Hello you all, Lately I've noticed that my X axis shifts to the left during the program by 0.68mm. The first time I noticed this was when I made a plaque with a 60degree VBIT and a lot of letters. I had divided the total program of letters into four and when he was done with that I saw that the bit had shifted again about 0.6 mm. Now I think the anti backlash nut is worn out and I will have to replace it. Is this correct or can I adjust the utility a bit. This afternoon I was working on a project where I used a 100mm long bit with a cutting length of 55mm and a diameter of 6mm. The total d.o.c. was 39mm. at the first cut it was 6mm wide but when the cutter was completely finished it was 6.68mm wide. So at that depth the bit rubs against the left side and you can hear that clearly. So my question is, what can I do about this? I would like to thank you in advance for your answer. Bert Klappe
You can adjust it yes, but also go over all fastners - if its been in use for a bit -some may have rattled loose. Also check your shaft coupler grub screws are still tight. Check that stop collars are still tight against the bearings and no axial play in the leadscrew itself is present That could also be symptomatic of Tramming - is the endmill perfectly perpendicular to the bed?
Hello Peter, Thank you for responding so quickly. I completely checked my machine two weeks ago and the tamming is also perfect. The bit is parallel to the table so I think it's in the anti backlash nut after all. Luckily I have a few more (5) and I'll be mounting and re-tuning a new one tomorrow. I'll check the grub screws right away and then do a new job again to see if it's improved. I will report on the outcome. Bert Klappe
Hello Peter, This afternoon I replaced the backlash nut. That took me about half an hour. Then I made a simple program with some letters in a panel of 297x210mm and I just milled it 1mm deep. In the end my machine always comes back to 0.0 and 5mm above the workpiece. Now I actually want to run this same program five more times from the same point to see if the machine still moves to the left during milling. Can I start tomorrow where the machine left off today without using the machine home and the probe? Thanks in advance for your answer. Bert Klappe
No, you will have to home the machine (its the only way it can establish a reference point), but you shouldn't have to reset the workplace zero. Alex.
Hi Alex, Thanks for your answer. How do I get my current o point to return to exactly the same place after homeing? Can I then home tomorrow, then try and start to carve or is there another way. I just mounted the limits last week and I've been working with the probe since this week, a newby, so could you explain that to me please. thanks in advance for your answer. Bert
The "zero" location is just an offset from HOME. Its stored in EEPROM. Rehoming re-establishes machine coordinates (as accurarely as your switches can) - which also restores all saved offsets (G54, G55, G56, G58. G59, G28, G30, etc) as those are all just "offsets" from machine coordinates. See Grbl v1.1 Commands · gnea/grbl Wiki So home, GOTO ZERO for a sanity check, then run (no need to probe or zero as it was stored last time you set it) Of course, you can also reprobe/rezero - if that feels better to you - unless the job's first run cut away the corner you were probing from and you cannot place the probe in exactly the same spot
Hello Peter/Alex Today I did a test using the same panel as yesterday still in the same place with the same bit (60 degrees) I ran the same program four times today and even on the fourth time you could still hear the bit scraping against the left side of the letters. However, so little was milled away at that time, I think 0.01 mm, that it is no longer visible. For now I'm satisfied and I hope it will be long time before I have to replace such a backlash nut again. Thanks for your help you both Bert
