Layout of centerlines

[JerryFlyGuy]

I'm faced w/ laying out some centerlines on my x axis. This normally wouldn't be a huge issue on a smaller machine, however in my case the centerline is 240" long and must be pefectly straight. I'm laying out the center line for mounting my linear rails and I've found that these rails aren't nesc. perfectly straight right out of the box. Mine have ever so slight a curve to them. This isn't really an issue as they are bolted down every 60mm and this can be taken out of them. But how do I get their mounting holes [in the sub structure] straight before the install? I'm not going to D&T their mount holes but rather just drill oversize mount holes and then add a nut to the bottom of the mnt bolt. I've got holes in the side of the mnt structure to reach through and put the nut on. This will allow me some lattitude to get things parrellel and sqr w/ the opposite rail [ which is 10' away]. However I do need to start w/ a master rail which is perfectly straight, and the second rail will then be slaved/matched to it. I thought about using fishing line and feeler gauges, any other suggestions?? I don't think a heavy pc of CRS would be straight enough would it?? Is there some trade secret out there that someone could pass on?? My sub-structure [ which the rails mount to] is composed of welded HSS, its very straight, but there are no garrentee's that there isn't a 1/32" [its small if there is any] bow in them [side to side] so measuring off the side of them isn't an option. I'm potting the rails down w/ Moglice so the elevation isn't an issue [ if there is slight warpage from welding]. I've purchased a master precision level [ 0.0005" level accuracy over 10"] which when used in conjuction w/ jig blocks that fit the rail and two set screws per jig block, I can get the rail as flat and level as it needs to be, I just don't know how to get the mount holes laid out perfectly straight. And once the rails are mounted there is still going to be the need to bolt them down straight w/out and curves in them.

Suggestions and opinions welcome as always.

Jerry

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[martinw]

I'm faced w/ laying out some centerlines on my x axis. I thought about using fishing line and feeler gauges, any other suggestions??
Jerry

Hello Jerry,

You could try using a laser level and use the beam as a reference, but, from my experience, the laser dot is always too big and it is hard to detect where the edge (or centre) of it is.

Your idea of fishing line and feeler gauges would be hard to use IMHO. It would be hard to detect when the gauge is touching........hence this mad idea...

Don't use fishing line, use thin solid copper wire (not insulated) , and get it really tight. Connect one end of the wire to a small battery's positive terminal. Connect the negative terminal to one side of a small bulb or buzzer. Connect the other side of the buzzer/bulb to a flying lead which goes to your metal feeler gauge. Make sure your copper wire and feeler gauge are completely free of grease and oxide. Bingo!

It should work.

Regards

Martin

[motomitch1]

Steel Music Wire tie off one end and hang a weight on the other end

http://www.shopaid.com/music.htm

[Geof]

You are probably correct that a length of CRS would not be straight enough for what you need; but it would be stable so what you need to do is get a piece and calibrate it. If you know the deviation from straight every 100 mm that would be good enough. Use the piano wire idea; I have uploaded a picture showing how you would stretch the wire along the length of cold rolled with identical size insulated spacers each end (glass rod maybe?). You are not worried about the exact distance between the wire and the bar just the difference from one point to another so rather than feeler gauges use the tapered wedge I show in the second picture. You hold this flat against the edge of the bar and slide it in until your electric circuit is completed. If the length is around 10 inches and the taper is something like .040 over the full length then 1/4" of movement of the wedge corresponds to 0.001.

Just mark which end of the bar you start your calibration table from.

[martinw]

Dear Geof,

Brilliant!

Best wishes,

Martin

[JerryFlyGuy]

Wow, you guys really think outside the box! Some good idea's here.. I was thinking about when I layout the centerline to drill the mount holes [ this stuff usually comes to me when I'm trying to sleep.. i was having a nap this afternoon ] I currently use blue-layout paint.. And If I was to string the fishing line down the top of the frame and then spray w/ blue-layout the string would block someof the paint from getting on the structure and there-by put a line on it right?? Or.. Coat the fishline in oil, and then use it like a chalk line, the blue-layout won't stick to any oil so when it dries you can just wipe to top surface and you'd have a perfect line that way too. I know the layout won't stick to oily area's because there was some oil residue left on the tube from my last drill proceedure and the layout didn't stick in those area's.

