Field of dreams 4' x 8' table build

[machinedude]

Well i'm new here and found this site from another member here on another forum. i never gave plasma much thought as direction i was headed in but somehow here i am i'm new to the process but do have some Laser background and they are the same in a lot of ways so diving in head first was not an issue. programming is not an issue since i am a machinist to begin with by trade so everything on that end is not to much of a concern either. i started this build 3 weeks ago but spent a few week doing some home work on the machine needs here on this site. this build is probably not normal compared to what most are doing but should work just as well.

[acourtjester]

Very nice, looks like a truck could run over the table and the Z would still work

[machinedude]

i did some crude testing on the forces needed for the floating head and break away and the floating head takes about 10 lbs or less since the scale only starts to register at 10 lbs and the break away magnets give in at 25 lbs of force, so i was happy with that for a starting point. tip ups happen a lot so looking over that aspect is foolish so it was worth some time working in that area,

i want as much precision as possible because it all stacks up in the end to affect cut quality. i also know that plasma is a dirty process and keeping the crud off the expensive parts is a must as well. i have plans to cover things up with bellow covers. i will make those myself the cost is crazy on buying them. so i was playing around with ballistic nylon and liked what i could do with it.

[machinedude]

little bit of progress this week but still have a bunch of work left on the gantry. i put a little extra effort in the uprights and spent a while making my pieces flat and square and then machined bosses for the extrusion so when it got put together the machine is already squared. i spent a lot of extra time working things in to +/- .001 on pretty much every thing on this build. takes a lot of extra time in the begging but saves a lot of head aches when your start putting things together later.

the plan is to drive this gantry from the bottom center and have a water try over top of everything to keep all the plasma crud off the drive screw. i'm not doing a welded tube table either after shopping around and pricing material shipping costs on long pieces kills any hopes of doing this in my budget so i will hit the local supply house and probably do the main framework of the table in 3/4 x 1 1/2 H.R. because it's cheap compared to the other options and i need some extra strength tubing and extrusion can't do. no sense spending extra on C.R. because i would have to machine it to get it accurate enough for how i am putting this thing together. a ton of socket head cap screws but gives me control over keeping things square

[machinedude]

little bit of an up date on this project. was a slow week due to my lathe giving me a hard time.

will be running a 4:1 ratio on my X and Y axis to get me into a better place on the torque speed curve of the motors i have in this build.

[weldguy]

Very nice build, love all the machined parts! Going to follow your build and wish you all the best with it

[machinedude]

thanks weld guy i guess if i was a welder i would do things differently but having the machines to do things this way and being a machinist by trade took me this way on this build. i see how quick some of these builds can go and that part would be nice but my machinist O.C.D. kicks in and this is where i end up hopefully i have a commercial quality machine for a fraction of the price in the end.

one nice thing about a bolt together design done well is if i want to move this table to a new location at any point, tearing it down and setting back up will be easy enough.

[ben de lappe]

Looks solid. Like a tank. USAF combined their welding and machining careers just as I went in and I feel tremendously fortunate to have partaken in that training, helped out in so many ways later. Out in the real world you don't see that too often so after service found myself mainly working in welding/fab shop atmosphere until I went into business for myself so it too was mainly welding/fab. While we all do things differently it doesn't mean it wont work remarkably well. I'm sure you're OCD side will ensure that, no matter your self admitted lack of welding skill.

Look forward to your progress.

[robertspark]

nice precision build

[machinedude]

i think it was Hypertherm's web site i seen an article about precision and cut quality. i do have some laser experience and precision is there to some extent with that process. so even though this is not in the same caliber of precision just for my personal experiences i would like to see how close it could get if a honest effort was put in? i have a curious mind with this stuff no doubt

i figured depending on which way the winds of fate blow it would not hurt to have a table solid enough to toss a router head on too so that explains some of the weight. but even though it is heavy for plasma i still have had the weight on my mind from the start. so it's about as light as i can get it and solid enough to cover the bases i'm looking to cover so to speak. plus the motors i have on this thing are huge and they will move every thing just fine even if it weighed twice as much as it does now. the way it is geared the extra speed i gained on the screw gets too about a 200 oz/in at the lowest drop on the motor side.it's gear the exact reverse of a rack drive is done because i have the resolution on the screw the stepper just lacks the speed to hit the feed rates i would like to get close to.

