Hello All,

I’ve had my CNC plasma table up and running for a couple of months now, and am finally getting around to doing a post on it. I’ve been reading through the “Zone” for a year or so and have found a great deal of useful information. This project would not have been possible without cnczone.com. This post is my attempt to give back a little to the “Zone”.

The machines working envelope is 61” by 61”. This was limited by the availability of linear rails on ebay and space constraints in my shop. I had a very hard time finding anything over 80” at a reasonable price. I looked into new rails, but the $3500 price tag was beyond my budget. I ended up with two 78” NSK20’s for the Y axis, one 65” THK35 for the X axis and one 28” IKO15 for the Z axis. The Z axis rail was cut in half to give me two 14 inch lengths.

The design is an open gantry (i.e.. the cutting/water table is separate from the drive/linear motion system). I like the fact that heavy sheets of steel placed on the table cannot deflect the linear motion components of the machine. I also thought it may be handy to roll the table out with a pallet jack, and allow me to cut stuff like 12 inch I-beam that would not fit between the gantry and table. The gantry is constructed from 3” square steel tube with a wall thickness of .125” and is anchored to the floor with height adjustable anchors. These anchors made leveling the machine a breeze…….. well maybe not a breeze. The legs of the gantry were braced with 45 degree braces due to this nasty little thing called “Inertia”.

The X axis and both sides of the Y axis are driven via rack and pinion. Each of the three use the same type of drive (all parts are identical). Basically I designed 1 drive and made 3 of them. Each drive pivots, at one end, on a ½” diameter precision shoulder bolt and is pulled toward the rack with a spring on the other end. These drives consist of a 270 oz stepper motor coupled to a 14 tooth XL timing belt pulley which drives a 60 tooth XL timing belt pulley which is coupled to a 14 tooth pinion gear. How’s that for a run-on sentence…. I used 16 pitch 14 ½ degree racks and pinions. The 4.29:1 drive ratio, coupled with the 14 tooth pinion gear, achieves .641” of travel for 1 revolution of the stepper motor. This ratio seemed like a nice compromise of speed and accuracy. With a 10 micro-step G201 Gecko drive and a 200 step/rev motor, one micro-step equates to .00032 inches of travel (200 X 10 X .0003205 = .641”). I’ve tested the machine’s rapid speed at up to 850 ipm. I suspect the machine could run faster with Mach3’s new increase in kernel speeds, but 850 ipm rapids scare me enough as it is. I’ve limited rapid speeds to 450 ipm. The acceleration values in Mach3 are set to 45 inches/sec/sec. I’ve run acceleration values as high as 150 inches/sec/sec, however the sudden jarring of acceleration and deceleration seemed a bit excessive. I was afraid of shearing the roll pins that I had used to attach the pinion gears to their drive shafts.

The Z axis motor is connected to a 14 tooth XL timing belt pulley which drives a 28 tooth XL timing belt pulley which is coupled to a 4 start, 8 pitch, ½” diameter lead screw. I used a multi-start thread in order to increase the distance traveled per revolution and thus increase travel speed. With this thread I get 1/2” of travel per revolution of the screw. Unfortunately this was a little too much, with my original 1:1 pulley to pulley ratio, and the weight of the Z axis would back drive the screw and the Z axis would slowly drift downward into the cutting table when power wasn’t applied to the Z axis stepper motor. The new 2:1 pulley to pulley ratio stopped this. With this setup I get .250” of travel per stepper motor revolution. I haven’t tested the Z axis for maximum speed. However, I've set it to 150 ipm, which seems to be more than adequate for what I’m doing.

If you’re thinking about adding a water table to your setup, I have 3 words of advice…. “Just do it!!!” You won’t regret it. Prior to adding the water table to my system, I would open every window and door, in my shop, and turn on the fans. I would still end up with a layer of black dust that settled on every surface perpendicular to gravity. This dust would not just settle close to the machine, but on every square inch of my 20’ X 40’ shop. Nasty stuff!!! With the addition of the water table the dust problem has been reduced by at least 95%. I don’t have to open doors and windows anymore when I’m cutting. I have three 8” ports in the walls that can be hooked up to a ventilation system, and have yet to use them. Plus, I get to enjoy an air conditioned shop, as opposed to the 100 degree outdoor temperatures we’re currently having in Kentucky. The water table’s construction is similar to that shown in a PDF file from Thermal Dynamics that I found on the net, which uses compressed air to raise and lower the water level. Water in an inner tank is displaced by compressed air and flows out and up into the area below the sheet that is to be cut. The top of the support slats are ½” below the top lip of the table. The slats are 2 ½” tall and are set into slots in 3 “hangers” which are welded to the top of the inner tank. The distance from the bottom of the slats to the top of the inner tank is 1”. Therefore if I’ve adjusted the water height to just touch the underside of a sheet, I have 3 ½” of water below the sheet. Personally I think a water level of ¼” below the sheet works the best. The green/amber color of the water is due to an additive called “Plasma Quench”, which is available from Koal Industries. Plasma Quench keeps steel from rusting and keeps the water from going rancid. Since the steel doesn’t rust I don’t get brown murky water. The cut particles of metal just sink to the bottom for later removal. The water stays a transparent green/amber color with no smell. Based on my limited time using it (about a month), Plasma quench seems like a very useful product.

