How the heck do you square the z axis????

[keith]

Hi there. I just purchased a PRT 96 and have it up and running in my garage. My issue is the z axis. I followed the instructions in the manual. Here's where I get lost. When I had to initially slide the z-axis assembly in between the two aluminum struts it wouldn't fit. I had to loosen the 5 bolts that are on one side so I could slide it in. And I needed to apply some force to it too - it wasn't easy! I squared it using a level, got it close, and then continued assembly. I then cut into some wood going just in the X, and just in the Y. Sure enough it's not level. Here's where it comes tricky. Standing on the left side of the machine (so Y goes right to left and X goes forward and back) I can't for the life of me adjust the Z because it's so tight (wedged in between the 2 aluminum struts). It won't budge unless I loosen all 4 bolts holding the Z axis AND the bolts that hold down the aluminum struts. Then it's almost too loose and I'm having trouble squaring it. For the time being, I actually took some shims and placed them where I thought they were needed, and used another recommendation from this forum to level the ring that the router sits in. It's late so I can't run it now....but will tomorrow in the evening. Any advice would be greatly appreciated.
THANKS!!!

[Brady Watson]

Keith,
Doing this the 1st time can be frustrating. Getting the Z dialed in is time consuming even for someone who has done it numerous times. On the newer gantry assemblies like you have, it is often necessary to loosen up one side of the AL extrusion, pin the Z in place and carefully snug up the AL extrusion again and tighten. The most difficult part of adjusting the Z is getting the Z dialed in the Y direction. The trick is to keep your eye on the level (make sure level is clamped to T-bar and NOT 2X2 part) and gradually tighten the bolts...all the while reading the level for changes. In some cases, the smallest turn of a bolt can move the Z out of adjustment...so do it slowly. If you get it set in the Y direction and pretty close in the X, then you can tap in the X direction with a rubber mallet.

The only other thing that I can tell you is that this operation takes finesse...so take you time and you WILL eventually get it perfect. This adjustment will affect your cutting quality more than any other; so it is worth getting right.

-Brady

[mikejohn]

Keith
You might like to look here (http://www.talkshopbot.com/forum/show.cgi?tpc=7&post=23016#POST23016) to understand why using just the level won't necessarily give you accurate Z square.

.................Mike

[gerald_d]

Keith, if your tower is really such a tight fit in the car, then you had better keep an eye on the tightness of the 4 rollers against the z-slide. That tower is fairly flexible and overtightening of the z-rollers may have spread it wider, causing the tight fit.

........Gerald <---- added a signature because the guys before me did

[kerrazy]

Keith,
I can not emphasize enough what Brady mentioned above. be very patient and allow your self an hour or two to play with getting your Z just right. Also don't be surprised if when you surface your table it leaves steps on the surface when completed. As I found on occassion where the router/spindle may not be exactly square so just relax and allow your mind to get in sink with what the tool is telling you. After surfacing the table with usually a 1.25 or 1.5 surfacing bit as this will exagerate any variation in the z, I then use a machinist square under the cutter, and use feeler guages to measure the distance under each cutter flute to see where I need to adjust further. I rotate the bit with my hand so its cutter flutes are parrallel to the x, and measure the space under each flute, then rotate so the flutes are parralel the y and then measure.
Follow Brady's directions above for the intial set up. and remember one overtightening can throw your bubble in you level off pretty quick, so tighten slowly for the Y and don't be afraid to use a firm hit with a rubber mallet for the X direction to aid in alignment.
Dale

[trevor_b]

i have been playing with this and i think the answer is to have some fine adjustment bolts applying pressure to the z in two planes.these could be bolts threaded into angle, and then setting up would simply be a matter of slacking the z, and using the adjustment bolts to tweak the z into square. one would be fixed to the Y on the z-motor side acting on the Z and one would be fixed to the z, acting down onto the y gantry.In their simplest form they would only work by pushing the z away from the angle brackets, but as long as you started with the z out of level the right way, it would be fine.

tell me why it won't work...!

Trevor.

[bleeth]

No reason why not at all. Sounds to me like the engineering of such a gib system would rank right up there with some of the great ideas other botters have come up with to stiffen their gantrys and cars.

