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- Oct 26, 2007
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I recently purchased a knife-edge plate kit with copper modules from Rick Trent's eBay store.
The kit comes with 1x base-plate, 3x aluminum blocks, 3x copper modules, screws and springs for mounting, and also some articulate metal arms (more on this later). Though the eBay ad specifies that no mirrors would be part of the kit, I was pleasantly surprised to find 3x high quality dielectric mirrors thrown in as well, in addition a spare mounting screw and spring. Here's a picture of most of the parts in the kit:
The aluminum blocks mount to the plate via long screws that have high-tension screws below to provide pressure. Here's a video of it in action from the eBay ad:
In order to prevent much wobbling, the springs need to be quite compressed:
Unfortunately, this still does not prevent the blocks from shifting and twisting. The twisting is especially annoying, and no amount of tightening really fixes it. You can see here that the blocks are angled differently:
The kit also comes with 3x copper modules. What makes these copper modules special is that they come with copper backs in addition to the lens-holder. This provides a large amount copper material to conduct heat away to the blocks. The copper backs are much better than the brass backs because they're not so hollow as well as can be seen in this picture:
The amount of copper in these modules is pretty substantial for their size, and they have a nice weight to them. Very good value I'd say.
The copper modules fit into the aluminum blocks cleanly and are held in place with a set-screw. Unfortunately, despite the extras in the package, I could not find any set screws in the box. I'll have to see what I can scrounge up around here.
Finally, the kit comes with a heap of little aluminum arms along with some screws to connect them together. The idea is that you can put a mirror or something else on the end of a chain of these articulate metal arms and position them in front of the beam for knife edging.
In practice, the articulate arms don't work very well. They're not very solid, and very prone to vibrations and coming loose.
Analysis:
The kit has some good points and bad points. I like the fact that it comes with some nice copper modules and some decent-sized metal blocks. I also received some nice mirrors that I appreciate.
For a precision knife-edge setup, the kit isn't that useful. The real problem is that a knife-edge setup really requires a very solid, precise mount and positioning setup. While there are screws to give the blocks tension, the screws are too thin for the holes. This allows the blocks to twist and shift on their mounts.
The articulate arms, while an interesting idea, just don't do the job either. Knife-edging or beam combining really needs a hard-fixed mount, not a long and bending arm that is prone to being bumped. Just the fact that it would be very hard to even position the arms while tightening them down would make it really difficult to really use these even in an experimental fashion.
Potential Improvements:
Rather than some articulate arms, other metal parts would be useful. Notably, a bunch of washers would have been nice to prevent the screw from grinding on the top of the aluminum modules. I would also like to see some nuts provided in order to allow the user to tighten the springs down or fix the blocks.
Washers + nuts could go a long way towards making this apparatus more solid, but really the whole mounting strategy needs to be revamped. Having four different screws to adjust the blocks just doesn't work. A better setup would be to emulate those adjustable mirror mounts. The blocks could employ a ball-bearing at the location of one of the screw holes as a pivot, some springs to provide tension, and screws to do the fine adjusting. You'd lose some of the up/down motion, but the whole system would work a lot better for actual knife-edging. I've actually attempted this with some ball bearings I have, but unfortunately the springs take up too much room for the ball bearing to act as a good pivot. I also tried using some PCB board stand-offs but they didn't have compatible threading (maybe motherboard stand-offs would work?)
For actual knife edging, perhaps the center module could be replaced with a mirror mount, and the side-blocks could fire towards the middle. Then multiple plates/blocks could be stacked up and combined. Really crappy mock-up:
I'd also like to see ways to mount heatsinks. The blocks of aluminum are nice and big, but there isn't a lot of surface area on them. For low-power reds this might be okay, but for higher powered lasers this may limit the overall power you can push through these. The screws on top also interfere with putting a big plate unless I want to mount the blocks directly to the heatsink.
As I can't really use the spring system without additional mods. I'll probably end up using these blocks without the springs and connect the base plate to a larger heatsink to help reduce the heating. For that it should be okay. This kit shows promise, but needs some extra work in order to be really useful.
