[trevorhinze]

As the title implies I have started building a very small and inexpensive CNC plasma gantry. I started on it earlier this week and plan to document the progress here as I make it. I have some goals for this project and they are as follows.
1 Small footprint-I have limited shop space because of all the other crap I have collected and therefore I am making this table as compact as possible so as to save on precious floor space. It will also be on wheels so I can roll it around when not in use.


2 Low cost- I am trying to build this thing as cheaply as I possibly can. I am using surplus/scrap/found/previously purchased materials whenever possible and buying as little new stuff as possible. Fortunately my cause is helped by the fact that I cant see good stuff go in the trash and I have been collecting useful stuff for years.

3 Quality-Cheap doesn't have to mean crappy! I may not be spending a lot of money but I am going to try to make this little thing as nice as possible. Most of the parts I have made so far are milled and many of them have pockets and curves even when a simple chunk of straight bar would do--it just looks better and gives me something to do with the milling machine that hasn't seen much use lately.( I forgot just what a mess flood coolant can make)

4 Other stuff- of course I would also like it to be fast, accurate, pretty and not smoky but that may be too much to ask for.

I do not have a plan, or a drawing, or too much of an idea in my head I am just working on one part at a time and hopefully it will fall together. It is kinda fun to design and make something when there really are no rules or anyone else to please besides myself. I will include pictures since they are the only thing that anyone else, including myself wants to see

[trevorhinze]

Here are some additional pictures of the limited progress so far. The rollers are a set of interesting cam followers of sorts that I acquired years ago from a machine that was being scrapped. (cant beat 10 bucks for about 40 of them) They helped track some high speed belts and had a crown to them so I made a mandrel to mount them on in the lathe and turned them down to a straight profile so that they would ride better on the 2" square tubing that I am using as guide rails.

[trevorhinze]

A few more photos..also in the previous group things were just mocked together and i just noticed that the seam of the tubing is on the "side" of the rail in those photos. As you can see in these pics the seam was installed in the down position so that the rollers only run on the three smooth sides of the tubing.

[trevorhinze]

Here is a link to short video taken during the milling of a bracket that I may or may not use. It shows the pockets getting finished up around the edges. I will also attach a pic of the bracket. I ground down the face of it which is completely unecessary but made it look nice I think.

Video:
[ame=http://www.youtube.com/watch?v=MsptmgZNjmI&feature=youtube_gdata]CNC bracket milling - YouTube[/ame]

[trevorhinze]

Merry Christmas everyone. I had a chance to do some more work in the garage today and took a short video of one of the roller guides getting trued up on the lathe. It is below.

[ame=http://www.youtube.com/watch?v=lF0GP_SnxEc&feature=youtube_gdata]Mach # lathe truing up Followers - YouTube[/ame]

[trevorhinze]

Here are some more pictures. I was able to get the X axis carriage cut out and put together. I expected it to roll pretty well but I am really pleased with the way that it rolls along the tube. It is so smooth and effortless to move and yet seems very solid and seems at least to be plenty accurate for plasma cutting. I guess only time will tell if I am correct or not.

[trevorhinze]

More pictures of the carriage assy

[trevorhinze]

The photos with the stepper just show it sitting in place as I play around with which way I want to mount it.

[trevorhinze]

I got one of the motors mounted on the carriage today. I also made a couple of brackets to attach the timing belt to and mounted them on the gantry rail. The timing belt is just held on with a couple of clamps for now soon to be replaced by a more permanent mounting block. I am very pleased with how the carriage slides along and how smoothly the belt seems to feed through the tensioning rollers on either side of the timing pulley.

