[UweKasten]

Hello

I am a teacher in a secondary school in the technology area.
I have problems milling Plexiglas which I never had before. I do something wrong but I can’t figure out what I’m doing wrong.

First of all a few information:

-cutter from MAKKO-CNC technique
-cutting motor from Kress (max 2700 Rev/min)
-VHM cutter 1,5mm/2mm (new) (one blade) from Hartmetalltools
-Plexiglas (different product mostly residual material from the internet)
My problem: After a few meters the cutter collects chips that stick tightly to the cutter and create unattractive circles on the material.


I have tried the following without success:

-decreased number of rev from 27000 to20000 Rev/min.
-decreased feed from 600 mm/min to 300mm
-limit milling depth to 1mm
-cooled cutter with water
- treat cutter with silicone oil
-milled the whole plate with a border completely under water- that stuff even sticks under water
I don’t have any more ideas what I could be doing wrong... i never used to have problems with that,
I would appreciate any ideas because the continuous stopping and cleaning of the milling machine also annoys the students.


Does anybody know a good book (that even a dumb teacher understands?). There is no further education for teacher in the CNC area..so I have to try it all out by myself.. that is sometimes really annoying.

Regards

[hapo]

First of all Plexiglas is no glass but a thermoplastic synthetic material that melds with sufficient heat.
The cutting data that you use are partly quite heavy..I can image that after 20mm the non-cooled miller simply rubs through the part.
With 27000rev a 2mm cutter had about 170m/min. With the single tooth cutter you get a feed of 0,02mm/tooth with 600mm/min which is acceptable.
To mill (non-cooled) (but moistened with light oil or petroleum) I would suggest using an uncoated, fine-grained VHM-2-blade cutter with large-volume helical grooves.
Cutting speed up to 10m/min, feed 0,02mm/tooth and infeed 10% of the diameter.
With a lot of water on the blade about 20m/min

If well moistened with a mixture of ethyl alcohol and petroleum -> up to max 30m/min and max 15-20% of the diameter as the infeed.

[General-5Achs]

Hello Uwe
In general one has to note that there are differences in quality. What you tried is not wrong but I would suggest going into a sport job and get some cooling spray. It’s mainly used in football.

You can test it regarding the surface compatibility and then use it for the cooling process but don’t forget fresh air... as an alternative you can also use a continuous jet of compressed air.
Plastics (like Plexiglas) always want to be machined with sharp tools. What also works would be having a cut break.
Therefore drive 5mm short hold and then continue – in that way the chip can break and fly away...

[Bender {MMO}]

Good morning

I would also use a new and very sharp special plastic cutter ( key word mirror-finish) If the chips are sticky then I can imagine that the cutter creates too much heat so I would try to increase the feed. Maybe the cutter gets too hot due to the dulled cutting edge...
As General also wrote, compressed air might help. Depending if your machine is capsuled or not, you can adjust the air jet directly on the blade and then use 6-6 bar... that way the chips will fly away nicely ( of course if the machine is open then it’s quite a mess)

Regards Manuel