Cost accounting for tumblers and unattended gear?

Alberic · Feb 14, 2021

HI Guys,

I'm putting in inventory software that'll help generate 'cost to produce' info that should be better than my excel sheet from hell.

This leaves me with a puzzlement: how to price time in the tumbler, or other automatic gear? (Not the CNC's.)

When the tumbler's running, it eats power, water, and abrasive. All of those I can more-or-less account for, at least in a general way. The real question is time.
I have a shop rate of "X" per hour to cover power/lights/people/paperclips, etc.
But when I've got parts in the tumbler, nobody's actually paying any attention to it, or 'working' it, except every so often to check the parts, or to load/unload, and that's reasonably quick.

So would you cost it out at shop rate *plus* abrasives/power/water, etc, or some smaller fraction of shop rate plus consumables, to reflect the fact that nobody's making it their prime mission, and they're all doing other stuff?

Thoughts?
Brian

Strostkovy · Feb 14, 2021

In my experience the biggest cost of "automatic" stuff is the loss of productivity to the other task the person who has to watch over it has.

Alberic · Feb 14, 2021

Strostkovy said:
In my experience the biggest cost of "automatic" stuff is the loss of productivity to the other task the person who has to watch over it has.

It's not too bad. It runs for a couple of hours at a cycle, and is pretty much 'fire and forget' other than remembering to go get stuff out when it's done. That's why I'm pondering it as a 'less than shop rate' process, because nobody's really wasting any time on it.
One of the two of them has an off timer, so it shuts down after a certain point. You don't even have to remember anything, except to go restart it and fish the parts out when it stops. Very low mental overhead.

Regards,
Brian

kb0thn · Feb 15, 2021

What is the goal of accounting for the cost? So you can charge it out? If so, do you need to be competitive? The tumbling shops aren't making the same hourly rate as the machine shops. If you go shop rate + consumables, that's going to put your deburring at way more expensive than outsourcing it.

Alberic · Feb 15, 2021

We're more of a manufacturer than a machine shop, so the goal is to figure out what the cost of goods for our product is. No need to be competitive with a tumbling shop. (Although the only tumbling shop in the area charges a small fortune. Beating him wouldn't be hard.)
This is more of a 'what the <blank><blank><blank> do these things really cost us to make??'

Thanks,
Brian

Pete Deal · Feb 15, 2021

I’m not very rigorous with costing such things as I need to be but it seems to me as you alluded to since it kind-of sort-of just runs the operator ought to be able to do other things while it’s running. Today i ran a cnc mill, deburred and polished parts for the mill and ran two tumblers (one deburr, one to burnish). I’d say cost it out at a lower rate- take a guess.

Steven-Canada · Feb 15, 2021

Time doesn't cost anything in itself.

But also pay for amortization of the machine, the interest you pay on the purchase of the machine.
the media

the wages of the time you actually do spend.

CarbideBob · Feb 15, 2021

I do load and unload at rate with a much smaller cost per hour on run or cycle time.
A four thou edge rad more cost than a one thou but not by much as eats not a lot of real world cost.
Then there is if you say six vibes and all filled with work?
Bob

Comatose · Feb 15, 2021

It still costs electricity, space in the shop. load and unload time, noise (which is a big one with tumblers and makes everyone in the shop a little less productive) media and don't forget having a real plan for the waste water. Plus you'd want a return on the purchase price in two or maybe three years.

So calculate that out, then add 10% or 100% or whatever number you like, depending on how much you like tumbling. That's your number.

Alberic · Feb 16, 2021

Comatose said:
It still costs electricity, space in the shop. load and unload time, noise (which is a big one with tumblers and makes everyone in the shop a little less productive) media and don't forget having a real plan for the waste water. Plus you'd want a return on the purchase price in two or maybe three years.

So calculate that out, then add 10% or 100% or whatever number you like, depending on how much you like tumbling. That's your number.

Yeah, that's pretty much where I got to. (We have a big huge multi-stage settling tank system for the waste water. So we're good there.)

The big thing is that we put the 'smaller' of the two of them in a noise isolating crate that we built up for it with egg-crate foam over 3/4 ply and some other tricks. Oh-my-god! What an incredible difference that makes. It's quieter than the Kaeser now. (and doesn't overheat or do anything weird. We've been running it that way for a couple of years.) If you have one where it's possible to build a sound box for it, DO IT! You will *not* regret it.

Thanks,
Brian

DDoug · Feb 17, 2021

Can you start with an estimate of the total life of the machine in hours ?
Add in how much electricity for those hours, and an estimate of number of media
changes in that lifetime.
Same with water, soap, and waste disposal.

Add it all up, get an hourly cost.

Mike1974 · Feb 17, 2021

No help to how to figure the rate, but an idea for tracking - I worked at a shop where if one guy ran multiple machines/jobs, one job would get the job number only, and the other jobs would get a -1 -2, etc so they knew two jobs were being run for by one person. I'm sure it did not affect the shop rate we charged the customer, but it allowed management to see *our* cost to run the jobs a little better.

Guest · Feb 17, 2021

I cost those things out just with the time it takes away from doing other tasks and what easily counted consumables are used. I don't bother figuring electricity or wear and tear on ceramic media. I will estimate cost on things like walnut shells or aluminum oxide as I can burn through a lot of those items. As for labor just load, unload and cleaning time are counted regardless if the items tumble for 20 minutes or 2 days. Pretty sure electricity and wear and tear on the tumblers themselves don't amount to much in my situation.

countryboy1966 · Feb 21, 2021

As some have mentioned:

-Media consumption per hour
-Machine cost (amortization of purchase/interest) per hour
-Electric consumption per hour (Easy to figure out.)
-Attended labor time (How long is a human involved per cycle)
-Any environmental waste stream costs for media and solution (If any)
-Maintenance costs per hour
-Whatever margin markup

SIM · Feb 22, 2021

countryboy1966 said:
As some have mentioned:

-Media consumption per hour
-Machine cost (amortization of purchase/interest) per hour
-Electric consumption per hour (Easy to figure out.)
-Attended labor time (How long is a human involved per cycle)
-Any environmental waste stream costs for media and solution (If any)
-Maintenance costs per hour
-Whatever margin markup

Add to that the time it takes to clean the parts after tumbling.
Clean media out for a different media.

Only seems like pennies here and there...but they add up quick.
And what is funny, you think its only 5 minutes to dump parts in and walk away...but 5 can be 10, plus stopped production on another machine.
Stop 6 times a day at "only 10 minutes" and its an hour, do that 5 times a week its 5 hours, four times a month is 20 hours...what your rate as that is a chunk of time and money..

Sometimes the other way I do it is I know its 3 minutes to debur by hand, so that's what I charge whether I run by hand or with tumbler.

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Cost accounting for tumblers and unattended gear?

Alberic

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Strostkovy

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Alberic

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kb0thn

Stainless

Alberic

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Pete Deal

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Steven-Canada

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CarbideBob

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Comatose

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Alberic

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DDoug

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Mike1974

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Guest

Guest

countryboy1966

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SIM

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