scribe troubles

[f_armer]

I just set up a scribe on my machine. A bulltear 4x8. I bought an SMC 16x100mm air slide, Sioux 5980 engraver, and 3way solenoid, regulator/filter and oiler for scribe circuit. For the slide circut I have a 5way solenoid, regulator/filter, and a 4-57psi regulator mounted next to the slide to control down movement air pressure.
it all seems to work perfectly, except im having trouble with down pressure setting, if I run more than about 3 or 4 psi the scribe will stall out. By running that low of down force psi, the slide goes down rather slowly, I have a 2 sec delay set, to give it time to extend. Its a bit inconsistent in its extending times also, I think because of the low pressure.
the Sioux engraver has a very sharp tip on it and it seems to bury itself into the metal quickly then when the gantry moves, it kinda has to yank it out of the hole sideways and it makes a skip.
im wondering if my issues are with the engraver. Is the cp9361 better suited? If you put too much downforce on them do they stall out? Ill post some pics of the setup

[f_armer]

I'll continue in a new post... I still have to organize my solenoid regulator setup obviously.
Im running just below 100 psi to the scribe, and 70psi to the slide(retract)and between 2-4psi extend. (Its hard to tell on the gauge, its basically on 0psi)
I've got my offset dialed in now.
Here is my first two tests. Ya I started out a bit elaborate for my first tests.

[blackandtan]

I have the CP9361 and it works good most of the time. For some reason on the first mark it will not always start scribing unless I manually turn it on over a scrap piece for a second. I guess it just needs to be warmed up . I think I am running about 8-10 pounds of down pressure and does not seem to cause any problems. I would guess that the lack of down pressure is what is making it move down too slow. I know when I turned my pressure down to do aluminum it moved slow and inconsistent so I had to put a long delay on it, but then it had dimples on the spots that it decided to move normal. I would like to see the JD label when finished.

[tnbndr]

Not sure it helps but mine is set at about 20 for down pressure and 90 for scribe. It hammers down to the metal very quickly and does not drag when scribing. Mine seems to have a rounder point though it is not sharp, could be from a good amount of scribing.
I believe it is the CP9361 scribe, it came with my LDR table.

[dhelfter]

Dennis,
Yes yours is a cp9361. The tip we get with the scribe is rounded. We had trouble with the tips that were extremely pointed.

f_armer,
15-20 psi down pressure seems to work well, but all depends on what diameter cylinder you are using. 20psi on a 3/4" bore will develop 9lbs of force, but 20psi on a 1" bore will develop 16lbs force. Down force is what is important, you just use psi to get it! We have found 7-10 lbs of down force works well for most applications. Again your ideal pressure will depend on bore size of cylinder.
We use to mount the valves on the side of machine, and found the slide would go down slowly, and inconsistent. The entire air line has to be filled with air before any motion. We mount the valves right next to the cylinder now so less than 12" of line needs to be pressurized when we turn valve on.

Thanks
Dan
LDR

[f_armer]

Dennis,
Yes yours is a cp9361. The tip we get with the scribe is rounded. We had trouble with the tips that were extremely pointed.

f_armer,
15-20 psi down pressure seems to work well, but all depends on what diameter cylinder you are using. 20psi on a 3/4" bore will develop 9lbs of force, but 20psi on a 1" bore will develop 16lbs force. Down force is what is important, you just use psi to get it! We have found 7-10 lbs of down force works well for most applications. Again your ideal pressure will depend on bore size of cylinder.
We use to mount the valves on the side of machine, and found the slide would go down slowly, and inconsistent. The entire air line has to be filled with air before any motion. We mount the valves right next to the cylinder now so less than 12" of line needs to be pressurized when we turn valve on.

Thanks
Dan
LDR

My slide is a 16mm x 100mm I'm thinking 16mm is the bore of the air cylinder so that would be about .62"
I mounted my down pressure regulator close to the slide thinking that would take care of any delay. But now that you mention it, having the solenoid closer would react more consistently, right?
I kinda think my scribe tip being so pointed is my main problem, it's like a needle. I can see a blunter tip being better.
Thanks for your suggestions.

[acourtjester]

I have a different setup the down cylinder is separate from the slide and the solenoid is about 4' from the cylinder. And it reacts very fast it has an internal spring return so I don't need return air to make it go up. Running about 5 PSI for the cylinder and 90 on the scribe.

