Z - zeroing problem

[mkcfl]

When I zero Z, it displays 1" in the position window, when it is done touching the zeroing plate. How do I change the setting, so I get an actual 0"?

[Ajcoholic]

It should be at the 1" position when finshed the Z zero routine, not at 0".

The readout on the computer screen doesnt always correspond to the actual position real time during the setup routines (zroing the table at the home position, Z zero routine, etc) it takes a second for the readout to "catch up" and display the real position of the tool.

AJC

[mkcfl]

The problem is that if I leave it at 1" when I start to cut, it plunges way too deep and into the table. The only way I can get it close to cut how it should is to manually zero Z after it has zeroed at 1".

[steve_g]

If the bit retracted after touching the plate, the 1” is likely correct. Where did you tell the program that zero is? Top of material or top of the bed?
SG

[mkcfl]

It retracted slightly. Just enough to freely remove the zero plate. I zero on top of the material.

[feinddj]

Over on the right side with the toolpaths is a dialog box Materials Set up. Click on that and it will allow you to set the z at the material or the bed. As a matter of preference, I set it to zzero at the bed. I suspect that yours is set to the material, which as you have it set would be the top of your table. I have made that mistake with a surfacing bit. ouch.

[steve_g]

Another possibility: check to see how thick your z-zero plate is set for in setup… it’s likely about .121” but if setup says its 1.21” ( misplaced decimal) that would mess you up!
SG

[mkcfl]

Thanks for those suggestions! I will try them out.

[harryball]

Without more details, another thought is perhaps the unit values are wrong. If those are not right then you could ask it to move 1" and it could move 2" instead.

/RB

[mkcfl]

I took a look at the settings and they looked right. No misplaced decimals.

I also tried to set (z)ero to the table in PartWorks for the part. When I did the actual zeroing to the table it was too low to give any clearance to the material. When I zeroed to the top of the material it cut to a depth of 0.473" instead of 0.25" as I had set it to in the drawing.

The closest thing to getting a correct depth is so far, zeroing Z after it has set 1", like I explained in the first post.

I am sure it is just some simple setting that I just can't find.

[harryball]

Try this for us, z zero to the table, then move the z axis to 1 inch and measure how far the bit is from the table. Then try 1/2" etc... if those are right we should be able to rule out the control software and bot itself.

Next, if the bot is good, make up a simple test file you think is right but behaves wrong, post that to the forum and someone can take a look at the file and see if anything looks wrong.

I remember starting out, it was an adventure. I'm sure I still hold the record of vac clamping myself to my table.

/RB

[mkcfl]

I zeroed to the table with the plate. After it was done, the bit was as usual just a little over the plate, just enough to pull it out, so about 0.121"/0.122" above the table. The position window said 1".
I raised Z to 2" and measured. I got 1.358".

I think, that the problem might be the zeroing process. It is jumping the part where it should actually raise the bit to 1", but instead stays at 0.121"???

[curtiss]

Say your plate is .121 thick.

When the bit touches the plate the z value on the screen should change to .121

See if this is what happens.

[mkcfl]

yes, it does say 0.121" for a brief moment as it touches the plate and then the number goes to 1", but Z does not move up.

[harryball]

yes, it does say 0.121" for a brief moment as it touches the plate and then the number goes to 1", but Z does not move up.

Then we found the problem, now why and how to fix it.

Have you tried to edit the zero routine?
Does it make any noise like it's trying to move but doesn't?
Does the z axis jog ok? (thinking maybe something is wrong and it can't move above a certain rate)

I think I'd replace the zero routine with the original and try it.

/RB

[srwtlc]

What type of machine do you have, standard or alpha? Take a look at the resolution multiplier for the Z axis under VU. Standard should be 1 and alpha 5. Take a look at the unit values also.

[ron_moorehead]

This sounds like a problem that has been showing up on some peoples ShopBots. I would call ShopBot for support.

[mkcfl]

Ron - Yep, I am sure that the zero routine is the problem. I have not tried to edit. I am not sure where to start. I see it says raise to safe height, but there is no value. I guess, that it is a command to use the safe height set in the Cutter tab.

It does not make any noise and jogs fine. I have been cutting with the machine by manipulating the Z height. X and Y works fine, but of course the depth is off.

Is there a place where I can download a new routine or should I just try to reinstall the software? I installed it myself, so there really shouldn't be any old settings that would interrupt.

Scott - My machine is a PRT standard. The resolution multiplier is 1 for all of the axis. I also looked at the PRTInchUnits table, and to me it looks like the correct settings for the pinion and gear ratio.

Ron - Shopbot have been an amazing help! Much more than I expected, but unfortunately for this issue I can't get any response.

[srwtlc]

What version of SB3 are you running? Do you have a Z axis prox setup on it?

So, your depth of cut is fine when running a part file, but it's wrong at the end of the zeroing routine? Did you say what your safe Z was set at in SB3 under VC?

Attach your copy of the zeroing routine, and we can take a look at it. If you reinstall, it will overwrite it and it may work, but it would be interesting to see if there's anything wrong with the one you're using now.

There has been a few issues that I've seen recently with the latest version, but you're not using that. The older versions did have an issue where the routine was looking for the safe Z in the my_variables file instead of the one set in the program or something like that. Been a while since I've looked at that one.

[JimMetully]

My unit values were off. The previous owner of my machine did modifications to it. When I downloaded software from the shop bot website, it was set to factory settings. I had to dig around to figure out how the previous owner had the unit values set. This is probably not what is going on with your machine, but accidentally messing with one of the unit values would cause your z axis to go to .473 instead of .25 (what you asked it to do).

My z unit value was set at 900ish and I needed it to be 4000 for my machine. I was manually zeroing the bit at the top of mdf spoilboard, then asking it to go to 1" above the table. That command would move it up less than 1/4". This made it so when I ran a program with a safe z height of 1", it would hog sideways through my part going to where it was supposed to start cutting.

It was also creating a condition that made me think there was a problem with my z zero plate because it would zero, then move to z1 (which was actually only 1/4" up off of the table). That led me to think that my thickness setting for my zeroing plate was wrong, but it wasn't.

[mkcfl]

I uninstalled Shopbot 3. When I installed it again (same version 3.4.27PRT), I got the option to update to a new Zzero.sbp program. I remember, that I did that the first time, without thinking more about it, except that newer should be better. Well, I decided not to update this time and now when I use the Z zero routine it works!

I did a test cut where I cut a pocket to 0.25" depth. I got 0.24". I am not sure what the tolerance is for my machine, but I can probably get a little closer.

Thanks for all your help, I really appreciate it!

[harryball]

That .01 could be the difference in your zero plate thickness and what is recorded in the variable. You will also notice small differences depending on the bit you are zeroing. I find vCarve bits zero "deeper" than flat bottom bits for example.

Glad you found it, enjoy!

[ron_moorehead]

The .01 could also be the difference between where you zeroed and the place you cut the pocket. When was the last time you resurfaced your spoiler board. I use MDF for my spoiler board and after a few days I find cutting a full sheet some places cut all the way through and other places don’t cut all the way through.