What the machine is
This is a floor standing vertical drum sander for curved work. The drum stands upright, a flat table sits around it with a hole the drum passes through, and you offer the workpiece to the side of the drum by hand. Because the working surface is cylindrical, it sands inside curves, which is what a flat belt sander and a disc sander cannot do.
The word sponge in the title is the important one. Under the abrasive there is a foam layer, so the surface gives a little and follows a profile instead of cutting a straight line through it. That is the whole reason this machine exists alongside a conventional edge sander.
The photographs show a large flat table with a green or blue edge band and a red feed direction arrow, a handwheel below the table for height, two quadrant scales at the front for tilt, and a cabinet with a louvred side panel. Consumables, guards and dust control are where the questions are.
Four numbers, and they are all in one image
The published specification opens with three commercial rows: brand, minimum order quantity and whether OEM is available. The engineering is in a strip inside one of the photographs, four lines long.
| Published row | Value | What it actually decides |
|---|---|---|
| Sanding belt size | 630 x 150 mm | loop length and sanding width |
| Sponge wheel diameter | 102 mm | the tightest inside curve the machine can reach |
| Installed power | 1.1 kW | 7.33 W for every millimetre of width |
| Operating voltage | 380 V | three phase, and nothing else is offered |
Four numbers is thin for a machine that sells on its ability to follow a curve, because not one of the four describes the following. But they are enough to derive several things that the page never states, and those are the ones worth having before you order.
The belt is a loop, not a sleeve
Start with arithmetic anyone can check. A 102 mm drum has a circumference of 320 mm. The belt is quoted as 630 mm long, which is 1.97 times that circumference.
A sleeve cannot be two thirds longer than the drum it sits on. So the 630 mm figure has to be a closed loop running over the front drum and a second pulley behind it, inside the housing that the photographs show behind the drum.
That also lets you check the geometry. For an open belt between two pulleys the length is twice the centre distance plus half the sum of the circumferences plus a small correction. Solving it for a 630 mm belt on a 102 mm drum gives the centre distances below.
| Rear pulley diameter | Centre distance that makes a 630 mm belt fit |
|---|---|
| 80 mm | 171.7 mm |
| 90 mm | 164.1 mm |
| 100 mm | 156.3 mm |
| 110 mm | 148.4 mm |
Every one of those lands between 148 and 172 mm, which is about the depth of the housing behind the drum. The numbers agree with the pictures, so the belt is a loop and the machine is a two pulley sander rather than a spindle with a sleeve dropped over it.
Why the core is sponge
Abrasive cloth does not like tight bends. Wrapped on a 102 mm drum it is bent to a 51 mm radius, and at that radius the cloth, the resin bond and the joint are all working harder than they would on a flat platen.
A foam layer under the belt absorbs that. It lets the cloth take the bend without the joint cracking, and it lets the surface deflect locally so the abrasive follows a curve instead of bridging across it. Remove the sponge and you have a rigid drum that cuts a straight tangent across every convex form you feed it.
Which means the sponge is a consumable property, not a detail. Its hardness in Shore A is what decides how much the surface conforms, and it is not published. A soft foam follows a tighter curve and removes less; a firm foam removes faster and flattens the profile. That is the number to ask for.
102 mm is the tightest inside curve you can sand
This is the most useful thing that can be worked out from the published figures, and no listing states it.
To sand an inside curve, the drum has to sit inside it. The drum is a rigid cylinder 102 mm across, so no inside curve smaller than 102 mm in diameter can be reached, and the tightest inside radius you can work is 51 mm. Sponge deflection buys a little tolerance around that, but it cannot make the drum smaller than it is.
The application photograph shows the point in practice: a laminated wooden ring, roughly 200 mm inside diameter, held against the drum to clean up its inner face. Two hundred is comfortably above 102. A 90 mm ring would not go on.
So before anything else, measure the tightest inside curve in your work. If it is under about 100 mm, this machine cannot do it and no amount of specification reading will change that. If your curves are chair backs, frames, rings and arched panels, the limit is not going to trouble you.
