Peculiar Engraving Problem

[junglebmx]

Hello,

I hope some of you are able to give me some suggestions my engraving problem because I am ready to give up and buy a new machine!

The problem is to do with misalignment of left-right scan and the right to left scan but only in the centre of the engraving... It is driving me mad.

Pictures are here: https://www.dropbox.com/sc/aod39ot6aq3ph64/JkMzpgc6hl

I have replaced timing pulleys and belts- there is no obvious play and belt is adequately tight. Tried various different stepper resolutions and currents as well as switching out the stepper driver. The test in the pictures is of varying speeds from 400 to 5 mm/s all with the same result- Alignment at the edges but dislocated in the centre.

I have also tried various engraving settings, acceleration settings including the pre-set fast-normal-slow instant recovery settings in user parameters.

The stepper on the X axis is not geared, is a (EMOT-57HS22) NEMA 23 57HS22 4A 360oz with (ECNC-2M542) 2 Phase 4.5A 1-axis Stepping Motor Driver. Support to Nema 16~34. Leetro replacement.

Any suggestions on the next step would greatly be appreciated.

Thanks

[Tech_Marco]

The OS was very old. Time to upgrade it. I just "PM" you new OS and new LaserCad. Make sure to format the USB memory stick with FAT32 or it won't be able to read the file. Try use 2Gb or 4Gb drive if possible. In some case, it may not read the file in time and you may need to wait tens seconds or have the memory stick in the USB slot, then hit RESET. That may help to 'syn' the memory with the DSP main-board.

The update take about 10second to complete. Do NOT interrup the update procedure or the mainboard will be "bricked" and non-functioning if you somehow stop the updating process or power got lost. Be careful!

Let me know if it works out fine after the patch. If not, then it is possible the hardware issue. What kind of machine do you have by the way? Did the problem happened recently or been happening since day 1?


Marco

[junglebmx]

Thanks for the quick reply!

I had the latest OS installed but I was having problems when half way through an engraving the machine would stop, ruining the engraving and sometimes slamming beyond the X/Y limits. It was like the file had only half been uploaded. This was a massive problem and waste of material due to unreliability. I installing the previous OS was a last resort and solved the problems completely.

I have now installed the new OS and unfortunately it is not that simple, the problem still exists.

The machine was originally a shenhui SH-G350 laser engraving and cutting machine but I have upgraded nearly everything other than the x/y frame and the Y stepper and driver.

I believe it may either be a controller problem, or a stepper motor problem.

The dislocation in the centre of the engraving happens on small engravings placed around the bed as well as across the full length. On engravings across the full length the dislocation is most noticeable and the best example.

I have noticed this problem intermittently due to doing a lot more cutting with my machine than engraving but really the first time I noticed it was the first time I upgraded and installed the controller etc. The next step I took was to replace the belt and pulleys with actually helped as maybe there was some play there but now I can assure you there is no play. The 5 mm/s engraving would show a different effect Vs the 400 mm/s but shows the same problem in the same places. Smaller engravings show the same problem on a smaller scale.

I have been searching forums for a similar problems for a while now...

I have just had a quick look and could not see anything but was there not once a AWC-608 upgrade chip?

Cheers

[Tech_Marco]

I don't think that it is DSP card issue. It's more likely the stepping motor driver or the hardware.
You can change the 'um' value to something else to see if it helps. For example, if you have 12.575, then make it 12.25. Give it a try.
Or, change the falling edge to rising edge or vice versa. If this doesn't work, then the problem might be the pulley or the belt. I have a machine from ShengHui and it is not good. I have to fix the gear and upgrade the DSP card. Also, I need to upgrade the laser power supply as well. Don't buy from them since their machines won't last long. I have been to their factory 3 times and I didn't like what I saw from their production line.

Marco

[tbirdglenn]

Hello junglebmx and Marco,

I have been doing bold engraving and didn’t notice the problem. Now I’m doing some very fine engraving and noticed the same problem you have described. In engraving small lines like script text, the point where the laser fires while traveling from left to right doesn’t match up with where the laser fires while traveling from right to left. A vertical line ends up looking like a zipper.

I have also tried very slow speeds so I'm confident backlash is not the issue. The offset is the same traveling fast or slow.

Is there some setting to calibrate the x-axis swing so the back and forth firings line up? I’ve tried adjusting the engrave acc. to various settings between 5,000 and 10,000, but nothing changes. Also, it does the same thing if I use the y-axis swing.

Glenn

[Greolt]

Look here