[InventIt]

Work on the router has been slow going because I had a little hitch in my plans for the Z axis. I original was going to use the Z axis assembly from my first router but realized it was too short to work on the 2nd router which has more height under the gantry. Also the old z axis is only 3/4" x 6" alum and most likely would not be stiff enough. So I decided to make a new z axis assembly out of 1" x 8" cold roll 1018 steel. However when I took my 3 plates to the same machine shop that did the machine work on the base and gantry, I got sticker shock! Almost 2k to rough 3 plates and drill/tap a few holes!!!! Ouch!
So, I figured it was time to look for a old manual mill. A few weeks later I had 5000# of good old American iron sittin in the shop. Sweet!

[InventIt]

Ok, now that I have a mill, I can get some work done.

The X axis bearing blocks, motor mount and delrin nut are done. 1100W servo with zero backlash coupler.

During tuning of the X axis servo the motor went into oscillation and before I could stop it it broke the coupler. Then I got the 3 piece coupler that is on it now and it went into oscillation again and before I could get it shut down it destroyed the red plastic spider. I was amazed how much power these servo motors have to be able to do that. So, before any further tuning i setup a E-Stop. Finally I managed to get the X axis tuned.

[InventIt]

A few pics of the X axis.

[InventIt]

The first of the 3 Z axis plates. This one is the X axis carrage and will have a few different sets of mounting holes.

[InventIt]

These 2 plates will be the complete Z axis assembly and will mount to the X axis carriage. I'm using a finer pitch thread on this for more lifting power and better resolution. 4 turns per inch vs 2 turns per inch on X and Y. The long plate which will be the tool mount and is 88 pounds alone, plus the linear rails, motor, bearing blocks and screw as well as the spindle which is probably 150 pounds or more. The weight is adding up quickly! Hopefully this rig moves in more then one direction!

[InventIt]

I'm using Delrin nuts on all axis and of course I had to make my own tap. Here is the tap I made for the 3/4-8, 2 start thread in action.

[InventIt]

Well... I finished the Z axis, mounted it to the gantry and ran it up/down a few times. Unfortunately it has bad vibration when going down. Running up the movement is perfect, nice and smooth. I tried using a heavy oil on the screw but it still does it. I think the problem is with the delrin and acme screw combined with the 90 pound sliding plate. It may be too much weight for a delrin /acme screw. So, I bought a ball screw off ebay that should be here next week. Hopefully that should solve the problem. Stay tuned for Z axis version II.

[Phife]

Ive been watching your build for a while and really looking forward to the results.

I have a similar issue with my delrin shop made nuts and acme screw.

I have to keep mine well lubricated with white grease or they start to make horrible squealing noises.

I have a split nut that probably helps a lot especially with getting grease to the center of the nut.

I see youve already went with a new ballscrew, did you figure out a way to keep the Z from dropping when power is off?

[InventIt]

Phife, now that you mention it, white grease my be better then the oil I used. Got a few days before I expect to see the ball screw, maybe I'll fit a grease fitting on the nut and try it that way. Either way I think I have to change it out. The motor seemed overloaded with the current setup.

Will I have a problem with the axis dropping? I got a fine pitch ball screw. Metric 20mm dia x 5mm pitch. The axis is quite heavy though, may be over 200# by the time i get done mounting a spindle. Suppose dropping is likely huh?

[jsheerin]

Especially with a ball screw - they're easier to back drive.

You could counter balance the z with an air cylinder. I have this in the works for my router when I switch to a water cooled spindle. Basically if you get a double acting cylinder, leave one end open and connect the other to a pressure tank that you pressurize to the needed pressure to balance your z weight, you should get a fairly constant force over the travel of the cylinder as long as the cylinder volume is much smaller than the pressure tank. Then all your motor has to do is accelerate and decelerate the load (which can still take substantial force).

[lukewarm]

Inventit my Z axis weighs about 200 pounds also. I'm driving it with a 973 oz-in stepper on a 5turns/inch ball screw and I don't get any droop. We considered putting an air cylinder on it but it doesn't seem to need it.

[madosta]

Awesome build!

[Phife]

Inventit my Z axis weighs about 200 pounds also. I'm driving it with a 973 oz-in stepper on a 5turns/inch ball screw and I don't get any droop. We considered putting an air cylinder on it but it doesn't seem to need it.

When power is off can you move the Z up or down by pushing on it? does it stay in the same place overnight/unpowered?

[lukewarm]

Cannot move Z up and down by pushing on it and it does stay in place overnight

[InventIt]

[nomedia="http://www.youtube.com/watch?v=dbIUzRVaNq8"]YouTube - Z Axis demo - pen plotting part file[/nomedia]


Quick video of machine pen plotting a simple part file with feed rates from 30 to 250 IPM and rapids at 600IPM.

[InventIt]

New (to me) Z axis ball screw 20mm dia x 5mm pitch courtesy of everyone's favorite online auction site. Hopefully this will be an easy swap.

[InventIt]

Got the Ball screw installed in the Z axis. Was fairly easy. Just made some slight mods to the original setup. I did spend extra time measuring and making sure the screw was set in just right so there was no binding.


Turned down the diameter of the ball screw to 5/8" on the drive end. Then made a sleeve to go from 5/8" to 3/4". That allowed me to re use the original upper bearing. I used the THK end block that came mounted to the screw at the bottom of the axis and the drive end bearing floats in the aluminum motor mount block. Then I made a block to mount the ball nut to the fixed z axis plate and finally a shim to set the lower bearing block at the correct height.

The next thing I will need to do is make a brake to hold the axis when the power is off.

[nomedia="http://www.youtube.com/watch?v=dt9paSCZvhs"]YouTube - 100 0480[/nomedia]

[InventIt]

Well, it's starting to get warmer outside and so I have been working on the cnc machine a bit more. Sure wish I had heat in the barn this past winter. could have got a lot more stuff done!

Anyway, I finished the Z axis. Mounted the cable chains for X, Y and Z. All I need to do now is finish the home and limit switches for X and Y and wire up a output to turn the spindle on/off. Also I would like to setup a mist coolant system, I am very impressed with the mist coolant I put on the old machine! It works great and it was free (made it from a soda bottle, an old air soleniod, a regulator, and some clear tubing).


Here is a video of a test cut run on the new machine. Cutting 6061 aluminum at 50 IPM and then 120IPM! Keep in mind the majority of the chatter comes from the Porter Cable router.


[nomedia="http://www.youtube.com/watch?v=a974jExoLak"]YouTube - Test cutting pocket in aluminum[/nomedia]

[jsheerin]

That looks like a nice cut. You were blowing through the aluminum way faster than my machine can and getting a better cut it looked like. I'd put that down to your beefy construction. Btw, it looks like you are going straight down into the material at the start of each cut. If you ramp into the cut at about a 10 degree angle your spindle bearings will thank you.

[InventIt]

Found a pic of the cut. Shows the surface finish a little better.