New Shark Pro HD

[kruizer]

Joe,.
I have taken the time to go through this machine and check for loose screws from top to bottom and found almost all of the screws related to axis control were loose. Tightening them has made a huge difference in the performance although the jerkiness is still there. The screws have been lubed with silicone as per NWA. there is no binding and as you say there may be a problem with the tap file on certain jobs. It is not possible for me to attach a file to a post as I am not sure how to do it. I am running a file that I down loaded from this forum and it does not look smooth but that is not the machines fault as the code generated from this file is kind of squirrely and does not repeat from one segment to another. It is a 6" dia trivet like form and I am not sure how to modify the geometry to get a smoother cut. I think I have dealt with the mechanical problems, now I have to learn more about generating program.
kruizer

[REG]

kruizer, Joe makes a good point about the file. If you grabbed a file from the forum and didn't review the file and the toolpath, it could be the contains hundreds of nodes. Each node in a vector results in a G code instruction.
My advice is to make a simple file in VCarve such as a square. Vector it, create the toolpath, save the file. If you are not certain how to go about it watch a couple Vectric videos. They are truely helpful.
Another note, make certain the PP chosen in VCarve is "USB Shark CNC inches" (or mm if you prefer the metric). If you have another machine selected it will cause incorrect PP instruction for your controller.

Now on quality control; you made a number of comments on the loose hardware. Since the Shark comes 75% assembled it is easy to assume everything to that point has been checked and properly torque. You are right in that assumption. I did it too. I had screws missing, connector plugs marked alike (I had two Y axis marked plugs) and I experiend the eventual loosening of the Y axis coupler to the drive screw. Yes, it is frustrating but an extra measure of checking all fasteners is worth the effort. Shipping stresses these fasteners some and HDPE is not the greatest in "biting" screw threads. In fact I removed the screws from my acme nut for both X and Y axis and installed machine screws with locking nuts. My X acme nut bumped out several times, Again this is because HDPE does not grab the screw threads. I believe the Z axis nut is begining to do the same but hard to tell since it is within the box that holds the Z axis components.
So tighten all the screws with a dab of Gorilla glue on the screw tip. Gorilla glue has urethane in it that expands and bites pretty good.

Good luck and have fun in learning your machine!

Bobby

[Bob]

Joe,.
I have taken the time to go through this machine and check for loose screws from top to bottom and found almost all of the screws related to axis control were loose. Tightening them has made a huge difference in the performance although the jerkiness is still there. The screws have been lubed with silicone as per NWA. there is no binding and as you say there may be a problem with the tap file on certain jobs. It is not possible for me to attach a file to a post as I am not sure how to do it. I am running a file that I down loaded from this forum and it does not look smooth but that is not the machines fault as the code generated from this file is kind of squirrely and does not repeat from one segment to another. It is a 6" dia trivet like form and I am not sure how to modify the geometry to get a smoother cut. I think I have dealt with the mechanical problems, now I have to learn more about generating program.
kruizer

Kruizer
I cleaned up the trivet. If you want to give it a try go here: http://www.cncsharktalk.com/viewtopic.p ... 5845#p5845
Bob

[kruizer]

Bob
Thanks alot for that. When I was looking at the cutter path, it looked like a lot of Zmoves where it didnt nned to be. I was trying to figure out how to clean it up and got nowhere so thanks again. Now I am trying to figure how to make your chip carved square and am having trouble making the proper depth.
kruizer

[rungemach]

Hi Bob

I downloaded the new circle 2 file, opened it in Vcarve 6.5, generated the tool path for the main carving, ran it on my pro generation machine (in air) with Mach3, and there was no shaking or pounding at all. However, though the cut speed is set at 100 ipm, in the short sections, my typical speed was bouncing around at between 30 and 50 actual ipm, only reaching 100 on the long circular passes. (you can watch that while the program is running in Mach3) The acceleration setting was holding the tight sections down to a reasonable speed. If it were moving much faster in those sections the machine would probably be objecting. (from past experience). I was reaching the full 100 ipm in longer sections.

Anyway, to try and make some kind of comparison, my shark ran the main carving in 24:17. If your machines are running it faster, I would think your acceleration settings are allowing faster stops and starts, holding the velocities in tight movements back less, giving you faster average speed, and a faster finishing time for the "obstacle course".

Granted I had to select a different post processor, which also is something different in the mix. If your times are similar, our motion dynamics are probably pretty similar as well. But at least this is some reference point to start with.

Hope this helps.

Bob

[kruizer]

My run time on the chip carved circle is similar so the accel decel is probably okay. I did a test today with a circle program to check the ability to cut round and it came out .030 out round. That is disappointing as it indicates a problem with doing inlays which is one of the reasons I wanted this machine. I will talk to NWA about this and see what they have to say. It also has a problem holding depth which varies as much as .010 around the circlethe variations are visible in the bottom of the cut. There is also a small jumping that occurs at the 90 degree and 270 degree points as a direction change occurs. that jump does not happen at the 0 degree and 180 degree points.
kruizer

[jeb2cav]

Have you tried the inlay method advocated by Vectric (it is machine agnostic)? I haven't myself, but have seen some projects and posts in this forum as well using this method and they seem to have success.

From talking with folks at the Vectric User's Group meeting, it seems like you never get that last 1/32", and this is the way to create inlays using CNC machines.

http://www.vectric.com/WebSite/Vectric/ ... inlay.html

[rungemach]

If you cut a plain circle, as you have, it should not be out of round.

It may be a backlash issue, so double check that your lead screws on x and Y are tight and gripping the shafts tightly.
also, check your router mount again to be sure it is holding the router body very tightly.

Then cut a test project like a 3" square and measure the x and y for differences at several spots, for true 90 degree corners, and for straight sides.
Then do a circle and mark the 12 O'clock position and measure the diameter at every "hour".

You should get a clean circle with very little difference in diameter ( like +- .002" ) if all is tight and calibrated correctly. your number of .030 seems very high and more than the machine backlash should be.

Don't do the cuts at high speed, take it down to 20 ipm with light cuts to minimize force on the tool influencing the situation.
You are looking for uniformity in these tests, not if the actual dimension is exactly right. That can be influenced by the cutter's true diameter and runout.

The z can be influenced by table tilt and flatness, so it becomes a slightly more complex situation.
Did you adjust your table to be the same distance from the bit at the 4 corners, and then mill down a cutting surface yet?

Bob

[kruizer]

So post your project and ask for feedback. You say really low feed rates and high feed rates. Hard to give you feedback with no project, or no cutter type/size/depth of cut/stepover/etc., what kind of wood/material you're cutting into, and your notion of low feed rate and what feed rate your found the jumping like St Vitus dance.

Hopefully I can get a file uploaded. This is the one where there are steps showing up at the ends of the ellipse.

[REG]

Hopefully I can get a file uploaded. This is the one where there are steps showing up at the ends of the ellipse.

Three things will cause steps in a circle
1) Loose coupling or slop (play) in the drive screw of Y axis or X axis.
2) Loose axis nut.
3) Node position in the file (nodes are in a curve but don't connect in a curve segment causing "stepping" between nodes).

The first two can be discovered by moving the axis by hand. For example, with the controller powered off try to move the Y axis along the axis by hand. A slight push and pull at the rail points - if there is a slight movement it could be the axis nut and the mounting screws for it or the coupler. An extra set of eyes will help so someone can watch movement at the coupler.
To have the node checked, you can upload your file. Any of us can run the file to look at the nodes.
My thinking is you tested a number of files and still have the "stepping" which is likely more mechanical than software.

Bobby