Grizzly Gunsmith Lathe Break
- Thread starter Pete Wass
- Start date
Pete Wass
Well-known member
Pete,
I hooked a braking resistor up on my vfd, and it works great. Cost about $40 or less and was very easy to hook up...and I am not an electronic wizard. It will stop my chuck at low speed in under .5 second. At high speed (2000rpm) about 2 seconds or it will override the system, and it will freewheel though still at a much reduced speed. I bought my brake resistor on ebay, and it was significantly less expensive than through automation direct or wolf automation, etc...
I hooked a braking resistor up on my vfd, and it works great. Cost about $40 or less and was very easy to hook up...and I am not an electronic wizard. It will stop my chuck at low speed in under .5 second. At high speed (2000rpm) about 2 seconds or it will override the system, and it will freewheel though still at a much reduced speed. I bought my brake resistor on ebay, and it was significantly less expensive than through automation direct or wolf automation, etc...
Pete Wass
Well-known member
Michael Huebner
Member
Keeping in mind that you need to consider duty cycle when using braking resistors especially if you desire an almost instant stop.
And not all VFD’s have the feature, especially some budget versions.
For the most part the VFD must be oversize (by a rather large amount) to withstand the huge currents and voltage steps that occur.
Solid state semiconductors are extremely vulnerable to excessive current and voltage.
This is not a 'duty cycle' heating type issue, but an instantaneous excessive voltage or current through the semiconductor junctions.
The actual breakdown value of almost all semiconductor junctions is pretty variable based on intrinsic defects in the junction.
The method generally is to grossly derate absolute peak currents and voltage by very large factors (sometimes many hundreds).
A very few volts over on a part rated many hundreds of volts is often all it takes to totally destroy the junction.
So instantly that there is no practical way to protect the part from destruction.
We used to have some rather spectacular explosions of high voltage transistors in 'hockey puck' glass/ceramic hermetic packages.
Pete Wass
Well-known member
Of Wet Blankets:
Please don't confuse with us wiith hard facts! it's way to hard to deal with!
.
Pete
Please don't confuse with us wiith hard facts! it's way to hard to deal with!
.Pete
Michael Huebner
Member
The ‘duty cycle’ I refer has nothing to do with the semiconductors, it is the braking resistor. You can over rate the power of the resistor but the cost would outweigh the benefit for hobby type installations.
IMHO it is best to program the VFD to as close as instant stop as you can get for E/Stop only and program a small time to ‘free run’ to stop for normally stop function.
I also install a OMRON Safety relay which stops the VFD transistors commutating and then cuts all power, when E/stop is pressed.
This is what I do, but those who install them on there machines can decide how safe they want there installation to be.
With respect to the need for an overly large VFD for a particular motor this isn't true for the units I purchased. I spoke with the manufacturers directly because I read this on various sites and it seemed counter to the websites advertising the drives. I have an automation direct drive on my mill and an Hitachi on my lathe. Both drives are matched to the motor HP within 1/2hp. According to the manufacturer there is no need, anymore, to oversize your drive. The hobby machines we are running just don't pull that much amperage, and as long as the unit you are buying covers the max amps of your motor (i.e my 2.2kw 3phase motor has a 10 amp max draw which calculates out to my hitachi drive drawing something on the order of 25 amps +/- at the breaker.) I doubt I will ever approach that level of draw and have programmed my VFD to ramp slowly over 5 seconds to avoid just that situation.
I am not the end all when it comes to the rest of the electronics, but I did talk to the source when it comes to this particular subject. Two separate companies.
I am not the end all when it comes to the rest of the electronics, but I did talk to the source when it comes to this particular subject. Two separate companies.
C
chino69
Guest
Grizzly lathes
Are these Grizzly lathes acceptable for precision barrel work?
Are these Grizzly lathes acceptable for precision barrel work?
As is with most things probably depends on the operator.
C
chino69
Guest
Grizzly lathe accuracy
Yes, operator skill and experience is one of the main ingredients. I was looking more for an answer as to whether the bearings, gearing, ways, cross feeds, etc. are of a standard sufficient to satisfy those who machine with extreme accuracy. There was a time when lathes such as Hardinge, Clausing and others were the gold standard albeit much more expensive than a Grizzly. I see certain gunsmiths endorse Grizzly but am always suspicious of bias when reading these recommendations due to compensation for their endorsement.
