Foam XL hot wire cutter

[Boyan Silyavski]

Hi, after adding some hot wire attachment to my main machine wich showed excellent results cutting 1200x600x50 foam sheets, i decided to build something bigger. And better.

At the moment i use DEVFoam LE to generate the paths and i believe this is the best program at the moment. Yep, tried them all before i purchased this one. Its worth every cent.

Basically i would like to be able to cut 1200x2300 foam blocks 10-1000mm thick. After considering this and that, i decided to purchase another application DevCNC Foam and drive the contraption using Arduino Mega and Ramps 1.4 which connects via USB to PC. Then from DEV CNC Foam on the PC i could visualize what's happening and most of all hit a button and all axis home and square. Aint that great. The big deal is that Dev Foam CNC has and upload feature to the Arduino, so hopefully i will not mess with firmware.

As you can imagine after calculating this and that price, for sake of sanity and simplicity i will have Hiwin 20 on all axis. Not Hiwin, but the copy they sell from Germany on ebay. Hopefully it will slide ok.


The challenge is what to use for linear movement. I wanted ball screws but price wise decided on lead screws as speed will not be big. So choice still is between 10mm and 8mm lead screw which will spin a whopping 2500mm length. I need 200mm per minute cutting speed which i find is the best quality wise, when cutting with 0.16mm constantan wire. So with 2mm 2 start lead screw / 4mm per turn/ i will need to spin the screw mere 50 times per minute. Anyway i decided to upgrade to 24V the Ramps board and use DRV8825 drives that will be coupled with the most powerfull Nema17 Step Motor 42BYGHW811 4800g.cm 2.5A 2Ph. may be even at 1:3 for the sake of resolution. thought at 50 steps per mm resolution will be 0.02 and if i use some micro stepping even better
I believe the motors have to be good enough to move the "gantry" at that low speed and low acceleration. I am somewhat more worried of the natural sag of the long lead screw. i will design and print the nut, so backslash is not a worry.

here is the initial design. It could be wide as much as i like in future by just changing a couple of aluminum pieces . i am still contemplating to fully separate the sides and connect only the " gantry bar" which is a must for everyday use as i will be cutting mainly letters not wings. Profile for the sides and gantry legs will be 30x60 Bosch. It must not vibrate and be strong even if i am radiation cutting, as if it vibrates in any way, then i have to sand. And that's a tedious process ... better to be perfect quality result from start


I have contemplated another linear solutions, offline controllers, bigger motors but at the end i believe this is the proper way to do it. FYI end result will be better than 6k foam cutter which dont even use supported rails

Hopefully i will even avoid separate PSu for the wire and heat it from Ramps

[Robin Hewitt]

I have a need for cast iron cannon axle boxes, a sort truncated cone with the inside removed. I have large lumps of elm wood in my garage waiting for them. I did get some bod up North to make me a pair but he decided to keep them in his garage rather than sell them to me. More than a bit odd. However this machine you are proposing could cut me a new pattern for moulding such things, easy peasy.

[Boyan Silyavski]

I have a need for cast iron cannon axle boxes, a sort truncated cone with the inside removed. I have large lumps of elm wood in my garage waiting for them. I did get some bod up North to make me a pair but he decided to keep them in his garage rather than sell them to me. More than a bit odd. However this machine you are proposing could cut me a new pattern for moulding such things, easy peasy.

Once is ready i could cut you whatever you like. but now you have got me- You have a canon at home???

[Robin Hewitt]

Doesn't everyone?

http://www.robinhewitt.net/Falkirk.wmv

[Boyan Silyavski]

Any idea for possible cheap solutions for the long rails ??? I decided on 1200 and 2200mm travel .

I am currently exploring options for the way to do it and its seems it is hit and miss

-The oozenest C beam seems perfect but they stock it up to 1500mm. And i need 2500mm

-Mjunit is ready made system but such lengths from China will be 1500euro in total to receive it here after customs

-Similar problem with Motedis, too long travel. I will wrtite them now but i see the 6mm steel bearing rod that fits

-meanwhile talking with Fred from BST

-The german CNc Discount does not answer me or i would have bought the rails from him


Any idea how to achieve that travel on the cheap? And best with stuff from Europe? And if not on the cheap, just on the reasonable side? I will not buy Chinese rails with Hiwin Price tag from EU. Now if they are cheaper ...

I am starting to think people don't want to take my money

[charlieuk]

I have been trying to come up with basically exactly the same thing for myself to cut eps block to put on my cnc to cut my surfboard however I need to be able to cut down 16' x 4' x 2' blocks.

I have been thinking about it for a year or so trying to figure a way to get some cheap linear motion. I was wondering about just using a wheel that runs on the ali extrusion but then thought maybe that would not be enough. then there are some of the methods available on cnc router parts but in the end I always come back to just trying to find some cheap low quality square rails as they will probably be better than all the above and a lot easier to set up.

my plan for the drive was a belt, it should be more than accurate enough

looks like your going for just two axis rather than 4? I would love 4 axis but think I will probably go 2 for simplicity.

[charlieuk]

the one in this vid uses booth belt and wheels straight on the extrusion giving something cheap and simple.

http://www.youtube.com/watch?v=-kWGnj5FeI8

[Boyan Silyavski]

the one in this vid uses booth belt and wheels straight on the extrusion giving something cheap and simple.

http://www.youtube.com/watch?v=-kWGnj5FeI8

Thanks for link, but i don't like bulky things


Deadly accurate, dependable, simple. Price starts from 16.900$

Thats exactly the machine type and design i hate. Big servos, where nema 17 will do the job, 10 times bigger than needed aluminum profile. In other words, overbuild thats showing absolute lack of understanding. Not me.

