Plunging too deep ( newbie )

Talk about all things CNC
Posts: 17
Joined: Wed Jul 02, 2014 4:21 am

Re: Plunging too deep ( newbie )

Post by Gooliez » Thu Jan 08, 2015 12:31 pm

yeah they are from inventables.. ok 200 steps, i'll change it around. hopefully that fixes it.

wont get to test for a couple of days, will post with results

Posts: 155
Joined: Wed Oct 01, 2014 1:59 am
Location: Madison, WI

Re: Plunging too deep ( newbie )

Post by tjshape » Thu Jan 08, 2015 1:28 pm

CraftedLabs wrote:
tjshape wrote:Be certain that they are both zero. I recently had an issue where I would hit the zero button and only one of those values returned to zero, with the other set at 3. That caused the first plunge to go in 3 extra mm until I realized the issue.

Sent from my iPhone using Tapatalk
I find the quickest way to avoid that is by closing and opening the connection to the controller rather than hitting the set zero button
Didn't work in my case. Nor did removing power/rebooting. In the end, I needed to run the command "G10 L2 P1 X0 Y0 Z0" to clear things up.

It looks like the 200 steps for this specific issue is the magic answer.

Sent from my iPhone using Tapatalk
Shapeoko 2, ACME upgrade, Belt Drive Z-Axis upgrade, Dewalt DW660

Posts: 17
Joined: Wed Jul 02, 2014 4:21 am

Re: Plunging too deep ( newbie )

Post by Gooliez » Sun Jan 11, 2015 9:22 am


however another problem and an additional question

Firstly... G90 was said to be added... what exactly does that do and how do i add it ? what is the command and what is the value ?

secondly the second problem
the feed speed is still WAY too fast i've adjusted $4=129 down to about 60, just for experimental purposes and it doesnt seem to be making any difference what so ever... am i changing it in the wrong place?

Posts: 1061
Joined: Sun Aug 25, 2013 12:44 pm
Location: Norway

Re: Plunging too deep ( newbie )

Post by Gadgetman! » Sun Jan 11, 2015 12:03 pm

G90 doesn't have any parameters. It's added to the beginning of the file, and it means 'Switch to Absolute coordinate mode'.
GRBL will assume that it's in absolute mode when it's started, but it's a good idea to have it there anyway.
(Another file might set it to G91 - Relative mode and not set it back afterwards)

The $ variables are the absolute max feeds that GRBL will allow. You shouldn't mess about too much with those, really.
Instead use the 'F' command.

Now, this depends on whether you're running in Metric or Inch mode...
G20 in the beginning of the file indicates Inches, an G21 indicates that metric(all masurements in millimeters)

Fxx sets the Feed Speed to that number of inches or milimeters per minute.
So in G20(inch mode) F20 means it will move at max 20 inchs per minute, which is about F500 in G21 mode.

Only G1 (cutting)operations will adhere to the Fxx speed, though.
G0 is for rapid repositioning of the tool, and will move as fast as the system allows($ variables)
CAM packages will automatically pick the correct G0/G1 operation, though.

The F command can be used anywhere in the file, and as many times as you want.
It can be on a separate line or even as part of the parameters of a G1/G2/G3 command.
(There's no 'scope of visibility' though, so even if it's set as part of a command, it will be valid of the following commands, too, until the next Fxx command)
Weird guy...
Shapeoko 2014F: 1000mm X/Y, 300W Quiet Cut spindle, Arduino Uno/G-shield and GRBL 0.9i
15x30 drag chains, custom spindle mount, 9mm belts, 8mm endplates, 6mm motor plates.

Posts: 17
Joined: Wed Jul 02, 2014 4:21 am

Re: Plunging too deep ( newbie )

Post by Gooliez » Tue Jan 13, 2015 6:28 am

awesome thanks for explaining that so well gadgetman.
i'll have another play when i get a chance !

Posts: 17
Joined: Wed Jul 02, 2014 4:21 am

Re: Plunging too deep ( newbie )

Post by Gooliez » Wed Jan 14, 2015 1:16 am

So i found out what the problem was, as usual, user error.

Yes it was the Fxx numbers that were wrong after looking through all the code ( after actually knowing what it now meant )

in aspire, the bit feed speed was set at 200.... however it was mm/sec instead of mm/min so yeah, it's was actually trying to cut at about 14,000mm/minute instead of 200 :oops:

Posts: 122
Joined: Mon Jun 08, 2015 9:18 am

Re: Plunging too deep ( newbie )

Post by apspurgeon » Thu Jul 16, 2015 7:18 am

Hi had a similar issue, everything on the X,Y was ok, but plunged too deep

The issue was the Z axis would go up too far (has a clearance of 20mm) and hit the 'stops' at the top of the movement. It thought it has gone up 20mm, but in reality only 10mm (as an example) after hitting the when it tried to mill it when down too far.

Was a simple observation at the beginning of the job, and an adjustment of the clearence setting and/or moving the spindle lower in the bracket.

Posts: 587
Joined: Wed Jan 08, 2014 11:33 am
Location: Birmingham, UK

Re: Plunging too deep ( newbie )

Post by RobCee » Thu Jul 16, 2015 8:14 am

Something to put on your to-do list is to upgrade your version of GRBL. It looks like you are using an old one and the later ones have some improved functionality which will help you. It isn't urgent, given where you are with things, but it may help later.
ShapeOko2 #3400 - Chinese 800W AC Spindle - Stiffened X-Axis - TR10 Z-Axis - Inverted Z Motor - Hall Effect Limits - Drag Chains & Custom Brackets

Post Reply