I have a pile of parts i need to cut, (48) each of 4 parts all from 1/4" steel plate. they all need to be identical within reason. my question is , for “precision” parts is it best to cut each part individually or as a group? by individually i mean, step through each feature of one part then move to the next. by a group i mean pop all the holes for the entire sheet then cut all the outside cuts. ive already nested everything in autocad, and it would be really easy to just import the whole sheet into sheetcam vs. placing each part individually.
I’m worried about the plate shifting as it heats and cools thus throwing off the round hole locations or the hex holes in relation to the parts they are in.
I’m 98% sure i know the answer, i just need a little affirmation before I scrap a few hundred dollars in plate.
SheetCAM has a “Thermal” feature to limit the heating of the plate. Have you activated that feature? I don’t have SheetCAM so I don’t know how to do it.
I would also make sure the water bed is very full to the point of licking on the bottom of the plate.
Many times I will clamp the plate down if there is concern of movement. If that plate gets too hot, there is not enough clamp pressure to stop the movement. I have not attempted anything like this. David does a lot of thick parts and uses SheetCAM. Perhaps he will weigh-in on this topic. (@ds690).
Odd. I was cutting 2 parts yesterday, a 6 1/2 x 18 and a 7 1/4 x 18, each with about 125 internal features. Created a DXF with both parts and imported into Sheetcam. Selected auto path with “Limit thermal Distortion” and a spacing of 4 in. The created path jumped from one part to the other multiple times. (Probably to meet the 4 in rule.)
That is one thing that the OP (Bill) wanted to limit for fear of less accuracy with the parts. So maybe the Thermal feature (even if it were available) would not be a good solution???
firecontrol feature “patterning” is pretty handy for multiple of the same parts. You create one cutpath per part and can cut a row at a time if you wanted.
So I am trying to see this straight in my head. If the sheet were to move a small amount would this effect the parts them selves much or more the placement of how the parts cut on the sheet?
I guess it would depend on how accurate the parts need to be, but to me it seems like maybe the error would be more in the nest then the part it self? ( does this make sense?)
I guess it depends on how much and when it moved. I would have never thought of clamping down 1/4" material seem to heavy to move.
You could always slow down your rapids to help with heat or pause part way through the cutting.
Your are corect. These parts are not critical if so I would sacrifice more material. The object is to get as many out of a sheet as possible.
Another note these parts only have 3 pierces I had set to something like 6 or 7 inches between cuts never worked but it does on artsy stuff and great. Other nests I do on 3/16 it will cut parts out individually. Just like it only works within a part.
There is actually a thread where all this was discussed in the project thread .
I honestly believe this is more stress relief in the material being released than a thermal issue. Even 1/4 plate comes in a coil
Ok now I get it I thought you were saying 3 total. I am having a hard time following along today.
I better get off here and go do something constructive!
I take it the skeleton lifting up is behind the cuts? So say it cuts a row and moves to the next, then it starts to lift?
That is right that plate is clamped on the right hand side . I am not sure if sheet cam dismissed the thermal distortion because it is such a small part. It works for me any way so.
I honestly believe this is more stress relief in the material being released than a thermal issue. Even 1/4 plate comes in a coil
the bowing of the sheet is another concern i have. i may have to max out my travel height. i have had the torch catch and drag a part before when doing a rapid move. if you aren’t standing there watching the hole time it can get ugly.
i’ve got a few things i need to do to the table before i attempt this project. need to check the torch alignment. i made my torch mount before i had a milling machine so it may be a little out of square.
hot rolled sheet or bar has a lot of stress in it. i machined a part out of a piece of 1" plate for a friend. i milled it down to about 3/4" then cut a dovetail in it. every time i took a pass on it with the shell mill and flipped it over it would banana by 3 or 4 thou.
managed to get all the parts cut without too many setbacks, kept getting loss of voltage errors and had to restart 5 or 6 times on each sheet. probably should check all the connections on the LS control box, and update the software and firmware. i have the “if it aint broke” mentality and up till now it was working fine.
I probably should have tested my dimensions before cutting 96 parts with hex holes in them… had to grind 30 thou off each flat of the shafts to get them to clear the taper of the holes. didn’t think a hex hole would have that bad of taper to it (3.43°). the outside edges were really close to square. thought only round holes tapered.
does anyone have a link to a good tapered reamer that will last reaming out plasma’d holes? I have several hundred 3/8" holes that need a little love so i can assemble this overly complicated boat anchor.
RE - reamer. Plasma leaves a hard crunchy candy shell in the neighborhood of 63 rockwell. Hell on HSS cutters. Carbide is your goal, and they don’t like interrupted cuts.
Buy a few .375 carbide end mills (maybe ball end), chuck them up in the drill press on max speed - as fast it will go, and go to it…Unless you have a mill and the proper holders.
a friend of mine is a scrapper when hes not at his day job. he’s going to put wire and other things through it to separate the metals from the garbage. i tried to tell him i could get one pre-made with tool steel blades from china for less $$ than i could make it. but he was paranoid about sending close to a grand to china… i cant really blame him. fun part is going to figure out how to power it. i’m thinking its going to get a predator 212cc gas engine. doubt he has power in his rental to run a 5+HP electric motor.
i was trying to avoid using the mill, i suppose i can make a jig to hold the pieces.
i’ve tried using carbide endmills in the drill press, its really hard on them both. if i have an opportunity to chip a carbide tool it happens, every time.
