Looping Question

[B. Jacobs]

I have three parts that I am running in a loop. I have a question that ya'll may be able to answer for me.
By the time my loop gets to the third part(I was running 4 parts but it didn't work) it seems as if the Z distance is changing. What I mean is that when the third part starts, the distance the probe has to travel till it makes contact is very short. On the first part it is the regular prehit distance. I tried a fourth part but it would always crash on the first hit. The first feature is a plane that is level with the table.
I Loop only in the X 4.5" only. No Y, or Z moves in the loop.
Any ideas what it might be?
IThe only time I am having trouble because of this is when I am trying to take a point hit and it crashes in the Z.

[TRD_racing]

I would recheck and verify that you alignment is correct, it sounds like it is off a little bit. Run a double alignment to tweak your positions if you need too. Hope this makes sense.

[B. Jacobs]

I will try that.

[TRD_racing]

Hey Bryan, I also have something else for you to look at. You don't have to have 4 parts to run the program. You can run it for as many as you have loaded. I will send it to you soon. Ok.

[B. Jacobs]

Go ahead and send away.

[B. Jacobs]

Found the problem

I would recheck and verify that you alignment is correct, it sounds like it is off a little bit. Run a double alignment to tweak your positions if you need too. Hope this makes sense.

Hey Dale,
I found my problem. I have my parts sitting in Vee Blocks. I ordered a small set a while ago to get started with. They worked great for these parts.
I ordered another set of the same Vee Blocks about a month ago so I could loop my parts.
The problem is that each set of Vee Blocks are off about .015. This is causing 2 of my parts to be higher thatn the first 2. Man it sucks.
I now know what the problem is and how to fix it, but I am oing to have to rewrite the program. Oh well at least I now know.
Thanks a bunch

[T Miller]

Could you not just shim the first 2 vblocks to match the others?

[craiger_ny]

You could open up your prehit/retract until you pick up part alignment. I am thinking if you program to accomodate the diference now what is going to keep your monkeys from putting the blocks in a diferent order next run?

Craig

[#2#]

Could you not just shim the first 2 vblocks to match the others?

I'm liking this idea. If you have machine shop capabilities you could also machine the taller blocks so that they will match the others.

[Perry Fisher]

I do this occasionally. I think Craiger's suggestion is the best. You don't spend time grinding Vee blocks and don't have to keep up with shims.

[tking]

I do this occasionally. I think Craiger's suggestion is the best. You don't spend time grinding Vee blocks and don't have to keep up with shims.

Craig and Perry have it right

TK

[Ravenmaniac]

Bryan...had a very similar situation to yours.....As a habit I have my own set of matched v-blocks that I keep under lock and key. I was doing a loop program to pairs of parts inprocess for a matched set of pieces for one of our customers that were running beautiful together and then one morning I came in and they were running O/T to each other by about .010-.018. I had the job stopped and started tearing into everything wondering why the parts were varying......found out the nightshift inspector tore out one of the v-blocks I was using in the twin setup and replaced it with another because he knew the one on the CMM was of better quality when checking a tight runout for a shaft. The one he replaced it with was different in size by about .02 because it wasn't part of the original matched set. Conclusion....machine down 3/4 of the day and then 8 hours to reset up from scratch and get it right. We were down for almost 3 full days............B

[Dennis]

match grind the vee blocks