i had the drives motors and power supply from something i started a long time ago but never really was happy with so it sat in the corner collecting dust with new hardly used electrical stuff. if i had to buy this stuff again it would be $1,100

so this is how this thing came to be found i new home for this stuff and have it mounted to something i happy with so far.

i have some leveling casters i plan on going with so i can move the table around if i have to and should have some cable drag chain in the next few days. i have to see if the steel distributor has more material in tomorrow i cleaned them out friday but have nowhere near what i need yet. this is week six and i'm still sitting on the floor

[machinedude]

tables are a treat to make getting HR flat straight before you can start working on attaching things together is a real treat to say the least. 10 foot long sides and almost 5 foot cross sections were not meant to go on a Bridgeport mill i started off with 140 feet of material and will still need at least another 40 feet before i have the skeleton frame work of the basic table. now that i have the sections square where they need to be things are moving a little faster but this is still slow moving. I've seen a few build logs where where people dread drilling and tapping the mounting holes for the linear rails and i agree those are not much fun. the 2800 mm rails i used have 47 mounting holes each and took 2.5 hours each just to drill and tap alone. taking a guess i think about 10 to 12 hours each it has taken me to make just those two sections when they are complete.tables are not hard parts to make the big thing here is the size issues with limited equipment to work with. so if you plan on going this route for a build hold on because it's a wild ride along the way.

[machinedude]

little more progress but still have a ton to do on the table still. hopefully by the end of the week i will at least get the gantry off the floor and test how things move around with no power for now. i'm curious to see how close i was a able to keep things? once i can get an indicator on the gantry to see how flat things are assembled i will have a better idea of precision of the table itself.

i still have plans to add some cross section across the bottom and add a set of casters in the middle of the table but ran out of material for the extra stuff i plan on adding to the basic frame. so far everything went together really well and the doweled frame works well in that respect. i'm sure i will appreciate the design when moving the machine later

[machinedude]

did manage to get the gantry on the frame. the frame is square as planned and the gantry moves up and down the table really well but i ran into some issues that need more attention so i have set backs as a result. i need more rigidity along the 10 foot run of frame work. would be an easy fix except for the drive screw running from the middle makes the issue more involved. getting the gantry on has let me know what i can do and not do to fix things so that's a start at least. i can shorten my span by 14" and that will help a lot but it's not enough so the plan is to turn the sections of frame that have the rails mounted to them into I beams basically.

It's more work and more material but hopefully a fix for the problem. while i'm at it i will be shortening the legs on the table seeing it together seems to high up so i will fix that too while i am at it. no sense in rushing things and having and end result i'm not happy with but it would have been nice to get things buttoned up before winter gets here. temps dropped at least 20 degrees this week so i'm running out of warmer weather

[machinedude]

little more progress but still moving in the right direction so that's a plus at least. i still need to address the top 6" of the table but below that i am pretty happy with so far. not the best pictures since the sun was to bright but good enough to give an idea of where i am at so far.

i did decide to add 4 more legs on this table rather than just 2 more in the middle. i had the casters so i just used them all on this to keep things rigid. once i get the slats of the top reworked i can start to address the support in that area. as of now the plan is to sandwich those between some 3/4 x 3 HR flats to lock everything together. i still plan to shorten my span as much as i can but i am holding off until i figure out exactly where the ball screw is going to fall so i can get that support in the right place without getting in the way of things.

i ended up taking about 6" off the height of the table by shortening the legs i had made so i feel better about the overall height of the table now too.

