questions about building - lnear bearings oil? and glue x-axis acrylic?

Hi,

My first post on the forum. I have got the limited edition Ormerod no. 318. Its a fascinating build. A long way off finished yet! I have some questions, thoughts etc though.

Question 1 .. Any reason I shouldnt glue the x-rib to the x-axis-plate with CA glue? N.B. Prior to gluing I intend to sand with fine wd paper and use masking tape to prevent glue from getting on the machine surface where the xcarriage roller runs.
To keep it straight I thought I would stick the x-axis plate on the big flat side of a spirit level( which is the best engineering flat surface I can find around my place) with double sided tape .

Subtext :

I broke the x-rib at the tenon on the motor end. I managed to get this glued back in place with CA glue.
I am now in favour of gluing the x-rib to the x-axis plate with CA glue, since I dont want to rely on my CA joint on the tenon which appears to clamp the x-rib to the x-axis plate using the x motor bracket.

(I fitted the x-rib and x-axis plate but noticed that the plate was bowed,causing the xcarriage to rotate around the 12x350 mm smooth rod as the carriage was slid up and down. After re-reading the instructions I
figured I should have done a bit more filing ! The tenon broke off as I disassembled the x rib from the x-axis plate).

Question 2

Should I lubricate the linear bearings with machine oil before I fit them? They feel a bit gritty when I slide them..


Thoughts.

Screws with Allen are problematic and increase the build time considerably.
Is there any reason not to use cross head screws for some parts?
The worst offender is the highly recessed screw used with a t-nut to attach the z-lower mount to the yaxis frame aluminium extrusion. I tried various ways to get my allen key in the allen key hole in the screw. Sighting down the hole using a torch and slipping an m3 washer over the allen key to help centering it in the slot. Took half an hour and dont really want to go through that again!


other thoughts that might be helpful in the docs.

Y-axis motor.
Requires use of a cross head screw driver ( not mentioned in tools)
to remove the screw from the motor. Since the motor screw is done up tight
do make sure you have the correct screwdriver that fits snugly( not just any old cross head screwdriver) to avoid problems knackering the screw.

Y axis drive belt.
Take care not to overtighten the screws holding the microswitch

Hi kwikius

1. Yes, you can try gluing the acrylic, to help support it. We're happy to resupply you with x axis lasercut parts under warranty, which have been modified for better fit, if you want; send me an email (we don't have access to the RS customer database) with your name, address, machine number and what you need, to support at reprappro dot com.

2. Yes, put a little light oil in the bearings if you wish, and wipe the rods before assembly. Because we're using larger 12mm bearings, rather than 8mm bearings used on Mendel printers, they are generally more robust. A drop of oil on the bearings very occasionally will keep the rubber seal lubricated; they can dry out and increase friction. I must add a maintenance/improvements page to the instructions...

Allen keys vs crosshead - I MUCH prefer the Allen heads, and don't really anticipate any change. Having long-shaft Allen keys, particularly with a 'ball' on one end, is an advantage, though. I don't remember having any particular problem with the deeply recessed bolt on the z-lower-mount; I think I turn the printer over to get to it, so the Allen key is going down into the recess. I find it much easier to butcher a screw with a crosshead screwdriver, particularly if one uses slightly the wrong size, or pozidrive rather than Phillips! No chance of that with an Allen key, unless perhaps you use an imperial set rather than metric...

I'll update the instructions with your suggestions, thanks for the feedback! Glad you're having fun.

Ian
RepRapPro tech support

1. Re gluing acrylic, I understand that you need a special glue for this (acrylic monomer) because most adhesives won't adhere well to acrylic.

2. Re allen head screws, after assembling a few joints I went out and bought 2mm and 2.5mm hex drivers, because I realised it would take an age to assemble all the joints using allens keys. I think this should be recommended in the build instructions. Once you have hex drivers, they are quicker to use than cross-head screws and screwdrivers would be.

"Allen keys vs crosshead - I MUCH prefer the Allen heads"

Ditto, I find long allan bits very usefull, these are the one I used for the Ormerod, from a box set marked "BaTo" (attached picture)

Hi All

I too was thinking the linear bearings feel gritty. I do hope the rods are well cleaned after grinding. Perhaps it is the ground finish itself we can hear/feel.
I was also wondering about lubrication my thoughts were with "copper slip" grease but maybee machine oil or regular grease would be better. Being an electronics engineer I am not too clued up on these matters. Something that does not rot the rubber seals is an important aspect.

Rory

Edited 1 time(s). Last edit at 12/26/2013 09:08AM by Rory166.

Quote
Rory166
.. my thoughts were with "copper slip" grease but..
Rory

Copper grease or any other grease with metal particles is a BIG no-no for ball or roler type bearings! - a thin layer of acid free oil would be my choice

168

Thanks I am so glad I didn,t act on my ill advised copper thoughts. Is 3in1 oil acid free?

Rory

Thanks for thoughts on lubrication, I hadn't thought of the copper slip issue and shall apply some good old 3 in 1 type oil. Living near the coast salt, laden air soon corrodes everything, so it was a timely comment to remind me to do this.

