How to hold the bed down? [SOLVED]

Has anyone found a good way to hold the print bed firmly on the heat spreader and not slip?

The foldback clips don't work for me even if I just clip them over the edge, because on the end of the bed nearest the Y-motor the fan housing fouls on them, and at the other end the IR sensor fouls on one of them. So only 1 of the 4 clips is usable on my Ormerod.

I tried attaching the bed with Kapton tape to the MDF. This was OK initially; but when I did a longer print, it didn't hold (became detached from the MDF on both sides). This cause the bed to rise and slip, spoiling the print.

I could try using four small pieces of double sided sticky tape, but this will reduce the contact between the plate and the heat spreader, and may make it difficult to separate the two.

I'm going to try using a heat spreader plate and glass plate that are oversized by 30mm at each end. Then I will be able to use the foldback clips There is the risk that the extra aluminium will suck too much heat away from the edges of the bed, causing the bed temperature to be less uniform. But this is not likely to be a problem until I start doing large prints. However, the aluminium sheet I have ordered to make the new heat spreader is not likely to be dispatched until next year.

In the meantime, does anyone have any suggestions? I'm reluctant to try any large prints until I have this solved.

Edited 4 time(s). Last edit at 12/28/2013 07:22PM by dc42.

I've used spring clips from cheap photo frames instead of the supplied clips. The frames in question consist of a glass panel and hardboard backing - held together by spring steel clips.
You may have to trim the clips with side cutters, the clips are very low profile and don't get in the way. Picture attached

Ray

great idea, I have some drawing board clips on order but your idea looks much better. Slightly frustrated that I must have thrown away loads of those things over the years.

Rory

Edited 1 time(s). Last edit at 12/28/2013 04:54AM by Rory166.

Great idea, Ray! I'll go out and get one of those photo frames.

Asked my young lady and she produced a small picture which is no longer in use, see attached out of focus photo, but you get the idea. This looks ideal, the original frame has routered slots, in the mdf, to accomodate the end of the clip and I wonder if this would be a good idea for a really strong fixing. I cant belive no one has thought of this before, Ray you are a star. XYL mentioned these frames have gone out of fashion possibly due to health and safety.

Rory

Edited 1 time(s). Last edit at 12/28/2013 07:28AM by Rory166.

@rayedge: That's a great idea! I'll suggest it to the team when we get back from the Xmas/New Year break. We were looking at using clips like those used on architect's drawing boards, but they didn't hold strongly enough, so we went back to foldback clips.

Ian
RepRapPro tech support

I just spent 59p at The Range on a 10x15cm frameless photo mount. The clips are about 25mm long, 13mm wide at the widest point, and protrude about 8mm below the heater pcb. As suggested by Rory, I'll cut pieces out the mdf that came with the photo frame to put under the heater pcb so that I can lock the clips into the slots in those mdf pieces, and enlarge the cutouts in the bed insulator to suit. Then I'll use 20mm or 25mm screws to mount the bed as in the manual bed-levelling instructions, to get the 8mm clearance. I'll post some photos when done. If this works well, I'll abandon my plan to make an oversized bed.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

DC

You shameless spendthrift.

Well now I'm off to the Range
where the deer and the antelope play,
to spend 59p
Im sure they'l be grateful to me

Rory

Edited 1 time(s). Last edit at 12/28/2013 10:34AM by Rory166.

Got the frame from Range. Mdf is too thick with the heater and all. It would be ok to cut slots in the cardboard insulator but I infact made a new one with norrower slots to accomodate the spring clip. See photos.

Looks ok to me may have to increase spacing a little as the clips protrude 5mm below the pcb whereas the cardboard only 3mm.

Rory

PS. I have awoken next day seeing a flaw in this design, the spring part of the clip is in direct contact with the heated pcb and will get too hot. I will make a new version where the cutout for the spring clip is just an indentation instead. Actually the original clips are in contact with heater so prhaps not such a problem after all.

