Converted X2 to CNC now trying to get my steps per adjusted... Help

[truckeic]

Ok I got my X2 motors turning all 3 axis. I am now doing my steps per adjustments.
I am using 8 MS 1605 Ball screws 1/8 200 steppers.
I tried to do the math then just turned to MACH3 Auto Setup.

So here is what i am doing:
Set Dial caliper up and zero out and move .75"
I am getting numbers from .752 to .7535
I know it's best to do this over a longer range but I don't have anyway to accuratly measure the distance traveled.

So are these numbers about right? Or do i need to get these better and where should I go from here...

Thanks

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[awerby]

If that's accurate enough for you, I don't have a problem with it. But if not, measure a longer distance, and dial it in tighter. Most dial calipers will measure up to 6", so why not try it over 5" or so and see if you can get within a few thousandths, repeatably. If you clamp something to the table that you can get a good reading on, use an edge finder to touch off to it, and you make all your moves in the same direction (so as not to confuse the issue with backlash) that shouldn't be too hard.

[truckeic]

If that's accurate enough for you, I don't have a problem with it. But if not, measure a longer distance, and dial it in tighter. Most dial calipers will measure up to 6", so why not try it over 5" or so and see if you can get within a few thousandths, repeatably. If you clamp something to the table that you can get a good reading on, use an edge finder to touch off to it, and you make all your moves in the same direction (so as not to confuse the issue with backlash) that shouldn't be too hard.

So guess I am stupid.. not sure how to get my dial caliper to read more than 1inch..
I guess I need to research that..

So if I do the adjustment over 5 inches and get those numbers and can repeat it...
Then are those good numbers

Thanks

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[awerby]

When you said you were using a dial caliper, I thought you meant something like this: Test, Measurement & Inspection | Calipers | 6" Steel Precision Dial Caliper | 534164 - GlobalIndustrial.com

If it won't measure more than an inch, then you probably have a vernier micrometer, which looks like this: https://www.zoro.com/mitutoyo-microm...E&gclsrc=aw.ds

Those numbers aren't terrible, but most machinists working in metals want their machines dialed in to within plus or minus .0005" or better. With patience, you should be able to get there.

[truckeic]

I guess I have a dial indicator.. You will have to excuse me I am new to this..

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[handlewanker]

An X2?/???....that is with Acme threaded screws and bronze nuts, dovetail slides and you want to get to a 4 decimal place in Imperial or 3 in metric.....ain't gonna happen.

Your best bet is to be satisfied with one thou repeatability over 6 inches.....after a few up and downs with the table the bronze nuts will start to wear and then all your readings will be meaningless.

Anyone converting an X2 or even an SX3 to CNC is expecting too much if 4 decimal place Imperial precision is the end desire.

Once you start machining metal the squareness of the various axes to one another will be a factor that outweighs any thought of 4 decimal place accuracy.

BTW.....a cheap electronic digital caliper will only set you back about $24....and I've seen cheaper.
Ian.

[truckeic]

An X2?/???....that is with Acme threaded screws and bronze nuts, dovetail slides and you want to get to a 4 decimal place in Imperial or 3 in metric.....ain't gonna happen.

Your best bet is to be satisfied with one thou repeatability over 6 inches.....after a few up and downs with the table the bronze nuts will start to wear and then all your readings will be meaningless.

Anyone converting an X2 or even an SX3 to CNC is expecting too much if 4 decimal place Imperial precision is the end desire.

Once you start machining metal the squareness of the various axes to one another will be a factor that outweighs any thought of 4 decimal place accuracy.

BTW.....a cheap electronic digital caliper will only set you back about $24....and I've seen cheaper.
Ian.

I stated in my post I installed 1605 ballscrews.. so I don't have the original screws.
And the reason for the post was to ask what I should expect...
Being new to this and all...
I have a 6 inch Caliper.. so tell me how I accurately measure the travel of one axis with one..