I also MUCH prefer the allen/socket head bolts and used a screw driver version with selectable tips together with round tip allen keys.
Cross heads should be avoided for the reason given elsewhere that they are so easy to damage.

".. Is 3in1 oil acid free?.."

I would think any universal household oil should be acid free but to be on the safe side, only use something marked as such
about the worry of corrosion, I wonder if the rods are made of stainless steel? - the colour of the steel would make me believe that this is the case

Erik

Edited 1 time(s). Last edit at 12/26/2013 11:05AM by ormerod168.

Erik

I showed the rods to our machine shop manager at work and he said they are silver steel, I assume he knows his stuff. Aparently it can rust. The finish is ground for a good tolerance. Whay country are you from Erik?

Rory

Edited 1 time(s). Last edit at 12/26/2013 11:09AM by Rory166.

We use 3-in-oil [www.3inone.com] on our production machines - just a couple of drops every couple of months. And this is in a fairly dusty environment (though generally low humidity), running 18 hours a day! It's just a light machine oil. Don't use WD40; it evaporates leaving a residue. PTFE lubricants can, again, dry out and leave a residue, in my experience. It's just trying to avoid anything that will gum up the bearings.

The rods are CK55 hardened ground bar, and are usually pretty clean when we get them. We don't do anything special to them.

Ian
RepRapPro tech support

Rory

Thanks, good to know, I better keep it lightly oiled then
I live in Denmark, my line of work is in repair of elektromekanics so I have no problem putting this most interesting thingie together...but 3D-printing is all new to me..or will be when I get there :-)

Erik

I thought of using some Graphite lock lubricant, which I got from Maplin
Greg

Thanks for all the replies. Will try gluing my xaxis parts with cyano and see how that goes. One further question re lubrication..

Quote
droftarts
[...]
2. Yes, put a little light oil in the bearings if you wish, and wipe the rods before assembly. Because we're using larger 12mm bearings, rather than 8mm bearings used on Mendel printers, they are generally more robust. A drop of oil on the bearings very occasionally will keep the rubber seal lubricated; they can dry out and increase friction. I must add a maintenance/improvements page to the instructions...
t

You say somewhere in the thread that you lubricate the bearings on your machines every couple of months. I have already partially assembled my machine. I assume its necessary to remove the bearings from the ground rods to lubricate them so do you actually strip down your machines every couple of months to lubricate the bearings?

I am assuming that adding some oil on the ground rods would only lubricate the oil seals.

regards
Andy

Quote
kwikius
Thanks for all the replies. Will try gluing my xaxis parts with cyano and see how that goes. One further question re lubrication..

Quote
droftarts
[...]
2. Yes, put a little light oil in the bearings if you wish, and wipe the rods before assembly. Because we're using larger 12mm bearings, rather than 8mm bearings used on Mendel printers, they are generally more robust. A drop of oil on the bearings very occasionally will keep the rubber seal lubricated; they can dry out and increase friction. I must add a maintenance/improvements page to the instructions...
t

You say somewhere in the thread that you lubricate the bearings on your machines every couple of months. I have already partially assembled my machine. I assume its necessary to remove the bearings from the ground rods to lubricate them so do you actually strip down your machines every couple of months to lubricate the bearings?

I am assuming that adding some oil on the ground rods would only lubricate the oil seals.

regards
Andy

My thoughts exactly

Rory

I would not worry about it, the bearings is in a closed system and the oil inside will last forever - just make sure to keep the sealing intact and the rods free from rust by adding a thin layer of oil now and then

Erik

Quote
ormerod168
I would not worry about it, the bearings is in a closed system and the oil inside will last forever - just make sure to keep the sealing intact and the rods free from rust by adding a thin layer of oil now and then

Erik

Exactly! No need to dismantle the axes. You keep the seals lubricated, and the rods clean and lightly oiled. Then the seals wipe any dust from the rods easily, and there's no surface problems on the rod to damage the seals. If you are using the printer in a cold and/or high humidity environment, eg garage, rather than indoors, it may be necessary to lubricate the rods more often to keep rust at bay.

Ian
RepRapPro tech support

Hi again,

Think I understand now re lubrication, and will leave that till its built!

Just a note regarding using cyanoacrylate to glue the x-rib to the x-axis-plate. I have followed through with this as detailed in my OP and am happy that its a worthwhile mod. The x-axis is now nice and straight. The x-axis is also surely stiffened considerably by gluing the two parts. The cyanoacrylate used ( A B&Q own brand) appears to bond very well to the acrylic ( after roughing with ( say 600) wet and dry paper). It also adds a good deal of strength locally to support the captive nut and washer that hold on the z-runner mount. You do need to work clean though.

As regards the use of allen screws, I bought some ball end allen keys and they have helped speed things up. I also used a torx bit (T6?) so that I could use a ratchet screw driver for initial fitting of the 2.5 mm screws.


Here is some feedback on the instructions..