Geof, on your CRS idea your thinking to just mark the corrected value/deviation at each location as you move along?? What about any sag in the copper line?? The CRS will only come in 12 [ or is it 10??] foot lengths so its to short to do it in 1 complete shot, you'd have to move it along, say 1/3 of the way and then continue for the next third then move it again, this way you'd have 2/3 of the crs clamped to a known straight edge and then the last 1/3 would be used to align the un-mounted part of the rail??

I'm wondering if I can't use the fish line idea's above and eliminate any of these issues, drill the holes to the proper size for a tight bolt fit [ possibly reamed holes] and be straight enough.. I'm gonna have to think on this a bit more.. maybe even test some ideas..I haven't decided what is an acceptable tolerance for this. I think though, if I had w/in 10thou over the length I'd be happy.. is that to huge or to tight??

Thanks for the idea's guys.. feel free to post more if you think of them!
Jerry

[ger21]

There's some info on this page about using highly tensioned wire to align linear rails. It starts by the 4th picture.

http://oneoceankayaks.com/madvac/machine_frame.htm

[JerryFlyGuy]

Thanks Gerry, I've read that before.. of course it was one of those " I won't ever forget that" kind of things.. which I promptly forgot about. I've emailed that gentleman to find out what multiplication value he used. Also I've been thinking more about this, I wonder if I couldn't use the same wire.. and mount a video camera to the carriage/truck and zoom in on the wire, it wouldn't matter to much how much zoom I got. then connect a screen of some sort [small tv or whatever] overlay it w/ a clear plastic overlay. Draw to lines which locate the edge of the rail and the wire and then adjust the rail as I slide the cammera assembly down the rail.. crazy idea??

I could do the same thing just w/ a microscope mounted to the truck??

Boy this is a long ways away from the route I was thinking of taking.. I gotta say that the "ZONE" is a great place.. filled w/ GREAT people!!

Jerry

[One of Many]

Thanks Gerry, I've read that before.. of course it was one of those " I won't ever forget that" kind of things.. which I promptly forgot about. I've emailed that gentleman to find out what multiplication value he used. Also I've been thinking more about this, I wonder if I couldn't use the same wire.. and mount a video camera to the carriage/truck and zoom in on the wire, it wouldn't matter to much how much zoom I got. then connect a screen of some sort [small tv or whatever] overlay it w/ a clear plastic overlay. Draw to lines which locate the edge of the rail and the wire and then adjust the rail as I slide the cammera assembly down the rail.. crazy idea??

I could do the same thing just w/ a microscope mounted to the truck??


Jerry

I have had to do this on an OEM router that never would run without a periodic servo current fault with the trucks bolted tight to the gantry. I used .025 music wire around some bolts fashioned similar to an instrument tuning peg. I first set the top straight, then from the side. Then of course used that rail as the master to re-align the other rail. The problem is where the rails actually have a slight tilt. The bearing trucks have specific class of fit. On our router, the truck specs are around .0015 rail to rail mis-alignment across the width of the truck. As ours does a rapid, you can still hear a minor change in servo load along different areas of the run. The machine runs within spec and no longer faults, but I am still suspicious of why the OEM couldn't do better.

What I do like about the link posted above is using 2 wire lines for each rail bed. If you did this for both rails, then strung another wire across all 4 wires at each end. You should end up with a decent reference plane. If it were tight enough, you could just use a light touch indicator under the wire.

Most rail manufacturers suggest the rail be set against at least 2 machines surfaces. That not always being possible, it is left up to the user to resolve mounting them aligned and free running. Then do it again after a crash.

DC

[JerryFlyGuy]

After re-reading One of Many's post. I went back and re-read the link. I dunno what I was on or smoking but it read totally different this time.. weird. Anyway what I've done.. or am going to try is using a metalurgist microscope to measure the gap between the wire and rail. I will still do the fine wire down the side of the rail and then mount this microscope to the top of the truck and focus it down the side to where the wire is. I figure w/ 10x magnification I should be able to measure the gap down to about 1/10 or less of a mm using the graduations inside the microscope. I'll let ya know if it works.