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[handlewanker]

Hi, my mistake, should have read the post again.......OK......you could set up 2 blocks of metal with your dial caliper 6 "apart and clamp them to the table then set an indicator on the face of the first one.... set zero and move the table to the next one an exact amount...6".... on your Mach3 readout.....you should get zero on the face of the next block.

You are actually testing the accuracy of the ball screw pitch that the manufacturer has made.

So, how do you set 2 faces apart when the caliper only measures between 2 faces or over two faces?.........well you clamp one block on the table and another 6" away from it by measuring over the end faces of each......then set a 3rd block against the 2nd block face....clamp it, and remove the 2nd block........two faces are now 6" away from each other and a dial indicator can be applied against both faces to test for zero to 6.000".

If your indicator moves from face 1 zero to face 2 zero and the indicator reads zero at the 2nd block you have 100% accuracy.......any difference....less or more.... is the sum of the ball screw tolerance and your best expectation.

I doubt that you will want to do pitching or finish dimension cutting at so accurate a dimension over 6" with a DIY CNC router........ unless you have the very best ground balls crews....your main concern should be to get the 3 axes square to one another......best of luck, it ain't easy.
Ian.

[truckeic]

Hi, my mistake, should have read the post again.......OK......you could set up 2 blocks of metal with your dial caliper 6 "apart and clamp them to the table then set an indicator on the face of the first one.... set zero and move the table to the next one an exact amount...6".... on your Mach3 readout.....you should get zero on the face of the next block.

You are actually testing the accuracy of the ball screw pitch that the manufacturer has made.

So, how do you set 2 faces apart when the caliper only measures between 2 faces or over two faces?.........well you clamp one block on the table and another 6" away from it by measuring over the end faces of each......then set a 3rd block against the 2nd block face....clamp it, and remove the 2nd block........two faces are now 6" away from each other and a dial indicator can be applied against both faces to test for zero to 6.000".

If your indicator moves from face 1 zero to face 2 zero and the indicator reads zero at the 2nd block you have 100% accuracy.......any difference....less or more.... is the sum of the ball screw tolerance and your best expectation.

I doubt that you will want to do pitching or finish dimension cutting at so accurate a dimension over 6" with a DIY CNC router........ unless you have the very best ground balls crews....your main concern should be to get the 3 axes square to one another......best of luck, it ain't easy.
Ian.

That does help thanks...
So I get the axis being square to one another... Guess I never thought of that ..so that brings up this question.. since the dovetail is what it is how would you check and correct that ..
And for the record..
I am mainly doing gun lowers and parts so not really going to be that long of cuts..
Thanks for the help..

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[handlewanker]

Hi....the X and Y axis is set when the slides are machined initially and probably are more accurate than you can measure etc.

If your X Y axis is significantly out of square, the only recourse is to machine the Y axis dovetail (the one opposite the gib strip) in the XY axis saddle......scraping is a very highly skilled process that done wrong is a total disaster.

To do any machining to correct any out of squareness requires another mill and measuring equipment.....a surface plate is a must have item.. .

If you have a 246 block this will more than suffice as a gauge to check the squareness with a dial indicator in 3 planes for the X,Y and Z axes.

If it shows any out of square in the Z axis,one solution is to rescrape the base/column interface but that is a skill intensive job....the other is to apply shims where necessary....very time consuming.

The problem with CNC machines is they produce finished work pieces that are only as good as the machine build when they come off the machine completely finished........back in the manual days we machined to a cut and try plan.

My suggestion would be to get the machine up and running and once you are happy it functions, then do a 246 block test on the 3 axes.

I just realised......you have the X2 and that means the column is tiltable left to right and bolted to the back of the base casting with that circular flat face, so the Z axis adjustment would be only in one plane by shimming between the bottom or top of the face as necessary.

All this is really nit picking as the Z axis head nod factor makes any out of squareness in the Y plane a variable uncontrollable factor you can never correct.....the Z axis gib must be slack to allow the head to slide freely up and down the column on the dovetails.
Ian. . .