Cost of Having Parts Cast

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Cost of Having Parts Cast

This topic has 24 replies, 6 voices, and was last updated 8 December 2023 at 16:08 by noel shelley.

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5 December 2023 at 19:18 #697604
Peter Cook 6
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@petercook6
I appreciate this is akin to asking how long is a piece of string! But the recent thread on getting parts cast piqued my interest. I am slowly progressing with my clock project, and am fabricating the frame from steel angle. However the original frame is cast iron, and the thread made me wonder what getting a frame cast might cost in iron or aluminium.

I wondered if someone who has had such parts cast might give me an idea of the order of magnitude of cost of getting it done as a one off. High tens, low hundreds, high hundreds or in the thousands?

I do have a 3D printer, but no experience of making patterns for casting. Excuse the decimal places in the dimensions, they are an artefact of my 3D modelling.
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5 December 2023 at 20:40 #697636
JasonB
Moderator
@jasonb
Is your CAD able to give the volume or weight of the part assuming Iron then I’ll be able to give you an ide abased on what the foundry that has been doing my castings charge.

Also what is the wall thickness as that may be a bit thin for iron?
6 December 2023 at 13:34 #697730
Peter Cook 6
Participant
@petercook6
Thank you Jason. Sorry for the delayed response. My CAD program (MOI) can now give me volume data – it’s just that I have never had the need to do so. So I had to find the external script that does so, remember how to install and run it.

To answer your question, the volume of the part is 175cm3. All the walls are 5mm thick. I am fabricating from 5mm angle so all the parts are based on that. The real thing has the walls 3/4″ thick, which would be 4.5mm to scale, but I simply chose suitable stock steel angle.

Thinking about it, I also wonder how the pattern would be put in/extracted from the mould, with the feet sticking out from the sides one way, and what is the top surface the other side. The original must have been done somehow as It shows no signs of seams or welding – although with a date of 1889, it probably predates gas or electric arc welding.
6 December 2023 at 14:12 #697739
Michael Gilligan
Participant
@michaelgilligan61133
Do you have any photo’s of the original, Peter

… they might prompt some useful discussion

MichaelG.

.

.

P.S. __ to preclude the “pedants uprising” I should mention that the apostrophe was placed intentionally … it stands for the omitted letters graph

🙂
6 December 2023 at 14:47 #697740
JasonB
Moderator
@jasonb
I must have a thicker pencil than you Peter, I sketched this out this morning and got 223cm3 which gives a weight of 1.57kg, though my feet have a bit more material in them I did opt for 5mm thickness. I’ll PM you what it may cost.

As to casting as well as the pattern you would ideally need to produce what is sometimes called a follow board. This is a piece to fill in the inside of the pattern when the first half is moulded right way up. It is then removed when the other half is moulded so the sand can fill the internal void. I’ll draw that up later as it is easier to see than explain. Someone casting at home where time is not a problem may simply scoop out the unwanted sand.
6 December 2023 at 15:02 #697742
Peter Cook 6
Participant
@petercook6
As requested.

The first is an overall view of the clock in it’s case (apologies for the case colour – I didn’t paint it!). The second is the the time train showing the suspension hanger with the strike train behind. The third is the chime train with the time train in the foreground.

The frame appears to be a one piece casting. It has casting flaws in places ( small blow holes etc). All the uprights are also cast and bolted onto the frame. I can’t see (or feel) any joints in the frame.

Other examples also made by Smiths (this one is dated 1889) seem to be much the same components. I presume it was delivered in pieces by horse and cart, probably either from the GWR station in Newbury or from Hungerford and assembled on site. The Lambourn branch did not open until 1899 – 10 years after the clock was installed.

Thoughts on its manufacture would be welcome.
6 December 2023 at 16:47 #697770
Michael Gilligan
Participant
@michaelgilligan61133
Many thanks, Peter

It should be a wonderful project

… pretty sure you have posted about it before, but it’s good to have it featured prominently on the new site.

MichaelG.
7 December 2023 at 08:41 #697882
JasonB
Moderator
@jasonb
So to mould the frame that I showed above you would need to make something to infill it so that you are in effect moulding a solid part, the infill would nee dto look like this

You would then stand the infill and pattern on a flat surface and mould the sand around them.

The box can then be turned upside down and the infill removed but pattern left in place, other half of the box positioned and filled with sand. This sand will then take the place of the infill so once the pattern is removed you will only have a void in the sand equal to the pattern which subsequently gets filled with iron.

You will need some draft angle on the “vertical” sides of the pattern so it can be pulled from the sand 2-3deg should be OK. A shrinkage allowance of 1% is what I tend to use for iron so pattern would be 166 + 1.66 = 167.66mm for example. Also a machining allowance on all surfaces that are to be machined which would be the top surface and the underside of the feet, couple of mm should do. Though think how you will machine them on a small mill.

