HELP Shenhui 690 inconsistent cutting

[Bec Fogarty]

Hi everyone,

We have had a blissful start to using our laser but now we are having issues. The mA meter on the top of the machine when working at 20mm and 90% use to bounce around in the 30-40 mark. Now it is no longer cutting through the leather when cutting it is only sitting around the 6 - 8 mA mark when running. It does not work when scanning at all we were scanning at 100 and 15% but in the last couple of weeks had to up it to 30% and now is not scanning at all. Here is what we have done to try rectify the problem.

We have emptyed and refilled our C5200 chiller
Checked the mirrors
Changed the lens
Checked the gorunding wire

Its broken down at one of the worst times my hubby is about to go away and I am flat out. Any help would really be appreciated.

Please HELP!

Bec

[walter hofmann]

hi bec
I am sorry don't shoot the messenger, but your tube is gone and you need a new one. you [probably have overdriven the tube with power of 30 to 40mA for 80W it should be no more then 30mA better 28mA if the tube should last longer.
the cooling water temperature and the current are the most dangerous elements for the life of a tube.
greetings
waltfl

[Rich Harman]

30 to 40 mA is well beyond the what that tube should be run at. If you have really been running that much current through it, well, sorry to say it is probably done for. Reci recommends under 26mA for long life. Hopefully that is not the case. The negative electrode will show some coloring if it has been run with too much power so I would check that first. I doubt they will honor the warranty if it has been run at too high power but at least those tubes aren't terribly expensive.

When cutting, the needle on the ammeter should not be bouncing. When scanning the needle will bounce around at a much lower value than the laser is actually running. The rapid on/off occurs too quickly for the needle to respond and instead gives you an average reading.

I haven't had to use Shenhui's tech support for a couple years but when I did, they were quite responsive. I would give them a try.

[Bec Fogarty]

30 to 40 mA is well beyond the what that tube should be run at. If you have really been running that much current through it, well, sorry to say it is probably done for. Reci recommends under 26mA for long life. Hopefully that is not the case. The negative electrode will show some coloring if it has been run with too much power so I would check that first. I doubt they will honor the warranty if it has been run at too high power but at least those tubes aren't terribly expensive.

When cutting, the needle on the ammeter should not be bouncing. When scanning the needle will bounce around at a much lower value than the laser is actually running. The rapid on/off occurs too quickly for the needle to respond and instead gives you an average reading.

I haven't had to use Shenhui's tech support for a couple years but when I did, they were quite responsive. I would give them a try.

Mi have emailed shenhui a few times they are going to pass the info onto the tech tomorrow. I have been out to check the tube for brown/yellowing as you suggested and there does not appear to be any signs of that. The reason my needle jumps when cuting is because it is consistently cutting 1.5mm holes for sewing in the leather. When it's cutting solid lines it does not bounce
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[Bec Fogarty]

you wouldnt beleive it went out to the shed this morning and the laser worked perfectly for 4 deck fulls of work then it started cracking the shits again!

The laser is working at 28mA when it is cutting and around 10ish when its engraving it bounces a fair bit when its doing that.

so I think we can safely assume the tube is ok and not over worked. The problem is certainly intermittent. The folks at shenhui had me change out the power supply this afternoon to a new one they provided with the machine but that did not make any difference.

any more suggestions. My work load is piling up so much so I might have to turn some away and can not really afford to.

Bec

[Khalid Nazim]

What type and thickness of leather you are cutting and what are your laser settings for cutting? 90% @ 20mm/sec seems too much. I cut 3-4 oz veg tan leather at 60% power @ 60mm/sec. I have the same laser as yours.

Regards
Khalid

[Bill George]

I would check the water flow switch and other safeties like the door switch. They can barely be making contact and effect the laser firing or not, at times. It happened to me.

[Dave Sheldrake]

Intermittent or top down Bec?

Lemme see if I can clarify?

Start of day = good - gets worse - gets worse - gets worse (Top down)
Start of day = good - gets worse - gets better - gets worse - gets better (intermittent)

If we can establish that it will be easier to suggest a cause. Based on top down at the moment I'm thinking heat or scatter (possibly trigger) but lets see anyways.