Jerry

[RICHARD ZASTROW]

JerryFlyGuy Or you could spend some money on an Ingersoll tight wire alignment kit complete with battery operated sound sensor / headset, micrometer/light indicator etc. Then find some Federal electronic levels for more big bucks. Then, rent them to the rest of us who can't afford them. JUST KIDDING

[energyforce]

See picture attached. These are for shafts instead of rails but maybe it will give you some ideas.....

We used something like piano wire yes, attached to a boat winch. We made a notch on one end and the same for the other end. We made sure the notches were accurate to 1/32 of an inch (just use tape measure). We then put the piano wire over the notches, secured it at one end and then used the winch to make it real tight. We then put a tape measure across and marked the hoels respectfully. We then drilled the holes 9/16 (we had a special rotenbrauch bit that could fit on a portamag sooo we went with this route). The bolts for the linear rails are only 1/4" so we have ordered large washers.

Our gantry on the other hand is fully machined. Everything is VERY accurate so the placement of the pillow blocks are ACCURATE. So we will be aligning our shafts with the pillow block. What i mean is move the gantry back and forth and back and forth and tighten it while we do this.

Hope this helps? I am a believer in fine tuning

Also a pic of the shafts mounted on rails on the same surface as the attached pic. http://www.ubcustom.com/cnc/index.php?img=51


Erik

[JerryFlyGuy]

JerryFlyGuy Or you could spend some money on an Ingersoll tight wire alignment kit complete with battery operated sound sensor / headset, micrometer/light indicator etc. Then find some Federal electronic levels for more big bucks. Then, rent them to the rest of us who can't afford them. JUST KIDDING

RICHARD!!! did your ma' ever yell at ya like that Tell ya what.. you tell me what they cost and where I can get them.. and then I'll rent them for 50% of the original cost w/ a 200% deposit before shipping to you Can you tell me how these choice item's are operated and their proposed alignement tolerance when "used as recommended"??


Jerry [anyone ever used a microscope like I just bought - but don't have it yet]

[JerryFlyGuy]

We then drilled the holes 9/16 (we had a special rotenbrauch bit that could fit on a portamag sooo we went with this route). The bolts for the linear rails are only 1/4" so we have ordered large washers.

Our gantry on the other hand is fully machined. Everything is VERY accurate so the placement of the pillow blocks are ACCURATE. So we will be aligning our shafts with the pillow block. What i mean is move the gantry back and forth and back and forth and tighten it while we do this.

Hope this helps? I am a believer in fine tuning
Erik

Erik, great minds think alike.. I too am using a MAGDRILL and Rotorbrauch bits, I love this thing.. 1.5" hole through 1/4" pl in under 30seconds.. which is a good thing as I have LOTS of these holes to put in. [ I pays to work for a steel fab shop which has all the tools <-- I just borrow them ] I've been thinking of good ways to aligne the two rails, once I get the master rail mounted and straight. I'm using linear rails [ instead of shafting] so I need to aligne them in two planes, the horizontal one is my issue. The vertical [ for flatness] will be done w/ my 'masters precision level' supposed to be able to measure level w/in 0.0005" in 10" [ no there isn't an extra zero there] amazing if it works.. I'm going to be getting little jig's cut which fit fairly tight to the rail shape, they are split in the middle and bolted together w/ a cross bolt, then they have two vert bolts D&T'd into them, one on either side of the rail. This will allow me to level the rail perfectly.. then use Moglice to pot it into position.. once that is done.. they will NEVER move.. I've thought about then using the gantry to aligne the other side, however my gantry is a weldment so this might not be such a great idea [mind you its not going to move once its welded so who knows might work], we'll have to see. Using a specially cut 3/4" x 3" CRS spacing bar might be the best way.. this allows me to use my jig's, level and get a good match.. I hope..

Jerry [suffering from welders sun-burn ]

[One of Many]

So, I take it you are planning on floating the Moglice to find it's own level?

