3D printing Harold Hall’s Grinding Rest

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3D printing Harold Hall’s Grinding Rest

This topic has 30 replies, 18 voices, and was last updated 31 May 2013 at 20:01 by V8Eng.

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29 May 2013 at 22:03 #120969
Paul tindall
Participant
@paultindall15814
I see there is an article on a Reprap 3D printer in next month's MEW. I too recently built one – the smaller Huxley version.

As a relative beginner to Model Engineering, I've been working my way through Harold Hall's milling course book, which inevitably means I'm building the advanced grinding rest.

I saw some queries in a post recently on how it all goes together, which I wasn't too clear on myself.

So, I decided to try 3d printing the parts, before completing all of the metal bits, to see how it works. This involved drawing the parts from the book in a CAD package (the very good OpenSCAD – see http://www.openscad.org/), and printing them. The photos show various parts: Top Slide(8), Slide Swivel(9), Lower Slide(4) and Table. The other photo show the table next to the real one and finally a partial assembly with a mixture of plastic and metal parts.

Was it worth it, well yes – I've learn the CAD programme and the printing process. I know what works and what doesn't. Don't expect precision, but it has its uses. I've also printed:

Its a very useful addition to the workshop and well worth having a play.

Edited By JasonB on 30/05/2013 09:51:32
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29 May 2013 at 22:03 #15641
Paul tindall
Participant
@paultindall15814
29 May 2013 at 22:32 #120978
John Haine
Participant
@johnhaine32865
That's brilliant Paul! The metal bits look well made as well.

John.
29 May 2013 at 23:18 #120984
MICHAEL WILLIAMS
Participant
@michaelwilliams41215
Am I the last person on the planet that can read a simple drawing and then just go and make the parts ????
30 May 2013 at 07:43 #120999
JasonB
Moderator
@jasonb
No your not the only one.

Does seem a bit of a waste of printing as if its been drawn in a 3D programme you could have assembled the parts there and by putting your mouse on the handwheels turned the feed screws or undone the levers and seen how it works.

J
30 May 2013 at 09:29 #121008
Trevorh
Participant
@trevorh
My son has just purchased one of these 3D printers and was looking for a project for it, I think I now have the perfect use for it

That does look good, what kind of precision did you get on the individual components?

how long did it take to print off

cheers
30 May 2013 at 09:48 #121010
Brian
Participant
@brian
This thread would be great if I could read it. The same old problem text and attachments being hidden by the addverts. Stand by for more comments like this.
30 May 2013 at 09:54 #121012
JasonB
Moderator
@jasonb
Is that any better now Brian, I have resizes the images. Although they looked fine on my computer anyway.

Back on topic. Treveor I don't think the idea is to actually use the plastic parts and I'm not sure how well they would stand upto a stream of sparks and grinding dust.

J
30 May 2013 at 10:07 #121014
Andyf
Participant
@andyf
My compatibility button usually does the trick, Jason, but not when images are side by side, as here.

A work-around is to highlight the text of the message, copy it, and paste it into the Reply box below, without actually sending it, of course.

Andy
30 May 2013 at 10:21 #121016
Paul tindall
Participant
@paultindall15814
Ok, I did this exercise more to learn about 3D printing than use the parts – they certainly would not be used in a real grinding rig. Critical to making the process usable is the CAD process.

Having drawn components in OpenSCAD I an now confident that I can quickly knock up (3D priniting is about rapid prototyping and making objects which are difficult/impossible to make another way). It also make little mess as it is an additive process – no swarf!

I'm achieving about 0.1-0.,2mm accuracy – not stunning but ok. I am still learning how to tweak the machine. Print time varies and depends on the slicing depth (how thin each layer is), the size and the fill ratio. The parts shown took 4 hours to print in total. A long time but you can just leave it to get on with it.

