Sunday, April 3, 2011

To Build from Scratch? Or Not to Build from Scratch?

To build from scratch? Or not to build from scratch? That is the question for this post.

I have done tons of research, came up with my own spreadsheets breaking down costs, and I finally have come to a conclusion. I have decided to build an SAE Prusa Mendel from scratch! Ahhh!!! Keep reading on to find out why I chose to try building a Prusa from scratch over a kit.

Cost

Typically the biggest concern when starting a project of this magnitude is cost. The kit is probably the cheaper option, but I wanted to be sure of this and I wanted to see how much I could save if I built it on my own. As an engineer I know how costs for a project can easily get out of hand, so I have learned how to guess costs for a project fairly accurately. The secret is to overshoot on EVERYTHING and plan to break parts and plan on buying extra parts that you might not ever need just to make sure things go smoothly. Another important secret is to include shipping in any cost estimates. I also decided to include 1lb of filament since I will need it anyway and it pays to save on shipping.

So, the Huxley kit came out to $630 from TechZone for everything I need and a initial estimate on the filiment came to $25 for a pound including shipping at Ultimachine.com. Now onto the expected costs for the Prusa.

  • SAE Printed Materials including Wades Extruder on eBay
    • $125
  • SAE Vitamins including Wades Extruder (the non-printed hardware)
    • $175
  • Steppers from SparkFun
    • $80.00 (15 each, 5 needed)
  • Hot Tip (Custom)
    • $90.00
  • Electronics w/ Optos (Custom)
    • $100.00
  • Filament 
    • $25.00
  • Print Plate (wood)
    • $10.00
This totals $605. Lots of these are initial guesses and approximations. Allow me to explain quickly how I came up with the more convoluted sections. The Hot Tip is more expensive than I would have thought. I came up with my baseline from the parts at mendel-parts.com, but I do think there is some room to save here considering I know some people who can machine anything for me at no cost, I expect savings of about $15 or so.

I'm sure your wondering how in the world I can get a set of electronics built for $100. To be honest, most people will not be able to do it this cheaply. Being that I am an electrical engineer, and I have TONS of parts and know of many cheap ways to get circuit boards built I can save lots of money in the electronics. I plan on making my own circuit board for Gen6 electronics; I will be documenting this in detail later hopefully. Additionally a fact that most people don't realize, is that many companies will provide free samples in small quantities of their chips or connectors. Please note, I did not include any costs for making the Prusa wireless at this point since I wanted to compare the two options I currently have.

It seems to me that it's basically a wash for the cost since I'm sure I will manage to spend $50 unexpectedly when something goes wrong, as it always does. In the end though I think this round goes to the Prusa since I can buy parts incrementally as I build the printer. I would much rather spend $300 getting started on all the mechanical parts of the design than $600+ on a kit all at once.

Part Procurement

Another typical hurdle to overcome when building any project is how easy it is to find the parts you need. If I buy a kit, theoretically I should have everything I need without spending hours online looking for specific hard to find parts. The time needed to find parts can be enormous if you do not know the places to look, and time is the most expensive thing we really have. This is not something that I wanted to overlook, so I set out on finding all the parts I need.

There are there major places I will be using to buy my parts: eBay, Mouser, and McMaster. There are some smaller parts which I will need to get elsewhere, such as the steppers from SparkFun, but those three stores generally will have everything I need. To be sure I looked up all the electronics on Mouser and all the hardware I need (in addition to the vitamins kit) on McMaster. I found everything I needed but one chip I needed on Mouser, which was the MOSFET which I found on DigiKey. Otherwise everything I needed is fairly reasonable on McMaster other than the brass block needed to heat the nozzle. More on this later.

It seemed to me that it was not unreasonable to assume I could get everything I needed to build a Prusa fairly easily. Hurdle jumped.

Typical Build Problems Faced

What is the hardest part of building a Mendel? I'm sure this differs greatly from person to person, but there seems to be two major problems that people face. The first is the electronics. There are many accounts of electronics not working even when you buy them premade; for me this was not a concern since that is where my specialty lies. For others though this might be something you need to seriously consider. Buying a premade electronics board might be the safest option even though costs will rise.

The problem that lots of people seem to have, which I am also the most worried about, is the extruder. In addition to there being many options on which extruder to build, the hot end seems to require lots of machining and expensive materials.

My Decision

As I mentioned above, I will be building the SAE Prusa Mendel with Wades Extruder. A few things came into place which really solidified this decision. The first was the cost, it seemed a lot cheaper to build an SAE Prusa than any other version of the Mendel. Second, there is a multitude of printed parts on eBay for very reasonable prices for the SAE Prusa.

Next post I will show where I decided to buy all the parts and discuss my idea's for the hot end and extruder.

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