2012/6/28 Yishin Li <[email protected]>: > > We were using Mesa's 7i34 as the pulse/encoder interface to servo drivers. > It was okay in one workshop with Hypertherm 45A plasma cutter. But, it > failed in another factory with 300A plasma cutter and large EMI noise > around that field. Our USB/FPGA link was full of CRC error messages, and we > couldn't understand why. We had all digital and analog I/O isolated. > Finally, we found the noise was coming from the pulse/encoder interface. > > We then developed AR02 in replace of 7i34, and it solves the EMI noise > problem in that factory. You may refer to http://en.araisrobo.com/linuxcnc for > the functional block of our control system.
Thank You! Do I understand correctly, that You are running both stepper and servo drives with step/dir signal and the difference for both is that servos do provide encoder feedback, while steppers do not? 2012/6/29 Tom Easterday <[email protected]>: > > There is also a fine steam vapor that fills the room if we are cutting > continuously. 10 minutes of cutting you won't see it, 30 minutes and it is > quite prevalent. Ultimately I would like to have a mist extractor hanging > over the table. Thanks! I was thinking about the water vapor to appear during continuous cutting, thanks for clarifying. > > ps: I have no experience with downdraft tables, and perhaps they are the > cat's meow, but I am skeptical that they could work as well as a water table. > The amount of force with which the dust is created seems like it would too > great to be carried away by a downdraft. There were several threads in cnczone I looked at, when searching for information regarding downdraft tables. And one guy from HyperTherm posted there their findings: watertable collects 95% of dust, if the water is right below the material. It collects 60% of the dust, if it is 10-15 mm below the material - it is crucial for planning the right power of downdraft. The thing with the fumes and dust is that vast majority of them are coming from the molten metal, removed by plasma. And it is under the material. Almost everything else is blown under material by the compressed air from torch. That is how water can collect 95% of fumes. The downdraft has bonus that it sucks the air , which enters the table from above, so it can collect also the dust and fumes above the material. Of course, it all depends on the power of the air sucking element, the size of table, the proportion of the surface, covered by material etc. So from the dust and fumes collection point, downdraft is better. Water is better for cooling the material and reducing deformations. Downdraft is better for easier usage, water is better for cheaper implementation. So I cannot really decide, how to do it best, as the plan is to actually build 2 machines - one for client (pure plasma with downdraft - that has already been agreed with customer) and the other one for my own use. And I want to use my machine not only for plasma also for routing/milling. Especially aluminum, so that I can make parts for similar machines in future. I have clear plan for the machine itself, but I am having trouble, how to design the table - for milling I need stiff surface (could be 8 mm steel plate with a grid of holes with thread to clamp material) and collection of the coolant (could be a pan under that plate), for plasma I will need bunch of slats with nothing beneath them, except for water and/or free space for downdraft. I do not want to have to 2 table surfaces to be removed and then placed on the table. Does anyone have something to suggest? I guess the best thing would be - use the water in watertable as the coolant for aluminum - water with rust-prevention could do. But then - how about the surface? I was thinking of clamping the material right on the slats, but they will not be very clean and smooth after they will have met plasma torch, so the level of the material surface will be "who-knows-what". And then I also did not like the idea of aluminum chips falling in the watertable, where it can meet the hot molten steel from the plasma cutting. I read about the hazards of plasma cutting of aluminum on watertable, so I do not want to be anywhere close to that - even not have aluminum chips in the water. But cleaning out table before plasma cutting does not sound nice - having the chips on a surface for easy collection would be much better. -- Viesturs If you can't fix it, you don't own it. http://www.ifixit.com/Manifesto ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
