Chinese laser cutter: Designing new tube brackets

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Chinese laser cutter: Designing new tube brackets

Postby xnaron » Mon Jul 16, 2012 3:50 pm

I bought a "50W" chinese laser cutter from ebay. I have been happy with it so far but the tube brackets leave a lot to be desired. I did some research and have a couple of ideas for making some new ones. I have a 3d printer and a CNC router so I can either print them or make them out of hdpe. I designed a bracket to fit based on the bdring 3 screw design. I plan to use 10-32 nylon screws to hold the tube. I have attached a picture. I designed the bracket so the tube will be centered with the center of the first mirror. My bracket will be held to the metal plate with 2 screws. The square cut outs will allow me to insert lock nuts. I made them wide enough to get pliers in there to hold them.

Those of you using this design....is there anything I should be concerned about with regards to adjustability or stressing the tube at the contact points? Do the screws hold the tube securely in place so it does not move when the machine is bumped or moved?

The machine is one of these http://www.ebay.com/itm/NEW-CO2-LASER-E ... 0686419181 . I would be happy to share if anyone wants the files (vcarve pro/STL/openscad) for the bracket.

thanks,
Brendin
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Re: Chinese laser cutter: Designing new tube brackets

Postby iGull » Mon Jul 16, 2012 5:51 pm

Hi Brendin

Rather than having me rant on about the type of laser tube mount you are considering, please consider this design ...

http://www.ebay.co.uk/itm/Good-Quality- ... 0791328783

It's similar in style to the one's I cut for my laser (blackhole 60w) - no axis interaction and the laser tube is fully supported.
I've never understood why the 2x laser mounts are upside down either ?

I you have a 3D printer, there's an opening for a decent mount design (no pun intended :D )

Cheers

Neil
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Re: Chinese laser cutter: Designing new tube brackets

Postby twehr » Mon Jul 16, 2012 6:56 pm

iGull wrote:Hi Brendin

Rather than having me rant on about the type of laser tube mount you are considering, please consider this design ...

http://www.ebay.co.uk/itm/Good-Quality- ... 0791328783

It's similar in style to the one's I cut for my laser (blackhole 60w) - no axis interaction and the laser tube is fully supported.
I've never understood why the 2x laser mounts are upside down either ?

I you have a 3D printer, there's an opening for a decent mount design (no pun intended :D )

Cheers

Neil


"Upside down" being a relative term...

With Bart's design, you have a single adjustment for elevation and two adjustments for lateral movement.

With this other design, you have to adjust two screws to get a combination of both lateral and vertical movement. Seems to me the latter is much harder, as you cannot adjust either axis independently - any movement in one direction will also induce change in the other.

So for me, the latter is "Upside down" :mrgreen:
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Re: Chinese laser cutter: Designing new tube brackets

Postby xnaron » Mon Jul 16, 2012 7:36 pm

I printed out one to see how well I can get the PLA to take 10-32 threads. One problem I have is the back adjustment screw will be hard for me to get at.
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Re: Chinese laser cutter: Designing new tube brackets

Postby xnaron » Mon Jul 16, 2012 7:37 pm

iGull wrote:Hi Brendin

Rather than having me rant on about the type of laser tube mount you are considering, please consider this design ...

http://www.ebay.co.uk/itm/Good-Quality- ... 0791328783

It's similar in style to the one's I cut for my laser (blackhole 60w) - no axis interaction and the laser tube is fully supported.
I've never understood why the 2x laser mounts are upside down either ?

I you have a 3D printer, there's an opening for a decent mount design (no pun intended :D )

Cheers

Neil


That style will be more tricky for me. I have only 49mm from the mounting plate to the center of the mirror.
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Re: Chinese laser cutter: Designing new tube brackets

Postby bdring » Mon Jul 16, 2012 8:20 pm

I use embedded square nuts in my design. I was finding that it took more labor to tap the parts than cut them.

http://www.buildlog.net/cnc_laser/erp/g ... ber=B30044
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Re: Chinese laser cutter: Designing new tube brackets

Postby xnaron » Mon Jul 16, 2012 8:27 pm

bdring wrote:I use embedded square nuts in my design. I was finding that it took more labor to tap the parts than cut them.

http://www.buildlog.net/cnc_laser/erp/g ... ber=B30044


I was thinking about that... Is it better to run the screws in that orientation vs what I have above? All the weight of the tube on 2 small points not a problem?
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Re: Chinese laser cutter: Designing new tube brackets

Postby iGull » Tue Jul 17, 2012 7:25 am

xnaron wrote:I was thinking about that... Is it better to run the screws in that orientation vs what I have above? All the weight of the tube on 2 small points not a problem?


Persactly, the complete weight of the glass tube PLUS the weight of the coolant is bearing down on two pins - I'm sorry, but that's not an engineered approach - or a safe one - nor is there any lattitude for thermal expansion in most of them.
An independant xy adjustment and complete support (as far as is possible) for the tube imho is a much better solution to the issue.
The only thing going for the three point system is that it's cheap and easy to make /rant :D :D

@Tim , the adjustments are not interactive, that is the whole point - you can adjust pitch and yaw independantly (as much as the engineering will allow of course).
My plates move in yaw via the extrusion slots and elevation via the upper plate slots. The adjustments are friction locked - you move them by levering with a screwdriver - which is very accurate. Finally tightening the allen screws. Cost was an issue too :D
Modifying the chinese item by adding an opposing pitch adjustment thumbscrew in the yaw would make it even better (left and right handed threads on the same shaft)- you could 3D print an elegant solution which might be difficult to injection mould or cut on a cnc router. Another option would be just opposing screws - in a push-pull arrangement.

Cheers

Neil
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Re: Chinese laser cutter: Designing new tube brackets

Postby xnaron » Tue Jul 17, 2012 9:09 pm

Here is another idea I am working on. It is more of a tube hanger. The tube craddle will use foam servo tape to craddle the tube and 2 zipties to hold it in place. I will leave the backing on one side of the tape to allow for thermal expansion. I will use 2 pieces of 8mm threaded rod that will be anchored into the craddle. There will be two nuts on each threaded rod piece on either side of the hanger to lock it in place. This should allow me up/down and left/right adjustment. Any thoughts?
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Re: Chinese laser cutter: Designing new tube brackets

Postby TLHarrell » Tue Jul 17, 2012 10:51 pm

Isn't this overly complex? My laser has the first mirror mount adjustable to center up the beam. The mounts for the tube are metal straps with foam tape.

And it looks like you have about 1/2" to 3/4" of adjustment. You wouldn't need anywhere near that amount. 1/8" tops.
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