Power Feed - table travel speed on a Mill?

[Alan H.]

What is the lowest table travel speed you'd expect to need on a power feed setup on a milling machine's x or y axis?

I can achieve 1/2" per minute with mine but the speed knob is mighty touchy at that level.

Edit: The 1/2" per min. is really not functional and it's really only works well at 3 or 4 times that speed, therefore my question here.

 

[pstemari]

What is the lowest table travel speed you'd expect to need on a power feed setup on a milling machine's x or y axis?...

Depends entirely on the size of the cutter, tool material, and the stock you are cutting. Answers are going to be very different for a 6" dia fly cutter swinging hss to cut tool steel from a 1/16” ZrN-coated carbide end mill cutting aluminum. Sent from my Pixel XL using Tapatalk

 

[Alan H.]

As often is the case, I haven't been clear enough in my question - apologies for that.

Let me rephrase the question. If you were outfitting a Taiwanese made 9 x 35 3 h.p. knee mill, what capability in minimum table feed rate would you outfit the mill with?

I assume a hobbyist like me is highly likely to buy an Asian sourced Power Feed. So what is a reasonable expectation for the functional minimum table feed rate performance of an Asian Power Feed? Examples of manufacturers might be ALSGS and Align (Chinese and Taiwanese made respectively).

For comparison, a US made 150 in-lb Servo brand is spec'd to perform at a minimum feed rate of 1/2" per minute. It also costs 2 to 3.5 times that of an Asian made unit. I do not think it is reasonable to expect the Chinese made ALSGS to handle the turn down to 1/2" per minute.

Would it be reasonable to expect the ALSGS to turn down and perform at a 2" per minute feed rate? By the way, I have not been able to find any published specs for the minimum table feed rate on the Asian units.

 

[Bob Korves]

The answer to your question, Alan, is also related to minimum spindle speed and materials being cut, along with how many cutters per rev. You don't want to be rubbing metal, you want to be taking a cut, and the feed x tooth count/rpm equals the chip thickness. It would be unusual to want a chip load of less than .001"/cutting edge. Unless you are doing something besides cutting...

 

[Alan H.]

Thanks Bob, I understand that feeds are related to material being cut, DOC, cutter type, and cutter speeds. So let me ask the question to you in a different way.

What minimum feed rate Power Feed would you put on a 3 hp, 60 - 4200 rpm Precision Matthews 935 knee mill to match the overall capability of the machine?

The question is driven by the objective to be limited by the capability of the mill itself, never by the Power Feed's capability.

 

[mksj]

The X axis Align AL-500P on my knee mill (3 Hp) will go down 0.5 IPM and the speed pot goes all the way down to zero in a linear fashion. Not a lot of power at that low a feed rate, but easily set. Most of the time I am using feeds in the 6-12 IPM, sometimes higher for aluminum. Rarely when I want a mirror finish using a larger cutter head maybe go down to 4 IPM. Steel alloys, I have probably gone slower, lots of factors. I do not recall needing anything in the 0.5 IPM range. Inserts specify SFM and In/tooth for different metals, also need to factor in the DOC, so one can do basic calculations for a speed and feed range. The usual insert feed range for steel and SS is something like 0.003-0.008 In/tooth. End mills also give ranges like 0.001-0.003 for HSS, but say you are using a 1/4" end mill, you are limited by the maximum speed of your mill for say aluminum, but probably not for steel. You can do some calculations off of the attached table. The low end of the feed rate I calculate out to something like 1 IPM for some high tensile alloys, faster IPM if carbide tooling or using inserts. I am very happy with my Align power feeds, seem to have plenty of power and they are nicely made. These days, they probably would be my first drive recommendation unless you have money to burn for the Servo drives.

 

[Bob Korves]

Thanks Bob, I understand that feeds are related to material being cut, DOC, cutter type, and cutter speeds. So let me ask the question to you in a different way.

What minimum feed rate Power Feed would you put on a 3 hp, 60 - 4200 rpm Precision Matthews 935 knee mill to match the overall capability of the machine?

The question is driven by the objective to be limited by the capability of the mill itself, never by the Power Feed's capability.