I am using Gecko 201’s to control each of the stepper motors. The Gecko’s are powered by a 42 volt power supply. The power supply was built according to the data sheets and information available from geckodrive. The parts to build the power supply were purchased from digikey. Once again, if you’re thinking about using Geckodrives, “Just do it!!!” They are a little pricey, however it’s definitely a case of “You get what you pay for”. You will be absolutely amazed at the amount of power Geckodrives can impart into a motor that’s barely larger than the palm of your hand (using sufficient power supply voltage, of course).

I am using cnc4pc’s C1G parallel port interface card . I’m using the latest lockdown release of Mach3 (Go Art!!!! Keep up the good work!!!) As for generating code, I think the simplicity and speed of Sheetcam is extremely hard to beat.

I’m using the THC300 torch height controller, available from Campbell Designs. As my local Hypertherm rep put it, “A torch height controller in NOT an optional item when it comes to a CNC plasma table. It’s a necessity”. After using my table with and without a THC, I wholeheartedly agree. It’s just something that you’ve gotta have. Figure it into your budget. Your cut edge quality, and consumable life will show for it.

If you’ve gotten this far, thanks, and I hope you’ve found some useful information.

Pictures of my machine can be found in the link to my gallery below.

Jcar,

http://www.cnczone.com/gallery/showgallery.php/ppuser/38704/cat/500

Absolutely great "presentation" ... by far the best I've seen. Congrats - it looks great. At your convenience can you take some close shoots at the whole assembly servo - belt - pinion - rack ? That will be helpfull to continue with my project.

Hello All,

I’ve had my CNC plasma table up and running for a couple of months now, and am finally getting around to doing a post on it.
http://www.cnczone.com/gallery/showgallery.php/ppuser/38704/cat/500

Great description of your recently completed project. Thanks for sharing the information!

The photos show that you have done an excellent job of construction & will surely be an inspiration to others.

Fine job on the drive pivots to keep the pinions properly engaged in the racks.

Now that one hell of a nice table! You have got some very good ideas there, I'm going to have to barrow a few of them. Great idea on separate tank and gantry setup.

Your tank is huge, why so deep?

The additive that you added to the tank, was it in the form of an orange powder that turn it that color and what did it cost you? I think I know what it is and may have an alternative source.

Great job!:)

I give ya two thumbs up on that machine! Looks 100% in every aspect.
Although I have to say that I now have a craving for some green Jello.:D

Looks great! and it's sooo nice and clean! and Is that an Xbox conroller or something...?

plasma quench is great. had it in my tank now for 9 months no smell no bugs
just add more water for evporation. i just haven't checked the ph balance. i did my tank with similiar design to the same one and it works great. my table is 67 x 129
bear

It is an absolutely stunning machine, looks very professional!

Very Professional looking table!
I like the separate stock support table from the motion frame.
I tried searching for the pdf from thermaldynamics on the water table, but had no luck. Do you still have the link to that?
I really like your water table and being in the northeast, being able to not exhaust ~1000 cfm in the winter would be enjoyable!
Thank you for sharing your table.
Cutmore

very clean table good job(nuts)

Well DONE Mr. C!!!! You really did one heck of a job on that. :)

Thanks everyone, I appreciate the positive comments.

At your convenience can you take some close shoots at the whole assembly servo - belt - pinion - rack ?
Just above the pictures, in my initial post, you'll find a link to my gallery. There are several closeup shots of the drive system in there.

Your tank is huge, why so deep?
The tank is only half full of water, the rest is air inside the inner air tank. With this arangement I can release the air pressure and drop the water level below the bottom of my slat holders. In doing so, I can get parts out of the tank without having to dig around in a tank full of water.

The additive that you added to the tank, was it in the form of an orange powder that turn it that color and what did it cost you? I think I know what it is and may have an alternative source.

Plasma Quench comes in liquid form. I purchased a 5 gallon jug of concentrate for about $60. This is enough to treat 160 gallons of water. According to the MSDS sheets, Plasma Quench's active component is Sodium Nitrite. It's the same stuff that's used to preserve packaged meats. Yum!!!!

Is that an Xbox conroller or something...?
Yep......play a video game, cut some parts, play a video game, cut some parts.........sorry couldn't resist :) . Actually it's a Logitech USB game controller. I use it to jog and re-zero my axis' before running a part. It comes in very handy when I'm cutting on the side of the machine that's away from the keyboard.

I tried searching for the pdf from thermaldynamics on the water table, but had no luck. Do you still have the link to that?

It appears that the original link is dead. I do have a copy of the file, unfortunately it's larger than 500k and is too large to post. PM me an email address and I'll send you a copy.

Jcar very nice work

cheers

Beautiful plasma setup. I've searched for Plasma Quench but have not found a supplier. Who makes it or where can I get it?

Cheers,
John

Will this work for a Z-axis ?
http://www.modularcnc.com/linear_slides
(of course the AL one)

Beautiful plasma setup. I've searched for Plasma Quench but have not found a supplier. Who makes it or where can I get it?

Thanks. I purchased it directly from the manufacturer at http://www.koalindustries.com/plasmaquench.html

Will this work for a Z-axis ?

I'd get the motor's torque specs from the seller and compare it to what everyone on the forum has been using. Other than that I can't see why it wouldn't work.

