Learning MadCAM-Problem

[phil m]

I just finished building my CNC and I've been playing around Rhino and MadCAM all day trying to cut a job.

I designed an extruded rectangle in Rhino, wirecut some blocks then filled the holes with new blocks that run halfway the thickness of the part. Here's a pic to give you an idea.



First problem: Each time I try to 3D pocket these holes MadCAM cuts all the way through the object, it doesn't stop at the middle of the thickness where it should stop. Is there a way to make it do that?? What am I doing wrong.
Also, can I edit the number of depth cuts it takes?

Second problem, madCAM put extra corners in my drawing for no reason, all my holes are perfect squares, yet, this is how the simulation looks, how can I fix that?



Here's a pic of some scrap mdf to try out the job, again this isn't square. Anyone knows what I should be doing?

I've had to edit the g-code myself to get the CNC to only cut two layers instead of it going through 6 layers and cutting right through the piece. I'd love to find out what I need to do to delete the extra cutting depths.



oh yes, problem #3, madCAM cuts 1.2mm depth in hole number 1, then move to the next hole, then the next etc... once its got all the holes done it moves back to the first hole and cuts the second pass, then off to the next hole...it takes an eternity to get all 6 passes done.

How do I get it to cut one hole at a time THEN move to the next hole?

[phil m]

ok, figured out some stuff so I might as well write it here so no one wastes their time answering my questions.

problem 1: turns out its not enough to extrude a new part in the hole, I need to do a boolean union on it, then madCAM will understand that it is all the same part.

I'd love to find out the answers to problem 2 (rounded corners on mdf) and 3 (mill a complete hole before moving to the next)

[svenakela]

Ok, first of all, of course there will be a radius in the corners. You can't make sharp inner corners with a circular tool.
On the other hand, on your test MDF it looks like your machine has either backlash problems or is weak in one direction. Maybe both. I assume this is a DIY machine and not a industrial mill, right?

The extra corners in the simulation is just another way to show a radius with poor graphics or low graphic settings (it's related to the first line I wrote).

To help you with the pocketing, I have attached a piece from a Madcam tutorial about pocketing. Actually, I changed it a little bit to describe exactly what you want to do. I had to compress it really hard to be able to post is here (size matters...) so if you want it in a higher resolution, send me a PM.

Best of luck!
Sven

[svenakela]

Seems to some problems with the file upload at the moment.
You can find it here in the meantime.

Regards,
Sven

[phil m]

Thanks for that, the machine is indeed DIY but is from 8020 and has ballscrews. I'd think the backlash would be minimal but really, I have no idea. I'll have to check into that.

The tutorial was interesting. I did it with 3D pocket, it selected and did everything on its own, obviously the disadvantage is I can't choose to do each pocket one after the other on that one. I guess the right way to do it would be wiht 2.5D pocket then.

My main problem is really that one corner that has way too big of a radius. How do I fix that??

[svenakela]

Originally Posted by phil m My main problem is really that one corner that has way too big of a radius. How do I fix that??

That is indeed a machine problem.

[phil m]

We figured out the problem, luckily it wasn't a machine problem, I would have had no idea how to fix that lol the problem was the "constant velocity" setting in Mach3. I fixed the problem by setting it at "exact stop" and now its all good.

Is there any printed material I can download somewhere or buy on MadCAM? The help file is not exactly that great to go through and the few video tutorials don't go in as much depth as I'd like.

[turmite]

Phil I have used constant velocity with Mach for 5-6 years now, still Mach 2, and have never had a problem like you showed in your photo. I am curious what your feed rate was for that pocket cut?

Mike

ps Thanks for keeping at learning Madcam.....I promise you that you will continue to learn and will soon discover that Madcam is very powerful for the $$.

[phil m]

1600mm/min (about 64ipm) the problem has been solved by changing the settings to exact stop. I'll probably try the job again at a lower feeds to see if that'll do it too.

[Dan B]

I've tried to copy toolpaths without success. I see you need to copy and paste, then move the toolpath to create a duplicate. Thanks for that tip, Svenakela. I can't wait to see the rest of your tutorial!

Dan

[ger21]

Rounding corners due to CV is proportional to acceleration. Increase the acceleration and the rounding will decrease, or maybe even disappear.

[svenakela]

Originally Posted by phil m We figured out the problem, luckily it wasn't a machine problem, I would have had no idea how to fix that lol the problem was the "constant velocity" setting in Mach3. I fixed the problem by setting it at "exact stop" and now its all good. Is there any printed material I can download somewhere or buy on MadCAM? The help file is not exactly that great to go through and the few video tutorials don't go in as much depth as I'd like.

Well, that certainly IS a machine problem.
You have different radius in every corner. The "error" should be similar in the opposite corner but it isn't on your machine.

The help file describes exactly what the commands do, but unfortunately they are on a very low level and assumes that the reader knows about the strategies. Tutorials exists, but aren't on the web site yet.

Regards,
Sven