[dhelfter]

acourtjester,
That is similar to our setup. We also have a separate cylinder and slide. And also use a single acting spring return cylinder. Sometimes the simplest setups are the most consistent.

f_armer
The regulator can be mounted on the machine base. The valve being closer to the cylinder is what will make motion happen faster. This setup also allows you to adjust air pressure, while scribing (during tests) without "chasing" the gantry.

Thanks
Dan
LDR

[_Ogre]

i only run the one 5 port 2 way valve, similar to yours
but i run full pressure into the valve
i have flow control valves on both up and down to control up/down speed
after the down flow control valve i have the pressure regulator, i run approx 5psi down pressure

first: remove the exhaust silencers and run, sometimes they come plugged up
2nd: move the pressure regulator to the other side of the solenoid valve, the ports in those valves are very small and your running 3-4 psi thru the small port, choking the flow of 3-4 psi. if you do this without a flow control valve in the return/up line it will hammer up, so have the line pinched to keep it from hammering up.
3rd: if suggestion #2 works install flow control valves in both up/down lines

with air you control the flow coming out of the control valve into the cylinder (reverse of hydraulics)
i deal with a guy called mettle air on ebay; good prices, selection and delivery
the valves come in a variety of sizes



this is my setup with same basic valve, flow control and pressure regulator after both going into the air slide
i do have a .5 second delay in the tool setup



and a youtube video showing my air slide speed with 5 psi down pressure
this video show the electric scribe https://www.youtube.com/watch?v=5O8rjZ_3c_4

[f_armer]

i only run the one 5 port 2 way valve, similar to yours
but i run full pressure into the valve
i have flow control valves on both up and down to control up/down speed
after the down flow control valve i have the pressure regulator, i run approx 5psi down pressure

first: remove the exhaust silencers and run, sometimes they come plugged up
2nd: move the pressure regulator to the other side of the solenoid valve, the ports in those valves are very small and your running 3-4 psi thru the small port, choking the flow of 3-4 psi. if you do this without a flow control valve in the return/up line it will hammer up, so have the line pinched to keep it from hammering up.
3rd: if suggestion #2 works install flow control valves in both up/down lines

with air you control the flow coming out of the control valve into the cylinder (reverse of hydraulics)
i deal with a guy called mettle air on ebay; good prices, selection and delivery
the valves come in a variety of sizes

I tried removing the silencers, it made no difference.
I moved the solenoid valve to the gantry, to see if was affecting it, it seemed better, but still not fast without turning the pressure up.
I have not tried moving the regulator to the other side of the solenoid, I have a regulator on the front side of the valve already, I wonder if I should just remove the regulator on the "down" side of the solenoid. I also already have flow control valves on the slide itself. Do you think that will work?
I going to attatch a schematic of how it is plumbed now.

[f_armer]

So I removed the low pressure regulator next to the slide, and tried adjusting the flow controls on the slide, it does seem to be more consistent, and I can make it move quicker. So I moved the solenoid back down under the table also, and it seems about the same. My 'up' movement isnt quite as quick, but thats probably okay. In the mean time I accidently touched the 110v output wires together(Iforgot to unplug the cord from the bladerunner box as I was unhooking the solenoid )
So I cant test it as of right now because it shorted something out and I have no movement

[f_armer]

Thought I'd update, when I shorted the wires from the control box, it never hurt anything in the box, but it took out the parallel port in my computer, so, easy fix. I just swapped out the computer for another.
After doing a bunch of experimenting with the flow control valves and moving regulators, and solenoids from down beside the table to the gantry, and back, I've come to the conclusion the scribe isn't suited very well for cnc work.
If I have just a few pounds of downforce the scribe will stall out (I can easily raise it with my finger while its scribing), and it seems to dig and get hooked in the metal at times. If I back the air pressure off anymore it takes forever to lower it down, then it just kinda floats on top the metal.
It works, but isn't reliable.
I'm going to order a CP9361 and see if that eliminates my troubles.
Is there a special round nose tip, or is the tip that comes with the 9361 already the one to use?

[_Ogre]

you can buy electric scribes at home depot all day for $17,
knowing that i'd be hard pressed to spend $350 on an air scribe
i had a cheap air scribe for a bit; sometimes it'd start, sometimes not
i went back to the electric scribe

[RGR]

Ogre. Do you have any pictures of the results the electric scribe can produce. I've never seen on used before. I'm curios.

[_Ogre]

if you watch this video... turn down the volume
https://www.youtube.com/watch?v=5O8rjZ_3c_4

i was scribing an angle finder for tube, pay no attention to the plasma cuts
i don't do any artsy work, mostly scribed bend lines