Idea for quick switch bed: feedback requested

[brvdboss]

Looks good. Seems like you’ve got a really good fit. Looks promising.
How will you attach them to the plates?

@nivekmai

The question now becomes what to mill out of, you all said were saying you’re using MDF/plywood, are you worried about the flatness of that at all? I’d be especially worried using magnets and screws in MDF that it would warp pretty drastically with temperature changes.

I deliberately chose MDF (not plywood/multiplex) because it’s more stable than natural wood and I have gotten the water proofed version so that the humidity in the air would have little to no effect.
I have been using it as a base for my print sheet for a few weeks now (without the quick switch part) and it has proven very stable for me.
Also MDF and not plywood/multiplex because if I want to mill the top surface flat, plywood would lose a lot of it’s advantages as you’re peeling of layers and it wouldn’t work very well either I think.

@nivekmai

Also, not trying to rain on your parade, but magnets and heat don’t usually mix so well, I’d be a bit worried about losing “adhesion” if the bed gets warm enough if using magnets to hold everything together.

I’m aware of that. However, the magnets I’ve gotten are rated up to 80°C. and there will be 18mm of MDF in between. So I don’t think I’ll get close to that 80°C that easily. I’ve been printing quite a lot the last weekend with a bed temperature of 90°C and if I measure with an IR-thermometer at the bottom of the plate it doesn’t get above 40°C. So I don’t think it would be an issue.

The same goes for the plastic you’re using as well btw, that too loses strength at those temps

[nivekmai]

@brvdboss

How will you attach them to the plates?

I was just thinking super glue. If I go MDF like you’re thinking though, I’ll probably have to do something else (the MDF would just tear away right?)

@brvdboss

rated up to 80°C

Nice, I didn’t know that was even a thing, I’d just heard magnets + heat = weak magnets.

@brvdboss

that too loses strength at those temps

Ooh, I haven’t actually played with the plastic at those temps (maybe PETG would fare better than PLA), that’s a good point. I was hoping to keep it as minimal height as possible so as to not shrink my build volume, but you’re right that it might be better to have it thicker to “protect” from heat creep. I just have a seemingly perfect bed level right now (had to up to an 11 point calibration, but after that, good first layers) and I’d hate to mess it up getting quick switch working.

[wje]

I’m the poster of the mag strip idea. I’ve done a few CNC jobs using them, no problem. Realistically, put enough strips on, the lateral hold strength is good, and the lateral forces the CNC head can generate are really small. Again, this is just my experience.

[brvdboss]

Ok, some delays on my side because, just life.

I’ve made an update on the base-plate of my contraption to reduce the weight. A bed sized piece of MDF weighs 1.3kg. Multiply that by two and it gets rather heavy. Nothing the SM2 won’t be able to handle, but it will increase the wear on the lead screws and might become an issue with faster movement of the bed.

A first idea was to get rid of the base plate completely and find a suitable spot to mount the magnets directly onto the bed. So I created this little thingy that fits in the corners of the carriage and helps to make sure the pot magnet is in a fixed location:

(Extra points if you know the exact location where it should go )

But that doesn’t level the bed and no decent way to cnc it flat as I wouldn’t know a good way to fix it in place. Except maybe gluing it place. And the difficulty of determining the exact location of the through hole as this was an experimental design and not just looking at the design file with exact sizes.

So then I figured I could just remove the excess material from the bed and cut away everything that’s not necessary:

So I set out to have that cut out.

Apparently the contour cuts I was using didn’t go great, and despite adding tabs to the file, one the parts that needed to be removed was ripped out, got stuck on the bit and ruined the rest of the work.
Luckily I found it only a few minutes after it happened. The spindle wasn’t turning anymore. The toolhead was still moving around, but without a turning spindle (Not sure why that happened).

After rebooting the machine, it did come back to life. I am under the impression it sounds a bit different, but don’t know. Did a 20 second just to try and it still seemed to do it’s job. so it might be ok. In this case I actually wish the bit just broke.

I’ll have to revisit the machining paths again and give it another go. Maybe I’ll just clear the entire pockets instead of using a contour. Will first need to do some testing to make sure the spindle is still ok.