I am finding numerous uses for it in the workshop, just as I did when i got my lathe and mill – I use it for all sorts of things. As mentioned in the 1st post (but obsurred by the photos) I have to date made:
- Vice Jaws
- Lathe Indexer for my Hobbymat
- Change gears for the above
- Drill/Milling cutter holders
- Cable clips – various
- Tool Hooks – various
- Angle jigs
In addition, other small items like trim parts for the wife's car.
30 May 2013 at 10:30 #121019
Trevorh
Participant
@trevorh
Hi Jason, Paul, I think you mis understood my comment, it wasn't to use the parts in place of but as an actual template.

A drawing even in 3D can only give a limited amount of "Feel" for the part you are designing or wanting to make, But to actually see it and "Play" with it often will give a better insight as to its design and what might need tweeking before committing to steel

I was also wondering as to what the melt temperatures are and are they adjustable as i work in the Extrusion industry all be it on a lot larger machines and as such also have access to all of the various resins/ploymers

cheers
30 May 2013 at 11:26 #121020
Douglas Johnston
Participant
@douglasjohnston98463
Hello Paul,

I have been fascinated with the idea of 3D printers for ages but have never done anything about it. Roughly how much do they cost to build and are the plastic consumables expensive to buy?

Doug
30 May 2013 at 12:07 #121021
Brian
Participant
@brian
Had to press the compatibility button to reveal all, you waved your wand, thanks Jason.

Brian
30 May 2013 at 12:22 #121025
Tony Jeffree
Participant
@tonyjeffree56510
Paul –

Not that I needed much persuasion, but seeing what you have produced has convinced me that I need one of these! Even if you plan to make the parts by hand, in metal, for the finished article, the ability to prototype relatively quickly in plastic to see how the design fits together looks very useful indeed – a great addition to any workshop IMHO.

Regards,

Tony
30 May 2013 at 12:41 #121029
Paul tindall
Participant
@paultindall15814
Hi,

answering a few questions:

Cost – well you can buy a kit from http://www.reprappro.com (no connection etc). I reckon that a model engineer can make one for £200 – 250, depending on what's in the scrap bin. Motors, and electronics are the most expensive, although the steppers are much smaller than those on a CNC mill. You can also buy 'comercial' hobby machines for £1-2K.

Plastics I use are various colours of PLA – 1.75mm filiament. Lots of suppliers on Amazon, ebay or google arround. Typically 20 to 30+ quid for a Kg. Quality varies. It can also print with ABS (as used in Lego bricks) and some have tried nylon..

Extrusion temps vary with plastic – PLA about 175C, ABS 220C although it requires experimentation. Its easy to vary the temps with the Open Source S/W which I use.

Paul
30 May 2013 at 12:46 #121031
Trevor Wright
Participant
@trevorwright62541
Paul,

You say you are getting a 0.1-0.2mm accuracy – do you account for shrinkage in your cad design? I ask this because mine will shrink around 0.5-0.7mm after printing.

I am using Faberdashery filament, the best, but reducing the print temperature only prevents extrusion, so I am intrigued as the to bed and hot end temperatures you are using. Your prints in the photos look much better quality than mine.

My machine is a Huxley rep-rap.

Trevor

Posted at the same time lol.

Edited By Trevor Wright on 30/05/2013 12:49:21
30 May 2013 at 12:56 #121032
Trevor Wright
Participant
@trevorwright62541
Building the Huxley is not as straightforward as it first appears, it took me 2 months before I was printing.

Mechanical build was ok but the wiring was a nightmare, due to bad instructions and photographs showing similar machines wired in opposite directions…….

The software would have had me pulling my hair out (if I had any)…..you need to read up on python software to get anywhere….Once installed and working you go to a front screen that works everything with a click………it's getting it installed that is the killer.

Trevor

Edited By Trevor Wright on 30/05/2013 12:57:46
30 May 2013 at 13:25 #121033
Paul tindall
Participant
@paultindall15814
@Trevor,

the temps I gave are text book temperatures. For my machine I extrude PLA at 202 deg C and heat the bed to 85 dec C. I also use PVA on the bed (20:1 water/PVA) as I had warpage issues with cheaper plastic.