Hi Jcar,
It's a great project. Is it possible to show any pictures after cutting with your machines? :)

Cheers,
Samak

Nice work.
Congratulations.:cheers:

I was looking at a water below tank but couldn't get it in to a collapsable frame. You must have around 450 lbs of water in that thing, takes some supporting. Sure is pretty though :D

It's a great project. Is it possible to show any pictures after cutting with your machines?

Thanks, Here's a few picutes.

It's a great project. Is it possible to show any pictures after cutting with your machines?

And a few more.

I was looking at a water below tank but couldn't get it in to a collapsable frame. You must have around 450 lbs of water in that thing, takes some supporting. Sure is pretty though

Thanks for the comments. Actually the table weights right at 500 lbs, and has about 1200 lbs (150 gallons) of water in it. According to the FEA analysis numbers, I get about .080" of sag in the middle of the tank, at the bottom, when it is fully loaded with water. Which is more than acceptable. The entire thing is made out of 10ga (.134") thick steel.

What a vulgar display of raw talent and ability. That is one gorgeous table
and computer set up. I have a plas table that I bought from a friend of mine. But I need to reconfigure the z axis and the controller. It is 96 x 240. Your table encourages me to work on mine, but to take the time and do it correctly as you have. Beautiful work.

What a vulgar display of raw talent and ability. That is one gorgeous table
and computer set up.

Thanks for the positive comments, :)

Good luck on your getting your table refitted. I too found the "zone" very inspirational durring the design and construction process.

96 X 240..... Man, that's a big table. I'd love to have something that size. Talk about the ultimate boatbuilding machine. Unfotunately, it would take up 1/4 of my shop floorspace.

Well, I have to admit that a table that size is a floor sucking monster in my shop too. I received the table from a friend of mine for $900.00. The frame rails for the machine are 24 x 7 inch I beam with .680 flange thickness. The flat iron for the top is 2.5 x .250 hrfb every 2 inches. The weight of the table is right around 5500 lbs. I think that Atlas could set the earth on it, if he needed to take a break. It has dual 3/4 inch thompson rail guides on each side to carry the gantry. I really need to get it going, or get it gone. It's too big to be sitting in a shop taking up that much floor space. Have a great day.

Makes a father proud :)

Great job, Jody.

Hi Jcar,
All are very beautiful.The edge of your job is smooth,not slaggy. I think that it may cause from the control of constant height with THC.
Jcar, I would like to request your help. Now,I have some problems with THC300 with connection.I am confused. I am not good at electronic circuit.Could you share the wiring diagram of THC300 correctly? How to connect?.Please have a look my problem from the attachment. :stickpoke


I use hypertherm 1000 for my project.
Cheers
Samak

Samakthachai,

The THC definately helps with edge quality. The parts that I posted had been cleaned up a little. Either a quick swipe with a right angle grinder, or 30 minutes in the tumbler works great. Prior to clean-up, my cuts have what amounts to about a .015" burr on the under side and a few dribbles of easily removed slag, in tight corners.

As for hooking up your Powermax 1000 to the THC. Take a look at page 3-11 of the following link. https://www.hypertherm.com/library/files/Manuals/Operator%20Manual%20(OM)/804290r1.pdf First you'll need to make sure you have the CNC inteface cable from Hypertherm, that plugs into the back of the machine. This cable has 2 pairs of leads. The green and black leads are connected to "Torch Switch". The red and black leads are connected to "Arc Good".

Now take a look at pages 3-12 and 3-13. You'll need to get some 18 gage or larger insulated wire prefferably in 2 different colors. Run two leads of wire through the strain relief connector beside the CNC interface plug, on the back of the machine. One lead goes to J15 (+ voltage) on the main circuit board and the other lead goes to J16 (- voltage) on the main circuit board. Take the other end of the two leads and connect them to the (+) and (-) connector labeled as "Tip". Make sure you get the polarity correct.

"Torch Earth" connects to your chassis / earth ground. Remember to follow the THC300's instructions http://www.campbelldesigns.com/files/thc-300S-user-guide-rev2.pdf and keep the sensor boards serial cable shell electircally isolated from your chassis / earth ground.

If nessesary, I can post a few pictures of the connections.

Hope this helps,

KitC,

Thanks, couldn't have done it without you. :)

Hi Jcar,
Thank for information and your advice. If it's possible,please help to post wiring diagram better than to prevent my wrong connection. :idea:


New hands
Samak

Hey Jcar,
What type of tumbler do you use? And how meny parts are you able to do at one time? I'm not sure...but did you make a dinosaur?

Vince

Anyboy looking for a good easy to connect THC system
Based on Mach3?
Go for www.cncdirect.co.za

That looks absolutely FANTASTIC and is a real motivator to get a good finish on my next machine. Very well done. :) Is it powder coated, or primed and painted?

What type of tumbler do you use? And how meny parts are you able to do at one time? I'm not sure...but did you make a dinosaur?

I'm not sure of the brand, but it's a .75 cubic foot torroidal bowl. As for how many parts, it really depends on the size of the parts. The bowl is about 24 inches in diameter and 8 inches deep.

Yes it was a dinosaur, I found the .dxf file on the net somewhere. It was a fun little test project.

That looks absolutely FANTASTIC and is a real motivator to get a good finish on my next machine. Very well done. Is it powder coated, or primed and painted?

Thanks, :) It was primed and painted with an HVLP spray gun.

