Confused about grinders - Page 8

Grinders are one of the keys to exceptional espresso. Discuss them here.
unfiltered

#71: Post by unfiltered »

Yeah that's pretty neat! Pricey though

Capuchin Monk

#72: Post by Capuchin Monk »

unfiltered wrote:The brushless DC craze is about to begin. The hype for the upcoming variable speed df64 is building, soon it will be a necessity on any grinder worth having. I'm interested in the cost and form-factor of this machine and how they nestle the additional and often hideously large power supply and driver into the design. Theres a good chance it will be separate but I hope they put in the effort and integrate it with the grinder itself. I wonder what will supersede the mighty BLDC motor?? Something that's for sure!
Brushed DC motor can work just fine for coffee grinders if variable speed is desired. It makes little more noise than brushless and shorter lifespan due to the brush wearing out but still sufficiently long lasting for coffee grinders. In other words, BLDC is a fad.

ira
Team HB

#73: Post by ira »

I would guess brushless DC is not a fad, the electronics required to drive one is getting easier to use and less expensive as time passes and is more powerful over a wider speed range, more energy efficient and less costly to assemble. Those should eventually mean being able to use a slightly smaller motor for the same task which will likely cause the reduction in cost from the downsizing surpass to the cost of the electronics. In my opinion anyway.

unfiltered

#74: Post by unfiltered »

BLDC do have their benefits, one that jumps to mind is their ability to hold rpm constant under varying load where as a DC or universal motor like the one in Niche, rpm fluctuates with varying load. Despite the qualities of the BLDC I agree it's probably a FAD and is primarily now being added to grinders as a marketing differentiator.

Estimated RRP of the upcoming DF64 variable speed anyone?

unfiltered

#75: Post by unfiltered »

Good points ira. Current BLDC offerings at coffee grinder wattages tend to have smaller diameter shafts than their induction counterparts. I wonder if shaft torsion will become an issue for lighter roasts creating inconsistencies. I guess in time this should eventually all be ironed out along with the other points you mention.

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Jake_G
Team HB

#76: Post by Jake_G »

unfiltered wrote:I'm interested in the cost and form-factor of this machine and how they nestle the additional and often hideously large power supply and driver into the design.
The trick Option-O went with is to use a motor compatible with rectified line voltage, rather than stepping it down to 20, 24 or 48V, like many motors require.

This allowed for a standard brushless driver to be incorporated into a small power supply board. With ~170V bus voltage, the required current for 300W is quite small (less than 6 amps) and with it, the size of the rest of the components. I believe the motor driver they sourced is rated for 700V and up to 50A of saturated current and supports both encoder feedback as well as running encoder-less using field-oriented-control (FOC).

The trade off is that the motors themselves are not terribly small for their rated power output, but that doesn't seem to be a problem.
LMWDP #704

unfiltered

#77: Post by unfiltered »

Ahh interesting. At 1400 revs I'm guesstimating the grinder will have a capable ~2.5 nm of torque. Nicely done

Quester

#78: Post by Quester »

Jake_G wrote:The trick Option-O went with is to use a motor compatible with rectified line voltage, rather than stepping it down to 20, 24 or 48V, like many motors require.
I appreciate you explaining this--interesting.

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AssafL

#79: Post by AssafL »

ira wrote:I will point out that buying a quantity one replacement motor for my monolith flat costs about the same as the P64 so it's possible the motor and controller combo in the Flat is significantly higher quality.
That is part of the fun. Pulling apart the Versalab to check the brushes (it is a brushed 130V DC motor) - They had less than 1mm wear. Still about 2cm left. This is after some 13 years. Probably won't have to change brushes in my lifetime.

Somewhat remarkable, but not much so if you realize the motor was meant to work outdoors in the sun/rain pulling some boxes up a conveyor belt for 5 years straight. So 4-8 shots of espresso a day - for 13 years - is peanuts for the industrial motor.

13 years later - and after playing with many other grinders - for me it is still the best.
unfiltered wrote:BLDC do have their benefits, one that jumps to mind is their ability to hold rpm constant under varying load where as a DC or universal motor like the one in Niche, rpm fluctuates with varying load.
Actually, the Versalab is very stable in RPM using a back-emf industrial speed controller. So you definitely can control speed without the hall-effect sensors of a BLDC.

There are probably other motor technologies that can provide useful torque at low speeds. One day someone will add a reluctance motor to a direct driven grinder (like the Panasonic reluctance motor used by Thermomix). It also makes interesting whining noises due to ripple torque...
Scraping away (slowly) at the tyranny of biases and dogma.

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iploya
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#80: Post by iploya »

Although the grinder is important, the quality of the espresso machine is not irrelevant. The best grinder and quality coffee won't save an espresso machine that is not up to the task. I have never owned a high-end espresso machine but I have had a crappy espresso machine and those are the pits. I have also had shots from specialty cafes with $20,000 espresso machines that were unlike anything I have pulled at home on any grinder. Like grinders, there are plenty of budget-minded espresso machines that do a good job for the money.