Bounce when you engrave isn't too unexpected, as the tube fires to engrave it is subject to a spike in current to fire the tube followed by a lower run current, next line of engraving = the same again so the needle may hop about depending on it's sampling rate.

cheers

Dave

[Bec Fogarty]

I would check the water flow switch and other safeties like the door switch. They can barely be making contact and effect the laser firing or not, at times. It happened to me.

Mine does noe have safeties on the doors well i can not see any.

water flow switch? I have the CW5000 water chiller it plugs directly into the back of my machine. It is also very quick to beep if anything is wrong.

[Bec Fogarty]

Intermittent or top down Bec?

Lemme see if I can clarify?

Start of day = good - gets worse - gets worse - gets worse (Top down)
Start of day = good - gets worse - gets better - gets worse - gets better (intermittent)

If we can establish that it will be easier to suggest a cause. Based on top down at the moment I'm thinking heat or scatter (possibly trigger) but lets see anyways.

Bounce when you engrave isn't too unexpected, as the tube fires to engrave it is subject to a spike in current to fire the tube followed by a lower run current, next line of engraving = the same again so the needle may hop about depending on it's sampling rate.

cheers

Dave

Its a bit of both dave.

Today the laser would not work at all. Yesterday is worked perfectly for 2.5 hours cutting 4 full decks of material then when i hit start on piece 5 the mA dropped and it was like it was scanning when it should be cutting. Then its just get worse and I have nothing at all then it comes back a little bit and scan the cut lines that is was happy to cut at the begining of the day.

I dont even know what to look at now. SHenhui think my laser tube is faulty.

My question for you is I did not buy an extra tube for the machine so can not test it with another. What is the best way to get my hands on a new tube and FAST?

[Bec Fogarty]

What type and thickness of leather you are cutting and what are your laser settings for cutting? 90% @ 20mm/sec seems too much. I cut 3-4 oz veg tan leather at 60% power @ 60mm/sec. I have the same laser as yours.

Regards
Khalid

Khalid I have been cutting 1.5 - 2.8mm leather depending on what i am doing its prefinished leather not vegetable tanned. I have also cut 1.1 vegetable tanned on it as well usually at 30mm and 90%

I tried the same setting as you when I first startedand it did not cut all the way through I wonder if perhaps the tube has been bad from the start? maybe?

[Martin James]

My meter bounces like that as well. (60 watt) I use 85% max power in the max user settings. And 85% max power for any given layer. When starting the next vector the needle jumps up to 30+ then settles to 22. I think the power coming on accelerates the needle and maybe the speed of that acceleration pushes the needle tip up past the actual level. It is after all a cheapo mechanical meter with a spring inside?

M

[Bill George]

My meter bounces like that as well. (60 watt) I use 85% max power in the max user settings. And 85% max power for any given layer. When starting the next vector the needle jumps up to 30+ then settles to 22. I think the power coming on accelerates the needle and maybe the speed of that acceleration pushes the needle tip up past the actual level. It is after all a cheapo mechanical meter with a spring inside?

M

His needle is bouncing because as I understand it, he is cutting holes in leather for stitching T

To the OP, have you checked All your input and output connections on the PSU and controller? I found a lot of mine very loose, in spite of the silicone sealer draped over all the wires, the screws under were loose. Also had a bad door switch that was intermittent right out of the crate so to speak.
After re-reading post #10 sounds more like a loose connection.... Very easy and fast to check.

[Dave Sheldrake]

I'm with Bill based on what you have said Bec, sounds like a lose control wire to the 5v rail on the card from the HV PSU, that will cause the power to go up and down with no real reliability.

cheers

Dave

[Bec Fogarty]

Ok so my dad came over this morning and checked a couple things and they were all good we had a bit of a play with the control panel on the machine and set the minimum to 98% and maximum to 98.1% and the laser started to work again kind of! I say this because 3/4 of the sheet cut properly but the right hand side when looking at the machine did not. I cut 2 sheets of the material and the machine cracked the shits again and went back to is usual tricks of only running at this time 2 - 8 mA.

This is killing me Dave where can i find the thing you are talking about? Sorry electronics are not my strong suit.

I will be trying to find the secret solution in a bottle of wine tonight. I really hope someone can shed some light.