Excellent writeup and work on your project. Very well thought out and definitely an inspiration to future builders like myself. I see that you are using NEMA 23 270 oz-in steppers with a 4.29:1 drive ratio for all three axes and I was wondering if you could offer any insight on the choice of this size stepper and ratio as far as the torque and speed are concerned. I am in the process of designing a plasma table and thought that I would need X axis steppers that were larger than a 4.29:1 ratio at 270 oz-in but your project is making me rethink this. The steppers and ratio that you are using are obviously enough but it is hard for me to get a good idea of what speed and torque I will need to adequately move the gantry and why I should choose a certain stepper size and ratio over another. I have read other posts on this topic and some say leave some margin on the stepper size while others say don't use a bigger stepper than you need because they will run hotter than normal. Is .641" of travel for 1 stepper rev a typical number? Also, I really like your idea of making all three drives the same. Thanks again for all the useful info on your project.

Koredova,

Thanks, I'm glad people are finding my machine and write-up both helpful and inspirational. :)

As for the motors, I find that 270's work very well with Gecko drives and a 42 volt power supply. I have the Gecko's limiting the current to each motor at 2.8 amps. The higher voltage power supply makes a huge difference in high speed torque. I've experimented with the 270's, an integrated 3 axis driver card, and a 12 volt supply. There was a very noticable decrease in high speed torque (we're talking orders of magnitude here). The Gecko's can manage up to 82 volts and 7 amps, I believe. The motors do get warm (almost too hot to touch), once they've been powered up for a while. However, I'm not getting anywhere close to the maximum operating temperature of 100 degrees C (212 degrees F). They don't sizzle when I spit on them...... :)

I estimate that my total gantry (moving part - XYZ) weight is around 100-120 lbs. It is moved on both sides by a 270 oz motor (540 oz total). If I increase the kernel speed in Mach3, to one of the higher settings, the gantry will rapid at 850 ipm. However, at 850 ipm, you can stall it with your arm and a moderate amount of force. At 450 ipm, I really have to put my body (230 lbs) into it, in order to stall the motors. At 250 ipm and less, I physically can't get the drives to stall. I've set my max rapid speed to 450 ipm, and have experienced no step loss in any of the 3 axis'. If I had it to do over again, I wouldn't change anything. For plasma cutting it works extremely well. It may be different it I were running a 1/2" diameter router bit, 1/2" deep in a sheet of MDF board, at 500 ipm. :)


As for the drive ratio, I've read anywhere from 3:1 to 6:1. To tell you the truth, I just shot for the middle and got lucky. I suspect that a higher ratio would be better with a heavier gantry, at the expense of top end speed. I feel that the system has more than enough acceleration (very important for plasma work). My system will run at rates higher than 45-50 in/sec/sec. However, the higher values seem a bit "harsh" to my system.

Hope this helps,

Jcar,

Gentlemen,

I've had several PM requests for drawings of my water table. I'm attaching a PDF file, which contains scans of the 3 layout sheets that I gave to my local steel supplier. I had them shear and bend the parts, while I did all of the welding. Cost for 2 sheets of 5' X 10' 10ga and labor was around $350 ($140 per sheet and $70 labor).

Here's a DXF file of the slat hangers for the water table.

How could I get the original file from Thermal dynamics?

Totalfab06,

Just Private Message me your email address, and I'll send you a copy.

Jody,

I also want to add that I welded X braces to the top side of part 2 and the under side of part 3 in the above watertable.pdf file. The braces on part 2 are located within the air chamber area just like the braces above them on part 3. They were made from .125" X 2" flat stock welded on edge.

Wow Jcar,
I have to say reading this thread of your build has saved me so many head aches. I'm in the process of contemplating a Plasma table build and you have hit the nail on the head with this design. I'm very impressed, the build quality is top class.
Can i also get a copy of the Thermal dynamics file. I will PM my address.
Once again well done.
Best regards,
D_G

Dizzy G,

Thanks for the kind words. If you need any help with your build, feel free to ask.

Jcar, what is the overall footprint of your table if you don't mind be asking, can you leave out the two support legs so i can get an idea.
Thanks,
D_G

Thanks Anvil, i had just come back to edit my post and ask the exact same question. Still hungover from the weekend so i forogt all about asking. :)

Beautiful machine Jcar. I've read your original post about 5 times and I just caught that you have 2 steppers running one axis. How does that work? Are the steppers run in parallel off one drive or did you split the step and direction signal to two different gecko drives?

Anvil: Sorry to jump in on a question to Dizzy_G but you can't run two steppers off one drive....does really ugly stuff to any anti-resonance circuit and causes interaction between two mortors youdon't wnat. You can (hardware) slave two drives together by running the same set of step & dir signals to them provided the interface (from the PC) has enough current capability. MACH software also allows you to software slave any two axis and that approach has some advantages (over hardware slaving). You can setup separate home swtichs that will automatically "square" the axis everytime you home. Dual drive systems are very common and offer a cost effective way to both double the drive torque and keep the gantry from racking. You can do it mechanically with a drive shaft but it adds to the mechanical complexity.

Hi Torchhead,
I had considered the mechanical approach but would be a slight problem if i was to follow Jcar's table design as the table is so deep.
So I could use two smaller motors for the x-axis along with two drives, instead of one large motor which is driving one side and may cause racking. Also would it be necessary to use a breakout board to add the second motor? Are the two motor drives effectively in parallel off the one signal line or is it two separate signal lines and the software "matches" the step pulses etc. and signals?
I can see how two motors on one drive would cause problems alright with step pulses being all over the shop, but I'm intrigued with the idea of the software being able to manage everything.
Which would be the better approach hardware slaving or software slaving? I assume software wins out with the dual homing option.
Thanks
D_G

Dizzy G,

The inside dimensions for my water table are 60" X 60". The top flange is 1 1/2" wide so the outside dimensions are 63" X 63".


