After much frustration I finally understand what’s up with the laser. First, the first carriage mirror keeps getting knocked out of alignment. Second the laser berm was hitting the air nozzle at minimal misaligned conditions. Third, there wasn’t enough air to keep the part cool.
I’ve realigned the mirrors so it’s very close to perfect. I termed the nozzle to give us more flexibility on allignment. Now the problem is the airflow. I rigged a paper nozzle to recover some velocity but this is not a long term solution. I recommend we install a secondary air nozzle of about 1/8 diameter to blow on the part, and tee a small line to the lense to keep smoke out. I can get started on this.
Interesting.
I believe the air is basically to keep debris/smoke out of the laser lens and secondary to cool the part.
I don’t think it has ever been a high velocity jet exiting the nozzle. The pump is pretty low pressure.
Perhaps by enlarging the final aperature the exit velocity of the air jet has decreased too much.
I wonder how robust the air path from the pump is? There could be multiple leaks. I don’t know if the rebuild work on the tube/mirrors did any work on the air piping. The flexible tubing required to the handle the gantry motion may be cracked and need replacing.
I may come out there this afternoon to drop off the cutting tools I got from the totally non addictive auction site. I can futz with the air system if needed.
This afternoon, Paul Marsh had some poor test results and approached me for help. We proceeded to clean mirrors and lens then align the big laser.
We first used the digital indicator to verify the knife bed is in plane. A large sheet of the grey plastic was placed on the bed. The indicator mag base was attached to the gantry carriage. As the carriage was driven over the range of the bed the indicator readout varied by a maximum of 2mm in the z-axis.
Front to back the difference is in the order of 0.5 mm. Given the nature of the bed construction one must conclude the bed is in plane. Sqr but in plane. HIVE quality. to be sure. Do note the honeycomb is seriously bent.
Starting with a target at mirror 2 we determined the mirror 1 was well aligned to Mirror 2 in both near and far positions. All tests were at 1% power using foamcore card stock.
Moving the target to Mirror 3 we determined mirror 2 was off by about 3mm at the far position. After Mirror 2 alignment the spots were concentric to mirror 3 in both near and far front and back positions.
Adjustments required less than 1/3 turn of the adjustment screws done a tiny bit at a time.
The target moved to the bed. The bed was raised to nearly touching the z-probe and a spot was fired, next it was lowered to the bottom. After some adjustment the spots were concentric.
A new paper cone was attached and Paul ran his same test. The results were greatly improved. He then proceeded to run a large job which used much of the bed area. Cut performance was good in all quadrants.
We do notice differences in the main exhaust air flow from front to back of the laser. Flow is better in the front. The air nozzle is too large and needs rework.
Possibly a second moveable flex air nozzle similar to a lathe cutting oil style could be positioned at the cut point. It would need to be reset each time the z datum was reset
Additionally there is a large build up of soot on the support bars which flashes into flame when the laser burns through.
It’s time to schedule another laser cleaning party to scrub the bars clean.