RC Keith CNC Hot Wire build log

[thenated0g]

Been looking at this build for over a year and finally decided to buy the parts and start working on it.

Link to website i am using with lots of good articles on everything: http://www.rckeith.co.uk/cnc-hot-wire-foam-cutter/

This is the same plans that Dave Foster (hazard wings) and Defiant wings are using to cut there wings that they sell.

The construction is very basic. Some wood, in my case mdf, some drawer slides, 4 motors.
The one thing holding me back was that you needed to purchase CAM software, usually Mach3, which costs around $200. Recently keith has got LinuxCNC going which makes this free.

CAM software is what takes care of sending the gcode "code" to the motors. In 3d printing this is usually included for free or comes built into a control board on the machine. You need a computer or something always sending this data. There are other options, but the ones with the most tutorials and online info are for Mach3.

Another thing that made me finally go forward was i made some contacts with people that are using this stuff daily and actually respond to my question lol. So i have some confidence to move forward. I am starting this build log to document everything so i can do a full youtube tutorial later for anybody else. This way i can incrementally build up the info for later.

Estimated costs are around $300. You dont need the same precision for hot wire cutting foam as you do 3d printing or milling so you can get away from a lot more parts from Homedepot vs a cnc store. IE using steel acme rods instead of specific cnc lead screws etc.

 

[thenated0g]

save for later

 

[thenated0g]

Parts on order:

www.omc-stepperonline.com
x4 - Nema 23 Bipolar Motors 1.8deg 1.26Nm (178.4oz.in) 2.8A 2.5V 57x57x56mm 4 Wires
x4 - 6.35mm - 8mm Flexible Coupling 18x25mm CNC Stepper Motor Shaft Coupler
x4 - Nema 23 Bracket for Stepper Motor and Geared Stepper Motor Alloy Steel Bracket

Order total w/shipping to US: $115

Banggood.com
2x 8mm 500mm Lead 2mm Stainless Steel Lead Screw + T8 Nut For CNC 3D Printer Reprap
2x 8mm 400mm Lead 2mm Stainless Steel Lead Screw + T8 Nut For CNC 3D Printer Reprap
10x limit switches (cherry switches)
Order total w/shipping to US: $34

Local Ace Hardware
2x 18" drawer slides - 100lb limit
2x 22" drawer slides - 100lb limit
plans recommend 24" but my store was out.
Order total: $50

3/4 mdf sheet of wood already on hand. Maybe $20? You dont need but half a sheet i think.

Total spent so far: $199

These items will allow me to build the two towers and get it fully assembled except for the wire and controller cards that send signal to the motors

Parts needed to complete:
12v power supply: $26
TB6560 cnc controller: $54
wire tension springs: $14
24g nichrome wire: $9

 

[thenated0g]

On the software side i am planning on using LinuxCNC for my CAM and NCGen plugin tools for sketchup for my design and gcode export.

http://linuxcnc.org/ FREE
http://www.foamcasualty.com/products/ncgen-2 $39.99

Depending on how linuxcnc plays with usb/parallel port adapters i may have to purchase some kind of adapter to connect my pc to the TB6560. But this is like a $19 purchase at most.

 

[thenated0g]

Here is Keiths cutting list and build instructions in PDF form. They are kind of hard to find on his website. The one change i am making is that instead of those end pieces of mdf and braces to hold the motor in place i purchased some $5 Nema 23 L bracket steel mounts.

How to Build a $200 USB Hot Wire CNC Foam Cutter - Free eBook - rcKeith

How to Build a USB CNC Hot Wire Foam Cutter - free ebook, plans and parts list. Using 3d printer electronics to keep the cost down.

rckeith.co.uk

 

[Michael9865]

That looks great!

 

[rockyboy]

YES!! I've had this on my 'to do in a couple years' list - working on getting more manual hotwire success first. I'll be eagerly following along - especially on the firmware/software side. Very interested to see how the LinuxCNC works for you!

 

[thenated0g]

Keith said he has linuxCnc working and is making the tutorial. Worst case i download the Mach3 demo which is limited to 500lines of gcode and i can still get my machine working for testing.

For a long time i was afraid of attacking this build. I really dont like programming even though i have been in IT for 15+ years. But after getting a CNC mill and 3d printer going i have a lot more experience with the parts and its not 100 new things at once its just a few things now.

 

[Michael9865]

Keith said he has linuxCnc working and is making the tutorial. Worst case i download the Mach3 demo which is limited to 500lines of gcode and i can still get my machine working for testing.

For a long time i was afraid of attacking this build. I really dont like programming even though i have been in IT for 15+ years. But after getting a CNC mill and 3d printer going i have a lot more experience with the parts and its not 100 new things at once its just a few things now.

Nate, You are killing me here. I also have a MPCNC that is 2 years old, I received a 3D printer as a gift earlier this year. I have been trying to talk myself out of trying a manual hot wire setup then I see this. Now I am starting to lose the argument and contemplating where I could locate a cnc hot wire setup in my two bedroom apartment. LOL
Seriously this is a very intriguing machine. I am anxiously watching your progress.

 

[thenated0g]

The nice thing about this two tower setup is that you dont need to construct the space in between them as part of the machine. You can just c clamp them down to two ends of a table, do your stuff, take it down and pack it away until next time. I purchased the NCgen extension for sketchup and started reading thru the manual today. I think it will make more sense once i have the towers in front of me moving.