Per my previous post. The first thing I did was level the 4 corners and center with our master precision level. When I had one rail straight on 2 planes. I used 2 trucks on that rail as the master. Our old router is only 56 inches rail to rail, 126" long. I made a make shift fixture that bolted the 2 trucks common to a section of angle iron about 12-14" apart. I then made that the base of a right triangle from more of the same angle iron that straddled both rails. A few brackets later, I had this right triangle riding on 3 trucks, bolted only to 2 on the master rail. The slave rail truck just supported the fixture, floating under it, but more importantly the fixture had a 1" travel indicator attached to it. Thereby indicating on the trucks side which helped me set the 2 rails parallel to each other within .001.

Parallel, may be a bit of an over statement, but they do follow each other fairly close regardless of the slight error in the master being copied to the secondary rail.

As I stated before, our rails do not have a decent mounting surface and therefore lean inward. rather than rework the whole mount under each rail, I elected to put shims under the gantry to allow the trucks to run free at a slight tilt. I think the total of the shims was in the .002-.007 range. I hated to do it, but it has been going well now for quite a few years. I just dread a crash since it throws everything off. Then I have to start the swearing all over again!

DC

[JerryFlyGuy]

Well, floating might be a bit to broad of a term. I'm going to jig this rail in space above the main structure, the rail is held down via its mounting bolts, yet held up [every 12"] w/ my little jig's. W/ the two screws on the jig I can tilt as well as elevate [ to level along the length] the rail. this gets me level in two planes, then I have to do the get straight part where the microscope comes into play. I'm 3/4 the way through welding one of my side structures [ which the x-axis rails sit on] and it has a slight [ no suprise really] curl to it of about 1/16" in the center. I'm going to try to pull as much as I can of that out but regardless it won't be perfectly straight, hence the question of how to lay out the centerline of my rail. I need to drill holes for all the mnt locations and while they will be oversize, I'd like them as "in-line" as I can get. Measuring off the side of the tube [structure] isn't going to be good enough. Using a tensioned wire gets me a straight line, then I need to locate my rail in ref to this straight line. I could in theory just move along the rail, clamping it and then using a hole center punch and center punch the hole centers as I move along, use lots of clamps and then take the rail back off and drill them. It might work, but is this measuring w/ a caliper, marking w/ a pc of chalk and cutting w/ a hand axe?? I've got 6mm holes in my rail so an 8 or 9 mm hole would give alot of room for alignment, maybe just mark it out w/ a tight wire and scribe that would get me w/in 0.5mm. Probably close enough. I like your idea for matching the second rail, I think I'll probably use some type of similar system to do mine.

any other idea's on how to get the master rail perfectly straight using the simple tool's I've listed already. Any flaw's you can see in what I plan to do?

Jerry [ I gotta get some Moglice on order]
Ps, the image below show's the rail jig, the red lines are the D&T'd bolts the blue line is the split line of the jig. The notches on the underside of the jig [against the rail] are for sqr keystock mat'l. This is the dam for the moglice.

[WhiteTiger]

Hmmm... If I had to do a low tech layout for a ref line that long, I'd go with the tight bare wire method and use an indicator led to display contact point. Then I'd make up a drill guide jig that could clamp to the side of the base rail and be screw adjusted until the guide bushing came in contact with the wire. Then it's just lock down all adjustments and drill the hole for that location then move on to the next.

Dunno if that made any sense, but it's as clear as I can describe offhand and atm I'm too lazy to draw up any clarifying illustrations


Tiger

[martinw]

Hmmm... If I had to do a low tech layout for a ref line that long, I'd go with the tight bare wire method and use an indicator led to display contact point.


Tiger

Dear Jerry,

If you go the tight wire electrical route, you will need to limit the current to prevent arcing. Arcing will jump the air gap and give bogus contact data. Put a series resistor in the circuit to limit the current to the LED to ,say, 4mA.

Best wishes,

Martin

[Geof]

......any other idea's on how to get the master rail perfectly straight using the simple tool's I've listed already......

Yes but you rejected it about five million posts back and I have been sitting in the corner sulking ever since.

[martinw]

Yes but you rejected it about five million posts back and I have been sitting in the corner sulking ever since.

Dear Geof,

Cheer up old bean!

Best wishes

Martin