I’m working on a project to make a bunch of coasters as wedding favors. Trying to minimize material waste, I wanted to set up a jig to drop in several pieces in a row of 1/4" Baltic Birch plywood. I tried cutting through the plywood, but couldn’t dial in the settings for a clean cut. I’ll have to finish it by hand anyways, so cutting them out on the table saw isn’t a big deal.
My goal was to get the material as square as possible, the new precise location features are amazing, but I didn’t have a reference on the crumb tray for where 0,0 is to set up a jig.
That’s when I realized I could put a strip of painter’s tape around the edge of the crumb tray, and use the new software to quickly drop in a rectangle offset by 0.25" on all sides from the edge of the cutting area.
A quick cut later, peel back the tape, and I now have a clear physical view of what’s inside and outside the cutting area. I can now use strong thin magnets to set up a jig to engrave multiple strips of plywood, accurately and repeatedly on both sides of the wood!
I haven’t seen this before, but apologies if I’m reinventing the wheel here. Hopefully it helps someone else.
PS - I’m not affiliated with this company, but these magnetic stud finders (https://hangmanproducts.com/products/stud-finder?variant=21545655815) are super thin, and awesome for flattening warped material. I put gaff tape on a few to add friction, that’s what I use as positive stops in my jigs. (EDIT these may not be a good idea see below)
Painters tape jigs like this are really handy, they definitely have their place. Great tip.
However, if both high accuracy and repeatability is necessary you’re going to run into problems for two main reasons.
1, on power up the Glowforge calibrates itself all over again. This will lead to slight variations in your zero position.
2, your tray has some slop. The divots don’t hold it absolutely in place. You can eliminate some of this by using @timjedwards’s tray boots (search the forum for them), but that won’t address #1, nor will the position hold if you have to remove and reset the tray, boots or not.
Of course this is only an issue if you need extreme accuracy, as in kerf-width or less. For most things this isn’t an issue so your tape method Is quite enough. If you do need that sort of accuracy, traditional one time use jigging is more successful.
As an aside, once you junk up the Glowforge from lots of cuts you can often see the cuttable area just by looking at the dirty parts of the tray.
As for your quarter inch Baltic cut problems, not sure how you tested but this method usually gets me on track:
This is a great solution. I did a similar thing, used cut a maximum-sized rectangle from a sheet of maple ply, then engraved marks to match the on-screen rules (by offsetting it to fit back in the printable area). I’ve posted pics of it here previously, used it until the calibration process was available as my camera alignment was horrible.
My tray sits in almost exactly the same place every time, it takes effort to “dislodge” it from it’s natural center position - I’ve measured it, and movement is right around 1mm. Obviously it slots in against the lower door, so it’s identical there.
As far as repeatability across power cycles, it is highly accurate. I posted this here at some point previously as well. This is two scores. I printed one. Turned off machine, moved the head a few inches forwards and over to the right side, turned on machine and printed it again. You tell me if this is accurate enough.
That’s really accurate, looks great! I ran the calibration for my machine when that update went live and got much more accurate results than when the laser was first delivered. The wide angle lens makes it tough to trust the edges of my material in the corners of the tray and ensure the sheets are squared to the laser movement.
My crumb tray has a fair bit of slop front to back, and side to side. I’m going to give the boots a try today to hopefully eliminate that movement. Then I’ll recut the tape to make my jig and engrave the back side of these 50 coasters I’m making.
Not sure why my tray seats in such a precise spot every time, but I’m not complaining. When people talk about it moving, I wonder if the design was changed at some point since I got my machine in late 2017.
If yours does move, however, then I am sure the boots will give you the same level of repeatability. Certainly, if you’re not removing the tray, you will get within 1/1000th" or so every time.
Note none of this uses or depends on lid camera accuracy. Once I had my designed placed, I just repeated the print. That was kind of my point - this is how we used to get accuracy before the camera issues were fixed.
Unless the magnets are shielded they can mess up the printer head when passing and shutting down the head fan there. If you hold a screwdriver lightly above the magnet the height of the gantry bottom and you can feel the pull then the magnetic field can do damage.
There are shielded cup magnets available or if you have many small magnets (>1/4") or best is to flip the material and hold it from the outside with bed pins.
I cannot be certain. I was way too free with magnets and in the end replaced the machine. There is at one extreme just the frequent flames that messed with the fans and other parts that sucked through the overheated air, but just how much trying to operate any electronics in a strong moving magnetic field depends of course on the strength of the field but the exact nature of the moving and just what sort of electronic mess is created is far beyond my ability to detail, but I don’t want to run the experiment anymore.
I’ve been using these since I got my machine in 2017:
They’re strong enough that if they slip onto the bed itself, I need a tool to pry them off.
The reports of issues seemed to be due to the machine sensing the speed of the fan dropping. The air assist fan is about all you can hear if you’ve got the exhaust fan disabled. I’ve never heard any change in tone as it moves across a magnet.
A strong magnet moved around next to the fan magnets might mess up its field, but having them on the bed won’t harm it.
I was too before I paid attention to when the head fan stopped working and started thinking through what was happening. The faster the movement the more it creates electrical force so naturally the spinning fan is most affected, and the specifics beyond that hard to calculate even in a given field, but the specifics of the field would be different every time. Having the fan stop or slow a lot is issue enough for the smoke to catch fire and make the cut not make it through.
Cup magnets or many small ones will do the same job without the field reaching as high as the fan.
I use similar thin bar magnets. I have had my machine stop when using them. I had ignored the warnings up to that point. I still use them, but only on the lower left, bottom, and right edges of the design, where I know the fan won’t pass over the magnet. This has been sufficient for me, along with hold down pins (I cut mine out of baltic birch rather than draftboad), to keep things flat.