Guys,
Any recommendations on cutting thick MDF, I have 2 sheets of 50mm mdf and one sheet of 18m that will be bonded. I’d rather cut all three or, two at least, after they are bonded, rather than individually.
I have big circles to cut out of them
Thanks
Impressive thickness if it’s 50 mm, never seen it. But you can’t cut thicker/deeper than what your router bit sticks out under your router. Plus the limit of the LR3/4’s depth. I certainly (when my LR3 was up n running) couldn’t cut 10mm of materials…maybe someone else here has some technique I’m not aware of. But if the circles need to match up with same distance from X/Y sides on the MDF, then calibration in a corner sounds like the best. Maybe make an L shaped corner that you screw onto your wasteboard and make sure all your MDFs are firmly secured into that corner and use it as a calibration point. I’m totally new at this myself but without any other knowledge I’d most likely do it this way.
Ah yeah error there, 2 sheets of 25.
Then 50 should be doable, however not sure with the 18mm as well, depends on the length of your router bit. Put the desired bit in and measure. If you’re not too aggressive with your feedrate, depth of cut etc you can have the bit stick out slightly longer but also depends on the thickness of the bit. The thinner the more careful (slower) you’ll have to be…but this is more of a hack that is not recommended if avoidable.
This would be the absolute maximum and your endmill still needs the travel of 3mm etc. This might be too much by a tad. But try it out, otherwise we are never going to know for sure.
Oh, and an endmill that can actually cur 50mm is pretty hart to get (or expensive) as well. I’d do the two circles and glue them afterwards.
Just get a 2" end mill and go shallow on the passes.
Or
Cut 1 side, flip and cut other
Or
Cut 1 circle, then glue up, finish with a flush router bit.
Chip evacuation would be difficult (if not impossible) trying to cut at that depth, unless you used trochoidal milling and created a wide slot path. Even then, the slot could easily fill and pack in with sawdust, creating excess heat and other issues.
Better (IMO) to cut each piece individually, and then bond them afterwards. Touch them up with sandpaper or a pattern bit once they are assembled.
What’s the reasoning behind wanting to cut it at 50mm depth?
I would cut the 2 pieces separately and maybe partially drill some alignment/dowel holes in them to register them together for gluing up afterwards.
Alternatively, you can take the approach that is by far my favourite way to route stuff out: Use the CNC to cut the shape you want as a template and then use a pattern bushing or a flush trim bit to transfer that template pattern into the workpiece. I’ve found that with a lot of tasks making the template is the slow part and cutting stuff out by hand can actually be pretty quick.
Another alternative that I’ve suggested to my Dad for using his LR3 before is to take the thick workpiece and just cut a single shallow slot around the surface of the part. That can then be used to trim the workpiece to size by hand with a jigsaw or a bandsaw by cutting along the slot by eye. A flush-trim bit in a handheld router can then use the inside surface of that slot as the template and then trim down through the workpiece until it’s fully routed out.
Can you use trochoidal milling on MDF?
Yes, you can
You can use trochoidal on anything really.
Just wanting to cut that thick for consistency. In the past I would. Cut the “faceplate” with my router jig.
The I would bond the sheets together, jigsaw most of the waste of the hole, and then use a flush trim router to trim out to the “faceplate”.
I was thinking with the cnc, I could eliminate the need to manually do the secondary sheets.
The way I see it with the cnc based on feedback, basically I will use it to cut the faceplate instead of using the router jig. Then I will bond and finish same as I used to.
If I cut 3 separate sheets, I worry that although close, I wont get the 3 sheets cut 100% matching. There will be 6 15“ holes cut in each sheet.
Can always try it and see how you go. If you’d normally do it that way then perhaps use it as an excuse to try cutting it in 2 parts with partial depth dowels for alignment and see how you get on that way?
Forgive my complete ignorance, but what on earth is “trochoidal milling” and is there any link or site I can learn more to broaden my knowledge of something I might want to know about.
You know that thing you do to make a ballpoint work again where you make lots of little loopdy loops? Trochidal milling is like that, moving in a line doing loops - this hugely reduces the lateral pressure on the cutter so you can take up to full depth cuts at one time.
The feed rate is slower but this is offset by only doing one pass and a finish pass.
I recently used it to cut the aluminum plates. It limits engagement for cooling and full depth cuts. It really is useful, but does use a bit more of a path to make it do what it does.
You can go full depth cuts with trochoidal, so you can reduce the number of passes required to one. But it does take longer (up to 3x) per pass, so the overall cut time may increase or decrease, depending on the thickness of the material and the associated # of passes for standard milling.
Some other CAM software calls it “adaptive milling”. Including fusion 360.