View Full Version : BUILD LOG: Giant hot wire cutter

04-01-2015, 08:26 PM
So after my giant router build the next thing on the list to think about is a way to chop the large blocks of eps up into usably pices which is normally just smaller blocks so a horizontal and vertical cut however it would allso be nice to have two and Possably four axis cnc posabilities in the future.

the blocks I cut range from 8'x4'x4' to 16'x4'x4' but normally 16x4x2 and weight about 70-80kg

the he machine is going to have to go in the shed were I store the blocks at the moment so restricted a bit by size

I'm not after super accuracy just a nice straight line that can be set up in minimal time and keeping costs as low as posable. I'm wondering if to start with rather than having it cnc I can just have it motorised and controlled by a simple switch or something to give a constant feed rate.

The first thing I have been trying to deside on is what liniar motion components to use. For this as nice as it would be to use Hiwin rails I'm hoping I can come up with a suitable and cheaper method with the 6meter long axis at least possibly something along the lines of the cnc router parts method of using barring and flat steal plate ( I will put a link to when I'm on a pc)

I have seen a few similar machines which has given me a few ideas some quite minimal and some a bit more substantial but yet to deside on how to do it myself.

04-01-2015, 09:18 PM
would it not be possible just to have a floor roller/conveyor system (powered or manual) and a goalpost arrangement with the a hot wire height adjustable spanning between the posts? G.

04-01-2015, 09:31 PM
With the goal posts fixed? Not unless I had nearly 40' of shed. I think it's going to have to be a moving gantry design of sorts. The one bellow is one I have seen on Google that looks rather nice but possibly a bitt by be over the budget to build the same.

04-01-2015, 10:35 PM
this was the other which is perhaps the opposite it terms of build strength but certainly simple ish

04-01-2015, 10:45 PM
and this is what I am wondering about for rails


however I cant help but think if I use extrusion there must be a way I could use the aluminum as the rail and have some sort of rubber wheel as the forces are going to be so low along with the weight of the gantry being pretty small all so. I am aware of the v rail aluminium but I don't think it comes in 6m lengths.

then there are the wheels you can get from kjn but not sure if they would be up for the job and there are quite pricey considering you would need probably 6 or 8 per rail.

05-01-2015, 08:10 AM
Hi Charlie
With the limitation on working area, best option would be to knock up a trolly with integral adjustable hot wire cutter and run it along the top of your block.
No need for anything complicated.

05-01-2015, 08:36 AM
If space is really tight have you thought about having your rails against the sidewalls of your shed with the gantry parking against the back wall?
If you used a system based on tube frame roller coaster designs you might get a large proportion of what you need from scaffold poles & fittings, with the outside faces of the horizontal runners free for adding support to get them straight and level,

05-01-2015, 09:02 AM
Ceiling mounted ?

05-01-2015, 11:15 AM
Thanks for those ideas they have given me a lot to think about. the idea of actauly just having a frame sit on the block would be a nice and compact however i would have to cut the full length each time to get a flat surface.

wall mounted could be a option but i would need to think about shifting the block around as they are so large and heavy and im my own most of the time. ceiling could work also although probably not the most solid part of the shed and im 6'2 so metal sticking down may get annoying but still worth thinking about

im wondering if i had something floor mounted i could possibly build a raised false floor around it so i could slide the blocks on and around easily with no lifting same goes i suppose if it was ceiling mounted

what ever i build i would like the option to be able to upgrade it to 2 or 4 axis cnc in the future

mike os
05-01-2015, 12:18 PM
I think if you really want 2/4 axis in the future you either need to part build it now (ie base etc but with only 1 axis, rest to be added later) or build a cheap machine to do what you want now and start again later

05-01-2015, 01:07 PM
Thinking about it yes 4 axis will probably mean a lot larger machine as each side would need to have two indipendant axis so that may be out for the moment two axis cnc would still be nice. What I was thinking was if it was a gantry type build then I build each side with two rails a horizontal and vertical and then ether drive the with desperate motors or connect them via a shaft and pulleys. The horizontal cut is the most important but I would probably use a open loop belt to drive all axis

Boyan Silyavski
05-01-2015, 06:10 PM
2 separate rails on the floor. The type they use below the sliding metal garage doors. Leveled and squared locally, then between them the floor leveled with mortar.



Then something similar like a DIY horizontal Band saw mill structure, only the gantry



How to lift the blade/wire/


Then some contraption with 2 end stops, motor, wire pulleys and steel wire cable, this to auto feed and stop at end.

05-01-2015, 08:45 PM
Thanks that has given me more ideas to think about. I will have to look into those rails and rollers and see what they cost. The other idea from this is perhaps using a T section on its side for the side of the bed and have the rollers running on that top and bottom perhaps.

Boyan Silyavski
05-01-2015, 09:50 PM
Another idea. Google search for diy dolly track from pipe and rollers. You can hammer some round iron in the floor , say every 60cm, level it and solder the pipe, then cement below the pipe and form the flat bed at the same time. talking about 2-3cm of cement.


look how the motor moves it, its not necessary to be in the middle of it.



It seems even they sell ready wheels at aliexpress


So it seems from some pipes and fitting you could do the whole thing for a day, without soldering, i mean also the gantry.

05-01-2015, 10:04 PM
the only thing with that is im not keen on just relying on gravity to hold it to the rail so I wound want a 3rd wheel at least but it would make a the long axis quite simple to do. The other thing as the base of the shed is timber boards so not reliable for direct fixing to much as it will probably move a little with temperature and climate

many thanks for all the idea