Precision Plasma 4x4 CNC Table Build

[unixadm]

I spent some time over the last couple of days working on my plate marker / scriber using a heavy duty rail and block, a pneumatic cylinder with enough spring force to pull the assembly back into it's home position, and a cheap CP-9361 Air Engraver clone.

I machined some Delrin in both 1/2 and 3/4", an aluminum mounting block, and the scriber mount. I used a ring clamp to mount the scriber and I think it's going to work out quite well. I need to tweak a couple of things and cut the backing piece to it's proper height. The assembly will be around 18" tall and it's BEEFY.

The 'el cheapo scribe was a joke. Upon hooking it up, it did nothing but hiss some air. Upon disassembly it was full of rust, filings, black dust, and dirt. I cleaned it out with solvent, scrubbed the piston with some scotchbrite and oiled everything with airtool oil. It works fine after that, but what a joke. It is less than half the price of the CP-9361 and it's an identical unit.

I'll be mounting the scriber axis on the gantry tomorrow, and hope to be doing some testing by the late afternoon. I picked up two carbide stylus tips for the scriber which fit perfectly, so I have everything ready to go. All that's left after I mount this assembly is to put my solenoids and regulators on the mounting plate, route the air lines using push to connect fittings, and hook up the dual 120V three way three port air solenoids. I already have tested the scriber post in Mach3, so all that's left after that is to know my offset and away I go to test.

[Torchhead]

If you are using SheetCAM TNG there is a POST included called MP1000-scriber that Les from SheetCAM wrote. It allows you to define an offset (in X,Y and Z) and just call a tool number GREATER than 100 in SheetCAM so you can go around and mark hole center using a "drill" tool or other things using an engraver type tool. You don't have to burn two different Gcode files and you can even intermix the two processes if you want.

If you are not using TNG then contact me. I have a Dual Axis Z POST that is being used on a custom table (has a plasma torch and a spindle) that does multiple operations and drills/routes, then cuts larger sections with plasma. I used a different method than Les did with the MP1000-Scriber. I just applied a G52 offset call (and cancel at any toolchange) and used the tool number to swap axis calls (we used B for the spindle axis) It has separate motors on Z and B but it should work with some modification to use just Z but with two different tool holders.

TOMCAUDLE
www.CandCNC.com

[unixadm]

Thanks Tom. I'm using Sheetcam TNG with the scriber post already. I'll probably have to tweak it a little bit but my offsets should be close.

I did a test once I got the regulators and solenoids fitted and connected, and mounted the marker attachment to the gantry. The marker is fairly slim and compact, so it fits nicely with the T45M torch. Other than the cheap knockoff scriber being so-so, it's working pretty well. There is a bit of play in the tip housing and the carbide tool, so making sharp corners is a bit difficult, but for what it is, the accuracy is good enough for me. The pictures and video below is marking 16GA CR steel sheet at 60 IPM, however in the video it's running at 40 IPM. This requires some fiddling around with to get the proper pressures and speed. Too much pressure and you can see the tip jumping, too little and the axis will not reach the material. For my set up it's walking a fine line of around 5 PSI. I have nice SMC regulators which go from 0-125 PSI and they have markers in the gauge you set for your optimum area. For the scriber I'm running at around 100 PSI and the 1-1/4" actuator around 32 PSI. I have fine control over the pneumatics, and the 120V solenoids worked perfectly with the coolant output on the CandCNC controls. I'll do some marking + plasma cutting later today. My marker axis delay is set at .75 second, and I think probably .65-.7 is going to be the optimal setting.

I need to figure out if I can keep the Z-axis from moving when it's calling for plate marking. Right now the Z-axis moves a bit and I have not researched why since only Tool 101 is in use on this particular program. I have some fine tuning to do still but for literally coming up with this on the fly out of my head I'm pretty happy everything worked out of the gate, with the exception of the engraver.





[nomedia="http://www.youtube.com/watch?v=aXYDC7dbtC0"]YouTube- Plate Marking / Scriber attachment on Precision Plasma Gantry[/nomedia]

[unixadm]

One more picture for the day and another video....

Now I need to tweak the delay time to see if I can clean up the entry point a bit.



[nomedia="http://www.youtube.com/watch?v=M0yMHN-H8jY"]YouTube- Plate Marker / Scriber on Precision Plasma Gantry + Plasma Cutting[/nomedia]

[unixadm]

Here's my first part off the table using the new scribe. It's the panel board to mount the regulators and solenoids. This is the second version I have made. The first had text cut through the plate and I didn't care for that, so this came out much nicer and is exactly what I wanted.






Video - I apologize for the shaky start. I had to mess around with the computer for a second, but it shows the process of making this mounting plate. All of my holes were in the perfect location and just required drilling out. In addition I drilled a few more holes after the fact as I fitted the piping and wiring, something I didn't really want to account for on the drawing.

http://www.youtube.com/profile?user=.../0/92MiZrY44tI

[jjellingson]

Keep up the great work and posting. I have found your thread very informative. Sadly, I have been slammed with work and have not had time to work on my project. I like your latest addition. Will you be offering these for sale in the future? I would be interested. Did you run into problems with your drives running out of step? Or did you just update before hand?

[unixadm]

Keep up the great work and posting. I have found your thread very informative. Sadly, I have been slammed with work and have not had time to work on my project. I like your latest addition. Will you be offering these for sale in the future? I would be interested. Did you run into problems with your drives running out of step? Or did you just update before hand?

