Hi,
At first, I want to say hello to the community, since I’m new here.
I just started my shapeoko 3 XXL, and I have some troubles with it.
I wanted to cut a panel in 2.5mm acrylic, with a 6mm bit 2 flute.
At first try, I let the CC settings for it. The job started, making terrible noise (but I had no idea it was normal), but the bit broke at some point.
It seems CC tried to cut the panel in one pass.
I restarted it but defined a DOC of 1mm, and another bit, same characteristics. Noise was way more acceptable.
But I got a problem with dimensions. To simplify, my design was a rectangle of 70cm x 40cm.
But as a result, I got a shorter side of the rectangle, around 65cm instead of 70cm… The opposite side had the good size of 70cm, and so finally I got a shift…
I checked belt tension, which seems ok. I noticed the movement on the axis was not completely smooth, with some very little slow downs quite frequently.
I tried to look at the belt and I didn’t see any tooth missed on the pulley…
I hope I didn’t damage motors with my first job which had probably bad settings.
You’re losing steps, almost certainly. Your feed rate is too high, and the steppers can’t do it.
You didn’t damage anything.
Were the slow downs while it was cutting or you moving the carriage by hand? If while it was cutting, that’s likely the steps being lost. If while moving the carriage by hand with the power off, that’s back emf powering up the boards, which powers the steppers, which causes them to stop, then power fades and they start moving again.
What seems strange, it’s that compared to firs job, feed was a bit slower (maybe 10% slower), and only 1mm for DOC instead of 3mm. So it was a lot harder for the machine in this 1st try, and apart of the horrible noise, I didn’t notice this problem of dimension…
So I don’t understand, but I’m sure you’re right and I’m losing steps. So I will make tests with lower speeds, and check if it solves the problem.
Belt tension — the Z-axis should be guitar string tight (but careful not to bend the motor shaft): http://docs.carbide3d.com/assembly/shapeoko/xxl/step-5-belting/ on deep cuts it may help to remove one spring from the Z-axis temporarily, esp. if one hasn’t added a spoilboard on top of the wasteboard — it also helps to install the router as low as possible (installing the Makita adapter upside down will help). Some folks have found it helps to remove the M4 Z-axis tension bolt, apply a thin bead of threadlock along the length of the threads, then reinstalling it after it has dried.
For your information, here are the settings I use while cutting acrylic with a 6.35mm endmill / 3 flutes:
RPM = 12000
Feed rate = 2000 mm/min
depth per pass = 1.5mm
Plunge rage = 635mm/min
But your endmill is 2-flute, so adjusting for that you could use feed rate = 20002/3 = 1333mm/min, or alternatively increase RPM to 12.0003/2 = 18000RPM.
As Will mentionned a possible culprit is belt tensioning, and judging from the figure you draw I would say the Y belts should be checked first, make sure they are string-tight.
You mentioned a 6mm end mill, are you using a 6mm collet in your router? The standard Dewalt collet is 1/4” which is 6.35mm. Could your end mill be slipping, then grabbing, then machine loses steps? If all of the above is correct then disregard, only mention it because some folks don’t realize there’s a difference between 6mm and 1/4” then chase other issues for awhile.
Hi Dan,
Thanks for your suggestion. I have a makita router with 6mm collet.
I did all checkings on v wheels, belts, but I saw the slow downs still happening even sometimes when the gantry was moving freely (I mean on movement without cutting).
And I finally found that connector of the right y-axis motor was not completely locked… I probably hade bad contacts sometimes then.
I’m not sure if I wrongly plugged it, or if some tension in the cable made it slightly pop out.
Anyway, now the movement is smooth, and I will get back on trying to cut acrylic.
Thanks all for your help. Good to see lot of people helping here.
