Project 1 from EmptyNester. Category: Custom Shop Tools - CNC Table

[Rambozo]

That is so not what I meant when I said I wanted a pool table.

[EmptyNester]

That is so not what I meant when I said I wanted a pool table.

Unfortunately, its a little leaky as pools go. I went through one round of patching holes but still have some left.

I probably shouldn't have painted it until after I tested. Now I'm not sure how I'll get the paint out of the corner that needs "patched".

[ShaneJackson]

Just get some of that liquid rubber spay they sell on TV. It will fix anything.

[EmptyNester]

I started final assembly of everything.


The X axis is fine and seems pretty smooth (only have 1 motor moutned on it currently).

I'm having trouble with the Y-axis. It will bind as I run it along the tube. When it binds the bottom of the vertical piece of the carriage seems to kick out from the tube.



I did a quick check and it appears that the top and bottom plate are much closer than the x-axis carriages. Around 1/10" on the side you see in the picture. I'm surprised I didn't see it sooner.

I'm guessing that the dimension is the cause of my problem, so I'll have to figure out how to fix it.

[Rambozo]

Unfortunately, its a little leaky as pools go. I went through one round of patching holes but still have some left.

I probably shouldn't have painted it until after I tested. Now I'm not sure how I'll get the paint out of the corner that needs "patched".

This is true. You also don't know if the paint is sealing other very small leaks. When I used to build oil pans, I found that testing for leaks with solvent or mineral spirits is better than water. Less surface tension and it seems to find everything.
I'm sure a little heat and a wire brush will burn the paint out of your corners enough to re-weld them. MIG and stick can be pretty forgiving about bits of paint, at least. Of course just coating with a sealer is the easy way out.

[EmptyNester]

Talked to Precision Plasma about the carriages. They said it's either the eccentric bearing adjustment or the carriage is out of square. I said I suspected the carriage and they suggested "percussive adjustment" with a vice and rubber mallet.

Instead of working on that, I wired the motors on the X-axis and gave it a try. Seemed to work okay. But, I'm assuming that the DRO reads in the units you set (I set inches). I must have done my calculation of steps per inch wrong because I was getting two inches of movement for every inch on the DRO. I'll have to redo the calculations and see if I can figure out what went wrong.

I was adjusting the direction of movement for the X-axis by changed the active hi/low of the direction signal. I accidently changed X and Y instead of X and A. It's pretty dramatic when the steppers go in opposite directions.

I'm curious if anyone has suggestions on maximum speed and acceleration rate...........

[Rambozo]

I'm curious if anyone has suggestions on maximum speed and acceleration rate...........

That all depends on the strength of your motors and the mass and friction of your machine. Ideally you want to be able to go as fast as possible without losing any steps. There are some motor tuning programs that will help you get in the ballpark. Also a lot depends on your step kernel rate in Mach. Run the drivertest to see what your system can support. Be aware that you can also have resonance problem at some speeds, there are tricks to fix that, if needed. One thing about steppers is that they have a wicked torque curve vs speed. So you need to test and tune from zero through your max feedrate, then at your rapidrate. If you have a resonance between max feed and rapid, you can live with that, but not if it happens below max feedrate. And of course you must never lose a step, no matter what. A general rule of thumb is to adjust velocity up until the motor stalls, then back down about 10%-20%. Then adjust acceleration as high as possible where they can still start from stationary. This will give the best position tracking. If you plan on using constant velocity, everything will have to be tuned really close, for exact stop you don't need to be as precise.

[acourtjester]

HI Empty
you may have the same problem I have with the "Z" axis, it look like your "Z" motor is a direct connect to rack via the motor gear.
What happens when you drop power to the motor the weight of the z axis will cause the motor to free wheel and the z drops to the limit.
Slam dunk kind-of-a-thing. I need to remember to prop it up before dropping power.

[SeanMurphy265]

This is an easy way to calibrate your steps per inch. I did mine with a tape measure because I do not have a dial caliper, but I'm ordering one soon. I'm not good at math, but this is an easy way to get it accurate.

[sportbike]

That thing looks pretty darned nice. I am looking forward to seeing how it works out. I have still been toying with the idea of building a small one for myself.

[EmptyNester]

I thought about a couple different ways to support the wire shelf for the energy cable. I ended up getting a U shaped wall bracket for holding shelf supports.



I didn't install the engery chain because I don't think the torch is long enough to make it. Hopefully, I'll have a longer torch in a couple weeks.



All I have left to do is:

• put in the X limit switches
• complete the wiring on the limit switches
• use silicone caulking in the problem area that may still have a leak
• finish leveling the slats

Before I try a test cut, I need to finish wiring my THC/interface. I don't plan on trying to get the THC working just yet, but it handles the relay for the "torch on".

[EmptyNester]

Rambozo - thanks. I ran that and it went as expected.

I took one of the odd ones I've generated and stepped through them to identify the commands. I deleted the circles. It seemed to work okay.

I'll spare the details, but I tried lots of different things and was always getting the conincentric circles in the Mach driver. I run Mach on a PC in the garage and have my drawing program and SheetCam upstairs. To try to save time debugging, I installed mach on the upstairs PC. Everything looks fine. The same file loaded on the table's Mach driver is messed up.

At this point, I think I have a very hosed installation/configuration on the table's Mach driver.

[EmptyNester]

I did start leveling the slats. Once I got enough to do support a test cut I mounted the floating head plate to my z-axis. I had to modify the mounting since I have a Precision Plasma carriage and a Shopdroids Z-axis. The mod I did put bolts in the way of the floating head. It reduced my z-axis travel from 6 inches to 2 inches.



John from Shopdroids was helpful with some ideas. I ended up making an adapter plate out of aluminum. Not pretty, but effective and it got the job done (I want to cut and I'm frustrated at falling behind where I want to be).



I got my energy cable today. I ordered (3) three meter sections. They were only $19/each on ebay. I looked at getting a wire mesh cable tray (used for hanging network cables in the ceiling). They were $100 for a ten foot section locally. Mail order they were only $20 each, but truck freight was $220. So, that was a non-starter.

I ended up getting a wire shelf at Home Depot for $20. I shortened it and made it narrow. I do need to give it a little more support, but I'm not sure the best way. I think that aluminium angle will work, but I don't know how much that would be.



I had thought of using conduit, but that probably has too much flex. Any ideas are welcome.