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I am in the stages of converting my brand new G0704 mill to cnc and noticed while tramming spindle to column that the spindle is leaning front to back. After measuring the thickness of the z slide its about .010" tapered top to bottom. Anybody else having this issue? Can somebody who has theirs apart mic the slide for parallelism? Looking at the pics the top of the slide is about .010 thicker than the bottom. Im pretty sure this is where the tilting is coming from
Which surfaces are you talking about?
Quote:
Originally Posted by arizonavideo
The ways that ride up and down the column and the actual face of the z slide where the head bolts up to. Its .010 thicker at the top so its like a wedge sort of speak
That sucks, those are ground aren't they? Have you measured the parallelism vs the Z column when it's sliding over the ways? Also have you checked the flatness of the two sides of the Z slide?
If you're really sure you could have a machine shop re-grind that.
Those surfaces appear to be scraped. I have not checked runout on the column ways yet. Looks like these parts will see a surface grinder soon
100% guarantee they are not scrapped. Maybe hand flaked for oil retention though.
How are you measuring this error? I wouldn't think that .010 is uncommon for these mills. You'll probably have to shim the head to get it square.
~Ninja edit~ Also consider that your head does not make contact at the very ends of the block, so the error that the head will actually see is much smaller.
Im just using a micrometer to measure the thickness at the corners. Its a new machine and it also seems i run out of gib travel when adjusting the gibs for the z axis. If I remove some of the material from the ways on the z slide that ride along the z column will it allow me to tighten up the gibs more? Or is it the other way around?Quote:
Originally Posted by CS900
You said it was brand new? You didn't say if you could tram the head (Y) to reasonable accuracy. If not call Grizzly, don't start grinding or removing any material. They are pretty helpful and their track record helping folks fix issues with these mills and other machines under warranty is fairly good. They should be able to tell you if its within specs. If not, they will likely send you any parts needed to fix it. They were very helpful to me and did so including free shipping.
I remember there being a test specs sheet in mine from the factory. I don't remember all the tolerances the factory noted on it, but if you have it check to see.
Important: Don't start your mods etc. until you get the issue resolved. Once you modify the mill it will likely void their warranty coverage if they are aware of that fact. Possibly even if the mod has nothing do to the issue or problem.
The spindle(head) is .006 out in y(front to back) from the column. I could shim the head to the z slide but im going to put on surface grinder at work and get it flat and go from there. I have already done oil grooves in all ways added oil fittings and machined ball nut clearance in saddle. Going to grizzly is a no go. Its definitely nothing I cant fix. Was just curious if anybody else had the same problem?
I doubt they would ask you to return the bad part if it's out of specs from the factory. I suppose it could possibly also be the column itself. The gibs are tapered, so are basically wedges. Adjustment is made by tightening one end adj screw (pushing the wedge in further) and loosening the other to accommodate it. Then snugging them down to avoid any movement or play. If you over tighten them, they will bow the gib causing binding. If you under tighten and the gib can move, it will bind going one way and losen going the other. If the adj screw is all the way in (on the thick side of the gib) and you still have play between surfaces, removing any material from the slide way will make it worse. A longer adjustment screw might fix it tho. If you are having a binding issue at one end of the travel when the screw is attached, also check your acme nut (or ballnut mount alignment. There is a small set screw that adjusts the "tilt" of the nut. And, loosening then tighten the nut mount screws for the other direction of nut alignment. If you have binding with the nut/screw disconnected, it's likely just a rough spot in the ways of the the column, or gib adjustment. But remember when adjusted and snug the gib is stationary in the Z slide so the binding is between the gib and the column ways, not the gib and the slide. The binding at one end or the other likely has nothing to do with the parallelism of the Z slide you mention. And, as I said the gib is stationary in the Z slide and won't ride closer/further at top or bottom due to it being out of parallelism. The way in the slide is also tapered to match the gib taper. I'm not sure how much (.010? never measured mine) but you have to compensate for the taper of the gib somewhere to get things back to equal. If you remove the taper in the way and make it flat, the taper of the gib will cause the slide to sit at the angle of the gib taper angle on that side. Then you really will have binding issues. You may be aware of all this and if so my apologizes, but hope it makes sense.
You may already be aware of how to tram these mills, but if so for others who come across this thread... make sure it's trammed properly.
As far as checking alignment, first tram/adj the head to align the spindle to the column (Y is not usually not required, but you can loosen the 3 bolts and add shims if needed). Clean the surfaces well and check for any nicks or debris that can also cause issues, then next tram the spindle to the table by adj the column at the base using shims if necessary. From then on re-tramming can normally be done by aligning the spindle/head to the table in the event you needed to rotate the head or crashed into something.
checking just the corners doesn't get you anything. Like I mentioned before only the areas that contact the head will effect the alignment of the head. You really need a surface plate and a test indicator to do it properly. That said, this may all be a moot point. You really should get your head mounted and swing a test indicator around the table to check alignment. Just because the slide is parallel to itself (and the column), that's not to say that your spindle bore in your head is perfectly perpendicular to the mounting surface on the head. It's a stack up of the errors in every piece that effect the tram. This is also why you should check the perpendicularity of the column to the table before tramming the head to the table.You may actually be making more work for yourself by grinding the slide if your head has a counteracting error to the slide.Quote:
Originally Posted by nickw226
As far as the gibs go, you can place a shim between the stationary side of the gib and the slide. This will effectively make your gib thicker and not as far.require you to tighten the locking screws down as far.
You got pictures of the oil fittings I was thinking about adding that?