannot go up or down it should be ok to allow it to be free to float side to side given that the first side is locked.

I have purchased a very cheap laser level to use as my external reference point to (hopefully) ensure accuracy.

Very much still a beginner

Andy

[cbass]

I hate welding...

Like Graham said, when you weld something, it will warp. Assuming you have no way of grinding everything flat after welding, I would suggest nuts and bolts...lot of them. Nothing wrong with them (i.e. they use them on bridges and airplanes), they just take more time to factor in.

Carlo

[andy_ck87028]

I picked up from Benny that I should use oversize holes with bolts that will enable me to position everything accurately and then I can weld after I have bolted it down ... how does that sound?

Andy