Edited 5 time(s). Last edit at 12/29/2013 05:10AM by Rory166.

Rory166 - nice, it's a good hack. At least you can't complain about our out-of-focus instructions photos!

Ian
RepRapPro tech support

I've completed this mod and it appears to work well. Here are some photos. First, the 59p frame kit:


After cutting 4 tabs from the slotted MDF:


After lengthening the slots in the bed insulator to 30mm:


After fitting the glass, heat spreader and mdf tabs together with the clips:


After attaching the bed assembly to the carriage, using 20mm cap head screws and extra nuts:


I found that I was able to use the clips to hold the glass, heat spreader, heater pcb and mdf tabs together, even though this was a little thicker than the clips are designed for. I may replace the mdf tabs by something a little thinner and more durable, possibly printed parts.

Edited 7 time(s). Last edit at 12/29/2013 03:07AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

DC

Superb pictures, what sort of camera do you use?

I suspect the MDF pieces go the other way up than shown in picture with cardboard. Do you glue the MDF to the cardboard? Otherwise how is the cardboard fixed? I would counsel against using PLA printed part instead of MDF due to temperature.

Rory

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Rory166
Superb pictures, what sort of camera do you use?

Galaxy S4 smartphone camera. It's a bit temperamental when trying to focus at short distances, otherwise OK.

Quote
Rory166
I suspect the MDF pieces go the other way up than shown in picture with cardboard.

No, they go that way up. Like I said, the glass+alu+pcb+mdf is a bit thicker than the clips are intended for, but it did fit - see last photo.

Quote
Rory166
Do you glue the MDF to the cardboard? Otherwise how is the cardboard fixed?

No, I want to slide the MDF pieces out with the the clips when I remove them. The cardboard isn't attached to anything, it just sits in the middle. The clips and the bed screws stop it moving very far. If it annoys me enough, I'll glue it to the pcb.

Quote
Rory166
I would counsel against using PLA printed part instead of MDF due to temperature.

I was thinking that if PLA needs nearly 200C to melt, it should be OK at 65C bed temperature - and if/when I get round to printing ABS, the tabs would be the first thing I print. But this is my first experience with PLA, so I don't really know.

Edited 2 time(s). Last edit at 12/29/2013 07:56AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

@dc42: at 65C, PLA will be soft. Themoplastics have two temperature points, the glass transition temperature and the melting temperature. The glass temperature ( [en.wikipedia.org] ) is the temperature it starts to soften; this is around 60C (but can vary) for PLA and 100C for ABS, which is why the bed is heated to just around this temperature. Being in such close proximity to the bed, with no airflow, it's going to get hot, so I don't hold out much hope that they will survive long!

Ian
RepRapPro tech support

Thanks, Ian! Sounds like I had better stick to mdf or hardboard for the tabs then.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I have no connections with any of the following companies, links are just to illustrate products.

Has anyone looked at any of these options? Most probably available from a car parts shop.
[www.bearingboys.co.uk] many other size options.

[brodak.com] look good but no dimensions!

There are also 'spire clips' which appear a too tight as standard for our requirements
and cable clips [www.designassemblies.co.uk] which may be suitable.

Anyone got a good scrap box with any of these to evaluate?

I found this supplier. The "Swiss clips" look ideal to me. It might even be possible to redesign the heated bed PCB with holes for them to lock into (if that doesn't make removal too difficult).

Edited 4 time(s). Last edit at 12/29/2013 01:45PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Just did the Range photo mount hack... Brilliant! ... Thanks

N.B I didnt use the small recessed pieces of mdf at all. I found it works fine with just the clips straight onto the heater pcb (EDIT : Actually it is better to use these tabs)

I also used the stock length screws and nuts. Without the mdf, I didnt find it necessary to add another nut in the sandwich.

I added the nuts under the MDF bed insulator to hold the heated bed securely to it. (This isnt in the Ormerod manual anywhere but saw dc42 did this so assume adding these nuts is correct. The nuts only just fit the stock screws so dont overtighten them!.)