Dave

[keith]

Gentlemen,

Thanks for your input. Here's where I'm at. I leveled the Z using a torpedo level off the ring that holds the router. I actually used 2 shims left over from the table on the left side of the Z. When I tested it travelling only in the Y - it was dead on. That is the hardest part - and I'm fairly happy with it. You're all right - it just takes patience. Now I'm squaring it in the other direction - and my time is limited so hopefully it'll be done in the next evening. Thanks for all your help....I'll keep you posted.

[mklafehn]

Keith,

I had a similar situation when squaring the z. I called tech support at Shopbot and they said that getting the z axis level in all directions is good, but you need to also make sure the ROUTER is square to the table. So what I did is level and square the z the best I could, then surfaced the table, you probably will have surfacing marks unless you are very lucky. Then I purchased a 30"x 1" piece of square metal tubing @ Home Depot, drilled a 1/4" hole in the center and put a 2" bolt through it, locked it down with lock washer and nuts. Then installed a dial indicator (purchased at a woodworking supply house for around $30, be sure it has 1" of travel)at one end of the tube. I put the whole assembly into the router (make sure it's unplugged) using the 1/4" bolt in the center as the "bit".

Then using the control software, lower the router until the dial indicator presses on the table, then continue about .01" more. Then you can swing the metal tube around and watch as the dial indicator tells you where the high and low spots are in the table. Just be sure you don't let the indicator land on one of the ridges in the table from the surfacing. With the knowledge of where the z axis has to be adjusted you can loosen the bolts and "slowly" begin the process of squaring the router. Tech support said to loosen the z, and use clamps on the z to push and/or pull the z axis into alignment. Believe me it is a slow process, but does pay dividends when everything is square.

When it is done you will have a z axis that is "dead on". I resurfaced the table after adjusting the z axis and there were no router marks, no ridges, just a very flat surface.

If your interested I can take a pic of the assembly to show you how the "arm" is constructed.

[gerald_d]

Mike, with respect, a 30" arm and a dial gauge is way too sensitive - you are going make people go mad trying to get the dial to stand still!

[keith]

Hi Mike, I'm interested in seeing a pic of this assembly if possible. Thanks for the help.

[gerald_d]

Keith, while you wait for Mike's pics, you can have a look at these (http://www.mechmate.com/Forum/messages/10/414.html?1134272787) trammels.

[mklafehn]

Kevin,

Here are the pics of my trammel. While it is sensitive, it is also easy to use and read since the arm swings out from the y car. The only change to my explanation is that I used a 1/2" bolt in the center(actually left over from bot install). This gave me more rigidity at the router.

I was able to square the router to within .005" over a 30" span.

When you read the dial be sure you are not pressing on the table because it will make a .002-.004 difference. Just swing the arm in one direction, read it then swing in the other and read.

As Gerald sites, there are many versions of trammels. This just happened to be the one I liked. Not to say that others wouldn't work either.

Good Luck
3350
3351
3352

[gerald_d]

Mike, I missed that the bolt is in the center - a 15" swing is much more practical than a 30" swing. Good way of counter-weighting the trammel, having a center bolt.

Now, if you had a dial gauge at either end, facing you.......

[mklafehn]

I thought about a second indicator, but I was concerned about the slight variance in the tube. I didn't want any other variable to enter into this procedure.

[keith]

Guys,

OK - I'm either square or really really close to square. How "square" should it really be? I have a dial indicator on an arm 15" from the router (swings a 30" dia circle"). Setting my dial indicator at 0 and slowly spinning it around, it varies from -.001 to + .003 inches. So, all said and done I'm only off by .004" Here's the kicker: I still think I feel VERY VERY slight ridges. I used the "cut rectangle" command to cut a 31" square with a 1" cutter and a 90% stepover in MDF. Should I call it a day and start making money with the bot....or shoud I be more picky??? Thanks.

[gerald_d]

Call it a day.

[mikejohn]

Keith
It's not that long ago I was in your position.
Someone (I think it was Brady) told me to stop fiddling and start making sawdust.
This is what I did, and carried on making sawdust for six months until I fiddled once more.
If you only think you feel VERY VERY slight ridges then you have no real problems.
...............Mike

[kerrazy]

reduce your stepover, and get rid of your rides entirley.
Then get at it
Dale