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Tips/Techniques RF-45 clone vs King PDM-30

Tips/Techniques
CWret

CWret

Ultra Member
Premium Member
These are both large bench top mills, but a rectangle column mill compared to a round column mill seems like an unfair/off balance discussion. Not to mention that the RF45 weighs 300 pounds more than the PDM30.
True enough, but it just so happens (that for 2 weeks) I have had both side by side in my small shop.

Just to clarify: my RF45 clone is a 3 year old MD45 from Modern Tool and my PDM30 is actually a 22 year old Grizzle G1006 Mill/Drill which is now sold as a Grizzle G0705. Here is the G1006 about to go into the trailer, thanks @trlvn and @Canadium for all your help.
IMG_3830.jpeg
Here they are set up in my very crowded shop space.
IMG_3946.jpeg

Configurations:
They both have nearly the same size table and x travel. The MD45 has almost an 1” more y and 3” more z travel. They both have 5” of quill stroke. They are both sold as 2 Hp machines but the MD45 motor is [email protected] while the G1006 has a much physically larger motor and is either 110V@23amps or [email protected]. Mine came factory wired as 110V. The MD45 has both motor and head cantilever on the front, while the G1006 has the motor at the back which sort of balances the weight of the head at the front. The MD45 motor is mounted on top whereas the G1006 motor is mounted underneath and more out of the way. Changing belts on the G1006 requires access to the right side and could be an issue. The MD45 is a 6 speed gear head, but the G1006 is a 12 speed belt drive. If my MD45 had 12 speeds I would not be considering a VFD upgrade. Also the belt drive is quiet. It is much easier and quicker to charge bells than I had imagined. Changing gears on the MD45 is super fast and simple- but it’s not that big of a deal to do a belt change on the G1006. I get that now. The HD base of the G1006 and large column diameter are very solid for the size of this machine. I was very impressed with its rigidity.

I did some aggressive EM cuts today on a piece of mild steel. WOW, the G1006 performed surprisingly well on just 110V. Also smooth and vibration free. It pretty much matched what I am use to with the MD45.
IMG_3957.jpeg

IMG_3960.jpegIMG_3963.jpegI joined the forum (3years ago) to help me figure out what mill to buy. New or used? I got great advice - thanks to all that helped me on that journey. I had some bad experiences with kijiji (wild goose chases). So decided a new machine was expensive but a better choice for this newbie. I was about to get a Precision Matthews mill but then found Modern Tool. I visited their shop/show room. They had a PDM30 sized round column mill (their clone of a PDM30) in their shop. Someone had ordered it and then changed their mind (it was close to a $1000 less than a MD45). Great price and included factory installed flood coolant system + x power feed. But i said no thanks because of the round column. If i had to do it over, i would have / should have taken that deal. Hind sight is 20/20.

CW

PS1: The Grizzle G1006 is very similar to King Canada’s PDM-30 except the Grizzly weighs 100 pounds more than the PDM-30. The Grizzle is made in Taiwan vs China for the King. This Grizzle has the optional conversion kit and is pre-wired for 110V but can easily be converted to 220V.
PS2: Here is a video from “that lazy machinists” that explains how to minimize the need to use the Z travel on a round column mill. He is a bit too long winded (like a lot of YouTube’ers) but has some good tips.

 
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Have a look at my post #13 from Feb8, 23. In thread “RF-45Mill/Drill Done


CWret

Post in thread 'RF-45 Mill/Drill Done'

NP: $4950 + tax.

