Machine cost per hour

Hello all,

I would like to offer in my city the 3d printing service but I need help from the experts on how to calculate the machining cost in an hourly basis.

I'm using skeinforge to get statistics about the printing and I have calibrated the material consumption but from your experience, what is the ideal cost/hour of the machine? Does this cost include energy and direct labor time?

Thank you

Edited 1 time(s). Last edit at 07/26/2012 09:48AM by epareja.

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Ernesto Pareja

dcctrains.netne.net

Personally I've never calculated this cost, but there are several factors you should consider - sunk costs, fixed costs, variable costs and overhead.

Your sunk costs consist of all the investment you've made in building your machine and the ancillary support devices that are required to run it. Since you own these outright (I assume) they are costs that occurred in the past and cannot be recovered, hence they are "sunk". While sunken costs are necessary, the tax code may allow for recovery of depreciation costs of your equipment. So there is a remedy for sunken costs, but only as an offset to income generated by the asset.

Your fixed costs are things that can easily be traced that support production. An example would be heating and cooling the work space - you would heat or cool regardless of where the machine is. Another fixed cost would be the electricity consumption of the powered-on state of the machine while it is out of production. You can extend this cost to the PC driving the reprap as well. Plug-in power meters are available relatively cheaply now, so that should make measuring the base load a trivial matter.

Variable costs are the running costs of the machine. Electricity draw while running, plastic, PC running time, etc. These can be easily traced to the production of a single item.

Then you have the ugly bit - overhead. Overhead costs are not easily traceable the production of a part. So they must be allocated. Welcome to managerial accounting! Maintenance costs can be either a variable cost, a variable overhead cost or a fixed overhead cost, depending upon how you perform maintenance. So there is no hard and fast rule for allocating overhead costs. But you must estimate overhead costs and allocate them to every job. For reprap, there are several things that come to mind. Maintenance costs (planned), downtime costs(unplanned), calibration costs, consumables (a kapton bed may last for several parts from different orders). Just because your machine isn't active doesn't mean it isn't costing you money - every moment of downtime is a lost opportunity. Overhead attempts to quantify this cost.

So I hope I've given you something to think about! If you don't fully account for the costs involved with starting a business, or discount the costs too much you run the risk of failure, so be conservative in your estimates.

Good luck!

Edited 1 time(s). Last edit at 07/27/2012 04:42PM by akhlut.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Quote

I would like to offer in my city the 3d printing service but I need help from the experts on how to calculate the machining cost in an hourly basis.

Likely, your customers won't want to rent a machine on an hourly basis, but get printed parts done. So, the real question is, which measures of the part are approximately proportional to the costs manufacturing it. Most services I've seen use part weight/volume and choosen material. Perhaps surface finish, too, if you can offer options here.

Putting emphasis on the part instead of on the time to create it has another advantage: in the beginnings, you have only few experience, but much time. So, it doesn't hurt too much if you have to make a part twice to get a good one.

BTW., never ever ship low quality parts. Customers will remember that and strongly prefer a service which does good quality on the first try.

My experience is, for customer satisfaction parts have to be pretty. Much more important than accurate measurements, as disappointing as this is. So, think twice before you start sanding them to improve measurements. In my Stereolithography days I had a sandblaster, just to make an evenly looking surface after sanding.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I do a lot of projects for people, mostly business related. ie: prototype housings, linkages, proof of concept, etc.

I charge a flat hourly rate, which I calculated based on average material usage, power consumption, machine wear, etc. I go straight off the time predicted by the slicer +20% for loading filament, removing any little bits of support, boxing parts, etc.

We have a very high (95%) successful print rate, so there is very little waste built into the cost. If you end up having a bunch of bad parts, you should account for that as well.

Keeping the quote straightforward makes my life easier and makes quotes more uniform.

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www.Fablicator.com

I work on NZ$5 an hour for my machine cost + material+ any design work I do at the normal rate of $25/hour

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__________________________________________________________________________
Experimenting in 3D in New Zealand

Thank you all for your tips. I sure will charge for the whole part and not for hours, but I need to charge more if the part gets longer to print.