[brvdboss]

Ok, short update,

Had the base platform cut out today. So this is the result of the “light” version. I didn’t do the cuts along the sides of the board. just the inner pockets. Mostly because the toolhead can’t reach them on all sides and I couldn’t be bothered by turning everything around etc.

To avoid the little mishap I had with the previous iteration I decided to create a toolpath that clears the pockets completely. 5h30min later this beauty came out of it (picture is a bit out of focus, but you get the idea)

This little “diet” reduced the weight from 1.3kg to about 750g. Still feels very rigid. Maybe in a next iteration it could be modified to replace the aluminum carriage completely and be mounted directly to the y-axis. Maybe for the top plates I could switch to a thinner sheet of MDF.

Next steps:

• actually mounting it, flatten it with a surfacing bit & make the cutouts for the magnet-holders and mounting those. (Couldn’t do those yet as I can’t get the depth right until it’s milled flat)
• Do the top plates, but those are mostly just boring some holes, so those jobs take about 15 minutes or so.

So hopefully, by the end of the weekend I’ll be switching plates faster than my shadow

[Defuselier]

Good morning. Speaking of being late to the party, I would like to contribute my version to the discussion if I may. I hadn’t seen the forums before I started working on this, so mine is a “clean sheet” design, so-to-speak. As with any engineering challenge, people will tend to gravitate toward common practical solutions. I’m glad a lot of the initial ideas I had also occurred to others. It tells me I was likely on the right track. Anyway, after numerous overly complicated designs, I finally pared away the extraneous parts and came up with the following solution. So far, it has worked out well for me and I’m happy with the results.

I’m using a variation on a magnetic mount. Two 3d printed magnet holders mounted from underneath the base web using the existing M4 holes. Simple ceramic magnets epoxied into the holders are flush with the top edge of the aluminum web.

Next, I machined three base plates from MDF which use the raised mounting “studs” to index the plate, with the bottom of the base plate resting on the top of the aluminum web. This arrangement is surprisingly solid, and lifts off and on easily. Two steel plates are epoxied into the rectangular cutouts to engage the magnets.

Now the various production bases can be fastened to the quick detach base plates, and more can be easily made as needed for custom setups. Total vertical loss is about 15mm, and nothing in the design prevents one from remounting a base with screws if needed.

I’m waiting on the arrival of a surfacing bit to face these to dead flat before permanently mounting the SM bases. Initial work using my first prototype to help machine the remaining bases worked quite well. I paused CNC operations, dismounted and remounted the quick connect base, and had no trouble with the accuracy of the operations. I haven’t run formal tests with a dial caliper yet, but so far, so good.

Constructive criticism welcome. And, if anyone would like the design files, just let me know.

Happy making!

[brvdboss]

@Defuselier

Now the various production bases can be fastened to the quick detach base plates, and more can be easily made as needed for custom setups. Total vertical loss is about 15mm, and nothing in the design prevents one from remounting a base with screws if needed.

I really like this idea, I had an initial idea to have the magnets attached to the base plate as well, but couldn’t find a good way to “attach” them, That’s exactly what your solution is doing. I was a bit worried that having them more centered than in my initial design would make it too easy to detach during cnc operations, but glad to hear it works out just find for you.

And you do lose a lot less vertical space and have less weight on the carriage. To be honest I never really considered gluing the magnets in place, I was fixated on bolting them down somehow.

Nice one. Thanks for sharing.

(My version is still where I left off last time, other things came in between making it less of a priority)

[Defuselier]

I went through a lot of mental “variations” and ideas before settling on this. Mechanical fasteners, pins, slides, brackets, etc. before I finally realized that there really isn’t any force in the negative Z axis, just X and Y, and positive (down force) Z. The web base’s built in “studs” (pins? Whatever the proper term is…) and frame provide plenty of stability in all three axis, so we just needed a way to keep the base from floating or getting pushed off the pins. As far as I can tell, only CNC ops provide any force at all on the bed or target, and not very much at that. I figure if the CNC manages to push it off the pins, I’ve done something terribly wrong already.