Now the long winded answer:
It came with a nice stand (which i have for sale in the CHMW classifieds).
They loaded it on my trailer in Newmarket.
I added a DRO and power X feed which Modern had as options. I got the X feed from Modern ($550) which was super simple to install. I sourced the DRO myself (which was a good decision).
I’m very satisfied with my Modern Tool experience.
I told Modern (Brad in Calgary) I was interested in early August. When they received the next shipment (from China) they shipped one to Newmarket so i could have first hand look and decide- no...
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Proxule said:
Now fill the base and part of the column of that rf45 with epoxy granite,
Click to expand...
I have heard that substantially improvements rigidity. It makes sense that it would. I’d like to know more about how that is done. Has anyone documented doing it and also have some measurable results?
My MD45 stand is very beefed up. It weighs over 400 pounds. Lot of 1.5” and 2” round bars built into the frame.

Edit - i just did a search for “how to build epoxy granite machine base” and found several examples (YouTube). I’ll have a look at them. It seems to be common when some converts to CNC.
 
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@CWret - I'd be cautious about what you found on the internet.

I was curious about your choice of search terms (build a base vs fill a base) so I did the same search just for shits and giggles. I was surprised to discover that the majority called the effort an improvement in strength and/or bending resistance. One even went as far as to measure the rigidity improvements on a surface plate!!! - NOT!

Clearly, this tells me that the majority out there do not understand the difference between strength and rigidity. While I'm pretty sure that strength improvements do improve rigidity (usually through natural frequency changes), I do not think that strength improvements achieve optimum rigidity results.

I got better results when I searched "fill mill base and column with epoxy granite" - as recommended by @Proxule, but still not really what I would have liked to see.

You might find that using your own engineering background to develop your own solution provides better results than what you find on YouTube.
 
I did mine using this formula.
60% gravel
25% sand
15% epoxy resin
give or take a bit.

My phone SD card died so there is no procedural photos.

I noticed the base does not flex when bolted to my less then flat 1/2" plate 400/500lb stand I made.

But no before or after numbers on performance, the day I bought my mill I stripped it down and started this procedure. I researched enough in the past to know it works and works well for light duty machines like thr rf45. Perhaps less popular on full sized machines or equipment with the proper mass and size.

Gluck
 
@Susquatch here’s a bit of info I found:
First off - as you said above, strength and vibration dampening are two very different animals (see video below). Using about 20% epoxy and 80% aggregate appears to be about right (15 to 20% is the range for epoxy). The aggregate can be sand and/or clear stone. If i do this i would use traprock because of its higher density than granite. Sand blasting media would also be a contender for the aggregate.

Here’s a few tips I picked up:
- wash and dry the aggregate.
- place the part (machine base or column) on a vibration table of some sort (a motor with an off balance weight attached) it is very important to get the air bubbles out.
- use slow set epoxy to give more time for the air to escape and also will dissipate the heat slower.
- use wax on any surfaces where you want the mixture not to stick



Adam Bender does a good job of explaining the difference between strength (from steel) vs vibration dampening from the epoxy granite:

Robert Steinwandel’s 5 minute video also had some good tips:
 
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@CWret - I also researched academic papers on the subject and found a study that evaluated rigidity improvements with Epoxy Granite (EG) Fills. The results of this study were staggering. A quick read of the results demonstrates why rigidity is more important than strength. I cannot attach the paper because it is protected, but I was able to copy the summary.
  • The suitability of epoxy granite (EG) as an alternate material for base of vertical machining center was investigated to achieve enhanced damping characteristics.
  • Scaled down model of EG base was fabricated. Static and experimental modal analyses were performed.
  • EG base exhibited higher natural frequencies and sixteen times higher damping compared to CI base.
  • Upto seven-fold improvements in directional stiffnesses of VMC with EG base compared to VMC with CI base.
  • A comparison of chatter stability revealed that EG base exhibited a three-fold improvement in material removal rate without chatter compared to VMC with CI base.
 
CWret said:
Here’s a few tips I picked up:
Click to expand...

I guess, the point I was trying to convey is that I think you will get more benefit from filling the column and base versus making a new base. I'm not saying a new base won't be better, just that a filled column and base might provide significantly more benefit.

If you don't want to fill the column and/or the base, I can understand - it's a much more permanent change. Only you can decide what is most important to you.
 
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