[machinedude]

managed to get some more steel on the table and just the layer across the top made a huge difference. i still plan on doing the same on the underside of the table top and once i get that put on i should be back on track. it's solid now but i want it rock solid. well over 100 tapped holes and over 200 drilled and counter bored holes by the time i finish adding steel to the top. moving forward so that's progress

[machinedude]

you see a lot of people add an air drill on the side to use with plasma but i had a mini mill spindle sitting around so figured i would see if i could find a use for it other than sitting around collecting dust. a lot of frames for plasma tables are light weight and not suited for this kind of application but i feel mine is a little more robust than some others. i had always planned on a multi function table for different processes and this was one of my idea's to try out. i know for sure it will cut aluminum since i had this spindle on a t slot frame in the past. the previous attempt at this had mixed results since the t slot frame was very light. this frame is not light so should produce something that makes me giggle just a little bit

this is a pretty small milling milling spindle so it won't break any records in material remove rates but if it does 1/8 or so step over at at least 60 IMP in Aluminum i would be happy with it. i had it doing a 1/16 step over at around 28 IMP in the past but feel the spindle can do more on a decent frame.

plus air drills can't do things like thread milling and 3D tool paths and the table should be able to hold +/- .005 i think since i spent a lot of time doing thing accurately. time will tell but i think it's possible with what i have so far.

mini mill spindle 2.jpg

mini mill spindle 1.jpg

mini mill spindle.jpg

[machinedude]

this part of the build is off topic for plasma but since it's interesting why not cover it too.

i would bet since plasma machines tend to be light and fast by nature. some of the folks that have add drilling on to there z axis in some way shape or form. when you get into secondary operations you now introduce forces that plasma generally does not see. as a result you see things like deflection show up. when you get into milling operations you introduces forces from all directions. so you start to deal with pushing and pulling forces along the side of the cutter on top of the forces pushing up on the gantry beam.

after mounting this small milling head and making basically a small light duty gantry mill i had this problem. on top of this the T slot extrusion is prone to resonate so that kind of vibration is not desired for your frame. this is why cast iron is used traditionally in machine beds since it can dampen vibrations.

so then you have the age old question to a DYI builder how to i deal with this stuff. some folks do home foundry work in the back yard i myself would prefer not to melt my face off or get burnt badly in the process of a build , so something a bit safer and just a good of a solution is a epoxy granite which i think does better at vibration dampening anyways.

so basically what i did was to fill the parts of the gantry cross beam not used and two large voids down the center of the t slot extrusion. what i started with was a gantry that flexed .030 to .040 inches and got that down to about .005 inched by adding around 10lbs to the over weight of the gantry. this is not a concern for me since the motors i am using are pretty big to begin with.

so i just figured i would share this part with everyone anyways. this part needs worked out before i can get back to the plasma end of things.

[cuttinparts]

Looks great man and I am enjoying following this

[SegoMan DeSigns]

this part of the build is off topic for plasma but since it's interesting why not cover it too.

i would bet since plasma machines tend to be light and fast by nature. some of the folks that have add drilling on to there z axis in some way shape or form. when you get into secondary operations you now introduce forces that plasma generally does not see. as a result you see things like deflection show up. when you get into milling operations you introduces forces from all directions. so you start to deal with pushing and pulling forces along the side of the cutter on top of the forces pushing up on the gantry beam.

after mounting this small milling head and making basically a small light duty gantry mill i had this problem. on top of this the T slot extrusion is prone to resonate so that kind of vibration is not desired for your frame. this is why cast iron is used traditionally in machine beds since it can dampen vibrations.

so then you have the age old question to a DYI builder how to i deal with this stuff. some folks do home foundry work in the back yard i myself would prefer not to melt my face off or get burnt badly in the process of a build , so something a bit safer and just a good of a solution is a epoxy granite which i think does better at vibration dampening anyways.

so basically what i did was to fill the parts of the gantry cross beam not used and two large voids down the center of the t slot extrusion. what i started with was a gantry that flexed .030 to .040 inches and got that down to about .005 inched by adding around 10lbs to the over weight of the gantry. this is not a concern for me since the motors i am using are pretty big to begin with.

so i just figured i would share this part with everyone anyways. this part needs worked out before i can get back to the plasma end of things.