[trevorhinze]

I was able to spend a few hours working on the machine yesterday and I was able to get it moving for the first time. I will post a video of its first movements after motor tuning below. In the video it is moving at 600 IPM as it cuts an 18" diameter spiral working from the middle outward. I am considering fitting smaller timing pulleys to the motors because I am willing to sacrifice some speed for some better acceleration. When set to 20 in the acc box I would sometimes get a little bit of stuttering so I backed it down to 17 and it seems quite happy. I really don't need 600 ipm on what is basically a 24"X" table as far as I can tell since I am pretty sure I cant cut anything that fast and the time it takes to rapid from one place to another is not a very big issue with such a small table. I am also wondering if I just ran the steppers at a higher voltage if I could get better acceleration? I am currently running them at 12 volts with LiniSteppers for Drives. Does anyone know if that would be a good idea? I was actually able to move the x axis carriage at up to 1200 ipm since it is so light but it was scary fast especially with no limit switches installed. I also wanted both axis to run at the same speed so I the Y axis which is moving around lots more metal is the limiting factor. Let me know what you think as you can see the belts are just attached temporarily with clamps and several other things need refined and finished including a z axis but it is exciting to see it move!

[ame=http://www.youtube.com/watch?v=mnmy8x7jbL0]Cnc Plasma Gantry First Test - YouTube[/ame]

[osphoto]

Gantry on the table saw... great idea! Looks "portable" so to speak.

[trevorhinze]

It is just sitting on the saw until it gets its own legs and wheels later on. You know how it is any flat clean surface is fair game!

[ron clapp]

Trevor;
is this table driven from one side like the other one you had?
the other table you had was driven with one belt and the other side was just stabilized by the roller on the x axis.
very good work here!!!!
keep up the good work Ron

[trevorhinze]

Ron, the end of the long axis is just allowed to follow along on two rollers and is not driven or captured in any way. It just goes where the other end goes and is only kept in guide by the rollers at the driven end and the rigidity of the tube. It worked pretty well on the last table years ago and its axis was considerably longer than this one so I hope it will work even better this time. Thanks for the interest. I will attach a couple of pics of the end roller assy.

Trevor

[trevorhinze]

I made some progress this week getting most of the z axis built and mounted on the carriage. I have now turned my attention to the control for awhile. I have the three Linisteppers mounted up on copper heat sinks each with its own fan to keep them plenty cool and I have begun wiring up all of the other junk inside of an old cabinet re-purposed form a project years ago. I will attach a few pics.

[trevorhinze]

I have the rest of the components for the z axis completed. As you can see in the pictures the torch holder is mounted to a short linear rail that allows the torch to "float" about one inch up and down. It is held down by gravity and I hope to be able to use this feature along with a switch of some kind to be able to do initial height sensing at some point in the future. This in turn is mounted on to a longer linear rail whose carriage is powered by the stepper motor and screw to move it up and down. The torch is simply retained by one thumbscrew and can be removed in about 5 seconds when needed for hand cutting.

Also attached is a picture of the brackets I milled out to support the water tray. They will also serve as the supports to hold the framework for the slats down inside of the tray. It is hard to describe how they will fit and I didn't take a picture but the groove that you see in them will fit down over the walls of the water tray.

[trevorhinze]

Here are a couple of pictures of how i tapped into the plasma cutter so that I could control it with Mach3. I found the two wires that came into the unit from the hand torch trigger. In the case of my unit it was a pair of brown and white wires. I simply tapped into these wires with a pair of scotch lock connectors so that the hand trigger would still operate normally whenever needed. I then wired these two up to a pigtail cord that exits the unit and has an audio connector on it so that I can disconnect it from the control cabined whenever I need to. The Plasma unit uses a 24 volt dc signal between these two wires to act as a trigger circuit. Whenever the circuit is closed the plasma unit fires. The current draw is very small so only a very small relay is needed to close this circuit and make the cutter think that its trigger has been pulled. All of this has been covered in much greater detail elsewhere but it is a very simple process all in all.

[trevorhinze]

I was able to do some more work on the table and after scabbing together some temporary slats and a pan that will eventually become the water table I couldn't wait any longer and made some test cuts of some little 4" x 4" gussets that I drew up. The results left more than a little to be desired and highlighted the need for tweaking and tuning in several areas but it was exciting to see all of the parts working together to actually cut something out of metal. I began this project back on the RD of December so I am pretty pleased with the time it took me to get to this point. Now I need to see it through and finish it rather than getting it 90% done and leaving it like i do with so many other projects! I also have a lot to relearn about feed rates and cutting amperage so that I can achieve nice square cuts and eliminate as much dross on the bottom as possible. I am hoping that the water table will also help some with the dross issue but I am not sure. I will attach a couple of pictures of the first cuts.