Originally Posted by HJG

Have not got a honeycomb bed yet as Light Object are unable to send a 900*600mm sized bed from USA to UK. Did you get yours from L.O. did it have any support bars either under the bed or integral with it?

I put a thread over there about this, but I think I put it in the K40 forum. Marco will see it. I got it from him.

The honeycomb includes U-shaped frame which goes around the perimeter. The machine frame has two parallel lengthwise supports that go under the long sides of the honeycomb. I may need to get some 8020 to go between them to support the center, but doing so they'll be getting hit by a lot of smoke, dust, and light.

Is it possible when you placed numerous sheets of balsa on it the exhaust system deflected it down?
If it sags 8mm with sheets of balsa its clearly not up to the job,

It's with NO wood on the frame that it does this. It's purely gravity pulling it down.

Is your honeycomb made from ally with a tight cell size or wide cell size? and does it have a good depth 30mm+ ?

It's about 30mm deep, and the hole size is roughly an oval 7-8mm x 5-6mm.

Thanks for the excellent questions, Henry.

Andy

I'm working on a small book shelf for our grandson. he's only 6 months old, but already getting a good book selection going. I built it fairly strong. figure at some point he will be using it as a ladder when mom and dad aren't looking...

I think the first few times will be with them watching, and it will be "so cute" that they'll photograph it and post it on Facebook. Then a week or two later they'll realize they were stupid for not stopping him from doing it while they watched.

Andy

How about light aluminum angle two places across under the honeycomb? I find it strange there is no support. A 1/8"X11/2" angle down should help lots. I think the beam should be far enought out of focus by then not to be a problem. If you made a bracket to hold them, they could be disposable as they are damaged.

L.

Andy,

Mine has no support at all through the middle (36"x24") and it only sags about 1/32" under vacuum. Thickness is less than 1" (probably 20mm).

I would add some angle or channel aluminum supports under it, or, see if you can find a better honeycomb. They come in different 'thickness' aluminum sheet. I think they are graded by how stiff they are for making structures.

charlie

Thanks, Charlie and Larry. I'll have to investigate both of those.

Andy

Light al angle can be had at Lowes.

L.

A few days ago I noticed that there was about a 10mm sag in the middle of the honeycomb. That's simply not acceptable, and it was very definitely affecting the ability to cut easily because of the change to the focus.

I think I found both the root cause and the solution.

Root cause: When I was doing final assembly, I had put my hand drill on top of one of the sides. At one point I bumped it, and it fell onto the honeycomb. That would explain why it sags so.

Solution: I went to Home Depot and picked up one of this: http://www.homedepot.com/p/Everbilt-...1987/204273937

I cut it in half, put one of the leftover 8020 corner braces on each end, and bolted it into place. They run front to rear and are spaced about 300mm & 600mm, making three sections that are small and well-supported. Because the 1/8" thick edge is facing the laser, they won't cause any issues.

To do this update I had to drop the smoke chamber underneath. There is no damage to any of the painted foil, so I'm sure that will work well. I'm glad it's a very lightweight box!

These additional braces have a slot which allows them to be adjusted vertically. I set them about 1.5mm proud of the surrounding braces to compensate for the thickness of the honeycomb frame (these are strictly within the honeycomb area).

After that, I re-leveled the honeycomb by using my focal length tool set to match in one corner, and then adjusted the other three corners to suit. I checked the center of the work area and it too was perfect. Now I can cut bigger stuff quicker!

Henry - it took me about an hour to do this. I strongly suggest that you do something similar if you're using an unsupported honeycomb. Also, you may be in overkill mode with 10mm MDF for the chamber. Mine is 6mm Coroplast with normal kitchen aluminium foil spray painted flat black.

If only that air adapter would get here...

Before doing this I played around with etching glass and slate. Cool!

Andy

Hi Andy,
Pleased you have come up with a solution, I am going to have to make a bed to custom size to fit my "firebox" either using honeycomb or metal lamina.
I agree that 10mm is probably overkill for the box but it looks o/k with its litho plate lining sprayed with high temp barbeque black paint. I have put my exhaust outlet in the bottom ( 150mm wide 6" in old money)
I believe you have the 3MD560 drivers , could you please tell me what settings
you have on SW1 throu SW8 ?

regards
Henry

You went all-out! I just used regular Rustoleum spray and normal weight foil!


There are two photos in this thread which show the settings. Look at these images at max res. My controllers came with the settings that were correct.

SW1 to SW8 are UP UP DOWN UP DOWN UP UP DOWN

Andy

https://static.rcgroups.net/forums/a...1-DSCF0647.jpg
https://static.rcgroups.net/forums/a...2-DSCF0598.jpg

NOTE: I just edited the bill of materials in post #1 to reflect the new materials added above.

Thanks Andy,
That's how mine came, however SW4 halves the 3.8amp current giving only 1.9 amps per phase which seems very under run when the stepper motors are rated at approx. 5.0 amps. Still if it runs ok on yours with those settings I will leave mine the same.
The motors will have greater longevity running cooler.

Henry

The only real loads they have is the acc-dec rates. I would bet you would be surprised how little time they actually spend at full speed.

L.

The higher currents are also needed if you're using them on a router.

The "hold current" control can be reduced with a laser too, since it isn't fighting a mechanical load.

Andy

Today I hooked up the output of the dust collector blower to an outside vent. MUCH quieter now, actually not that bad but still louder than I want.

