I just wanted to verify that when using the auto-zero touch plate for xyz before each job there is no reason to home the machine, is that correct?
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@DavidB I don’t know if I would go so far as to say that there “is no reason”. There are benefits to having limit switches and homing the machine. I don’t have switches, so I will leave it to others here to explain those benefits.
That said, I have the standard touch plate. I zero the axes using it and run my jobs. I have not missed not having limit switches and not having the capacity to to home. For all that matters, for the majority of my project s, I set XY0 in the centre of the material and only use the touchplate for Z0. Each to his own.
Hi David,
Like Grant, I have a machine without limits (It’s a freedom machine!) I however do have an autoxyz. I have used it and since I cannot home, I can say that it works without homing.
Like Grant I moved on to centre zeroing, leaving the autotouch collecting dust. I too touch off z with the simple block. I do use dimples for lost zero points, where I assume a homed machine would simply know where the zero point was.
@DavidB There is no need to home before each job IF you do not power cycle the SLB in between jobs.
Or to put it differently, you should home after every power cycle. The machine X0Y0Z0 should be at the same position (top-left corner) after rehoming.
Also, I jot down the machine coordinates of my workspace zeroes in case there is a power outage during a job or if I accidentally zero my axes. After the outage, I re-home, manually jog to the machine coordinates I jotted down and then set the zeroes again.
Note that you should periodically check your limit sensors. Mine became loose after several hours of use. A loose sensor will affect the homing sequence and ultimately, the position of the machine zeroes.
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But that isn’t necessary if I use the Auto-zero plate, right?
Okay.. so why are you doing center zeroing instead of using auto-zero touch plate? Seems like more work to find the center then to just use the plate to zero on the corner?
@DavidB I believe that you are confusing machine zero-home with material zero. Limit switches and the homing cycle return your machine to the same location each time. That location is machine zero. It has nothing to do with material zero and vice-versa.
As to why I set XY0 in the centre of the material, the main reason is that I design in VCarvePro setting material zero to the centre of the material. That way, all my designs are concentric around the centre. Now, after the design is complete, I could re-set material zero to a corner. I simply choose not to. I frequently use material that does not have square corners. The touchplate is not made for that. On the other hand, I can find the centre of off-square material quite simply. Then, I use a cross-hair laser to make it easier to jog my machine over the centre that I have marked on the material. It is very quick and easy. Then I use the touch plate to set Z0.
As with pretty much everything else, there is no right or wrong way to do this. Find one you like and stick with it.
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You don’t even need to set machine zero if you are using the auto-zero touch plate though, right? I currently am homing to set machine zero after power cycling the SLB-EXT but I was thinking that isn’t necessary with the touch plate if I am probing for XYZ anyways.
@DavidB Necessary? No. Good practice ? Yes. Like I mentioned, if you lose your zeroes for some reason, writing down the machine coordinates of the zeroes before your job starts will allow you to set the zeroes again. Doing it with the AZTP may not be possible if you removed the material at that location. That’s only possible to do accurately if you home first.
I guess the question is why wouldn’t you home after a power cycle of the SLB? It’s a 60s task.
Okay.. Yes, that is what I figured.. I was just trying to understand the basics.
Related to that.. is there a reason gSender goes back to home every time it finishes a job? Since I’m still a noob I was post processing individual tool paths out of Fusion 360 so I may have 2 or 3 jobs that are sent in gSender and after each one gSender sends the spindle back to home. Am I missing something? 
@DavidB Hmm, not sure.
GSender can be configured to run tasks before or after a job. Do you have anything there?
Could Fusion be adding a G28 command at the end of your g-code? I think that would be defined in the post-processor. Actually, I think another user asked that before. Let me search for that post.
Here you go. The post-processor edits in Fusion are definitely more difficult to do than for vCarve.
Ah yes.. thank you so much. I see the G28 there.
Like you David I initially only worried about setting XYZ zero to the corner of my work piece with the XYZ touch plate. However, after loosing a couple of projects due to (1) power failure and (2) a broken bit, I started to home the machine at every start up and then reposition (via a macro) to the location i normally place my work piece and then reset X & Y to zero in gsender. This allows me to always return to the same start point even if I have changed my bit. I can even shut the machine down and start again the next day and get the machine back to the same starting point. Hope that makes sense. Regardless, it is still a matter of personal choice.
Len
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I “upgraded” my CNC to SLB-EXT and related closed-loop kit. I too found that my Y2 limit switch messed up once. It was very disruptive but a simple fix once I was made aware of that possible cause of the Error 2 message I was getting.
I have the SLB and limit switches. I use the lower left corner as my origin most of the time. When I shut down my machine, I usually leave it at the XY origin point. When I start up, I home the machine, then go to my XY starting point that is stored. I still use the auto-zero touch plate to set XYZ, just to be sure, even though in my scenario, only the Z needs to be set. I’ve done it both ways and never have an issue.
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First thing i do after power on machine and get it connected is to home. I just have a thought process that i should know its in a known state. When i am working on a project i autozero, once i do that the X Y X are all set to 0 and my vcarve all runs from that origin. I can see where if there was a power loss etc that it might be important to re reference from home but i believe you would have to know the correlation between the home coordinates and the xyz zero coordinates. I should note that i try not to carve out my zero location (either leave excess and trim later or do the last toolpath to cut the part out). if you carve it out because you have to it becomes more important to have a known reference.
yes and no. if you want to get back to the same location (job Zero), it’s better to home first then take note of the dimensions of the new zero of your job, that way you can enter the numbers of the job Zero instead of using the touch plate to find the job Zero. if you don’t home first, you probably won’t be able to get back the same job Zero by entering the numbers since you don’t know for sure where the home Zero was located or if it moved for some reason. I have had this issue my self where the job zero was move a little when using the auto zero touch plate.
Mark
It’s mostly not finding centre, it’s more like setting it. Sometimes, when material is tight, I do like Grant and cross out the centre, but mostly I have enough wiggle room to simply nominate a point as the xy0 and go with that. As a safety I will put a dimple on the waste material side with a known offset from the nomi ated xy0 as to be able to come back to it, with either a laser or after a whoops moment.
I use this method primarily because I like a one solution for all, without the need to introduce a failure point on mistaking the method used for zeroing in the design. Since organic material like tree trunk plaques can only be done with a centre zero unless using a jig with external xy0 point, introducing more, not less ways to design around a zero point, I have ditched all but centre as my togoto method.
When you are customised to it, I feel it to be quicker than corner zeroing, but speed has never been a high priority.
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