Anvil,

Thanks. My system is controlled by 4 Gecko 201's. X axis, Y axis, Z axis, and B axis. One side of the gantry is controlled by the Y axis motor and it's gecko drive, while the other side is controlled by the B axis motor and it's Gecko drive. The B axis is "slaved" to the Y axis in Mach3's configuration settings. When Mach3 sends signals to the Y axis motor and drive, it also sends the same signals to the B axis motor and drive.

Thanks Torchhead. I've been thinking about using two steppers on one axis for a while. That is exactly what I needed to know.

Thanks Jcar I think I'm going to use a similar setup. Did you use the extra slaved stepper on the Y axis specifically to eliminate racking or does it have other advantages? It seems like one big stepper would cheaper.

Anvil,

I used 2 motors to both eliminate racking and to double the power. I initially looked at using one large motor with a drive shaft running to each side of the machine. However, after a little bit of CAD time, I found that this was actually a more complicated solution.

Very professional looking table. Thanks for the water table heads up.

Jason

Thanks. Not a problem.

Jcar - Great table design, this is one of the best I have seen on this site. I was so impressed i used this design for building my second table. My first table is under the thread "4 x 8 plasma table plans", and it works great. I decided to build the second table do the reduced "plasma dust" , better detail and the rack and pinion design. I am in the process of building a new shop and and working on this new table so completion is a couple months away. I feel it might be more appropriate to share design pictures on this thread vs starting a new one because it is modled after your table. With your permision I would like to post these pictures here. I chose to make a 5 x 10 table. This table was basicly designed from your first pictures and reverse engineering these pictures. A picture is worth a thousnd words. I have the water table completed, I am completeing the rack and pinion frame now, and have most parts in house with exception to the THC, which I am saving for.

Andrew

Smilewizard,

First of all I'd like to say thanks for the comments. I've read through your 4 X 8 build thread a number of times. Nice machine. I really like the way you continously updated your tread. Very cool.

I'd have no problems with you adding your machine build to this thread. I think it would be a cool idea, and an interesting thing to see.

I added a couple of gantry beam support brackets to the machine this weekend. I was experiencing a small amount of flex/deflection when rapidly changing directions in the Y axis. The brackets were added to both sides of the gantry. The picture shows the right side bracket.

Here are a few pictures of the table I am currently building. I will take some pictures of the components in the next few days.

Jcar

How heavy is your gantry?

Smilewizard,

I've got a bad case of table envy!!! Wow, very nice!!! I wish I could have made a larger table like yours. I can't wait to see the finished machine.

I'm guessing my gantry, minus the side plates and Y axis motor assemblies, weighs around 100 lbs.

Wow smilewizard really nice table on the way there. Funny that you have made Jcar envious as I think everyone had been envious of his, I know I was. Your design looks good so far, I have been thinking of a build along the same lines, water table, rack and pinion etc. What THC are you thinking of using, it certainly is the most expensive component of the build, Are there any plans for a DIY electronic one around?
What size motors are you going to use and what type controllers if you don't mind me asking?
Keep up the good work guys. (Sorry for being so full of questions the whole time)
D_G

Here is a thread from a guy that is building one for $10.00. Might check to see how that is coming along.

http://www.cnczone.com/forums/showthread.php?t=46175

Sir once again amazing job.

I downloaded your water pdf and am not quite sure how it works.
You mention early in this thread that you add or subtract air to raise and lower the water level? So when you add air is the table bubbling from leakage?
How does it seal?
I would have thought a bladder of some sort would be needed, maybe this is obvious but I don't get how it works



Many many thanks for ALL your sharing and help

Mark
www.mjpcarbon.com

Ok so I am stupid I reread the very first thing you wrote. The inner platform IS welded to seal and the air pumps out the extra water thereby raising the level.

Smilewizard,

I haven't seen any updates from you in a month or so and was just wondering how the table build was going?

Sir glad you asked, I have all the electronics working in a breadboard fashion.
Tomorrow I think I will have the X and Y axis done with motors installed.

For the immediate moment I am going to use a fixed Z axis til I am sure that it is working.

Hopefully I will be able to get the machine to produce an accurate scale drawing\part. It has been some time since I messed with the electronics part and I sort of forgot the whole half step whole step part so I am banking on being able to adjust the scale in Mach to compensate.

I draw in Mastercam and have a post that seems to produce a nice code that works at least on the bench.

Wish me luck and you guys are awesome.

Oh yeah I am having trouble getting response from the guys at Plasma Quench,,,,

Mark
www.mjpcarbon.com

Jcar thanks for asking, the table build has been in a holding pattern since the last post. I am in the process of completeing the shop, which will house this table as well as my first table. I plan to have postings of both the table and new shop in January. Should have the heat installed in the next few weeks, and this will help.

AJ

I plan to have postings of both the table and new shop in January. Should have the heat installed in the next few weeks, and this will help.

AJ

Ahhhhhh Heat a very good thing. LOL


I always feel good when using the oxy fuel on my table in winter. I feel like I'm cheating the electric company on those days. LOL

IT Works, Gentlemen it works and works well I might add but I do have some questions.