Yes, operator skill and experience is one of the main ingredients. I was looking more for an answer as to whether the bearings, gearing, ways, cross feeds, etc. are of a standard sufficient to satisfy those who machine with extreme accuracy. There was a time when lathes such as Hardinge, Clausing and others were the gold standard albeit much more expensive than a Grizzly. I see certain gunsmiths endorse Grizzly but am always suspicious of bias when reading these recommendations due to compensation for their endorsement.
I have a 1985 Grizzly Model DF-1237G and it has provided everything in regards to accuracy that I have asked of it. For several years I yearned for something possibly better than but I just haven't been able to justify why and what could I personally gain. But I am also a retired home shop smith and time doesn't matter in regards to how much longer it might take me to turn out the same as those with higher priced machines. Overtime time I have learned how to work with it and to get the precision out of it and to date it has yet to let me down.
C
chino69
Guest
OK.... old guys look away cuz dude gonna' blaspheme here.
First of all, I'm not a machinist by trade so alla' YOU'SE guys look away too...... and
secondly I'm not "Ford/Chevy/Dodge" supportive of ANYthing.
I left gunsmithing school and gunsmithing almost 40yrs ago because I couldn't afford it. It took me 20 of those yrs to be able to buy a lathe..... a Grizzly. From Shiraz' very first boatload of gunsmithing lathes.
Ever since I got it it's been completely satisfactory....... MUCH the better machine than I expected, doing everything I'd learned in the gunsmithing machine shop, better....... BUT...."Machinists" have always badmouthed Grizzly while extolling the virtues of the mighty "Heavy Ten" claiming the South Bend is completely adequate for barreling work.
AND, I'll admit to also extolling the virtues of the Heavy 10 as a home lathe for all those years before I bought my Grizzly, but for different reasons. For SAFETY reasons. I'll still recommend a Heavy 10 to learn on. I feel the Heavy 10 is a SAFE lathe to learn on cuz you get wrapped up in it the lathe will stop before turning you into pulled taffy.
Well, not taffy exactly, more like pulled pork.....
but anyway
Safety Rant OFF
So, I hadn't touched a South Bend since the early 80's..... and I always wondered.....so I bought one. A GOOD one. Maybe paid too much, and,
I'll say this once. It's quiet..... I LOVE that..... but can it do anything better than the Grizzly G4003G????
Sorry, IMO it's not even in the same ballpark. Yeahh, the Grizzly's a noisy cheap lathe. Running it sounds like running logging roads in a '76 Ferd Three-on-the-Tree........and you in the back......
But it does good work. And when I DO have to trust it or risk ruining the part, It hasn't let me down.
(I still don't trust it much, but that's ME... and I don't much trust ME neither LOL!)
First of all, I'm not a machinist by trade so alla' YOU'SE guys look away too...... and
secondly I'm not "Ford/Chevy/Dodge" supportive of ANYthing.
I left gunsmithing school and gunsmithing almost 40yrs ago because I couldn't afford it. It took me 20 of those yrs to be able to buy a lathe..... a Grizzly. From Shiraz' very first boatload of gunsmithing lathes.
Ever since I got it it's been completely satisfactory....... MUCH the better machine than I expected, doing everything I'd learned in the gunsmithing machine shop, better....... BUT...."Machinists" have always badmouthed Grizzly while extolling the virtues of the mighty "Heavy Ten" claiming the South Bend is completely adequate for barreling work.
AND, I'll admit to also extolling the virtues of the Heavy 10 as a home lathe for all those years before I bought my Grizzly, but for different reasons. For SAFETY reasons. I'll still recommend a Heavy 10 to learn on. I feel the Heavy 10 is a SAFE lathe to learn on cuz you get wrapped up in it the lathe will stop before turning you into pulled taffy.
Well, not taffy exactly, more like pulled pork.....
but anyway
Safety Rant OFF
So, I hadn't touched a South Bend since the early 80's..... and I always wondered.....so I bought one. A GOOD one. Maybe paid too much, and,
I'll say this once. It's quiet..... I LOVE that..... but can it do anything better than the Grizzly G4003G????
Sorry, IMO it's not even in the same ballpark. Yeahh, the Grizzly's a noisy cheap lathe. Running it sounds like running logging roads in a '76 Ferd Three-on-the-Tree........and you in the back......
But it does good work. And when I DO have to trust it or risk ruining the part, It hasn't let me down.
(I still don't trust it much, but that's ME... and I don't much trust ME neither LOL!)