Re: shrinkage, well I guess I should have allowed for it depending on size etc. In practice, I printed a calibration cube (Thingiverse.com) and adjusted x/y parameters accrodingly. My biggest problem is surface finish. I've improved it by removing as much backlash from the axes – keeping the belts tight, lubricating the moving surfaces regularly. This helps, but for me the biggest effect was to remove slop in the table (supported by 3 spring-loaded M3 screws. I was getting quite a bit of movement here. Temporarily, I've put a spring on one of the mounts, which takes up the slop (the forces on the bed are pretty small so this seems to work).

Building the Huxley took about 2 weeks of evenings. Mechanical instructions were pretty good. Wiring, I agree the instructions lacked a bit. I do electronics an s/w for a living so I managed to work it out.

S/W installation was fine for me. I quickly switched to Repetier (www.repetier.com) for the control software.
30 May 2013 at 13:51 #121035
GaryM
Participant
@garym
While not wishing to resurrect the debate about hidden text and page displays, I was having trouble with this page and found that if I turn compatibility view off the page displays perfectly. If I then turn it on again text is hidden. Weird? I'm forced to use IE at work but detest it like the plague.

Gary
30 May 2013 at 14:57 #121041
Russell Eberhardt
Participant
@russelleberhardt48058
Posted by Trevor Wright on 30/05/2013 12:46:34:
You say you are getting a 0.1-0.2mm accuracy – do you account for shrinkage in your cad

Surely the shrinkage depends on the size of the part. I used to be involved with plastic mouldings and we allowed 0.5 % for shrinkage after it came out of the mould.

Russell.
31 May 2013 at 12:38 #121118
Trevor Wright
Participant
@trevorwright62541
Paul,

temperatures are spot on to my optimum, I ditched the m3 screws and replaced them with studding, locking with nylocs to the cradle, springs then another nyloc to adjust the height.

Wish I was a software engineer – understanding the jargon was the hardest part.

Never thought of calibrating the X/Y axes, will give me something to do tonight.

Don't use PVA, but clean with acetone instead. That sticks – I have to design a screwdriver pocket on each component to jemmy them off after they cool to below 35°C

Trevor
31 May 2013 at 12:59 #121121
Bazyle
Participant
@bazyle
Most impressed. This is the first time I have seen anything useful done in amateur printing. I couldn't think of anything I could use it for previously. It woud be interesting to see some of the other things you have made. Are the hobbymat gears strong enough?
31 May 2013 at 13:09 #121122
Speedy Builder5
Participant
@speedybuilder5
I reccon the process could be good for making one off drilling jigs (bush the holes), milling wedges / fixtures etc. I saw on TV also, that they are developing metal deposition and ceramics, such that it could be possible to print electronic components.
31 May 2013 at 13:18 #121124
JasonB
Moderator
@jasonb
I saw a godd video the other day of printing sand, saves having to allow any draft angle on patterns or using loose pieces as there is no pattern to pull from the sand, just print and pour. Prints the feeders, runners and cores as well.
31 May 2013 at 14:49 #121130
Paul tindall
Participant
@paultindall15814
Re: Shrinkage/calibration, the X/Y axes are scaled according to a calibration scaling factor held in the firmware. By printing a 25mm calibration cube, you can see how long/short you are in each axis and scale accordingly. This should take out the shrinkage ratio, provided it is constant across length. I suspect it is approximately so.

Re: Hobbymat change gears – I use them for indexing – so strength not an issue. I am going to print the small 30T gear – which takes a hammering, and use it for power feed, so will let you know how strong it is. When indexing, I tend to scribble on the gears with marker pen, so I don't lose track. Using printed gears keeps my original set pristine.

However, I am considering not using gears at all, but use depthed holes at the angles I require, and use simple rod to lock them. I can also just print the exact number I need, eg 18 holes, and print numbers on the face so I don't forget where I am.

Re: other stuff printed – I will add to my album when I get time ….
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