Assembly trouble, stuck heater cartridge

So, I finally received the correctly sized tapered brass nut.

Now assembling the hot end, I seem to have gotten the heater cartridge stuck in the aluminum heating block..............



It went in with some diffuculty about half way and just got stuck, I can't push it in any further or remove it..... I'm not entirely sure what it's stuck on, maybe some debris or swarf in the hole? I now completely understand the E3D heating block that clamps around the heater...

I've tried:
putting the whole thing in the freezer for 15 minutes
heating the heating block with a lighter
and putting some 3 in 1 oil in hole opposite the cartridge....

I haven't tried sticking something in the other end and using a hammer to bash out the cartridge... fairly certain this would break it...

So far no luck... any help would be appreciated

PS yes I know this should be connected to the cooling block/fan etc assembly... I took it off when the cartridge got stuck to get at it better.

Edited 1 time(s). Last edit at 03/10/2015 11:18PM by shadow651.

Support the heater block from underneath, for examble with the block on top of the jaws of a vice, so the heater cartridge is between the jaws, but not clamped, underneath. Then find an M5 bolt (the hole is 5mm, but the thread is just under this size, so will fit through cleanly), or use the M5 Z leadscrew, and use it as a drift to gently tap the heater cartridge out. Check the heater cartridge; it may just have a slightly raised area, you can probably gently sand it flat with sandpaper, and try fitting it again. Pass a 5mm drill through the heater block, to check it is the correct size.

Ian
RepRapPro tech support

Quote
droftarts
Support the heater block from underneath, for examble with the block on top of the jaws of a vice, so the heater cartridge is between the jaws, but not clamped, underneath. Then find an M5 bolt (the hole is 5mm, but the thread is just under this size, so will fit through cleanly), or use the M5 Z leadscrew, and use it as a drift to gently tap the heater cartridge out. Check the heater cartridge; it may just have a slightly raised area, you can probably gently sand it flat with sandpaper, and try fitting it again. Pass a 5mm drill through the heater block, to check it is the correct size.

Ian
RepRapPro tech support

Thanks Ian,

I'll try that tonight, I should be able to get an extra M5 somewhere on my way home. Although I don't think I have an 5mm drill bit, and it'll take a couple of days to get one from amazon...... For whatever reason, hardware stores in the US refuse to sell metric drill bits, but they carry all sorts of metric sockets, bolts, etc.... although they might carry a small chunk of 5 mm smooth rod or something
I do have a caliper, so I can measure either side of the hole for starters anyway... but it seemed like the hole was the right size, probably the cartridge like you mentioned.

I'll get it out first and see if the cartridge has a lump or something.

So,


Using the M5 bolt worked great for getting it out.

I tried sanding the cartridge down some, but it didn't seem to help. With a caliper I couldn't find any real variation in the cartridge diameter... I concluded that the hole in the block was too small,

As stated above, no US stores stock metric drill bits and Amazon's are 2 to 3 months backordered; but there are ones on either side of the metric numbers, which most of the time are 'close enough'. So I had either a ~4.978mm bit which fit though very tightly, but didn't really remove any material, and didn't help the fit... and a ~5.054mm bit. I decided to risk it and use it to expand the hole (it's only 54 μm (+1.08%) too large after all). and it made the hole a bit too large (shocking I know ). I feel the heater could fall out.... and it's probably best/safe not to use. So I guess I junked that heating block....

But, I had the Huxley hot end I got sent by accident instead of an Ormerod, and the heating block is the same (at least it looked the same, and assembled fine). The cartridge went into it's slot just fine, as one would expect, a tight fit but easy enough to insert all the way, but not about to fall out either.... and I was able to assemble the hot end with that. I guess I must have just gotten a cooling block that got hot during machining or something and wound up with a slightly small hole for the heater.

I'll probably have to buy another cooling block for the second hot end I want to have, but at least I can have it shipped with the necessary parts to cobble together an ormerod hot end from the huxley parts.

At least I got the Heater out and into the 'spare' block and got it all assembled.... now onto assembling the electronics..... hopefully I'll be able to commission the printer this weekend.....


And I guess I'll have to look at getting a metric drill set... I swear..... it's the only metric thing in the US thats hard to find! (but we carry metric taps in all sizes?!) And the stores I found that stock it don't carry every size and nothing in the small sizes below like 10mm. Cause there are ones that are 'close enough' I know know that close enough doesn't exist...
I don't know why we don't switch to metric and be done with it. I had to get the 2mm needed for the bowden on Amazon, but I was able to order it ahead of time, and it was Prime so 2-day shipping......

