Wednesday, October 14, 2009


Costing Mendel

Mendel comes in at £395 for the lot (in the UK).

Assumptions are:

- Using RS (UK) for bought in standard stock (fasteners, bearings, bars, studding and belts)
- 4 off NEMA 17s, @ £20 each
- RP parts @ material cost of £20 (assumes no commission)
- Thick sheet cost (inc cutting cost) @ £20
- Electronics are Zach’s Gen3 @ £110

Raw data can be found in the Mendel assembly data sheet on the wiki. A tabular summary is also available on the wiki.

Here’s a graphical breakdown:

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Thanks for the breakdown, eD. That's very useful, as well as being something that you should be well proud of.
At this price I can no longer put off a purchase. Any idea if or when a full kit might become available? Soon I hope.
You may want to look at for the fasteners.

My initial estimates in A2 stainless come in at £62

They also sell A2 stud @ £3 a metre
Stop it, I am going to have to buy the bits now! I think there is a local steel merchant I can go to for the metal but I don't know where to go for the plastic bits. I did think of making them out of wood but that seems quite time consuming. Any help with the plastic components is welcome.
> Any help with the plastic components is welcome...

eD glossed over it a bit in a prior post but we're in the middle (well more like beginning) of setting up a mini factory, so that we can sell the plastic bits to you guys at cost. No idea of when this will be up and running, but it shouldn't be too long...
Right if you go to

Got it down to £34.86 inc vat and free next day delivery

Thats all A2 stainless except the M4x40's which are only available in mild steel.

A2 Stud is £2.12 +Vat per metre

@annodomini2 superb to see this! Thanks for your research - please could you capture it on the assembly data sheet (wiki) so that everyone gets a good deal too...? It's save the whole community a load!
@all: ano's already slayed the cost by £40, it'd be great if anyone else can get it down in other areas too! Getting it under £300 would be very cool.
Well if you use the MakerBot motors the you save $68, if you are in the US.

You could use pipe instead of smooth rod. Although pipe is not as smooth as rod, because you are using bearings everywhere, jamming should not be a problem. Pipe is cheaper than a rod of equal stiffness, and pipe can be cut with a cheap pipe cutter.

You could try to use more of the cheaper 608 bearings instead of only 624 bearings.

You could try using two smaller stepper motors for the z axis and drop an endless belt, like Nophead did for the Darwin:

Since all the Mendel parts can be printed on a 10 cm x 10 cm bed, a mini Mendel with a 10 cm x 10 cm build area would still be able to build itself and the original Mendel. Since it would use smaller motors, belts, rods/pipes, thick sheet, etc.. the price of the mechanical parts would be roughly halved.
More optimisation with a combination of A2 and BZP from the orbital place its now down to £19.21 Although under £20 you lose the free next day delivery so you may want to tweak it slightly.

BZP Stud is £4.86 for 9 lengths inc vat

Building up the spreadsheet atm, will modify the wiki when I get chance. have NEMA 17 25Ncm Steppers for £11.23 each, believe this is plus vat, not sure on delivery as they require registration.
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HI i am new to reprap and was wondering if i could cut the parts instead of printing them as my father has a large flatbed router, also do rs sell a suitable stepper motor as i already have an account there
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What do you mean by course? M8 x 1.25 is the course thread and that is the normal thread for nuts, bolts and studding. Are you saying Mendel uses finer than that?
Oh I am being so daft, The other day I read that there was two pitches for M8 on wikipedia,

Then, wondering which thread I needed I decided to read look at the reprap wiki and must have read "All studding (i.e. threaded rod) is M8. BZP is fine" as

"All studding (i.e. threaded rod) is M8 fine"

I am glad, because my 9 meters of studding M8x1.25 arrived today, and I no longer have to send it all back,
@liam RS do not sell the nema 17 steppers (AFAIK) you can get them from or

As far as making a mendel using parts cut from mdf, I think this would be quite tricky because of complex 3d nature of the parts.

However some of mendels parts are cut from thick mdf sheet. Prehaps you could ask your father to cut those parts for you, and if you, do please make some extra ones as I would like to purchase them from you ;)
I am a bit confused i have ordered the fastners from orbital fastners and they arrived on tuesday

I have 14 off M3 Nuts and 54 off M3x20 Cap screw but the nuts don't fit the screws.

As it happens the 14 nuts are used as spacers anyway so I don't think it matters, but whats the deal here? If they are M3 nuts they should fit M3 screws right?
Yes M3 nuts fit M3 screws in my experience!

Looks like they sent you the wrong parts.
The shank of an M3 screw should be about 3mm and the head of the nut 5.5mm across flats. If it is 7mm AF then it is most likely an M4 nut.
I don't have an accurate way of measuring things, but I have a pair of vernier callipers in the post. (Its a Christmas present and I am not supposed to know)

Either way, I do have a socket set and the M3 nuts fits snugly inside a 6mm socket.
If they are loose on the bolt then perhaps they are M3.5

If they are lose in the socket then perhaps the bolt is M2.5.

M2.5 is common. I have never encountered M3.5.
Thanks nophead that table was really useful

I think the cap screws are M3, the orbitalfastners order also included 38 M3 nylock nuts which fit onto the bolts fine.

Of course those could also be wrong but those nuts do not fit into a 5mm socket, meaning they can't be M2 or M2.5, so by process of elimination I think they must be M3.

The other 14 nuts are just wrong they must have messed up my order, I think they must be M3.5 as you say. Again I am not sure it matters as the nuts are used as circuit board spacers on the mendel as far as I can tell. But I feel inclined to return them on principle.
Well the Vernier Calipers arrived, and the so called "M3" nuts are 5.98mm across flats!

I ordered 4 Nema 17's from motioncontrolproducts today aswell, note that the price of 11.23 does not include VAT and shipping is £12 making the total cost +VAT & Delivery of 4 nema 17's £65.46

I also realised that the Nema 17's from makerbot have a shaft diameter of 4.78mm wheras the motioncontrolproducts one has a shaft diameter of 5mm, I think the mendel parts assume a 5mm diameter, but it may not be a problem, something to be weary of though.
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