You could 3D print the patterns from several parts and join them together or use a hardwood or even MDF but choose a decent one like Moisture resistant MDF as it is a lot denser than shed bought MDF.

As for the various attached cast posts etc at that size I would tend to go with silver soldered steel fabrications rather than castings with the possible exception of the arch-shaped one which looks a bit thicker. If these were cast they would be quite thin and you risk the problems of them cooling too quickly which can result in hard areas that become difficult to machine. Consider having all the sheet metal parts of the fabrications laser cut if you don’t want to mill them.
7 December 2023 at 12:10 #697927
Peter Cook 6
Participant
@petercook6
Thank you very much Jason. As a pattern making 101 tutorial that is just superb. I think I now understand what would need to be made, although whether my skills are up to doing so remains to be seen. It would probably be 3D printed, as my woodworking skills are very limited!

Thank you for the advice on draft and shrinkage – something else for me to learn about and experiment with on the 3D models. When I next go to wind the clock I will take a square or something similar with me. I am interested to see if the original has draft on the sides. I have assumed it was square, but I am not sure I would notice a 2° angle on the sides.

Thank you also for the advice on the posts. I had planned to fabricate them all as you suggest, and based on your advice I will continue to do so. The mill (SX1LP) is just about long enough to fly cut the 372mm top faces in one pass with very careful setting up. The bottom of the feet will be two setups, but if I have a flat top as reference fairly easy.

I had already planned to get the three winding ratchet wheels and the strike ratchet laser cut from 4mm plate, mainly because I could not work out how to shape them on the equipment I have. Now you have planted the idea I will probably get the uprights done the same way. I was planning to rough them out on the bandsaw and finish on the mill, but 4mm steel plate is fairly slow going on my little mill.

Thank you again for the help.

PS wonder if Santa could be persuaded to spring for a bigger mill!!
7 December 2023 at 12:27 #697929
duncan webster 1
Participant
@duncanwebster1
Not that I’m an expert patter maker, but could you make 5 loose bits to fit from inside, mould the outside, turn it over, remove the loose bits and do the inside.

If it were me I’d fabricate it
7 December 2023 at 13:26 #697933
JasonB
Moderator
@jasonb
have a look at my recent post here to see how I included tabs so that the steel parts almost held themselves together during soldering.

This base is a bit of a toss up as to which way you can go as it is not too hard to fabricate from Angle or too hard to make patterns for. If the original does turn out to have vertical sides then I’d be more inclined to stick with the fabrication method, certainly looks quite square in the photos and I even wondered if it could have been done with four separtate castings, one for each side that were joined together. Other images (second down the left column)suggest there may be something going on in the corners but that could simply be where it has been done with a multi part pattern that could have been extracted from the sand without draft.

Other items may lend themselves more to casting such as if there are a lot of curves and or taper. I’ve been drawing up an engine over the last couple of evenings that fits that description with the intension to cast the main parts but it’s hush hush at the moment so can’t show my progress suffice to say I can’t wait to get my hands on a set of the castings. On the other hand that frame in my link above was best suited to fabrication as it would have been hard to cast it so thin.
7 December 2023 at 14:44 #697935
Peter Cook 6
Participant
@petercook6
Thanks again Jason. Much thinking is needed over the Christmas ( workshop too cold) season.

The Smith’s clock in the restoration images was dated to 1922 so 30+ years later than mine, but more importantly post the first world war when welding (arc & gas) moved from ideas into mainstream. So it’s more than feasible that post war Smiths adopted more modern manufacturing methods.

It’s interesting that on my clock the front plate reads J Smith & Sons. Midland Steam Clock Works. Derby. On the later one the same plate reads J Smith & Sons. Midland Clock Works. Derby. Eng.

The reference to Steam as a symbol of modernity having been dropped, and Eng. added, possibly a pointer to a more international business.

Thanks again to all for the thought provoking discussion and ideas.
7 December 2023 at 18:02 #697948
noel shelley
Participant
@noelshelley55608
An interesting challenge to make this base – and look right ! Wonderful drawings that Jason has done. I would agrree with his figures for draught angle but shrinkage I would check with the foundry before making a pattern. A 3d printed pattern may need considerable extra work to give a useable surface finish for molding. Casting could be done using the false cope method but the time and cost would be better spent in fabricating. 4 sides brazed together and then a bit of extra work to do the flare on the feet. Brazing rather than silver soldering on grounds of cost and also as braze will form better fillets. Decorative castings in iron are often only 3 or 4 mm thick so this being 5mm would be possible, but it would need the right grade of iron to avoid hard spots or skin. Remember that cast iron can be very brittle and may crack if of thin section. Bridport Foundry know about making small cast parts and the right grade of iron.