As regards fitting the x axis belt, The alignment of the pulley seems quite critical. Ideally stating an actual point to align with would help. I believe that the inside face of outer lip of the pulley should line up with the joint between the xaxis plate and the x-motor bracket. You can offer up the stepper motor on the end of the x axis to see if its in line. etc ( or whatever is appropriate).

Feeding the x-axais belt through the slots near the motor was tricky. Couldnt figure out how to do it. Eventually popped it through somehow by moving the x-axis motor up and down in the slot and rotating the pulley to pull the belt though. Perhaps some more guidance on the jiggery pokery involved here?

Should thermal grease be used on the cartridge heater?

The brass parts and the bowden tube. I found this really tricky! I think a section drawing of what I am trying to achieve here would help. What should the cross section of the ptfe tube inside the brass union look like? I found the only way I could get the ptfe tube to come right out to the end of the brass union was to pare it away with a knife and rescrew it several times. I did this on the hot end but just screwd the other end in as afar as I could and left it after checking the filament would go through.

All the mechanical parts done. Now on to the electronics!

Also found more tools required which could be added to the tools list

pencil sharpener
2 mm drill, 4 mm drill
hand chuck or pin vice
mole grips ( or bench vice)
hot air gun

and materials :
thermal grease ( optional for th hot end but to not do this is a bit like eating a beefburger without onions aint it )

regards
Andy

Hi kwikius

Thanks for the feedback! I have started an 'instructions improvements' forum thread here: [forums.reprap.org] - they are a bit off-topic posted here!

x-axis pulley - "The pulley needs to sit right on the very end of the motor shaft, as shown in the picture." - 1st instruction here: [www.reprappro.com]

x-axis belt feeding - yes, that is tricky. I haven't worked out a particularly easy way of doing it, either, though turning the motor pulley helped. I think I'll ask our design department to make the hole around the pulley bigger, so that the pulley can move past the belt with the belt slack, but in-situ. Then the belt could be fed through without the motor being in place, which would make it a lot easier.

Thermal grease - not supplied, no need to use it. The cartridge should be a close fit in the heater block, and there's plenty of surface area in contact to transfer heat. Also, thermal grease is usually only rated to 200C max, which is the operating temperature for the cartridge, though can be more for ABS printing.

Bowden ends - I 'tap' both ends using this method: Take the brass end with a thread on it (rather than a slot) and screw it into the aluminium cooling block. Use a pencil sharpener to lightly taper the end of the PTFE tube, then thread the brass union onto the end. It should be easier to turn with the aluminium block on it. Finally, remove the brass union, and repeat at the other end. The threads should be about 10mm long, and it will be easier to screw each brass union on, once threaded. Use a 2mm drill in the end of each brass union (and into the end of the PTFE tube) to make sure there is no constriction on the filament. Check, and clean any debris out, by pushing a piece of filament through the tube.

The hot end instructions need updating with more pictures, and styling to match the rest of the instructions.

Thanks for the extra tools (I'm always forgetting to add to that list), I'll update the page.

Ian
RepRapPro tech support

kwikius

"..The brass parts and the bowden tube. I found this really tricky!.."

Me too, especially the lineup of the parts, ptfe is quite soft and if you start wrong seems to try to move "out of the tupe"
but thats an easy fix - inside diameter of the brass and tube is a bit over 2mm, a 2mm welding rod will fit right in, cut of 100mm of rod, buffed both end so not to scratch the ptfe
used the rod as a guide to line up the parts whilst screwing in the brass (see pic.)

and there is no need to clean out the pfte with a dril bit if you do it this way, the ptfe will "cold form" and stay put around the 2mm guiding rod, you have to use a lot of pressure though

Ian

"..Use a pencil sharpener to lightly.."

A kingdom for a pencil sharpener! - who has such a thing theese days he he...well, easy to make a poor mans version, (see pic.) and again the 2mm welding rod came in handy

Erik

Quote
ormerod168
kwikius

"..The brass parts and the bowden tube. I found this really tricky!.."

Me too, especially the lineup of the parts, ptfe is quite soft and if you start wrong seems to try to move "out of the tupe"
but thats an easy fix - inside diameter of the brass and tube is a bit over 2mm, a 2mm welding rod will fit right in, cut of 100mm of rod, buffed both end so not to scratch the ptfe
used the rod as a guide to line up the parts whilst screwing in the brass (see pic.)

and there is no need to clean out the pfte with a dril bit if you do it this way, the ptfe will "cold form" and stay put around the 2mm guiding rod, you have to use a lot of pressure though

Ian

"..Use a pencil sharpener to lightly.."

A kingdom for a pencil sharpener! - who has such a thing theese days he he...well, easy to make a poor mans version, (see pic.) and again the 2mm welding rod came in handy

Erik

This looks good to me. I'm sure the way I have it now is rubbish . Once I have tried the printer out I will certainly give this a try. Just need some 2 mm rod!

A cutaway through the finished piece to show what I am trying to achieve would also be good!

reghards
Andy