Thanks. I have plans to offer a scribe axis in the future as an add-on for plasma tables and I'm going to be prototyping a plasma table or plasma table plans going forward as well. I'm also willing to help anyone out if you wish to build your own, but the axis isn't cheap. On this prototype I used a used Bosch hardened ball bearing rail that is extremely stout. By using Delrin I increased the costs, but it was easier to machine and quicker to prototype with than using aluminum. I actually like working with Delrin, though it's not exactly cheap either. I believe a slightly smaller rail and a 1-1/16" cylinder would be the ideal combination. I'm currently running a 1-1/4" cylinder and it can easily lift the gantry off the table if I wanted it to.

[magma-joe]

unixadm,

Nice table build. I like the scribe attachement you have built. I incorporated a scribe unit on my table as well. They are very useful. I use mine to engrave as well as "punch mark" precise locations for punching holes with the ironworker.

It appears by the pics that your scribe is always under pressure from the air cylinder. Not sure but, it seems like this method would require alot of adjusting air pressures to keep the scribe from digging into the material, stalling, or lifing the gantry? Some machines use a floating scribe which is the method used on my table. It has about 1" of floating travel which allows it to scribe a variety of uneven surfaces. Since there is no pressure being applied to the scribe tip by the air cylinder, the only 2 adjustments to be concerned with are the travel speed and "intensity" of the scribe.

Using the floating method does require a way to adjust the height of the slide assembly as you always need to be in the 1" floating range distance from the material you are marking. Going from a piece of 1/4" plate to a 3" x 3" square tube would of course require a 3" rise for the slide assembly. Something to consider. It does work well on my machine.



Keep up the good work!

Love the pics and vids.


Magma-joe

[unixadm]

It appears by the pics that your scribe is always under pressure from the air cylinder. Not sure but, it seems like this method would require alot of adjusting air pressures to keep the scribe from digging into the material, stalling, or lifing the gantry? Some machines use a floating scribe which is the method used on my table. It has about 1" of floating travel which allows it to scribe a variety of uneven surfaces. Since there is no pressure being applied to the scribe tip by the air cylinder, the only 2 adjustments to be concerned with are the travel speed and "intensity" of the scribe.

Using the floating method does require a way to adjust the height of the slide assembly as you always need to be in the 1" floating range distance from the material you are marking. Going from a piece of 1/4" plate to a 3" x 3" square tube would of course require a 3" rise for the slide assembly. Something to consider. It does work well on my machine.

Your observations are correct, but the scribe is only under air pressure during a call for a particular scribe segment. Since you're always applying the same pressure to the cylinder, whether it stops at 1.5" stroke or 2.5" stroke, the pressure against the cup in the cylinder is going to be roughly the same, meaning the pressure against the scriber tip and the work is going to be roughly the same. I have scribed from 16GA to a little PN on a 2x2 tube with the same results. You do need to be careful with the pressure, however my SMC regulators are so fine in the adjustments that I can dial that cylinder in to where it just pushes the scribe, to giving is 10lbs of downward force to get a good bite for deeper engraving. I never really considered having the scriber float because there were times I knew I wanted to apply some pressure. After some adjustments, my air cylinder is only running at around 22 PSI, and that's not even close to the pressure required to lift the gantry at any extension of it's stroke. It's just enough where there's resistance against retraction, but the cylinder can easily be pushed upwards with one finger. You would be surprised with the proper air regulation just how easily you can dial in these cylinders. A smaller cylinder would be even easier as the pressures would increase and give you a wider band to work with. On mine, I have around a 5 PSI working range.

I'm not sure I would want to scribe uneven material. The scribe can handle uneven sheet because like I said the axis rides up and down and can easily be pushed upwards due the low pressures being used. I could easily get a 3x3 tube under the scribe if I simply cut off the lower portion of 3/4" Delrin which is unused below the present scribe mount, and machine another location above the current scribe mount to move the shaft collar up another inch or so. I'd rather adjust the scribe mount than adjusting the rail on the gantry. I also plan to fabricate a small flip stop that will keep the guide block in a lower position when I'm scribing, since it will shorten the throw required to reach the material. Then when I'm done, I just flip the stop and the block will retract up the extra 1.75 inches or so. This will require adjustments to the M08 delay to prevent digging into the work.

If I wanted to add a floating scribe, it would be easy to do on the 2x3/4" thick Delrin scribe mount I have right now. I'd just add a small linear rail, and attach the scribe to the block. For now though, this is just an added expense that I'm having a hard time seeing a need for because I can scribe on any material I've put on the table. Perhaps if I wanted to scribe diamond plate or something, but for what I'm planning on the table what I designed is working well, but then again what I have may work for that since I'm operating under such minimal pressures. I appreciate the feedback and in the future should I need that, I'll adapt a small slide and post an update. In all honesty I could have a fixed and linear slide for the scribe, and you could select between either depending on the job. The issue with slides are finding one that does not have slop in it, though allows easy movement. Any slop will translate into large errors in the work. When I went from the knockoff scribe that had extra play in it's nose between the actual carbide tip to the CP-9361 which has better tolerances in the nose, the quality of the engraving increased by a large margin.

[foam27]

Nice job man

Is the gear rack replaceable?

How is it attached to the aluminum?

[unixadm]

Nice job man

Is the gear rack replaceable?

How is it attached to the aluminum?

Yes it's replaceable. It's attached with VHB tape and isn't going anywhere.

[unixadm]

Here another video of my scribe axis in action. I am cutting a small bracket which I will bend 90 degrees on my brake after it's cut. I'm using it to mount my regulator/filter/desiccant filter on my 60 gallon compressor. This bracket will slip underneath one side of the motor and be held down with the motors bolts, and then I'll drill two holes to mount the actual pneumatic assembly. It came out perfect, now I'm just watching the paint dry.

[nomedia="http://www.youtube.com/watch?v=FexVafKl5JU"]YouTube- CNC Plasma Cutting and Engraving[/nomedia]