 

[thenated0g]

Going in to this there were 2 things that i didnt really know how to do. Setup the CAM software and setup the gcode generating software. Well today Shawn at defiant wings helped me get the Sketchup extension NCgen going. So thats 50% of that done. Pretty happy.
This is just a test wing i generated and its cutting bottom up instead of top down, but it was just a test and it was working!

 

[thenated0g]

Received my nema23 motors, motor mounts, and 6.35mm to 8mm couplers. These connect the nema23 motor shafts to the 8mm lead screw.

This morning i was thinking about the success i had in getting NCgen setup in sketchup and thinking ahead to need to now get the CAM software setup to fully understand this whole process. In my mind the 2 top choices are Mach3 and LinuxCNC. Mach3 is an industry standard. Its been around and used for a long time, meaning there are lots of people using it and therefore lots of videos and people to ask questions. But its around $200. Which for DIY purposes almost doubles the amount of money to get this project going. Instead of around $300 your looking at almost $500. LinuxCNC on the other hand is free open source, but for this specific application of 4 axis hot wire cutting there are not a lot of information or videos. Now Keith is working on a tutorial to get this specifically working and so this should be an option soon. But than i remembered that Mach3 has a demo that you can download and one of its limits is that it only runs 500 lines of gcode. So i opened the cut file i made yesterday for this swept wing slope plank and it was only 255 lines. Im going to make a couple more quick designs of different sizes and see if there is a upper limit i can find. This would be a great free option if most wing cutting is under the 500 limit.
http://www.machsupport.com/software/downloads-updates/

 

[Michael9865]

Great to see it progressing along.

 

[thenated0g]

I talked to Shawn at Defiant wings today and he confirmed that most of his wing gcode is around 200-300 lines of code. So the mach3 demo is definitely going to be something i try. Limit of mach3 is an older computer. 32 bit xp or windows 7 32b.

 

[thenated0g]

There is some interesting geometry when trying to figure out the layout and size of your table. First off you have to remember that you are cutting a wing half, not an entire wingspan. So if the biggest fpv swept wing you are cutting is going to be 60" you need to subtract the center section, lets say 6", and divide the remainder in half. Thats a wing core that is 27" wide. So your table needs to be a little big larger than that. But sweep also needs to be taken into account. The more swept back the more offset the two towers have to get from each other to get in position to make that cut. (Not saying there are not ways to layout your wing to do this with less movement, just using this with as an example to show the type of positions you need to think about.) Initially i was going to use slides that had 19" of travel on the X and z axis. This is the base axis that is on the table and moves the towers. The A and y axis move the wires up and down.

Looking at the pictures above, cutting out the exact same wing, you can see the limits imposed by this shorter 19" slide. It would require the two towers to be 15" away from each other to get in position. Now looking at the picture on the right we can see that by instead getting 28" of travel drawer slides i can now set the towers 29" apart.

I bring this up as you really need to think about what it is that you are going to be cutting. The towers can be moved farther or closer very easily, but to redu the very bottom x and y axis is going to be a lot of work. So figure out the most common types of cuts you are going to be doing and find a setup that is going to work for you. In this case after i actually started visualizing what the machine was going to do i ordered these larger 28" travel drawer slides so that i dont have to make any changes in the future.

If what you are interested in is really long straight wings, you dont need a table as long as that wing or even half of the wing as i stated above. You can cut the wing up in sections and glue together.

 

[thenated0g]

Just putting this here for future reference for anybody using the NCgen plugin. This is a needed adjustment to your generated gcode that Shawn told me about and i verified by running some gcode of my own.

There are two lines at the top of the gcode that get the towers into position, the entry point, of the foam. There is a starting position that is drawn, usually a straight line that goes straight down to the trailing edge of the airfoil and than it begins tracing that airfoil. The problem is how the machine gets the wire to that position at the top of the light.

First it moves the X and Z towers. This is a horizontal movement. Being that your HOME position is all the way down against the table, this makes your hot wire cut thru the foam horizontally. Than it does the vertical axis, A and Y. This cuts the wire vertically up to that starting position. Depending on what you are cutting out of the foam it may have just destroyed the foam as it cut thru the area you needed.

So the very simple fix is to open the gcode in a txt editor (Notepad ++ is my pick)

So we can see that first, at Line 10, it is telling the horizontal axis X and Z to get into position. THEN it moves vertically into position at line 11.
All you need to do is swap these two lines.

So now, starting at the very front of the machine, outside of the foam, it will raise the towers (Y and A) to the entry point position. Then it will move horizontally ABOVE the foam into starting position and begin your cut.

 

[thenated0g]

28" full extension 100lb drawer slides came in. Cost about $50 total to get 4 rails. In this picture they are in the spot the table is going to be installed at. They are 40" apart which is what i think will be a good build area for most things.

 

[thenated0g]

Keith released his LinuxCNC info today, that was the final piece i was waiting for to start on this build:
http://www.rckeith.co.uk/foam-wing-free-cnc-software/

 

[PsyBorg]

Making a lot of progress on this project. I can't wait to see it actually cut a wing. I'll bet your brain is a tad warm absorbing all this new info.

 

[thenated0g]

yeah. i have a shelf full of parts waiting to go. My buddy is coming up holiday monday this weekend and we are going to have a build day so i should have the time to start cutting the mdf and assembling. I now have 3 people that use this equipment all the time and almost instantly reply to my pestering, so should move along quickly once i get going. Just trying to get that f-100 maidened so i stop worrying about it lol. Than i can focus.