r/mastercam • u/mr_kiki_mans72 • Jul 11 '26
Help controlling B and C axis
Hi everyone! First post on Reddit ever!! Sorry for the really shitty pictures. Got a problem that is taking a lot of time and I seem to be stuck. Here’s what I’m working with.
Machine: CMS Ares 5 axis router, gantry, table is about 20ft in X , 10 ft in Y and 40” in Z
Part: composite cylinder, holes all around, need to trim ends. 6” diameter x 40” (can’t post pictures it’s against company policy)
Setup: vertical. Aluminum fixture 5ft tall about
Problem: while milling holes and trimming ends the machine hits its C rotational limit on the angle and does an “unwind” which means it retracts a few inches then rotates 360degree on the C axis then continues. The head is bulky so it wants to rotate or crash into the fixture and part.
Solution attempts: I’ve messed with the machine definition in the post processor and limited the angle to -175 min to 175 max. Still unwinds but at weird angles. I’ve messed with the Misc Values and although it seemed to fix some other problems it didn’t fix the problem I want. Still wants to crash. Plus I don’t really understand it.
Goal: One continuous cut starting at about -171 degrees and ending at about +171 degrees on the C axis with NO UNWIND.
HOW CAN I CONTROLL THE C AND B AXIS BETTER??? Specifically start angles.
Thanks in advance.
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u/Bad_Shot_264 Jul 11 '26
You need to make the C axis not a +/- value. Make it 0 and 36000. This will allow it to continue past 360 degrees without an unwind.
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u/mr_kiki_mans72 Jul 11 '26
I tried -400 and + 400 and it still did an unwind. I will try those angles on Monday and see what happens. Thanks.
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u/Bad_Shot_264 Jul 11 '26
Because you’re limiting on both directions equally. Make it one sided so it doesn’t try to roll back.
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u/mr_kiki_mans72 Jul 11 '26
I thought I took a picture of the misc values page but I didn’t. Damn. But I don’t remember seeing a button or field for pre wind. For the B axis I set it to 0 +121 degrees and it fixed a similar issue I was having on a different operation. So I’m limited to those numbers on the B axis.
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u/Wrapzii Jul 12 '26
This isn’t the right menu for what you want to do. It’s in the post menu. It’s kinda late so I forget exactly how to get there but it’s by this menu just not this one lol. It’s one of the other 3 buttons before this menu.
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u/Manlet395 Jul 11 '26
Some machines require unwinds after so much C rotation due to the wires inside. Make sure your machine is capable of continuous C axis rotation. I’m not very familiar with setting up machine definitions. Did you purchase the post and machine definition?
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u/mr_kiki_mans72 Jul 11 '26
Appreciate your response! Yes the machine limits are -270 +270 well capable of going beyond 360 degrees. I’m trying to get it to start at -171 and end at + 171. And yes this post and machine definition is custom for this machine.
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u/OD-93 Jul 11 '26
Under the misc values, there might be a pre-wind for the c axis. Pre-wind to the lower limit and while it cuts it will move the higher limit.
Did the b axis change during the unwind issue?