My motors are six wire is there a performance gain with the two striped wires. currently I am using the solid colored wires.
I am using a Xylotex 3 axis board.

Next what is better more or less steps per unit in the software?

Mark

More steps will give you better resolution

mjp,

As millman52 said, more steps will give you better resolution, while fewer steps per unit will give you more speed. However, if you already have the machine running and are past the design phase, this number is not variable. The steps per unit are used to tell Mach how many steps are needed to move one inch (assuming you're using inches on your system). It's dependant upon the pulley/gear ratio between your motors and the final drive.

Just enter some number, say 4000. Now, zero out the DRO for the axis your experimenting with, and jog your machine some distance. Next, check the actual distance the machine moved, with a dial indicator, ruller, or tape measure. If the DRO is the same as the distance you measured, than you're good to go. If the the DRO is longer than the measurement, reduce your steps per unit. If the DRO is shorted than the measurement, increase your steps per unit. To reduce the amout of experimentation time use the following formula after you've done your first trial:

((DRO value) X (Current steps per unit)) / (Measured distance) = Actual steps per unit

Progress update :
Ok so to get accurate movement I have to have 6500 steps.
I have the following setup:
Direct Drive
8 tpi screws
Xylotex board/Eight step( should I change this?)

The whole thing works rather well except for the rapid between cut moves. The motors are not happy and I cannot for the life of me find out how to slow down the transition speed in Mach 2
Can anybody direct me on how to slow down the jog/rapid speed. If I disable the jog the machine works fine but transition is rather slow.

mjp,

Go into your motor setup and reduce your maximum speed until the motors sound good when doing rapids. Most people will go 20% below this to ensure they don't have intermittent stall problems.

1/8th steps will be fine.

Well here is where the confusion lies on my part.
In motor setup I have Velocity and Acceleration
First I don't know the difference as to what affects what.
Next Accel is set to 3.4 and Velocity is .46 so I am almost a Zero on both ???

Velocity is the maximum speed and accel is how quickly the motor gets up to speed. I'd raise the velocity to 5 and drop the accel to 1 or 2. Slowly raise the velocity until the motor stalls and back it off a little. Next, start raising the accel until the motor stalls and back it off a little.

Will do
What about my rapid feed rate. The machine cuts parts to scale and the speed for that is fine. Its the rapid/transition speed that I am unable to control unless I turn off the jog mode

I'm not sure I understand what you mean by "rapid/transition speed"?

Rapid or transition- Once it is done cutting one part and quickly moves to its next location. On my Router and Milling machine this speed is faster than cutting speed

Progress update :
Ok so to get accurate movement I have to have 6500 steps.
I have the following setup:
Direct Drive
8 tpi screws
Xylotex board/Eight step( should I change this?)

The whole thing works rather well except for the rapid between cut moves. The motors are not happy and I cannot for the life of me find out how to slow down the transition speed in Mach 2
Can anybody direct me on how to slow down the jog/rapid speed. If I disable the jog the machine works fine but transition is rather slow.


Where did 6500 steps come from?:confused:

steppers have 200 steps per rev. With 1/8 microstepping you need 1600 pulses from the computer to turn the motor one rev (360 deg).

Now with the listed leadscrew thats 8 rev of the motor to move one inch. You need 8 * 1600 steps to move 1 inch or 12,800 steps.

Unless you have 2 start leadscrews (which would make the actual TPI = 4) that number is 12800.

Now, the Steppers with a Xylotex can only spin about 400 to 500 RPM before they run out of torque. If your frictional forces are high it might be less than that. So given that limitation you can only move the axis about 50 IPM (max velocity). You need to set the velocity in MACH low enough so when you jog at full speed (shift-arrowkey = fast jog). the motors run smooth.

Accel is in seconds units rather than minutes. You need to keep the number around 2 to 5 times the max velocity. Since max velocity is in Units per minute you need to mentally multiply the accel by 60 to hit the velocity. So for accel of 3X of the velocity of 50 IPM (150 IPM) the actual accel value would be 2.5.

Too high acceleration will cause lost steps and motor unhappiness!

The size of the motor has little to do with upper RPM limits and in some cases bigger motors actually will run out of torque at lower RPM's than a smaller one.

How fast you can spin a stepper is a function of the motor voltage. That is limited on the Xylotex to about 28 VDC.

Tom Caudle
www.CandCNC.com

Tom thanks so much for any input.
I went to 6400 to get my scaling right.
I will mess with the Acel and Vel on Monday trying your settings
Mark

Tom,

You stated that accel values should be 2 to 5 times the velocity value. Is this a general stepper motor rule, or does it come from personal experience. Just curious.

Here is a picture of the new shop that is the cause for the table build delay. A Amish built barn about ten years old, about 1400 Sq. Ft. work space with a 400 sq. ft. office. When complete will have a bath room upstairs and down. Bottom half is 75% complete. Forgot to take pictures of the office, will do when compete. Office has heat and air, shop will be heated and have swamp cooler.

I also included a picture of the linear rail system for the THC.

Andrew

Forgot to post picture.

Andrew

Tom,

You stated that accel values should be 2 to 5 times the velocity value. Is this a general stepper motor rule, or does it come from personal experience. Just curious.