Edited 1 time(s). Last edit at 03/12/2015 12:00AM by shadow651.

Nice to know our tolerances are pretty close! Maybe order a metric drill set from Canada? [www.amazon.ca]

I think I would have probably pressed the heater cartridge into the heater block with the vice, but that's just me. You may still be able to use the old block. I haven't got one in front of me, but you could drill and tap a hole into the block, and use a grub screw to hold the heater cartridge in. Other companies do this, but usually because their tolerances are rather slack.

Ian
RepRapPro tech support

Hi
I have had this problem- the solution was to gently heat the block with a blow torch and the cartridge literally fell out

Hope this helps

Bob H

Quote
droftarts

I think I would have probably pressed the heater cartridge into the heater block with the vice, but that's just me.

I'd considered that, but I wasn't sure of the best way to do it.... I was concerned that the wires sticking out of the cartridge make it a bit difficult to force in without damaging them... I'd also considered trying to 'crimp' that side of the block in the vice.... but if I ever needed to replace the heater, I would've needed a new block....

The grub screw solution would probably work fine though, I should've thought of that. Would you recommend a flat tipped, pointed, or other shaped tip grub screw? Or does it not really matter?


On a side note, I noticed that the technical drawing on GitHub for the Heater Block doesn't have any tolerances listed.

I wonder whether you could hold the heater in with some sort of fixative? I'm thinking of something like plaster of paris or a wall plaster repair substance such as pollyfilla, or even ordinary building cement (which seems to last OK in a brick fireplace).

Dave

Quote
dmould
I wonder whether you could hold the heater in with some sort of fixative? I'm thinking of something like plaster of paris or a wall plaster repair substance such as pollyfilla, or even ordinary building cement (which seems to last OK in a brick fireplace).

Dave

I'd be concerned that anything like that might be fairly non-conductive and interfere with heat transfer to the heating block.... Idealy the cartridge should be in direct contact with the aluminum block.

Quote
shadow651

Quote
dmould
I wonder whether you could hold the heater in with some sort of fixative? I'm thinking of something like plaster of paris or a wall plaster repair substance such as pollyfilla, or even ordinary building cement (which seems to last OK in a brick fireplace).

Dave

I'd be concerned that anything like that might be fairly non-conductive and interfere with heat transfer to the heating block.... Idealy the cartridge should be in direct contact with the aluminum block.

Many electric stove hotplates, kettle and immersion heater elements have a central heater wire or coil encased in 3mm or so of cement-like material, and it's likely that the heating cartridge for the Ormerod follows a similar construction - it seems to be the usual way of electrically insulating a high-temperature heater resistance wire from a metal casing. A few micrometres of plaster will have an insignificant effect on heat transfer in comparison. I do not know of any substance that is a good heat conductor but an electrical insulator that can withstand red-hot temperatures.

Dave

Quote
shadow651
The grub screw solution would probably work fine though, I should've thought of that. Would you recommend a flat tipped, pointed, or other shaped tip grub screw? Or does it not really matter?

Flat grub screw and fingerspitzengefühl, you don't want to crush the heating element inside - mine was a very lose fit too but have no problem keeping the heater (and temp. probe) in place with cables properly secured - and I added a touch of heat paste before mounting




Erik

We used to wrap the wire-wound resistors, that were used before cartridge heater, in aluminium kitchen foil if they were too small to fit the hole. But I think it would be too tight for even one layer of foil!

Ian
RepRapPro tech support

One thing you have to be very careful of on the heating cartridge is the wires coming out the back - I managed to break one off about 1mm from the end. You cannot solder it on again - I tried crimping it, but the connection was too dodgy and would glow red!
I had to buy a new one in the end.

If I would to press the cartridge into the block I would use a vice and go leads first into the block. Applying pressure to the flat end of the cartridge. Using a pice of pipe on the lead side makes room for the leads. It is rather important in these kind of situations to have the force lined up with the hole in the cartridge. Otherwise it will pinch and get stuck, it is easy to apply a lot of force with a vice so if it gets stuck one could probably squash the heater cartridge.

Another suggestion for increasing the heat transfer is to use copper paste. It may smell some when the lubricant gets burnt away, leaving the copper.