150 mm is the widest face
The other dimension that comes straight off the specification is the sanding width: 150 mm, the belt width. That is the widest flat face you can cover in one pass, and it is also the length of drum in contact, which sets how much heat and dust the machine makes.
For comparison, a 150 mm drum against a 102 mm diameter means the working face is 1.47 times as long as the drum is wide. On curved work that ratio is what gives the machine its reach.
The 500 W vertical belt and disc sander guide covers the flat alternative: a 100 by 914 mm belt with a 150 mm disc, for straight edges and end grain. That machine has no answer for an inside curve at all, which is the trade you are making.
380 V is three phase, and that decides whether you can run it
The fourth published number is the one that stops installations. In a Chinese machine specification, 380 V on its own is the three phase line voltage. There is no single phase 380 V.
So this sander needs a three phase supply. At 1.1 kW it draws about 2.75 amps per phase, which is trivial for any three phase service and impossible for a shop that only has single phase 220 V.
The same motor rewound for 220 V single phase would draw about 8.2 amps, three times the current for the same work. No 220 V version appears on the page, so if your workshop is single phase, that is the first thing to settle, before price, before delivery, before anything.
Power density is worth a glance too: 1.1 kW over 150 mm of width is 7.33 W per millimetre. That is a finishing machine, not a stock remover. It will clean up a sawn curve; it will not take 5 mm off a hardwood blank in a pass.
Belt speed is missing and spans four times
Surface speed is the single most important process number on any sander, and it cannot be calculated here because the spindle speed is not published. What can be done is to show how much it matters.
| Spindle speed | Belt speed at a 102 mm drum | Against the 12 to 20 m/s band |
|---|---|---|
| 700 r/min | 3.74 m/s | far below |
| 1,000 r/min | 5.34 m/s | below |
| 1,400 r/min | 7.48 m/s | below |
| 2,000 r/min | 10.68 m/s | just below |
| 2,800 r/min | 14.95 m/s | inside |
| 3,000 r/min | 16.02 m/s | inside |
Wood belt sanding generally runs between about 12 and 20 metres per second. Across the plausible range of spindle speeds this machine could have, the belt speed goes from 3.7 to 16 metres per second, a factor of more than four.
At the bottom of that range the belt will burnish rather than cut and the abrasive will load up. At the top it behaves like a sander. So the missing number is not a detail; it separates two different machines. Ask for it in writing, and ask for the pulley diameters so you can check it.
The photographs show two models
The eight images that come with this machine are not all of the same machine. Most carry MM2115 on the cabinet. The last one carries MM2215, in the same typeface, on the same cabinet, with the same table and handwheel.
| Detail | MM2115, most of the pictures | MM2215, the last picture |
|---|---|---|
| Model on the cabinet | MM2115 | MM2215 |
| Drum surface | a stack of narrow abrasive rings with gaps between them | one continuous 150 mm wide sleeve |
| How the abrasive is held | rings slipped over the foam drum | a clamp bar with two bolts across the top |
| Finish across the 150 mm | banded, unless the work is moved along | continuous |
That is not a cosmetic difference. With rings, the working face has gaps, so the finish is banded unless you keep the work moving along the drum. With one continuous sleeve, the finish is even across the full 150 mm. And with a clamped belt you change one consumable; with rings you change a set.
The four published numbers do not say which model they describe. Ask for the quotation in the model number, and ask for a photograph of the actual machine that will be crated.
The consumable is described two ways
The specification names a sanding belt, 630 by 150 mm, which reads as one endless belt. The production photograph shows a row of machines whose drums are loaded with a stack of narrow abrasive rings, with visible gaps and alternating colour between them.
Both are legitimate ways to build a drum sander, and they are not interchangeable at the point of purchase. A single 630 by 150 belt is one part number and one price. A stack is six or seven rings, each a separate item, and the working width is set by how many you fit.