Too many variables, Alan. I have a Servo drive meant for a BP on the X axis of my Millrite, and have not used anything even close to the slowest speed available so far. I don't think in inches per minute, I think in inches per tooth. Still, I normally do not do the math and just use the TLAR method (that looks about right), then tweak by sound, vibration, chips, and surface finish as the cut progresses. Sorry I am not more help, but with so many variables it often becomes art rather than science. I actually have a difficult time choosing to use the power feed for more than rapid traverse, because I have learned to feel the cut with the handle and adjust on the fly. I feel a bit disassociated with the cut using the power feed. But I am new to power feeds on the mill, and learning...

 

[Alan H.]

Too many variables, Alan. I have a Servo drive meant for a BP on the X axis of my Millrite, and have not used anything even close to the slowest speed available so far. I don't think in inches per minute, I think in inches per tooth. Still, I normally do not do the math and just use the TLAR method (that looks about right), then tweak by sound, vibration, chips, and surface finish as the cut progresses. Sorry I am not more help, but with so many variables it often becomes art rather than science. I actually have a difficult time choosing to use the power feed for more than rapid traverse, because I have learned to feel the cut with the handle and adjust on the fly. I feel a bit disassociated with the cut using the power feed. But I am new to power feeds on the mill, and learning...

Okay Bob - thanks for feedback. If I had a Servo, I probably wouldn't be fretting over this. The turndown on mine is not as functional as I'd like. I am trying to decide if my expectations are unreasonable. At the moment, I think not.

 

[Alan H.]

The X axis Align AL-500P on my knee mill (3 Hp) will go down 0.5 IPM and the speed pot goes all the way down to zero in a linear fashion. Not a lot of power at that low a feed rate, but easily set. Most of the time I am using feeds in the 6-12 IPM, sometimes higher for aluminum. Rarely when I want a mirror finish using a larger cutter head maybe go down to 4 IPM. Steel alloys, I have probably gone slower, lots of factors. I do not recall needing anything in the 0.5 IPM range. Inserts specify SFM and In/tooth for different metals, also need to factor in the DOC, so one can do basic calculations for a speed and feed range. The usual insert feed range for steel and SS is something like 0.003-0.008 In/tooth. End mills also give ranges like 0.001-0.003 for HSS, but say you are using a 1/4" end mill, you are limited by the maximum speed of your mill for say aluminum, but probably not for steel. You can do some calculations off of the attached table. The low end of the feed rate I calculate out to something like 1 IPM for some high tensile alloys, faster IPM if carbide tooling or using inserts. I am very happy with my Align power feeds, seem to have plenty of power and they are nicely made. These days, they probably would be my first drive recommendation unless you have money to burn for the Servo drives.

Thanks Mark,
From my recent research the Align units are made in Taiwan and they have a good reputation.

The specs on your model are impressive and of course, the unit comes at a premium compared to a Chinese made ALSGS which is what I have. The speed pot operation being decent on the Align is what I'd like as well. The speed pot on the ALSGS is not linear and leaves a lot to be desired from my viewpoint. I recently faced a cast iron casting and I could not get it as easily adjusted as I thought it should be and as you point out, not a lot of power at low speeds. That is what really drove me to dig into this topic.

So my view now is that one should buy a bit more torque in the PF up front and make sure the speed adjustment pot is decent. BTW, here are the specs on yours from the Align website and it appears the torque is quite substantial compared to others I've looked at. (the spec is showing max torque)

 

[Alan H.]

I gathered some data this morning on table speed vs. Pot position on my ALSGS Power Feed. I used the table speed function on my DRO to get the readings. While the data is rough, it clearly demonstrates the issue that I dislike.

The potentiometer (Pot) has rotation indicator numbers on it indicating tenths of a rotation. The Pot only rotates about 8/10 of a full rotation. Here's a graphic of the data. It shows clearly what I dislike about this Power Feed's adjustment.

If a table speed of 1 to 12 in/min is a reasonable common operating envelop that one would want a Power Feed to easily adjust to, this Pot's range for that is half a mark. If it is 2 to 5 in/min, it is roughly 2/10 of one mark or less.

In other words, this thing is hard to adjust and it is overly sensitive on the lower end. If you are trying to get 4 or 5 in/min. I am having to dial the knob with rotational changes that are simply way too small to comfortably get it to the mark. It is achievable but is a PITA and you sure don't try to make changes on the fly at this level.