There is some merit to what you say however there is industrial high definition / drill / tap units out there with 1000lb gantries that do amazing cuts. I am one of those with an air drill in the design of the unit, I have a 4"x6"x1/8" gantry 9+' long to offset any deflection. The steel tubing has the same weight per/ft as the 8020 profile of similar dimensions and costs about 75% less with ext. length delivery fees. The air drill will be removable with 4 bolts and some quick couplers on the air lines, the trouble with plasma is you can not produce a clean tapable hole with out secondary processes.

By having an air drill it will allow this process to take place on the first pass, you can even add a tapping head to the air drill. These process's along with a scribe for marking bends or naming parts will compete with water jet tables that run at 3x the cost. Most of your thicker metals are cut in the less than 50ipm mode so speed is not always needed. It all boils down to what your intended use for the table is.

[machinedude]

steel is by far a better choice from a deflection stand point no doubt. but in order to make it accurate it needs to have extra material for a mounting point for all the precision stuff welded to it so they can be machined after the fact. this way of building is widely practiced. steel tubing can also be filled with an epoxy granite material for extra stiffness and vibration dampening so this is not just something for Aluminum Extrusion. here is were the extrusion surpasses steel tubing. the end holes can be tapped for mounting point the material is pretty flat and square from the beginning. the T slots give you extra mounting point for ease of use. and to get into the accuracy of the extrusion. i checked my z axis and cross beam off the machine on the Bridgeport mill put the extrusion in the vise and a indicator on the mounting plate for the Z axis. ran the Z axis up and down the rails over the length of the mounting plate which is 6.5 inches. my Z axis ran out .0005 of a inch over 6.5 inches. so that there gives you an idea of where the differences are. with steel even if you machine it after welding you could very well need some kind of stress relief before machining too it get things accurate.

the way i built the entire machine it just bolts together and works as it should. i have not had to indicate a single rail in because i have everything doweled in place or a boss milled into the mounting points to locate the rails. i went through a lot of trouble to make it go together so rails are square to the other axis's and parallel to each other along with being on the same plane to maintain the flatness across the table. easier said than done on a frame 5' wide and 10' long. so once i get things under power the table top will get a skim cut to make it perfectly flat.

the plan at this point is to mount a 1" thick Aluminum T slot table top and most likely fill the the steel frame top with epoxy granite under the T slot top. when plasma comes into play a removable water trey that sits on top of every thing. i keep plugging away a little at a time when money permits. so this is not going to be a quick build by any means. it's already being going on since last July.

well if nothing else what i do is entertaining at least so that makes it all worth it regardless of how it's made

[machinedude]

started on the ball screw drive for the 8' axis and once the end was fixed i was able to drive the gantry up and down the table with a cordless drill with the clutch set on the lowest setting so you can basically stop it with your hand with no trouble. everything works really well. not to bad for a gantry that weighs around 230lbs.

[SegoMan DeSigns]

Looking good!

I agree with the bolt together concept as welding tends to warp things. When I processed my parts I had the drill press next to the tapping machine, I could drill and tap a 3/8" hole in a little over 2 minutes.

[machinedude]

did some digging on my cordless drill in high range and it does 2000 rpm so that puts me at 400 IMP and it was running pretty smooth at that speed so i feel i can get more out of it without to much trouble. i was concerned with whip but it looks good at that speed so i know i'm at least good up to there. takes no effort to move things with 5mm lead ball screw so the acceleration should be really good and i am probably more into having the machine accelerate quickly than rapids for both milling and Plasma.

one thing with milling you can cut threads with the milling so if you have a large set for threads you have that option as well. i have no desire to hand tap big threads to much work

[machinedude]

got the drive sorted out for the 8' axis but need to make another motor mount since i borrowed the one off the gantry. maybe i can get another made tomorrow before the weekend is over for me? getting closer at least

[machinedude]

one other thing about the the T slot 80/20 has been around for a long time but i found another supplier that is compatible with 80/20 and a little cheaper. the selection is not as big but the quality is still there and the hardware and machining services are much cheaper than 80/20.

check out www.Tnutz.com if your into the extrusion it's not bad stuff and they were quick and professional with my order.