Since the abrasive is the only thing you buy again for the life of the machine, this is worth settling before the order rather than after. Ask which system the quoted model uses, what one replacement costs, and whether the rings are a standard size you can buy locally.
Two colours and two switch types
The pictures show the same design in a green and white finish and in a blue and white finish. That is cosmetic and probably a batch or market difference.
Less cosmetic is the switch. Some photographs show a pair of red and green push buttons on a small plate. Others show a single red rotary knob on a black plate. A rotary switch is a different control from a contactor with start and stop buttons, and it changes what you can do about a machine that restarts unexpectedly after a power cut.
Ask which control station ships, whether there is a no volt release, and whether an emergency stop is fitted. On a machine that holds a moving abrasive surface at table height, that is not a small question.
The table tilts and nobody says how far
The first photograph shows two quadrant scales at the front of the table, each with a pointer, one on either side. That is a tilting table with an angle readout on both ends, which is the right way to build one because it keeps the table from twisting.
The tilt range is not published anywhere, and neither is the table size or the table height. Those three numbers decide what work the machine will physically accept and whether you can stand at it all day. A table that is too low is the most common complaint about floor standing sanders, and it is cheap to check before you buy and expensive to fix afterwards.
No dust port in eight photographs
Every one of the eight images has been read for an extraction connection: a spigot on the drum housing, a hose port on the cabinet, a blast gate. There is none visible on any of them.
A 150 mm wide abrasive surface running at wood sanding speed makes a lot of fine dust, and fine dust is the fraction that matters for health. Some machines of this type collect through the cabinet and some through the drum housing, and some have no provision at all beyond a louvred panel.
So ask for the port diameter and its position, and if there is no port, budget for a hood or extraction at the table. Do that before you decide the machine is cheap, because extraction is part of what the machine costs to run.
Oscillation is not described and not visible
Most spindle sanders of this shape oscillate the drum up and down through 20 to 25 mm while it turns. The stroke spreads wear over the full width of the abrasive, stops the belt loading in one band, and removes the line that a fixed drum leaves at a constant height.
Nothing in the published specification describes oscillation, and none of the eight photographs shows the eccentric, the link or the sliding housing that would produce it. The drum appears fixed to its bracket.
That is consistent with a hand fed machine aimed at profiling rather than finishing, but it is a question rather than a conclusion. If the drum does not oscillate, expect to move the work up and down yourself, and expect the abrasive to wear in one band.
Twelve questions
| Question | Why it decides the order |
|---|---|
| Is the quoted machine MM2115 or MM2215 | The photographs show both, and the four published numbers do not say which one they describe |
| Does the drum use one 630 x 150 belt or a stack of rings | The specification names a belt, the production photograph shows rings |
| What is the spindle speed, and therefore the belt speed | It spans 3.7 to 16 m/s across plausible speeds, a factor of four |
| What is the sponge hardness in Shore A | It is the whole reason the machine can follow a curve |
| Does the drum oscillate, and over what stroke | No oscillation is described and no linkage is visible |
| What is the table size | The largest workpiece is set by it and it is not published |
| What is the table height from the floor | Decides whether the operator stands comfortably |
| What is the table tilt range | Two quadrant scales are visible, the range is not given |
| Is there a dust port, and what diameter | None is visible in any of the eight photographs |
| Is a 220 V single phase version available | 380 V means three phase, which many small shops do not have |
| What is the net weight and the crate size | A cabinet machine of this size is not light, and freight needs it |
| What does a replacement sleeve or ring set cost | The abrasive is the only thing you rebuy, for the life of the machine |
How to decide
Measure two things in your own work first. The tightest inside curve, because 102 mm is a wall you cannot get past. And the widest flat face, because 150 mm is all the belt you have.
Then check the supply. Three phase or not decides the whole thing, and it is the one fact that cannot be worked around with a bigger breaker.
