Variable Speed RF45 Clone or Geared Head?

[Mark SlatterParticipant @markslatter13251]

Hi folks,


I'm looking at options for a milling machine, and one contender is this:

http://www.amadeal.co.uk/acatalog/A…gital-Read-Out-MI_AMA45V_R8M_DRO.html#SID=376

I was wondering what your thoughts were on this versus a standard geared head RF45 clone?

I'm no electrics expert and was wondering if it would be giving up anything in terms of torque to a geared head, it has a 2.2Kw motor compared to a 1.5Kw of the geared head…is this to compensate for the reduced torque? The VFD also runs off single phase, and I understand it might be better to run VFD's off of 3 phase motor to maintain torque at lower speeds. What do you think?

The variable speed also gives up 400rpm's of top speed over the geared head, which isnt the end of the world for me I'll be machining steel mostly although some aluminium parts and even wood will definitely be cut.

For people who have used this style of bed mill and Bridgeport size knee mills…should I be putting the same money into a used Bridgeport or are you happy with your RF45 and clones?

Any input appreciated, thanks!

[Mark SlatterParticipant @markslatter13251]

[MikelkieParticipant @mikelkie]

Table looks light and flimsy, geared head nice but are gears hardened & ground or plastic / fibre? 2.2Kw motor for a R8 spindle nice and strong, Rather go for Bridgeport

Edited By Mikelkie on 05/08/2017 20:35:52

[Anonymous]

It makes no difference what supply the VFD runs from. It will drive a 3-phase motor whether the incoming supply is single or three phase. Simplistically running from a single phase will require the motor to be wired as delta, whereas for 3-phase it will be wired as star.

It's not so much a torque reduction as a power reduction. Below base speed the motor will be running at constant torque, but as the speed reduces the power will reduce. For a geared head the power tends to stay constant as the speed reduces, which results in an increase of torque. That's where the apparent 'loss' of torque comes from.

I can't help with the specific mill as I've never used one. I run a 1.5hp varispeed head Bridgeport and a CNC mill with nominally the same hp as the Bridgeport, but driven from a VFD. I tend to run them differently, I use large drills and cutters on the Bridgeport, with backgear engaged if required. On the CNC mill I rarely use a cutter bigger than 10mm, but I run at much faster spindle speeds and feedrates. I take care to ensure that the CNC mill tends to run the motor above base speed so there is no loss of power. The only exception is operations that need to be slow, such as tapping under power.

Andrew

[Clive FosterParticipant @clivefoster55965]

Mark

That mill looks very similar in size and capabilities to the "one-off" VFD driven square column mill I got from Chester years ago. I never had problems with power or speed ranges. I suspect the speed figures given are a little incorrect as mine had considerable overlap between the two ranges. Overlap is desirable because you don't want to keep shifting belt positions. Especially if its like mine was with a close coupled B section belt, somewhat under engineered tension adjustment and a distinct lack of space in the belt area. Hopefully the Amadeal version uses poly-Vee belts which will be much easier to handle in the inevitably limited space. Given the speed range overlap I found it perfectly practical to keep the same belt setting for a whole job having decided at the beginning whether it was a high speed or low speed task. In practice I think mine had too much speed overlap provided. I've suggested in another thread here that tweaking the gearing, reducing the overlap and extending the low speed end of the range might have been a worthwhile improvement.

Although it was an effective metal remover and, in practice, of similar rigidity to a Bridgeport mine drove me nuts. I was delighted to see the back of it once I got my new workshop built and a Bridgeport installed. Main issues were visibility and lack of table space. I found that the big square head seriously got in the way when working on smaller features. Even with the quill further out than ideal the viewing angle tends to be much more sideways than you'd like. Something you can learn to cope with but I found it made life too much harder. Especially with ageing eyes. Other issue is the relatively small table which limits the space available for setting up. I got fed up with winding the head up to the top and ejecting tooling just to get space and visibility.

if that screw up and down quill depth stop is anything like mine was it won't be long before the toys really do come flying out of the pram! Fortunately there is a simple modification to make it all behave. Combine the modification with that digital display for quill travel and you'd have really good system. Better than the equivalent on a Bridgeport actually.

Bottom line is, providing the build quality is good, its potentially a very effective and very capable machine. Issues are more operator side than machine side. It would push all my buttons with a fifteen pound sledgehammer. You might find my complaints minor niggles entirely acceptable given the small amount of bench space needed to accommodate such considerable machining capability. As always different folks have different views on what is or is not acceptable. However if you anticipate much 12 inch to the foot scale work coming your way a Bridgeport will be much more appealing. Realistically if you can lift workpiece unaided you can pretty much do it on a Bridgeport.

Clive

[Paul LousickParticipant @paullousick59116]

I used to have a Sieg SX3 with variable speer DC motor but traded it for an RF-45 clone when the electronic controllers starting to give problems. Replacement boards are expensive.

The SX3 column would twist under heavy loads. The RG-45 much more stable.

The SX3 had a brushless DC motor and speed changing very easy by turning a dial and had reasonable torque at low speed but not as much torque as a geared drive. The DC motor has a cooling fan attached to its spindle and when running at low speed is not as efficient and overheating the motor can be a problem.

Paul

[Chris Evans 6Participant @chrisevans6]

I love my Bridgeport with varispeed head. Downside of Bridgeports now is finding one that is not totally worn out so I can see the appeal of the RG-45.

[Mark SlatterParticipant @markslatter13251]

Many thanks for the replies everyone, it’s greatly appreciated! It seems the general consensus is to hold out for a Bridgeport or similar.

Clive you make a good point about accessibility, we have a Gate 1100 mill at work and that produces some interesting body contortions when getting in close to small parts to check clearance etc. As you suggest that’s going to be made harder with the rf45. My only concern is not having a decent enough budget to buy a mill with some good precision left in it. A good excuse to haunt the classifieds and view some machines! Thanks again.

[JonParticipant @jon]

Agree with Clive but would go a few stages further, hold out for an 836 or similar.

Looks like they haven't given the actual speed ranges on the 6 speed which is geared head. I will tell you its top whack 1250 rpm since we run at 50hz. I get by but takes an eternity, for compare on a 942 running over 3k rpm a certain part used to take me 17 mins. On RF45 it takes 7hrs+
Heads very heavy with the gears in, the only problems will have is the bearings about £60 for SKF and the selectors.

Geared head wont handle faster speeds due to the bearings, there used to be a US company modifying them to operate over 2k rpm. 3phase one wont have geared head but will have the better modded casting to accept faster spindle speeds.
I can stall my RF45 putting too beefy a cut on which aint that brilliant, especially drilling. Twice the pony 3ph motor to make up for losses, hopefully.

Main weak points are the lead screws and the castings used, they wear. Even my quill moves 0.45mm off centre with quill lock, the castings worn oval.
Accuracy mine isn't, for years have visually seen a bow in the X bed.

First thing will notice with a semi worn 942 is the ability to put a cut on and leave a respectable finish in one go. Machines much heavier and resilient to flexing and vibrations, cutters last hell of a lot longer and leave an uncomparable finish.

Accesability ok not much worse than most others, and that's using MT collets with no loss of height or extra forces imparted using ER.
If theres a need to horizontal bore or drill the part in question will need jacking up from bed 9" to centre line to clear left hand controls.

If only got £1425 go for the Warco or £1700 ish with powered head. Above that theres a massive jump to better around £5k+ for an 836.
What annoys me is the price of the secondhand machines, KRV2000 was £3600 brand new 25 to 12 years ago, now wanting £4k worn out.

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