It's basically a "rock over the fence" type of number. Because no two tables are alike the number scan vary wildly. If you look at the numbers for accel it means you go from 0 to full speed (Max velocity) in from .5 sec to .2 sec (200 miliseconds). Think about the gantry rolling along and having to change direction. It decels' at the rate then re accelerates in the opposite direction. Try that in your car but you better be belted in (:-o

You want as high an accel number as your machine tolerates because it makes for square corners and tighter curves. Too high and you get servo faults or the dreaded lost steps on steppers.

Does anyone use Oxygen rather than compressed air in their Plasma cutting ?

smilewizard,

I like your shop. You've got 2 things I wish I had in mine, a seperate office area and a bathroom. The 50 yard walk to the house seems so much farther when you've really gotta go.:)


Torchhead,

Thanks for the reply. I'm sure everyone appreciates the clarification. My numbers are very close to your 2 - 5X rule (6X), however I got my numbers through experimentation/trial and error.


mjp,

I'm affraid I'm just a plain ol' compressed air guy. From what I understand, oxygen is the gas of choice for high carbon tool steels. You get a much better edge with less dross and edge hardening. Unfortunately, from what I've read, sytems are designed specifically to run oxygen and I don't think my Powermax 1000 is such a system. According to Hypertherm's site, oxygen eats electrodes for breakfast, if special circuitry isn't used.

I am going to stick with compressed air for now. No need to look for problems.

Here is my first cut, gotta mess more with speeds,height etc.

Also time to build the water table now that I see it works.

Plasma quench is on the freight truck headed my way as we speak.
This is without any lead in lead out so forgive the piercings.
I also think my plasma machine is too powerful for what I am presently cutting and may have to buy a smaller machine.

how long are your belts for your gear reductions?

Bigtoy302,

They are 3/8" wide XL 150's (15" outer diameter).

Jcar,

Hi Jcar,

I was wondering if you have any close up photos of how you mounted the motors/shaft and bearings for the X&Y axis. I'm specifically interested in how you mounted the bearings for the shafts. Did you use flanged bearings and rely on loctite to resist any thrust on the shaft? If so how are they holding up? If not what method could you recommend?

D_G

Dizzy-G,

Not to hijack this thread. I used a double flanged bearing on my table. http://www.cnczone.com/forums/showthread.php?t=31133&page=3 Post # 28 is the Y. here are pics of the X & A, http://www.cnczone.com/forums/showthread.php?t=31133&page=4 Posts 45 & 46. Here is a couple pics of the assemblys after mounted to the table & springs added to keep the pinion in constant mesh with the rack. http://www.cnczone.com/forums/showthread.php?t=31133&page=5 Post #59

The bearings I used have set screws on the inner bearing race. So far they have held great.

Hi Millman,

Thanks for the info, the pictures give great detail. I'm trying to think of different methods of mounting the shafts so its great to get different methods.
Nice looking machine too, you put some good work into it.

D_G

Dizzy G,

Yes, I used flanged bearings with the non-flanged sides facing outward. The side plate holes, for the bearings, were machined on a CNC mill for a light press fit. The timing belt pulley has a set screw which locks into a milled flat on the drive shaft. The pulley is sandwiched between a .010" washer and bearing on one side and a spacer and bearing on the other side. I used the .010" washer to keep the pulley from rubbing the bearing flange face. The spacers length was adjusted to allow for a few thousandth of side to side play.

Did you use 3/8 or 1/2 for the drive shafts?

Jcar,
Thanks for the info I really appreciate it, that makes perfect sense and well done. I now need to try and get access to a CNC mill as I know I can't do accurately enough myself. I don't want to skew the bearings when they go in and cause them to wear quickly. :(

Bigtoy302,
I think 3/8 was used as its the size that would fit the 14 tooth pinion (I have only seen 3/8" bore for 14 tooth 1/2 face width, larger face widths have larger dia's) and the 60 tooth XL pulley comes with either 5/16 or 3/8. So I think it was 3/8. Jcar will say for certain, I'm just going on assumptions.

D_G

Dizzy G,

You can use a boring head on a manual mill as well. The CNC just makes it easier to sneak up on the press fit size. I did a press fit because I tend to be a little anal about my machine work :). A few thousandth of tolerance wouldn't hurt anything, on a plasma machine, in my opinion.


Bigtoy302,

Dizzy G is correct. I used 3/8" diameter shafts. I used the case hardened/precision ground Thompson linear bearing stock from Mcmaster.com, precut to length.

Thanks Jcar, I was thinking of drilling the plates in pairs on a pillar drill to try and ensure all the holes line up. I may have to chat nicely to a guy in the maintenance department to see if he will do a bit of machining for me, I'm not in the company long so not sure if he'll help me out, I'm from the same town as him so fingers crossed he'll help a "neighbor" out :)

Did you buy the linear rails from McMaster too? They are extremely expensive, been thinking of a DIY approach but not too sure yet, i still have lots of thinking to do first. Thanks again for the info on the design.

Dizzy G,

Drilling them in pairs would be the way to go if you're doing it on a drill press. If the mainenance department has a reamer sized for the bearing O.D., have them drill it slightly undersize and then do a final ream.

I managed to find all of my rails on ebay. It's the only way I could afford to use them.:)

The biggest problem I foresee is that I'm getting most of my components from McMaster and the majority will be imperial, I live in Ireland so most of the tools over here are metric. The guys have bridgeports here so they maybe able to just mill a hole the correct size for the bearing, will have to quiz one of them up when the time comes, should have stayed in my old company the guys there were great, used to get in on Saturdays to do my own work. Ah well I'm sure I can jump that hurdle when I get to it.
I will have to go the eBay route myself for the rails I think but the shipping will be a killer.