If both of those come out in your favour, the machine is a sensible way to sand curved profiles that a flat belt cannot reach. Then spend the questions on the things the page leaves open: which model, which consumable, what belt speed, what dust port. Those four decide whether the machine you receive is the one you thought you were buying.
Frequently asked questions
What is a sponge drum sander for?
Sanding curved profiles, and specifically inside curves. The drum is vertical and the abrasive wraps a foam layer, so the surface deflects and follows a form instead of cutting a straight tangent across it. A flat belt sander and a disc sander cannot reach an inside curve at all.
What is the smallest inside curve it can sand?
102 mm in diameter, because the drum has to sit inside the curve and the drum is 102 mm across. That is a 51 mm inside radius. Sponge deflection gives a little tolerance but cannot make the drum smaller. Measure your tightest inside curve before ordering.
Why does the belt length matter?
A 102 mm drum has a 320 mm circumference and the belt is 630 mm, so the belt is not a sleeve on the drum. It is a loop running over the drum and a second pulley behind it, which puts the pulley centres around 148 to 172 mm apart for plausible rear pulley sizes.
Can it run on single phase 220 V?
Not as published. The specification gives 380 V, which in a Chinese machine specification is the three phase line voltage. At 1.1 kW it draws only about 2.75 amps per phase, but the supply has to be three phase. Ask specifically whether a 220 V single phase version is available.
How fast does the belt run?
It cannot be worked out from the page because the spindle speed is not published. Across plausible spindle speeds the belt speed would go from 3.7 to 16 metres per second, and wood sanding normally wants 12 to 20, so the missing number decides whether it cuts or burnishes.
Is MM2115 the same as MM2215?
The photographs show both model numbers on the same cabinet design. The visible difference is the drum: MM2115 pictures show a stack of narrow abrasive rings, the MM2215 picture shows one continuous 150 mm sleeve held by a clamp bar. Ask which model the quotation is for.
Does it collect dust?
No dust port is visible in any of the eight photographs. A 150 mm wide abrasive surface makes fine dust, so ask for the port diameter and position, and budget for a hood or extraction at the table if there is none.
Key specifications
Frequently asked questions
- What is a sponge drum sander for?
- Sanding curved profiles, and specifically inside curves. The drum is vertical and the abrasive wraps a foam layer, so the surface deflects and follows a form instead of cutting a straight tangent across it. A flat belt sander and a disc sander cannot reach an inside curve at all.
- What is the smallest inside curve it can sand?
- 102 mm in diameter, because the drum has to sit inside the curve and the drum is 102 mm across. That is a 51 mm inside radius. Sponge deflection gives a little tolerance but cannot make the drum smaller. Measure your tightest inside curve before ordering.
- Why does the belt length matter?
- A 102 mm drum has a 320 mm circumference and the belt is 630 mm, so the belt is not a sleeve on the drum. It is a loop running over the drum and a second pulley behind it, which puts the pulley centres around 148 to 172 mm apart for plausible rear pulley sizes.
- Can it run on single phase 220 V?
- Not as published. The specification gives 380 V, which in a Chinese machine specification is the three phase line voltage. At 1.1 kW it draws only about 2.75 amps per phase, but the supply has to be three phase. Ask specifically whether a 220 V single phase version is available.
- How fast does the belt run?
- It cannot be worked out from the page because the spindle speed is not published. Across plausible spindle speeds the belt speed would go from 3.7 to 16 metres per second, and wood sanding normally wants 12 to 20, so the missing number decides whether it cuts or burnishes.
- Is MM2115 the same as MM2215?
- The photographs show both model numbers on the same cabinet design. The visible difference is the drum: MM2115 pictures show a stack of narrow abrasive rings, the MM2215 picture shows one continuous 150 mm sleeve held by a clamp bar. Ask which model the quotation is for.
- Does it collect dust?
- No dust port is visible in any of the eight photographs. A 150 mm wide abrasive surface makes fine dust, so ask for the port diameter and position, and budget for a hood or extraction at the table if there is none.