Another Question (sorry)

[Dave Hutton]

Apologies in advance if this has already been asked but couldn't find an answer.

I'm looking at a chinese import laser from HPC (thanks for the recommendation DaveS :-) but there's small issue I'm trying to get straight in my head which anyone with one of these machines will probably haver an easy answer to (its possible that its not an issue at all but as my wife says I do tend to over think things!)

The bed has a slatted base which by all accounts is a good idea. However it doesn't appear to have any frame or stops at the left and top. I've seen these on other brands (some with measurements) and the work piece is placed against these stops to presumably allow for consistent alignment of repeat work i.e.. say there are ten jigsaws to cut, all exactly the same - place wood sheet into machine against stops, check alignment/layout etc and press go, when finished remove and place another sheet of wood in and press go etc.etc. Makes sense to me, especially if you have some jigs made for smaller items that need accurate repeat alignment.

So have have other users got around this?

I have spoken to a couple of people at HPC and not really had any sensible suggestions as to how this could be done sorted other than placing a board down and burning an outline, then aligning to that each time, which sort of defeats the object of having a slatted base if there's a burnable board underneath your work, plus that's puts a lot of responsibility in the hands of the operator to get it right every time.

It sounds like I'm asking for 'tartan paint' again but seems logical to be able to do that.

Apparently 'modifications at cost ' have been done on machines previously to accommodate this simple scenario but no pricing was forth coming. So any suggestions for a real world way of doing this I'd be obliged.

On the upside - after several weeks of searching I have a solution (assuming the material cuts well enough) to my 'laserable vinyl' requirement to make some masks for sand blasting. I understand this is a fairly common thing from forum posts but non pvc material seemed hard/ipossible to find here in UK. However it turns out that a material that I already use for something else and I have a box of is in fact pvc free, adhesive and 'should' be cuttable/rasterable whatever the term is, with a laser assuming its possible to get the depth of cut accurate enough. Other material of similar thickness works ok so pending tests by the nice chaps at HPC I'm good to go, so hurrah for that.

The material for anyone else thats interested is a printable polyester film such as that you might use for printing adhesive car graphics etc. It comes in big rolls, but I have a supply of A4 and A3 sheets.

Cheers

Dave Hutton

[Dan Hintz]

Those tables are meant to be quick and dirty. Go buy yourself some aluminum angle at the local BORG and a few screws... put on your own edge.

[David Somers]

Dave,

I have a Chinese laser and I noticed that too. The knife blades of the table had no guides. And the honeycomb that lay on top of those had no guides and wasnt constructed square to start with.

That just bugged me and when I asked the Chinese about it they basically said "huh? What is it you want? Why?????" Oh well. Just proved to myself I was anal I guess.

Along the lines of Dan's suggestion. Make sure your knife edge slats are all level with the gantry. You will be able to adjust each one. Once they are all at the same level to the gantry consider putting a drop of loktite on each adjustment thread so the set screws dont wander over time. And you might also consider a drop or two of thick superglue to hold each slat in place so whatever you use for a guide bar has a consistent surface to set on. Super glue (any cyanoacrylic glue) can be undone with a sharp wack or a bit of heat from a small torch so while it is a solid hold it is not "permanent."

Then consider using a steel square, as large as you can get from the big box store, and use that as your edge. You could use N52 magnets to fix it in place but let it be moveable. Or you could use a few drops of a thick super glue (cyanoacrylic glue). Or you could use something like Sugru, a product made in the UK that is a terrific silicon putty that sticks to most anything. sugru.com.

If you have a honeycomb table you end up work with get the slats fixed up like I described. The use similar ideas to create an alignment bar so when you lay the honeycomb in place it goes on the exact spot each time. Once it is in place, make a guide bar for it out or a steel square as well, and fix it in place with a dab of CA glue or magnets or whatever appeals to you.

Now you have a honey comb whose position is repeatable. And a knife edge surface that is repeatable and solid and has its own guide.

Now if someone could explain why Chinese laser operators just dont seem to care about this you will make my day. As an anal wood worker I just dont see how they work efficiently like that. And I am not even in production work. The lack of easy repeatability drives me buggy! <grin>

Dave

[Keith Winter]

GREAT DYI instructions David! Dave ask them if they offer a honeycomb. Sounds weird but my honeycomb on my chinese laser actually sits on top of those blades.

