Dave's Build Thread

[bjesson]

too bad you did all that sanding, you could have fixed by sliding the rails at the left end of the gantry in a hair and adjusted the bearings that square the gantry on the right. I had a similar issue on the left side but was able to fix by sliding the rails inward and did not need any realignment. Also looks like you have a tight fitting gantry tube, my machine has an 1/8th inch clearance from the right rail, yours looks a lot tighter. Don't worry too much, you will be doing plenty more alignments once you start running things

billj

[kemper45]

Billj, you are correct about the right side of my gantry it is very tight to the rails.

Quick update as not much has happened since last time. I have installed the PSU and G540 into the side bays.




Also put in a terminal bus as per Randy's design to make wiring a bit easier. Apologies for poor quality of photo



Tonight was spent looking and thinking about options for home and limit switches. I know what I want to do with the X and Y axis at this point but less sure on Z axis. I also decided before I get too far with that it is time to move the CNC dedicated computer into its new home (the garage) and hook it up and see if we can make motors spin and things move.

All for now, Dave

[groswald]

Looks good Dave.

I've about decided to forgo the Z axis home/limits. I'm not sure how much value they would have. I definitely want to install a Z height setter though.

Randy

[kemper45]

Well after several months of build up the moment finally arrived..... will this thing move??

First attempt........... nothing. What have I done wrong? Poked around to check cables, re-read posts I have saved that give explicit direction on what to do the first time. Unplug the parallel cable and disengae the charge pump. Works fine. Reconnect the parallel cable and notice this is a tough fit so I give it a extra push. Hmmmm maybe I didn't get the cable in quite right the first time.

Turn charge pump on, start Mach3 again, hit reset icon and green light.

Up arrow, movement. Down arrow, more movement. Side arrows again more movement. Page, page down, watch that z axis in action. It works.

Push e-stop button in, red light. Twist and release, green light. Can I just say like a kid in a candy store.

Thanks so much folks for the help. It is a great feeling to start with essentially no knowledge of CNC, woodworking, metal working, electronics and to just see the thing move made my day. Can't say the SO was quite so happy.

Ok so now its time to start fine tuning the bearings, squaring up axis, levelling working surface, installing limit/home switches, attaching router and then making some chips fly.

Some questions :

- has any one installed a simple switch between the wall plug and the connection to the PSU? Plugging and unplugging is going to tire quickly.
- how come my shop radio goes all crackly when I plug in the CNC to the same outlet as the radio?
- Is it really necessary to use shielded wire for limit switches? From Randy's build thread photos it looks he is using telephone wire.


Cheers, Dave

[momus_cnc]

Congratulations Dave! And this is perfect timing, now you've got the entire weekend to ignore all other obligations and play with the machine. You'll be making chips in no time.

-Bob

[kemper45]

Thanks Bob. Perfect timing except that my son is in a baseball tournament for the weekend. We're at the ball diamond right now. Maybe get some time tonight. Really getting anxious but don't want to mess things up at this point

Thanks, Dave

[revwarguy]

Congrats on your first movement. Now on to cutting something!

Some questions :

- Is it really necessary to use shielded wire for limit switches? From Randy's build thread photos it looks he is using telephone wire.

No, its not necessary, but here's why you might want to:

If you don't, noise might trigger a false switch setting. If you use limit switches, then that stops the machine cold, and this may ruin the piece you are cutting. This noise may be intermittent, so it might or might not happen, but it usually does at a really inconvenient time. If you only use home switches, its not a big deal as long as you get a reliable home reading for each axis during setup. One approach is to try it unshielded and see if noise is a problem for you - you can then try to do something about it.

What can you do to limit noise problems on switch lines?

1. Reduce the source of the noise. This can be accomplished to some degree with shielded stepper wires and shielded power cords (like flex conduit) to your router, but this a bit pricey.

2. Shield the signal wires. This will indeed help reduce capacitance coupled noise on a noisy signal line. (Make sure you only ground one end of the shield.)

3. Reduce the bandwidth of the signal. You can do this with some electronic filtering, as well as using a debounce circuit or enabling debounce software. If you are running inputs through a G540 for instance, it already provides a debounce circuits on its inputs for you. Also, Mach3 has some debounce capability settings that helps reject transient noise that you can apply.

4. Perhaps the most important - Do NOT run signal wires along side inductive load wires, like the stepper wires or your router power line. Shielding (on either the power or signal wires) is not very effective at reducing inductive noise coupling that you get by having the wires run along side of each other. Lots of builders want to run the signal wires in their e-chains along side the stepper and router power wires - this is not a good idea with limit switches.