So once I had slipped the clips off the photo frame, the only customistaion required was cutting the cardboard insulator... so this is a really easy peasy mod.

Now to retry the axis compensation...

regards
Andy

Edited 1 time(s). Last edit at 01/02/2014 04:50AM by kwikius.

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

Quote
kwikius
Just did the Range photo mount hack... Brilliant! ... Thanks

Glad it worked for you! Credit to rayedge for the original idea.

Quote
kwikius
N.B I didnt use the small recessed pieces of mdf at all. I found it works fine with just the clips straight onto the heater pcb

Watch that the clips don't slide off by themselves. Swiss Clips like these are designed to lock into a hole or slot in the backing to keep them in place. That's why I used the MDF tabs.

Quote
kwikius
I added the nuts under the MDF bed insulator to hold the heated bed securely to it. (This isnt in the Ormerod manual anywhere but saw dc42 did this so assume adding these nuts is correct. The nuts only just fit the stock screws so dont overtighten them!.)

I added the nuts on the bottom as per the optional manual bed-levelling procedure (here about 2/3 down the page), which I did to get the extra space for the clips.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42

Quote
kwikius
N.B I didnt use the small recessed pieces of mdf at all. I found it works fine with just the clips straight onto the heater pcb

Watch that the clips don't slide off by themselves. Swiss Clips like these are designed to lock into a hole or slot in the backing to keep them in place. That's why I used the MDF tabs.
.

Yep! I've had to use the mdf tabs now, since I decided to try out the manual levelling with the 20 mm screws.

Also found a use for the foam packaging that came with the glass bed. I added it as extra insulation under the cardboard. Not turned it on yet though ( as everyone is asleep here!) so hope it doesnt melt , but looks like the foam they make scourer pads from, so should be good for 100 deg c..

Thanks to every one involved with this mod. Works great!

regards
Andy

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Ormerod #318
www.zoomworks.org - Free and Open Source Stuff

I now have Mk.II versions of the bed clips. I wanted some that would hold 4mm glass as well as 3mm glass, and that were easy to release when the bed is hot. This is so that when one print finishes, I can remove the glass bed, replace it with another, and start another print right away without having to wait for the first one to cool down.

I bought 11mm clips from [www.ukpictureframingsupplies.co.uk] (also available in quantity at better prices from [www.lionpic.co.uk]) and cut pieces of 3mm MDF to serve as backing (see photo). The small holes are 2.5mm, the large ones are 5.5mm and they are 36mm apart.



In use, the protruding tabs make the clips easy to remove. Put your thumb on top of the protruding tab and your finger on the metal clip underneath, then squeeze them together to release the clip. To make room for the clips, the heater pcb needs to be spaced at least 10mm from the bed support using the bed support & levelling screws.

Edited 1 time(s). Last edit at 02/09/2014 02:05PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Brilliant!
Im going to order now.

Thanks

For anyone else thinking of making the MDF quick-release tabs pictured 2 posts above this one, the tabs need to be wider than shown. Two of my original ones eventually broke during removal, because the MDF was not strong enough in the areas either side of the 5.5mm hole. The originals were 14mm wide. I suggest 20mm wide, at least in the area around the 5.5mm hole. Alternatively, make them out of a stronger material, but not one that conducts heat well. I have some 2mm fibreglass board that I am going to try.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

What's the long term verdict on these DC? Are you still using them?

I would really like to get rid of the bulldog clips, I had a close call with the sensor today and was lucky not to do any damage.(I think I am going to print Kim's sensor cover next!)

Regards,

Les

Yes I'm still using them, although I remade the mdf bits in 2mm fibreglass.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I got some of the 7.5mm ones along with the 11mm. I have just snapped off the hook part on the 7.5mm ones and so far they seem to work nicely on my setup. (cardboard. PCB. alu plate & glass)

Regards,

Les