[SEK22Hornet]

I have an Ajax DM45nc CNC mill with a Centroid control. It is the last version of the Linux software (upgraded from version 1.01 to I believe it is 2.72 - have to look to be sure).I know that I have some Z axis backlash - maybe as much as .005" - I need to look into that to see if I can reduce it by adjusting the bearings, but that is a separate issue. This machine uses manual homing, and the procedure I'm using for startup is this - power on and let the machine boot up. Hit Cycle start to home the machine - no errors - it homes just fine. I use a Fowler Electronic Edge Finder for all setup. I set my reference (tool 0) by lowering the Z axis to a 123 block on the table - sliding the block under the tip of the tool until it just lights the led. I make three or four parts on this machine right now (just hobby work). All my tooling is in tool holders and the tool numbers are loaded into the machine. I have set the tool lengths on all tools using the same 123 block on the table as I use to set the reference tool. After homing I set the part 0 using the Fowler Edge finder. In my mind - I should be ready to make parts. Saturday I went through and reset the reference tool height - it was a few thou different. I reset the tools I was using on that part and everything was fine all day. Sunday I set my home and my part 0 - same tools as the day before. The Z axis was now off by about .020". I've been using this machine for a couple years and the Z axis has always been a bit touchy - I'm wondering if the encoder is starting to miss counts once in a while. This machine uses Brush type DC servos. Should I be doing a complete reference tool set up and reset all tools I am using every time I start the machine up? I would think that once the reference tool is set and all tooling is set up, all I should have to do is home machine and reset the actual part 0 and go. Thanks - Dan

[cnctechml]

You are correct in that you should only have to set the Z Reference and tool offsets once. It could be that your Z axis is physically slipping on you. Please provide a current report from your system. Out of curiosity, are you seeing a message about the encoder counts being different when you're homing?

[SEK22Hornet]

No message about the counts being different when homing. Have had that once in a while on the Y axis since there is no homing mark on that axis. The Z homes at the top of it's travel and is pretty repeatable. I'll try to run a report tonight when I get home. How important is it that the reference tool be the longest tool, as noted in the manual? At one time it may have been but it isn't now. Also, when setting up and re-checking the tool offsets, should I reset the reference tool first, then the other tools? That is the order I use now, since it makes sense to set the reference first, at least to me.

[SEK22Hornet]

Here is the report from tonight - had a crash Monday night (really stupid setup mistake on my part!) so decided to take a day away from it and start back tonight. Things ran good tonight. Dan