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Problem with ramps and lead in Fusion.

Posted: Sun Feb 07, 2016 3:44 pm
by Auarhau
Probably not a fusion specific question. But are anyone else having problems with ramping and lead in? I mean it works, but my machine sounds awful. It stutters and vibrates and it sounds to me that the steppers are getting too little current to smoothly execute the slow ramp and lead in tool paths.

I am running my stepper drivers at 1,4 amps. And the specs for my driver is:
"Continuous current per phase: 1.5 A2
Maximum current per phase: 2.2 A3"

My motors could handle a little more current (1,7amp I think), but I don't think I would like to run the drivers any higher then 1,4amp (?). I do have heat sinks and a fan on them. But they do get hot.. And so far I have never experienced a missed step (that I know of), and I would like to keep it that way:)

So, anyone else experience this? I think my solution would have to be to stop using ramp, and just plunge in. Either that or speed up the ramping a lot, which perhaps defeats the purpose a little?

Re: Problem with ramps and lead in Fusion.

Posted: Mon Feb 08, 2016 7:48 pm
by op117
i have the same problem in inventorHSM if u have a post option to change it from

G0 ramps to G1 try that or set <all ways use high feed>on post of that operation see if that works.
hope this helps!

the reason is because the ramp is eater running to fast or slow depending on your setup for the running code.

Re: Problem with ramps and lead in Fusion.

Posted: Mon Feb 08, 2016 11:13 pm
by DRobs86
I am curious what your ramp feed, speed, and material being cut is.

Be sure that your ramp is slower than your normal cutting feedrate for a given material. The bottom of the endmill is engaged to some extent in a ramp. In some materials this may mean chattering.

Are these profile ramps or helical plunges? What are your acceleration and microstep settings?

Re: Problem with ramps and lead in Fusion.

Posted: Tue Feb 09, 2016 9:49 am
by AnonymousPerson
As a "covering the basics" question (to be safe), are you 100% sure the end mill you're using is designed for centre cutting?

Asking because early on I learned the difference the hard way, by plunging/ramping with non-centre cutting end mills. It made very unhappy sounds, which kind of sounds like what you're describing. ;)

In F360 these days I normally turn off lead in/outs and just do straight plunging at a slow rate instead. eg 30mm/min for MDF. 10mm/min alu 6082. That's when I know for sure the end mills do centre cutting though.

Re: Problem with ramps and lead in Fusion.

Posted: Tue Feb 09, 2016 2:38 pm
by Auarhau
It's not a cutting problem at all. It's the same "air cutting". The vibrations and noises are from the motors. It's either just because ramps are so slow, or there is something funky going on with the ramp g code that grbl doesn't like.
And yes ofc all my end mills are capable of center cutting ;)

I'll play some with post processor and speed/acceleration settings when I get the time. Normal plunges works great (by the way AnonPerson, your plunges are terrible slow :p I use 150/200 mm/sek for woods and 100mm/sek for aluminium. Works for me with my setup at least)

About micro stepping; why does that matter? I have the default settings recommended in the instructions for the GAUPS shield, whatever those settings are. I'd have to check my dip switches, I don't remember :D

Re: Problem with ramps and lead in Fusion.

Posted: Tue Feb 09, 2016 3:06 pm
by AnonymousPerson
Auarhau wrote:by the way AnonPerson, your plunges are terrible slow :p I use 150/200 mm/sek for woods and 100mm/sek for aluminium. Works for me with my setup at least
Yeah, it's on purpose. Was experimenting with milling some shapes out of 6082 aluminium on the weekend, using a 2mm (2 flute) end mill. The much slower plunge speed had a better result than going faster. I don't have a reinforced Z-axis plate (yet), so I'm thinking it's probably just a flex thing there or something, and the speed reduction was letting me get away with not reinforcing it so far. Total guess though. ;)

Re: Problem with ramps and lead in Fusion.

Posted: Tue Feb 09, 2016 5:22 pm
by cvoinescu
The Z motor may make a terrible noise when ramping. I'm pretty sure that's normal. It happens when the move is too slow to be continuous, so what you hear is a lot of separate steps in quick succession. Reducing current will make it quieter, but you increase the risk of missing steps, so probably not a good idea. However, if you're at 1/2 or 1/4 microstepping on the Z axis, you may want to try 1/8 or 1/16 (and change your steps-per-mm accordingly).

Re: Problem with ramps and lead in Fusion.

Posted: Wed Feb 10, 2016 2:14 am
by Rubes
I have a similar problem. I used F360 to create a pocket with 2d adaptive clearing. It creates a circular spiral down that works great, but once down at the level, the "smooth sweeping arcs" that the adaptive clearing are supposed to be sound like what you are saying, and it slows to less than a crawl. And yeah, this is just air cutting too. Still messin' around with various options, but wanted you to know your not alone.

Re: Problem with ramps and lead in Fusion.

Posted: Wed Feb 10, 2016 7:50 am
by Auarhau
Rubes wrote:I have a similar problem. I used F360 to create a pocket with 2d adaptive clearing. It creates a circular spiral down that works great, but once down at the level, the "smooth sweeping arcs" that the adaptive clearing are supposed to be sound like what you are saying, and it slows to less than a crawl. And yeah, this is just air cutting too. Still messin' around with various options, but wanted you to know your not alone.
This is more or less the opposite problem of what I have. Sounds like your helical ramp works but not the 2d adaptive part. I know I have had problems with tiny arc's before, so your's might be a post processor issue? Some g-code senders also have an option to trun arcs into lines or something like that, might be worth experimenting with.

Re: Problem with ramps and lead in Fusion.

Posted: Wed Feb 10, 2016 7:53 am
by Auarhau
cvoinescu wrote:The Z motor may make a terrible noise when ramping. I'm pretty sure that's normal. It happens when the move is too slow to be continuous, so what you hear is a lot of separate steps in quick succession. Reducing current will make it quieter, but you increase the risk of missing steps, so probably not a good idea. However, if you're at 1/2 or 1/4 microstepping on the Z axis, you may want to try 1/8 or 1/16 (and change your steps-per-mm accordingly).

Ok thanks, at least I'm not doing something destructive then (probably... :mrgreen: ). I'll try adjusting the micro stepping if my other experiments fail.