Thank you Traumflug for the recommendation about quality. I will sure keep it in mind!

Thank you akhlut for your costs explanation.

I have configured in skeinforge the hourly cost for the machine in US$5 and the ABS filament per KG about US$45. With those two values I get this values for this file Greg's Accessible extruder
Cost
Machine time cost is 11.81$.
Material cost is 1.47$.
Total cost is 13.27$.

I have quoted this part in several 3d printing services over the web and the average cost is 110 US dollars.

There is a big difference!!!!

Quote

Machine time cost is 11.81$.
Material cost is 1.47$.
Total cost is 13.27$.

What about the time for aquiring, data preparation, postprocessing, shipping?

Quote

I have quoted this part in several 3d printing services over the web and the average cost is 110 US dollars.

You should reduce that difference, even if you manage to be that cheap. Customers won't believe it.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

How accurate is SF's machine time estimate? Does it include the acceleration of the machine?

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www.Fablicator.com

I've found SF is always pessimistic in time estimation but in my opinion very accurate. for example a 45 min estimated resulted in 40 minutes in real time.

How could it include acceleration? That is set by the firmware so it has no way of knowing what it is.

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[www.hydraraptor.blogspot.com]

I use SF41 the old version and it's times are out qiute a bit so I build in an error calculation of 15% and then it's about right for time. I just do this with a calculator afterwards

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__________________________________________________________________________
Experimenting in 3D in New Zealand

@nophead, it's been a long time since I've used SF. If you put the machine acceleration settings into the slicer, it's reasonable it could compute the 'actual' print time. Surprised it hasn't been implemented yet, actually.

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www.Fablicator.com

I find that if I use 1500 acceleration and 10 for xy jerk in Marlin my prints are about right on the Pronterface estimate for time. When I was running higher accel I was beating the estimate by quite a bit.

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www.Robosprout.com RepRap Mendel parts and accessories.
Message if there is anything you need...I have more than what is listed on my site.
Located in the Spokane, WA / Coeur d'Alene, ID area.
Contact: Robosprout@gmail.com Flickr: [www.flickr.com]

What should be the desired value for acceleration and Jerk in Marlin?
I had them in the default 3000.

#define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000} // X, Y, Z, E maximum start speed for accelerated moves. E default values are good for skeinforge 40+, for older versions raise them a lot.

#define DEFAULT_ACCELERATION 300 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_RETRACT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for r retracts

/
#define DEFAULT_XYJERK 20.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)

Does this could have an impact on qualtiy?

The default accel in yours seems to be set to 300...default is 3000. I use 1500 as a starting point...2000 is probably good also. I leave the max acceleration where they are. Then on my machines I set the default xyjerk to 10.

I personally prefer slower prints to skipped steps or other issues related to accel ("ringing" around holes in the prints for example).

I play with my accels during prints via M204 Sxxx (for normal moves) M204 Txxx (for filament moves). It is an easy way to tell if you are having issues related to accel.

There have been times (printed gt2 pulleys, concentric/concentric fill) where I lowered the accel down to 500.

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----------------------------------------------------------------------------------------------------------------------------
www.Robosprout.com RepRap Mendel parts and accessories.
Message if there is anything you need...I have more than what is listed on my site.
Located in the Spokane, WA / Coeur d'Alene, ID area.
Contact: Robosprout@gmail.com Flickr: [www.flickr.com]

C. Cecil Wrote:
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> The default accel in yours seems to be set to
> 300...default is 3000. I use 1500 as a starting
> point...2000 is probably good also. I leave the
> max acceleration where they are. Then on my
> machines I set the default xyjerk to 10.

I found that setting xyjerk that low causes the printer to start stuttering while printing circles. At 20 they get cleanly printed at constant speed (at least for 50mm/s).

