Newbie- Hot wire foam cutting with EMC

[linuxstep1]

hi,
I'm new here and I joined this forum, because I plan to build a hot wire foam cutter. Main purpose of the cutter is to create parts for model aircrafts (wings etc).
The cutter will have four axis for wire moving (as usual), but with a less usual bipod kinematic. Additionally a turntable is planned.
My plan is to configure EMC with linear axes XYUV plus a rotary axis A for the turntable. This is probably the standard layout for this kind of machine.

I have already installed EMC2 on top of an existing Xubuntu hardy on a laptop. It went smoothly within less 1/2 h.

I know laptops are not recommended, and have already seen the latency is more than 1 msec ! For 1st tests it may be ok, but for real work I have to choose probably another hardware.

Now the first task is to create suitable ini and hal files. I will report progress from time to time.

Any suggestions, feedback, examples are welcome.

greetings

Gerd

[Nick1983]

I am new when it comes to hot wire cutting. I am assuming you are cutting eps, is that correct?

Have you ever tried Crosslinked PE? I am going to try and v profile a thin piece of xlpe (approx 3/8" thick) down .33". I am setting up a manual fixture, no NC. Any advise?

[nikodell]

I would be interested to hear how you set up the bipod kinematic's could post what you did + code.

[linuxstep1]

a short report about the result:
enjoy some pictures about the machine and a cutting sample.
Attached also the kinematics and ini, hal

Gerd

[vlmarshall]

Nice work, thanks for sharing it!

[nikodell]

Nice Work I will have a look now as I have some time again.
Thanks for posting the work>

[dpuch]

Very nice, and thank you for sharing the files.

A bunch of questions about how well it is working for you.
Have you had any issues with it? Like the bow swinging or the lines not wrapping right. What about repeatability from cut to cut, do the lines stretch causing problems?
Are there any problems with the wire position if you transition to an angled cut? Say X+3" and U-3" will the wire change height any? Granted I think that would depend on how your lines connect to the bow wire.

Dale

[linuxstep1]

Originally Posted by dpuch Have you had any issues with it? Like the bow swinging or the lines not wrapping right. What about repeatability from cut to cut, do the lines stretch causing problems? Are there any problems with the wire position if you transition to an angled cut? Say X+3" and U-3" will the wire change height any? Granted I think that would depend on how your lines connect to the bow wire.

Repeatability and accuracy is good enough for the given purpose (model aircraft parts).
Swinging of the bow is not a real problem, because the bow may swing but the wire moves straight.
The Material for the lines is Dyneema (used for fishing and kites). It is said that it does not stretch, and I believe it.
Angled cuts are generally ok. There are small geometric unaccuracies, because the point where the lines are connected to the wire are fixed. I thought about an additional "fixture" to keep the lines always "upright". But I think its not worth.

Biggest problem is the cutting speed. I became aware of the following:
A G1 command with X-Y-U-V axis is executed in EMC2 with the given speed always related to X-Y. The U-V axis move with a speed depending on the distance of UV relative to XY. This is a problem when the XY distance is very short compared to the UV distance. Then the UV side tries to move very fast.

regards, Gerd

[dpuch]

Originally Posted by linuxstep1 Biggest problem is the cutting speed. I became aware of the following: A G1 command with X-Y-U-V axis is executed in EMC2 with the given speed always related to X-Y. The U-V axis move with a speed depending on the distance of UV relative to XY. This is a problem when the XY distance is very short compared to the UV distance. Then the UV side tries to move very fast. regards, Gerd

I guess the ideal setting would be the feed is a max feed regardless. Good to know to put the large ends to the XY side though.

The simplicity of the build has motivated me to make one myself. I have wanted to put one together for a while for the same thing, airplane models.

[linuxstep1]

Originally Posted by dpuch I guess the ideal setting would be the feed is a max feed regardless. Good to know to put the large ends to the XY side though.

Yes, but there are some more special considerations, depending on how the G-code is created. I use an italian software called profili.

Originally Posted by dpuch The simplicity of the build has motivated me to make one myself. I have wanted to put one together for a while for the same thing, airplane models.

Yes go ahead, its really simple to build. Would be nice to see some photos.

And this is the original site: cnc-hotwire (in german)

regards, Gerd

[nikodell]

English translate

http://translate.google.com/translat...-hotwire.de%2F

[dpuch]

And I thought yours was simple