Luke11CNC Build Log ,I'm so naïve

[Jonathan]

Jonathan just looking at your nut mounts you have done, nice job i might add.. but i looks like you could do with a de-buring tool, cleans them edges up a lot nicer then the good old file.

Those pictures were probably taken before I de-burred them...either that or I forgot to do it! I've never got one of those tools as I didn't know if they were actually good, or just a gimmick, but since you've recommended that one I guess it's worth a try.
Generally to de-burr aluminium parts I use the edge of a steel ruler - probably not good practice but it's effective. Similarly if it's a hole de-burr by hand with a drill that's bigger than the hole.

[luke11cnc]

Well after a long long week

LUKE has broken his foot now

So I have decided to crack on with the CNC machine

Now the frame is true and square (spent all day Friday doing this) fitted ONE side of the gantry side to my ballscrew but I have some binding on the other side (about 5mm out)

My rails are square and parallel but the gantry still refuse's to play. One side hits the end of the table and the other is around 5mm off (I can force the other side to meet the side at a right angel) but this is not right (every fibre of my body says "no, it’s not right") but I am all out of ideas

I am going to look at the bearing today to see if they are mounted correctly (all facing in the same direction) would this throw my gantry out of square??

I am at a loss to where things have gone wrong??

Does it matter if the bearing are pointing in the same way ??

The only two ways I can get the X-axis to run true is to force the right side over by about 5mm or have the table out of square

I’ve just taken some images of the machine and its now only out about 2mm
So I think I was over reacting and it was just crabbing

But I think I would still like a second opinion

any way here we have Luke striping out the old computer (sorry but Luke is in a bad mood :twisted::twisted:(tired me thinks)) not one smile and he told me not to take any more photo's of him















do you like my drives two Bosch drills :naughty::naughty:


today I'm going to tap my M10 T-nuts and start mounting the Y-axis

James:tup::tup:

[Web Goblin]

James,
it shoudnt matter which way round you mount the bearings. Keep up the work, your doing well. Can you post a photo of where the parts dont meet so we can get a better idea of whats happening?
How do you manage to synchronize the bosch drills:heehee:

Ian

[luke11cnc]

Thank you Ian I couldn't do it with out help from this web site and it's friendly members

Here is the two images of the x-axis bearings they should be in line but as you can see the right one is not tight to the MDF (about 1.5mm gap) But I can move it by hand.

this is the left side

this is the right side

Is this just crabbing or should it be in line as It's not under any load ??

James

[Jonathan]

The joint where the 6" wide plate bolts on to the back of the gantry would have to be perfectly square for the gantry to also be square. The distance is so great that the angle on those joints doesn't have to be out by much at all to get 1.5mm out. Also I'd be amazed if the frame is actually perfectly square, so using it as a reference could be misleading. The other thing is the position of the X bearing mount plates and hole positions - they could be slightly out too. All these tolerances stack up, so it's hardly surprising to me that there's a 1.5mm error ... don't worry about it.

If in the end the machine still wont cut square there's ways round it. If it's not much at all then you can position the X-home switches so that mach3 bends the gantry very slightly to square it when it homes. Clearly that's a bad plan if it's out by a lot as it would put a lot of strain on the structure and motors. You can also compensate in mach3 by using 'formulas' which enable you to make one axis a function of another axis. So you just put X=mY in the X formula box where m is the measured gradient / error. The difficult bit is measuring the error to start with as there's no straightforward reference.

How do you manage to synchronize the bosch drills:heehee:

Maybe he's using the steppers as encoders to provide feedback...

[luke11cnc]

Thank you Jonathan
I feel a lot better now did you get my email?

I think the slight whip on the 12mm gantry support rail is not helping, I should be flat when both extrusions are bolted up to it. I was quite surprised when I offered the extrusion up to it and had to G clamp to get it flat.

all going well but I don't have a M10 starter tap, so I will have to get one in the week.

So a change of plan for today's work I'm going to mount the drivers in the old computer case

after I tidy my workshop/garage up (what a mess but not as bad as yours Jonathan:rofl::rofl:)
James

[Jonathan]

You're welcome to borrow taps from me... but long term you might want your own anyway.

I got your email, thanks.

[Web Goblin]

Luke,
did you measure the diagonals of your bed to make sure it was square? Its not out by alot.
If you are interested in taps I have some for sale at the moment. Pm me if you are interested.

Ian

[luke11cnc]

Thank you for the offer Ian and Jonathan But I have just bought some from ebay

I have a kit tap but it has no starter tap

yes the diagonals are spot on and all the material for the CNC machine has been digitally cut by the supplier

James

[JAZZCNC]

James if your only 1.5mm out then thats only 0.75mm across the diagonal. If the machine is not bolted securely to the floor then the frame could very easily bend or move this amount just from moving the gantry back n forth.
If you intend to move it around or it bothers you then put some diagonol adjustable tie rods braces so it can be adjusted and held square. I did this with my machine while building then re-adjusted when I eventually found the place in shop it was going to live then bolted it to the floor . Only then did I tighten and true the gantry/rails etc.

Will it affect the accurecy of cut.? . . Well Yes if your working to high precision then this amount would be considered massive but for oridinery woodworking etc then it's acceptable to some degree.?
I say some degree because there's another issue and IMO better far more important reason to find the inaccurecy and square the frame to near perfect as can be.!

Like jonathan says you can effectively cheat and square the Gantry by forcing it square using the motors.!. . . Problem with this route is that it puts components under constant stress, bearings and even the screws are fractionly twisted this over time leads to premature wear or failing. . . . Much better to find the cause NOW than replace parts or worse still be constantly chasing inaccurecys or even missed steps etc from binding as parts slowly wear away losing performance.!

Taking the time now will pay dividends later down, don't fall into the trap of rushing the machine into service only to pay a big price over the coming months.
Promise you even if it takes a few days to sort this inaccurecy now it will save you weeks of hassle and unneccesary expense months further down the road.

Pulling and holding the frame square with Diagonal tie rods (M12 Threaded rod works good) then bolting the frame down BEFORE finally trueing and bolting the Gantry and rails etc makes the process so much easier and accurate without stressing important expensive components like Ball-screws and linear bearings. This way Only frame is then under tension.!

Edit: I know the T nuts did but have any of those Jigs turned up yet.?