Also, since the extruder has very little mass to accelerate (basically just the motor's rotor, the gears and the geared-down bolt are probably insignificant), it's safe to use a very large acceleration parameter and get fast retractions.

You are not just dealing with the weight of the gear and bolt. You are also dealing with the filament tension on the idler (which many have too high, including myself at times), the suction of pulling the filament out fast, and the reversal/restart pressure (as in the force it takes to reprime the nozzle) which is where it usually skips if it is going to. I have seen this many times in IRC where people have issues that simply changing retract accel solves, usually when there is blobbing or holes in the print from retract my first question is "Is the extruder going the same amount forwards as it is back on retracts?". I cannot say that is always the issue...but it is very common.

I don't seem to see the same problems with the holes you are seeing at low jerk rate also. If you have a pic for comparison I would be interested to see the difference.

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----------------------------------------------------------------------------------------------------------------------------
www.Robosprout.com RepRap Mendel parts and accessories.
Message if there is anything you need...I have more than what is listed on my site.
Located in the Spokane, WA / Coeur d'Alene, ID area.
Contact: Robosprout@gmail.com Flickr: [www.flickr.com]

C. Cecil Wrote:
-------------------------------------------------------
> I play with my accels during prints via M204 Sxxx
> (for normal moves) M204 Txxx (for filament moves).
> It is an easy way to tell if you are having
> issues related to accel.
>

Thello Cecil,

As far as I understand M204 modifies the hotend temperature. I tryied yesterday to modify the accel in my Marlin Hardware to 1500.

Thank you all!

From the Marlin wiki:

M204 - Set default acceleration: S normal moves T filament only moves (M204 S3000 T7000) im mm/sec^2 also sets minimum segment time in ms (B20000) to prevent buffer underruns and M20 minimum feedrate

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----------------------------------------------------------------------------------------------------------------------------
www.Robosprout.com RepRap Mendel parts and accessories.
Message if there is anything you need...I have more than what is listed on my site.
Located in the Spokane, WA / Coeur d'Alene, ID area.
Contact: Robosprout@gmail.com Flickr: [www.flickr.com]

Why would one need a minimum feedrate?

I am having problems getting the first layer right with Marlin. It seems the slower I have it, the less plastic I get. Could this be why?

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[www.hydraraptor.blogspot.com]

Not sure why you would need a minimum feedrate but I do know in certain instances taking too long to do a layer causes delamination when using ABS. There are certain parts that work great with 2 on a plate but if I use 4 of them they typically delaminate (MendelMax Lower vertex for example). I am sure a heated build chamber would help with this.

I have started using 115% layer height for the first layer to make it easier to stick as well as not having as much of an issue with z home postion being a problem. I also use 50% speed for the first layer typically...sometimes 30%.

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----------------------------------------------------------------------------------------------------------------------------
www.Robosprout.com RepRap Mendel parts and accessories.
Message if there is anything you need...I have more than what is listed on my site.
Located in the Spokane, WA / Coeur d'Alene, ID area.
Contact: Robosprout@gmail.com Flickr: [www.flickr.com]

If you get de-lamination with more objects it probably means you are not extruding hot enough, so are relying on the last layer being still hot to form a weld.

When I try to increase the build speed I reduce the first layer % to keep the first layer slow but for some reason I seem to get too little plastic on the first layer outline, which is 50% of the infill speed.

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[www.hydraraptor.blogspot.com]

When I went to less parts I also raised my temp by 7c. It was not really a traditional delamination...more like a cracking at one spot in the print...I think, like you said, it was just cooling too much before the nozzle was coming back due to the multiples and the slowdown I put in on short layers...also it was a cheap plastic.

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----------------------------------------------------------------------------------------------------------------------------
www.Robosprout.com RepRap Mendel parts and accessories.
Message if there is anything you need...I have more than what is listed on my site.
Located in the Spokane, WA / Coeur d'Alene, ID area.
Contact: Robosprout@gmail.com Flickr: [www.flickr.com]