The kit comes with 1x base-plate, 3x aluminum blocks, 3x copper modules, screws and springs for mounting, and also some articulate metal arms (more on this later). Though the eBay ad specifies that no mirrors would be part of the kit, I was pleasantly surprised to find 3x high quality dielectric mirrors thrown in as well, in addition a spare mounting screw and spring. Here's a picture of most of the parts in the kit:
The aluminum blocks mount to the plate via long screws that have high-tension screws below to provide pressure. Here's a video of it in action from the eBay ad:
In order to prevent much wobbling, the springs need to be quite compressed:
Unfortunately, this still does not prevent the blocks from shifting and twisting. The twisting is especially annoying, and no amount of tightening really fixes it. You can see here that the blocks are angled differently:
The kit also comes with 3x copper modules. What makes these copper modules special is that they come with copper backs in addition to the lens-holder. This provides a large amount copper material to conduct heat away to the blocks. The copper backs are much better than the brass backs because they're not so hollow as well as can be seen in this picture:
The amount of copper in these modules is pretty substantial for their size, and they have a nice weight to them. Very good value I'd say.
The copper modules fit into the aluminum blocks cleanly and are held in place with a set-screw. Unfortunately, despite the extras in the package, I could not find any set screws in the box. I'll have to see what I can scrounge up around here.
Finally, the kit comes with a heap of little aluminum arms along with some screws to connect them together. The idea is that you can put a mirror or something else on the end of a chain of these articulate metal arms and position them in front of the beam for knife edging.
In practice, the articulate arms don't work very well. They're not very solid, and very prone to vibrations and coming loose.
Analysis:
The kit has some good points and bad points. I like the fact that it comes with some nice copper modules and some decent-sized metal blocks. I also received some nice mirrors that I appreciate.
For a precision knife-edge setup, the kit isn't that useful. The real problem is that a knife-edge setup really requires a very solid, precise mount and positioning setup. While there are screws to give the blocks tension, the screws are too thin for the holes. This allows the blocks to twist and shift on their mounts.
The articulate arms, while an interesting idea, just don't do the job either. Knife-edging or beam combining really needs a hard-fixed mount, not a long and bending arm that is prone to being bumped. Just the fact that it would be very hard to even position the arms while tightening them down would make it really difficult to really use these even in an experimental fashion.
Potential Improvements:
Rather than some articulate arms, other metal parts would be useful. Notably, a bunch of washers would have been nice to prevent the screw from grinding on the top of the aluminum modules. I would also like to see some nuts provided in order to allow the user to tighten the springs down or fix the blocks.
Washers + nuts could go a long way towards making this apparatus more solid, but really the whole mounting strategy needs to be revamped. Having four different screws to adjust the blocks just doesn't work. A better setup would be to emulate those adjustable mirror mounts. The blocks could employ a ball-bearing at the location of one of the screw holes as a pivot, some springs to provide tension, and screws to do the fine adjusting. You'd lose some of the up/down motion, but the whole system would work a lot better for actual knife-edging. I've actually attempted this with some ball bearings I have, but unfortunately the springs take up too much room for the ball bearing to act as a good pivot. I also tried using some PCB board stand-offs but they didn't have compatible threading (maybe motherboard stand-offs would work?)
For actual knife edging, perhaps the center module could be replaced with a mirror mount, and the side-blocks could fire towards the middle. Then multiple plates/blocks could be stacked up and combined. Really crappy mock-up:
I'd also like to see ways to mount heatsinks. The blocks of aluminum are nice and big, but there isn't a lot of surface area on them. For low-power reds this might be okay, but for higher powered lasers this may limit the overall power you can push through these. The screws on top also interfere with putting a big plate unless I want to mount the blocks directly to the heatsink.
As I can't really use the spring system without additional mods. I'll probably end up using these blocks without the springs and connect the base plate to a larger heatsink to help reduce the heating. For that it should be okay. This kit shows promise, but needs some extra work in order to be really useful.