I have been trying to come up with basically exactly the same thing for myself to cut eps block to put on my cnc to cut my surfboard however I need to be able to cut down 16' x 4' x 2' blocks.

I have been thinking about it for a year or so trying to figure a way to get some cheap linear motion. I was wondering about just using a wheel that runs on the ali extrusion but then thought maybe that would not be enough. then there are some of the methods available on cnc router parts but in the end I always come back to just trying to find some cheap low quality square rails as they will probably be better than all the above and a lot easier to set up.

my plan for the drive was a belt, it should be more than accurate enough

looks like your going for just two axis rather than 4? I would love 4 axis but think I will probably go 2 for simplicity.

Mine will be 5 axis in fact. But it will be used as 2 axis most of the time as what i will be cutting is letters mostly. Plus i dont have the place to fix it properly for now. So it will start as 40cm wide 2 axis, that could be transformed to 2m wide 4 axis for under an hour, when need arises and when i find bigger place.

To sum it up for the linear movement and structure:

1. Motedis failed me this time. Blah Blah Blah, we dont cut and ship anything larger than 1980cm. Though it says on their web if one needs such thing to contact them to arrange. Now the funny thing is that i found DOLD Mechatronik in germany, that is their partner and does that, plus he has 3m screws and is willing to ship them to me. WTF. I am in the process of buying the profile from him.

2. I prefer the leadscrew TR10x2 for now, simply put - it will be more reliable and cheaper. Screw is 20 euro per 3m . Double row angular bearing pack is 2 euro from china. All else will be printed or machined from plate of aluminum. It could be made also with the Gt2 steel belt , it will be same money but will take me more time to design it, as i don't like much long double belts.


3. I have changed all structure from 3060 to 2040 slot6 , as it will be good enough for the job. I know, not typical for me to not overbuild, but it's not needed here. Final length will be 1300x2600mm travel will be around 1200x2400, as i remembered that locally i have 600x2400 foam sheets

-The original Hiwin for 6x1300 and 6 carriages / yes i will be but connecting them/ is around 800$ and after all will be around 800 euros. Quite expensive

-The Chinese MGN12 6x1300 and 6 carriages will be 300$ and say 60 euros import tax. Probably they will do the job, if something does not move right, will open it and change the balls, as i have seen people on Youtube do. So thats the winner

-The Mjunit is around 1500euro after taxes . is very nice looking but at the end of the day is just aluminum profile with steel rods and U bearings. But again i will say it looks very professional.

-The C beam from Oozenest Looked nice but is only 1500mm so again has to be attached together. Will cost me as much as do all from Chinese MGN12, so better not deal with rollers/ if they are not angular contact?/

-I lost patiance trying to explain Chinese that i need it for a slow foam cutter, otherwise there are some that could make me the whole linear movement cheap from 1204 ball screw , alu profile and square rail. Shipping would be then 300$ for that lenghts .


4. Now some interesting stuff. Long ago where there was no 3d printing and i had crappy belt driven machine, i have tried to make something with delrin ball that could slide on top of Bosch profile. Nowadays its even easier. Couple that with 2040 profile and we have a winner. 500 balls are 20$, each carriage has around 18 balls i believe. So i could use them for even something else. I will buy the balls even if i go with Hiwin

No plans here, but i have figured it out with 8mm balls:




Another one, looks nice and have downloaded the files. Waiting for him to see if he will pass me Step file, no just STL:



Check how they compare:




With the preload feature i dont see a reason why it will not work perfectly for a foam cutter especially where they will not even make a noise., Not to speak of that i could print them in POM. I will wait a day though as i have another idea inspired from i don't remember which bearing block.as i simply like them less bulkier.

There was a bearing that looks like hiwin block and inside it has 4 big spheres that enter the rail channel in a very similar way as abobe. But inside the block there is arrangment of very small bearing spheres that the big sphere lay on. So basically no recirculation as the above but a kind of. The only benefit will be to lessen the bulk and make them look more professional.

[charlieuk]

i wasn't talking about the motors or the price just the simple drive system, and if it does the job then ....

I cant see the point in the printed carriages they will never last under any sort of load and ether the plastic will fail or the surface of the aluminium will deteriorate. I would rather just use something like a cheap set of skateboard bearings and make a arrangement that runs down the groves of the aluminum that way at least the have a larger contact area and the aluminum should not deteriorate

8 x 4 eps blocks are not light but if your frame is not supporting the foam and on a solid floor you can probably get away with a smaller frame I wouldn't even consider anything lighter than 40x40. you need a relatively high tension in the wire to reduce sag and drag if you want straight lines and want any sort of reasonable speed without to much curf. and if you are ever going to do 4 or 5 axis you will need stiffness in the frame to get that, unless you build a complex frame that will likely cost as much.

[Boyan Silyavski]

any idea of the force needed to tighten the wire for radiation cutting? i think its less than 1 kg in mass, if weight is used. i cut now using 0.16mm wire and a small spring, for sure less than 1kg pull.


I see the benefit of the big aluminum profile and 20 size rail, as that was my initial design, using 3060 profile. But that's more for industrial use where somebody will work for you and will not take care of the machine. Doing it for myself, i think 2040 is enough. Still have not bought either yet. And have a day or 2 to think it over. Price wise will be just a bit more expensive.


By the way cages could be printed from Delrin, so they will be ok for the job. I have read reports on a printer after 1500h was perfectly fine