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.