I would go for fabrication ! Noel

PS, you mentioned aluminium, it has a higher rate of shrinkage at about 1.65% but check with foundry.
7 December 2023 at 19:49 #697956
Michael Gilligan
Participant
@michaelgilligan61133
I presume you are familiar with the engraving on the Smith’s historical timeline, Peter … but have you seen how the bed of the clock at St Mary’s Ilkeston is actually constructed ?

.

https://youtu.be/k8o9vtbhZu0?feature=shared

.

Aside from the motorised winding … I wonder how much of that bed is original.

What was actually delivered to them ?

MichaelG.

[ just an interested bystander ]
7 December 2023 at 20:02 #697957
JasonB
Moderator
@jasonb
How would you say that one is constructed, Michael? I could not say one way or the other if it is a steel/iron fabrication or based on castings. Would help if the ends could be seen.
7 December 2023 at 21:32 #697959
bernard towers
Participant
@bernardtowers37738
Most of the ones I have seen from this era whilst on clock tours have been cast iron and in one piece
7 December 2023 at 21:56 #697973
Michael Gilligan
Participant
@michaelgilligan61133
On 7 December 2023 at 20:02 JasonB Said:

How would you say that one is constructed, Michael? I could not say one way or the other if it is a steel/iron fabrication or based on castings. Would help if the ends could be seen.

It has the look of a “fabricated prototype” to me, Jason

it rather looks like a load of small castings sitting, interlocked, in shallow channels.

… I’ve been busy scheming block-work and insulation [for a proposed extension] today, so haven’t done more than glance at it, but I will have a good look tomorrow

What it certainly is not … is what’s shown at 1864 on the time-line.

https://www.smithofderby.com/home/history/

MichaelG.
7 December 2023 at 22:11 #697983
Michael Gilligan
Participant
@michaelgilligan61133
7 December 2023 at 22:46 #697984
Michael Gilligan
Participant
@michaelgilligan61133
The church website has this wider view … but the image quality is not good:

http://stmarysilkeston.co.uk/wp-content/uploads/2012/01/clock02.jpg

MichaelG.
8 December 2023 at 11:56 #698243
Peter Cook 6
Participant
@petercook6
Judging by this page The Church Clock – St Mary’s Church, Ilkeston (stmarysilkeston.co.uk) the clock is not one of Smiths. It was apparently made by G. & W. Cope, Makers, Radford, Nottingham, in February 1864 who are named as members of the committee. According to the same page, the clock was electrified by Smiths in the 1980’s. Loomes has G&W Cope of Radford as being in business from c1855 to c1928.

I am swinging back to fabrication! The bearings for the great wheel arbours on all three trains are bolted to the sides of the frame – front and rear.

Any draft angle on those surfaces means they would need to have flats machined (there is no sign of that on the original), or the bearing mounts would need to be angled to suit. The alternative presumably is some sort of multipart pattern that can be removed to leave vertical surfaces – so the complexity of the learning curve goes up!!
8 December 2023 at 12:40 #698245
Michael Gilligan
Participant
@michaelgilligan61133
Thanks for making the point about Cope, Peter

… it seems to be ‘confirmed’ by Wikipedia

https://en.wikipedia.org/wiki/G._%26_F._Cope

.

Which rather calls into question the History on the Smith’s web-page.

MichaelG.

.

Sorry for the digression

Your question is already interesting-enough !
8 December 2023 at 13:08 #698248
JasonB
Moderator
@jasonb
I was looking at quite a few of the cast ones last night and think they may have been cast in another way, the odd bit of roughness in the corners a scan be seen here may also indicate how they were cast without the draft angle as they do look to be vertical sided.

It would need the pattern making in four parts that can be extracted from the sand by moving them into the central void so no draft needed and then a sand core would probably have been used when casting. May also explain why the feet are not the same at the ends as they are on the faces.
8 December 2023 at 13:45 #698250
Michael Gilligan
Participant
@michaelgilligan61133
Clever stuff, Jason !

MichaelG.
8 December 2023 at 15:09 #698256
Peter Cook 6
Participant
@petercook6
And way beyond my (non existent) pattern making skills.

Thank you all again. What started as a simple question has become a very interesting learning exercise for me. And to some extent that is the whole point of this hobby – at least for me.

Thanks again for spending your valuable time educating me.
8 December 2023 at 16:08 #698261
noel shelley
Participant
@noelshelley55608
The draft angle whilst making molding easier is NOT a prerequisite ! It can be done without but does need a perfect pattern with a very good finish, draw plates and VERY careful removal of the pattern. The extra cost would be small compared to the overall cost of a clock and if that’s what was needed then it could be done ! Noel.
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