[Dave Sheldrake]

I have an L bracket made of Acrylic fixed to the left hand side of the bed (the surround past the rail bed) easy enough to locate from that for both top and left position, you could add graduations to it I would think but on mine it's just there to get repeatability

I'll get a pic when I get to work in the morning

[Rich Harman]

I use magnets. 1/2" x 1/2" x 2" neodymium magents. When I need to run the same file over and over again I will place two of them against the left wall of the machine so that they are standing on end - pointing to the right. I can slide the sheet right up to them and they will be in the exact same place every time. Two more on the honeycomb will locate the top edge.

The vast majority of the time I have just the two magnets that locate the top edge of the honeycomb. I have considered installing some sort of guide rails, and still might someday. It's just that the magnets are so handy and versatile that I have not really needed anything else.

Incidentally, if I ever do make guide rails I will make them removable. There are cases where having a rail there would be a nuisance.

[Dave Hutton]

Glad it's not just me that wondered about that then. I was hoping HPC might have an out of the box solution but sounds like a diy job then.

I believe the the knife slats things are alloy so magnets might be out but I like the idea of a set square or magnets on the casing. I have plenty of assorted glues and putty so should be something suitable.

i don't think it has a honeycomb bed as a standard option but looks like they're available online for reasonable money, so maybe Ill add one of those if required.

Pictures would be good of any suitable bodge fixes.

thanks for the input chaps

dj

[Rich Harman]

I believe the the knife slats things are alloy so magnets might be out but I like the idea of a set square or magnets on the casing.

Steel honeycomb is the way to go. Shame that so many lasers have aluminum honeycombs, they are missing out on a key feature.

[Ron Gosnell]

I have an L bracket made of Acrylic fixed to the left hand side of the bed (the surround past the rail bed) easy enough to locate from that for both top and left position, you could add graduations to it I would think but on mine it's just there to get repeatability

I'll get a pic when I get to work in the morning

I agree that the ruler isn't as important as the repeatability of alignment.

Gozzie

[Kev Williams]

Not sure if this will work on a knife table?

Check this pic of my Triumph... For alignment purposes, scrap plastic is my friend! My table is steel honeycomb with a steel U cap(?) all around. No scales, and who knows if they're straight...

Along the top, you'll notice a black strip of ABS, which as been there since day two. It's against the table's edge and I taped it there, and let the machine cut it. So I know it's straight...

Along the right, a piece of scrap plastic, that's placed against the gantry frame. The vertical edge is laser cut, so it's straight. Not shown, I also have a similar piece on the left side...

Those purple things? I have scads of those a customer left here years ago. They're exactly 2" wide, and make great shims and stops. I have several plastic shims of
different widths for different reasons. Mostly to do with "reach". This machine is BIG. It's also why I'm engraving on the right side of the table, that's where the keypad is, and
it's easier to jog and SEE when it's within arm's reach of the button!

SO, with my "default" plastic shims in place, I always have a pretty close "0-0" to start from, just need to tweak. And once I've found my corner(s) repeats are no problem.

With these machines, you do whatcha gotta do!

[David Somers]

Dave,

You asked for photos of different approaches?

I had a thread going a bit ago that showed the changes I made to do this.
http://www.sawmillcreek.org/showthre...les&highlight=

I also stuck it in my blog entry on SMC so you dont have to search.

Dave

[Dave Hutton]

Thanks again chaps - didn't consider cutting a guide with the laser (duh) that way it should be straight with the cutter, makes sense really. I did find that you can buy a 600x400 metal square, which if it can be fixed somehow would be bang on.

good ideas chaps - thanks

dj

another question coming up I feel :-)

[Lee DeRaud]

Those tables are meant to be quick and dirty. Go buy yourself some aluminum angle at the local BORG and a few screws... put on your own edge.

Or double-stick tape. However you do it, you'll want to be able to undo it for the times you need to cut a hole in the middle of an oversize piece. DAMHIKT.

[Dave Hutton]

Or double-stick tape. However you do it, you'll want to be able to undo it for the times you need to cut a hole in the middle of an oversize piece. DAMHIKT.

Good point Lee I'll bear that in mind.

Dj

[Bert Kemp]

Holy smoke Rich how do you get them off the table when they fall over I use 1 " sq by 1/8 thick and there a chore to pry off the honey comb

I use magnets. 1/2" x 1/2" x 2" neodymium magents. When I need to run the same file over and over again I will place two of them against the left wall of the machine so that they are standing on end - pointing to the right. I can slide the sheet right up to them and they will be in the exact same place every time. Two more on the honeycomb will locate the top edge.

The vast majority of the time I have just the two magnets that locate the top edge of the honeycomb. I have considered installing some sort of guide rails, and still might someday. It's just that the magnets are so handy and versatile that I have not really needed anything else.

Incidentally, if I ever do make guide rails I will make them removable. There are cases where having a rail there would be a nuisance.