I also corrected some wiring for the mA meter. The input power was not stable, so I hooked up a battery to power the meter instead and instantly it worked properly. Next step was to insert a 24V-to-5V regulator. I'll test that next time, but I'm pretty sure it will solve the problem.

The only thing I have to make now is a micro to integrate the PWM to give me the use time of the bulb. This will be a simple micro project that I'll probably cover in a separate thread.

Andy

Now that sounds a very good idea Andy, any chance you will implement with a
"PIC" micro as I have a pickit 2 programmer.
I have also bought Jermy Blums book on the Arduino and started to read through.
so if you picked one of the Arduino boards I could program it over usb with the built in bootloader.
Just a quick thought , would you not have to monitor the TTL low connexion rather than the PWM connexion? since I always understood that the PWM sets the power level.

I will monitor both, actually, so the signal is properly gated.

The PWM controls the power by controlling the time that the laser is turned on relative to being turned on all the time.

I have to check the timing with a scope to know what I can implement it with. I used to do lots of PIC programming (it's how I made my living), so it's actually quite simple with one if I can run the processor fast enough. I would use TMR1's "gate" mode to measure it, and every time it overflows just bump a counter telling me that so many microseconds (depends on clock speed) have accumulated.

Read up on T1GSS and T1G0 to see what I mean. Just a little glue logic in front of it (controlled by TTL from controller) will do what I need. Should be brain-dead simple. I also plan to include the regulator to take the 24V down to 5 or 3.3 depending on the CPU.

Andy

Looks like you have it solved already Andy, will follow thread with interest.

Henry

To make it easier to work with the laser, I added some 6' shelves to the wall above the laser. This is sorted from 1/32" to 1/8" bottom to top, with 3" stock against the wall and 4" stock closer to me. There are also some sheets of ply and some wider wood up there as well.

Each stack is then sorted by weight, making it easier to get matching sheets when I need them, or to make individual parts from lighter or heavier material.

That wood used to live in 36" boxes from my old kit business. That was good because it kept them stable. I expect to be cutting it quickly enough that it won't matter too much

Oh yes, and MERRY CHRISTMAS!

Andy

looks great, Andy, and Merry Christmas to you, too!

This his been an amazing project to watch and I am blown away by the speed with which it has come to fruition. It really looks like a great machine and the short videos I've seen of it working are way too neat. Seems really exciting to be able to manufacture pieces/parts/kits to your own exacting specifications and to be able to quickly edit and cut a new piece that might not have worked originally.
I won't blow any more smoke Andy....but...outstanding!

I'm glad you enjoyed it. I just cut lettering using it. I had the power a little too high, so the backing is cut through in places. I forgot the right setting to use, but I just found it again

I have some Monokote trim film that I picked up at a swap meet our club hosted a few years ago. I also had a PDF of the text I wanted. One of the guys at work took the PDF and made a DXF file. After a little fiddling with paper to make sure the letters were shaped OK (they weren't, and I had to tweak them manually, and they're only OK now, not perfect), I put the film in and cut it. The edge is as nice as knife-cut vinyl.

Next I weeded them and then used transfer tape to keep them spaced properly when applied to the model. A little Windex to the wing allowed me to position it properly and remove any bubbles. Right now it's drying off.

They aren't as nice as Callie does, but I can do them here. When I need good ones, I still know where to go for them. It'll take a lot more practice for me to be making them as nicely.

Andy

Last night and today I was able to cut and mount some sheets to enclose the frame. This is mainly to keep dust out and laser reflections in.

The clear top is 1/4" Lexan and the red sides are 1/4" acrylic sign material. I still need to add a wood panel behind the door over the laser tube, and I need to cut the control panel to replace the luan-and-paper one you see here. That will require air assist, which I'll be able to do after the adapter arrives next week.

Andy

Looks like your almost ready to be a real cut-up!

L.

Andy,

Took a pic of my laser bed when cleaning it today. The bed itself is al box. You can see the cross struts that support the honeycomb.

charlie

Thanks Charlie. Looks like it's about the same idea as mine! Good to know I'm not that far off base.

Andy

Hi Andy,
Well done with your laser build, thanks for your detailed build log, If I attempted
a build log people would fall asleep waiting for something to happen.
Must go into the shed , put the heater on and shake off the January "blues",
my laser is still work in progress. I am going to try and place my limit switches in posn today on the X axis , must check on your build to see how you did the Y axis.
So TTFN & belated happy new year wishes to all.

Henry

There were pre-drilled holes for mounting both limit switches for the origin. I have considered adding switches for the high limit but the software seems to do a good job there, so I haven't gone further.

I still need to install a switch for the door interlock. The wiring is in place, the software is configured, but the leads are just shorted together for now. I'm looking at a refrigerator switch to control it, but Marco recommends a proximity switch.

Andy

Andy, you might want to add max limit switches as well. Or have overload protection for your motors. There always seems to be a way to make the head take a "nose dive". Sending a file that is offset, wrong scale, setting wrong max and min, etc, etc, etc.

Any switch should work for the interlock. Mine has hall effect switches, but, just about any micro switch should work.
charlie

Originally Posted by portablevcb

Andy, you might want to add max limit switches as well. Or have overload protection for your motors. There always seems to be a way to make the head take a "nose dive". Sending a file that is offset, wrong scale, setting wrong max and min, etc, etc, etc.

I come from the industrial motion control field. We always had limit switches and the only time I've seen them needed was because of the programmer - me.

Exactly.

Watched two multimillion dollar accidents from just that issue. 25,000lb objects spinning because of software glitches and no limit switches ("the software will control it, no problem").