Table Heigth

[kubotaman]

I purchased a new 5x10 Alpha and have read of flexing in the z axis at full extension, which in my case is a 12" Z axis. I experienced the flex as of yesterday. I was using a 3/4" bit, taking a 1/8" pass in red cedar yesterday. When I would go slightly faster, 1" per second, it would wander off track by a 1/4". I feel that the drag of the bit, angled to the grain, was overcoming the ability of the y axis to the prevent movement. In other words the drag of the bit was overcoming the power of the y-axis motor to keep on track. What is your opinion? If I slowed down to .7 IPS it cut fine. It just took too long. I have decided to extend a portion of my table up so I would have a normal 6" z axis. What do some of you guy's do as far as material to use for the "extension" table? I feel I would be better off using aluminum tubing, 2"x6" square, and have it welded together than using a wood product. I feel the wood will wander and not stay true. Again what do you do to extend the table heigth? I have posted this also to the trouble shooting section. Thanks!

[Gary Campbell]

Daryl...
The problem is most likely not in the Y motor. Alpha steppers do not lose position. The problem is most likey in the geometry of overextension created by the 12" Z length. That is why they only recommand the 12" Z for foam or other light duty cutting.

Many of the guys that have made these "riser" tables have used sheetgoods, with varying success. Let us know what you did and how it works.
Gary

[kubotaman]

Gary I understand what you are telling me. Is it possible, in your opinion, for a stepper motor to be overcome by the pressure a bit puts on it? Lets face it a 12" z axis puts a lot of strain on the motor and all components. I cut today at .7"IPS and the cut was fine, no problems. If I speed up it will not cut correctly. That is why I think at the faster speed, 1"IPS, I am over coming the ability for the Y stepper motor to over come the pressure being put on it, since I am cutting at an angle to the grain of the wood.

[Gary Campbell]

Daryl...
It is possible, but extremely unlikely. IF the Alpha stepper is up against more resistance than it can overcome, it will go into fault mode, lights will be lit on the control panel and you will have to reset the drivers.

When I purchased my machine I had geometry similar to yours. After fighting the same issues that you are, I purchased new side plates and a shorter Z. At present, I could cut your Red Cedar with a 3/4" bit, 3/8 per pass at 6 ips. That is the difference.

That is exactly the reason I would always steer someone that wasnt going to cut foam or similar light materials to the lower Z configuration.

Have you taken the time to adjust your Z extrusion guide rollers? You have to keep an eye on them, especially when new. A little play at the roller can mean a lot of play at the bit.
Gary

[kubotaman]

Okay I did check my rollers on the z-axis today and I have zero play in them. What plates are you refering to? If I just raised the table, say 6", isn't that the same as a 6" axis machine?? I will make the table 4x10 since I have a 5x10 table. That way I can use the 12" axis over the "Trough". Seem reasonable?

[Gary Campbell]

Daryl...
After rereading all your posts I am more convinced that you have something out of adjustment. Even with the 12" Z, with the cuts you describe, I might guess .050" at most deflection at those feeds and speeds. .250" is an excessive amount for any machine.

There are at least 18 V rollers between your bit and the table that all need to be adjusted to eliminate play. They also need to be parallel, coplanar and seated properly on or in the rails that they run on. There are also many bolted connections that are important also. Remove all motors and check them all by disassembly, relubricate and reassemble making sure of the following:

X rails are perfecly straight, level and equidistant throughtout their complete length.

That all 4 X car rollers are centered over the rails and there is no "teeter totter" effect. Roll X car back and forth by hand and give it some good shakes or start/stops (remember pinions are not holding it on the rails)

Check the YZ car rollers for loose bolts and adjustment. roll back & forth, adjust rollers to where rolling resistance is felt. resistance should be the same for the complete length of Y extrusion

With your spindle/router removed work the Z through its complete movement by hand. I prefer to do this with the springs removed and adjust the rollers to snug+ check the fixed rollers to make sure they are tight. this is not a fast process due to the number of adjustments.

Hopefully this will help to eliminate your problem.

The plates I was speaking of are the blue side plates on the X car that hold the Y extrusion.

Raising the table should help, but no it is not the same as a 6" setup. There is the possibility of cutting forces flexing or moving the table. Unless it is heavy and bolted down it may add to the problem by moving with vibration. You also have inherent flex added by the side extensions.

There will always be more flex built into the long Z models, but you should be able to reduce that to a bearable amount with light cutting as you describe above.
Gary

[kubotaman]

Gary, thank you for the information. I will give my machine a good look over today. Hopefully I can find the problem that caused my going off track.

[kubotaman]

Well gave my machine a real close look today. Guess what? Nothing was even close to being loose!!! I will call tomorrow to see if they have any suggestions. Thanks, I will post if I find anything out!