One good idea is just not use limit switches, but use "soft limits" with home switches. There are lots of other advantages you will see later on by using home switches, aka running the machine "referenced." Once the machine is homed to stationary switches (it doesn't matter where on each axis they are placed, as long as they don't move and are repeatable) which takes place well before cutting anything, Mach knows where the limits of travel are for each axis and will not let any machine movement exceed those limits. If noise should cause a false trigger of a home switch while cutting something, it is simply ignored. Limit switches are usually treated as e-stop conditions, and everything comes to a halt, sometimes irrevocably.

I used to use shielded limit switches, thinking that was better than not having them, but I have since changed my mind about that. Once you get used to using home switches - doing a ref zero for all axes on startup so that the machine now knows where table zero is - lots of other advantages like goto tool change position, automatic tool height setting, etc. are opened to you. Note this is NOT the same as the zero position or origin that has been specified for the work you may be cutting - that's a different zero point.

Running the machine "unreferenced" and using limit switches to avoid a disaster may seem simpler at first, but not after you begin to use it a while, IMHO.

[kemper45]

Revwarguuy,

Thanks for the detailed and thorough reply. Unfortunately most of it is over my head as I am really not good at this electronics stuff. I do have some two wire plus shield cable that I picked up from cnchubbard on ebay which I could use. Or stick with the 22 gauge wire and see what happens. I will take some time looking through my Mach3 manual and their video tutorials to look into "soft limits".

Other than that exactly zero has happened since my last update. I am also working on the conversion of half my garage to a workshop and it is a toss up most nights as to what project I want to work on. In between kids' ball games this past weekend it was shop planning and new router admiring.

There is always tomorrow.

Cheers, Dave

[revwarguy]

Revwarguy,
I do have some two wire plus shield cable that I picked up from cnchubbard on ebay which I could use. Or stick with the 22 gauge wire and see what happens. I will take some time looking through my Mach3 manual and their video tutorials to look into "soft limits".

Other than that exactly zero has happened since my last update.

Hey, take the time to enjoy the build - the garage or the CNC table!

If you are going to run inputs (limit or home switches or a probe) into your G540 (and I would), then it does the debounce filtering for you. Once you reference the home position, you can specify the maximum distance Mach will allow in either direction per axis. This is what is referred to as "soft limits." Sorry if that wasn't clear before.

The other big thing you can do is just try to keep your input wires at 90 degrees from your stepper or AC power wires as much as practical - don't run them along side each other, even if you use shielded wire.

Then, just use what wire you have (the shielded wire you mentioned would be great for your home switches and a probe) and lets see if there's a problem.

Mach is a large program, and the more you learn about it the more you realize it can do. There is some good tutorial info out there to quickly set up a 3 axis mill type configuration, though.

[kemper45]

Progress has slowed up as I have spent most of my time on workshop projects. However I did get some time this past weekend putting the back part of the cover together and mounting it to base.



The rear door is sitting inside the base right now and I will decide later if I am going to attach it. Still undecided on the clear cover versus some sort of chip collection system. One of the things that attracted me to the Momus Design was its self contained attribute but I may forgo that for a shopvac and dust boot system.

Randy's clean up of the wiring got me looking through my odds and ends bin. I found a 25 pin pass through cable from an old flightsim project so I put in to see what happened. Turned the machine on and checked to see that the right things happen when jogging. Not so good. The x axis is racking and won't go front to back under motor power. OK under manual power but gets hung up when motor is being used. Notice that the gantry is now 'wobbly' between the rails so it looks lke I need to have a go at tuning the bearings up. Odd that it worked before but not now.

I will keep updating as I proceed although it may be at a slow pace.

Cheers, Dave

[kemper45]

Not really an update as there has been no activity since my last post of over a month ago. I have been concentrating on my 'shop' projects. I have decided to put the CNC project on hiatus for now so that I can concentrate on the shop stuff before winter sets in. The shop is half of our unheated two car garage so I figure I have until late October/early November before our Canadian winter drives me indoors. The CNC machine will come in with me and I will then have time to start tweaking the various axes, learn Mach 3 and other software and actually try to cut something.

See you in a few months,

Dave

[Bob Adams]

Dave,

Your left X-rail looks like the same crappy piece I had. The edge contacting the bearing wasnt as pretty as the right rail that had a nice flat edge for the bearing to ride. Here's a shot of what I switched it out to which was a huge improvement in quietness since it eliminated the vibration I was getting from the uneven finish.

Billj

Were did you buy your rail? I have the same except my Cold Roll is has a curved across the 2.5 and not flat on the .25 thickness.