That sir is a down right gorgeous job on your table. Thank you for posting those pics. I would also like to compliment you on your shop. It looks like tilt up or possibly prestress or precast concrete. Should last the rest of your life w/o any problems (grin). Now get it dirty. Lovely computer set up - I saved the pics for future reference.

Thanks. My shop is indeed poured concrete with lotsa' rebar. Not only should it last forever, but it's fire proof as well..... :)

Excellent work on the table! Your start and stop look great on those parts and the accuracy of the steppers look great in the arcs! You should really post up some detailed plans for others.

Where did you buy the motors and gecko's from?

Ryan

carbidecraters,

Thanks, I've been very pleased with the accuracy of the machine. It's better than I expected.

I've been thinking about posting detailed plans of my machine, it's just a matter of finding the time to do it.


Bigtoy302,

I purchased my motors and Gecko's from homeshopcnc.com. If you buy a motor and Gecko 201 from them, you get the Gecko 201 for $99.

Jcar,
This has to be one of the cleanest designs I have saw. Have a couple of questions for you; did you ever consider using nylon belt pulleys in lieu of aluminum? I notice that nylon is a lot more cost effective, but perhaps they don't wear as well. How well have your 1/4" motor shafts held up with the belt tension on them? Is the motor pulley cantilevered or is it supported on the inboard side by a bearing?

Thanks for all of the helpful hints you have provided.

drafterman

Drafterman,

Thanks. I was concerned about the longevity of the nylon pulleys. I was afraid that the constant torque/direction changes would loosen the interface between the nylon pulley and it's aluminum hub. I don't have a lot of experience with the nylon pulleys, so to be honest, I can't say that they will or will not hold up. I took the "better safe than sorry" approach and used steel pulleys from McMaster.

The motor pulleys are cantilevered and I haven't seen the slightest hint of problems with the 1/4" motor shafts. If you go back to my initial write up, just above the pictures, you'll find a link to more pictures of the machine. There should be a few close-up's of my drives in there.

Hi Jcar
Great Plasma Table, I am really jealous! :D
I am thinking about building a Mark 2 Plasma Table, and I like the idea of the adjustable water level :)
I have looked at your Water table design, and I have a few questions for you.

1) The section that houses the airtight water tank, do you fit your slats on the top of this?
So when you lower the water level it leaves the top section 'dry' so that you can easily retreive small parts?
With my water table it is like a 'Lucky Dip' trying to find the parts in the bottom of the tank :)

2) What happens to the segiment (Fine Dust) that you generate, where does this settle?
Does it get into the airtight section, or does it settle in the area where the 3 slots are?
If so, would it not have been better to have raised the slots an inch or so off of the bottom so that the segiment can't easily get into the airtight section??

Thanks

Andy

Normsthhname,

Thanks :)

1) The section that houses the airtight water tank, do you fit your slats on the top of this?
So when you lower the water level it leaves the top section 'dry' so that you can easily retreive small parts?


You are 100 percent correct. I have "holders" welded to the top side of the air tank that have slots in them to accept my slats. The water level does drop below the top of the air tank when it's lowered. It definately makes finding parts much easier.

2) What happens to the segiment (Fine Dust) that you generate, where does this settle?
Does it get into the airtight section, or does it settle in the area where the 3 slots are?
If so, would it not have been better to have raised the slots an inch or so off of the bottom so that the segiment can't easily get into the airtight section??


Most everything ends up on top of the air tank. This is due to the fact that I rarely cut over the deep end of the table. A very thin layer of fine "dust" has settled on the area in front of the air tank slots. This has taken 9 months to accumulate and the amount is so small, I have yet to clean that area of the tank. Originally, I had planned to make a screen basket that dropped into the deep area of the tank to catch sediment. However, since the amount of sediment is so small, I haven't seen the need for it.

ohh ! it looks like a monster( very good ) :)

hey im new here and i am interested in your build if possible. how much did it cost to build the machine ur cuts looks amazing. thank you

Thanks. I spent around $7500 for everything, which includes $3000 for the Powermax 1000 and machine torch.

Hello All,

I had a very hard time finding anything over 80” at a reasonable price. I looked into new rails, but the $3500 price tag was beyond my budget. I ended up with two 78” NSK20’s for the Y axis, one 65” THK35 for the X axis and one 28” IKO15 for the Z axis.

http://www.cnczone.com/gallery/showgallery.php/ppuser/38704/cat/500


Just wondering if i'm missing something. I'm looking at rails and they don't cost $3500.

Please post some links. Im sure everyone would like to know where they can get a good deal on rails. As for the price difference, I suspect your not looking at quality Japanese THK or NSK rails in lengths over 1600mm. There's a large difference in price between Japanese and Chinese rails.

Hope you are all doing well. Well Im back. After being downsized a couple of years ago I finally am to the point where I want to get this table going. My original table has been doing all of my cutting, but I would like a little more accuracy and less bounce you get from that type of table. I will try to post pictures as I go forward as I am now starting to try and find all my notes and being the thought process again.

J-Car any updates I should be aware of from your table. I look forward to hearing from you guys again and seeing what projects you have done.

Andrew