One thing I have noticed is vertical flexing when the CNC plunges at the front or back of the platform since it’s only supported in the center. I guess the next project will be some kind of bed stabilization under the bed at the X axis line where the tool head pushes down. I have an inkling, but will have to take a look at the motion and clearance to see if it’s viable. Any good ideas out there?

Thanks

[sdj544]

@Defuselier

Any good ideas out there?

My new Snapmaker 2.0 A351

Based on that great idea I am trying to replicate the linear rail setup. I ordered these linear rails that fit perfectly lengthwise in the enclosure: https://smile.amazon.com/gp/product/B07M8T1NG1/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1. (800mm length). The height between the bottom of the rail and the Snapmaker base is 3/4"+3/16" (I used some magnetic shims - still figuring out how to install this more permanently) and due to some clearance issue on the Snapmaker bed used a small wa…

Snapmaker A350 attachment additional linear guides by gojoetofly

Holder for support bed by Martinsys

-S

[brvdboss]

Apart from what was already mentioned, there also this simpler solution, yet less structural than the already mentioned solutions:

Bed too flinsy for a CNC face operation?

I’ve designed and printed a small sliding support that clips on the underside of the base and floats 0.2mm above the actuator (see dark blue piece). When there is downward pressure it will contact the actuator and limit the vertical movement of the bed. If you make 4 of them (2 of each side) and install them in the front and back you will get containment in both directions. Here is a link to the geometry in thingiverse: Snapmaker A250 Sliding Support by ppmendonca - Thingiverse. It’s still a w…

Snapmaker A250 Sliding Support by ppmendonca

[tom_sanchez]

Your idea sounds very interesting! can you share the files to give them a try? I do not have the rectangular magnets but do have neodymium round magnets… need to check diameters and other sizes of those magnets but will need the files to match them easier… you mind to share them?

[scyto]

@tom_sanchez there are quick change designs on thingiverse and paid files on Etsy, no idea how well any of them work, but seem quite simple and only ad a few mm to the height of the bed. Will be interest to hear what you end up with.

[tom_sanchez]

Yes mate, but still waiting reply from our friend @Defuselier … Mine is a A250 and haven’t been able to find a bed or platform draw for the 250… I am looking to make it by myself! But will see what I can do without compromising height … but also @Defuselier idea seems to be real good!

[tom_sanchez]

How can I get the draw or file you have on the pictures of the bed? I need it for a A250

[scyto]

maybe you could resize this design for the 250? Quick Change Laser Plate Holder SM 2.0 A350 by knightrider_007 - Thingiverse or maybe one of these guys has a premade STL for the 250 (unfortunately these are paid files) Snapmaker quick change bed | Etsy

[Defuselier]

Hi Tom,
Quickbase.zip (529.4 KB)
Here are the Fusion 360 files for the magnet holders and wasteboard sub-base for the A350. Let me know if you need something different.

Now that I’ve been using these bases for a few months, I wouldn’t change a thing. The design has proven to be practical and very stable. If they could be machined from aluminum, that would be even better, but MDF seems be good enough.

[Defuselier]

Found this for the A250. It should help you to design the sub-base.

The holes are 10mm diameter by 5mm deep.
The magnets don’t actually have to contact the metal plates embedded in the sub-base. As long as they are close, they will provide enough down force to prevent the base from lifting under CNC stresses.

[tom_sanchez]

Incredible job buddy…hahaha the only problem is that I am not an expert and technically I am trying to understand what you sent… its time for me to learn from youtube and figure out how to do this for the A250. I am more interested on the change from 3D to laser… then try to do something for CNC, trying to loose not many space. Your file its a start so thank you very much… The last file sent will also be helpfull so I really thank you a lot, will help many people here! If I get something good that works awesome for the A250, I will share it here…

[nivekmai]

If you’re only switching between 3dp and laser, you can cheat by just taping/glueing the laser beds to the first 3dp bed you manage to ruin, then your laser bed can magnetically mount to the heated bed.

[BluegrassBlaster]

That’s exactly what I did. I used the old woodworking trick of painters tape-superglue-painters tape to put it on. It’s rock solid and does great.