Here we go again! Am I loosing steps?


I haven’t had the opportunity to cut big thinks on the last 2 monts but recently a customer asked me to cut him an archtop molding jig, that is basically made with multiple layer of MDF.

I really was excited to do that since I had recently found that my belt tension was uneven on both Y axis, so I bought a digital fish-scales and managed to set a proper and equal belt tension on both Y axis.

Following the @PhilJohnson advice of some week back I setted the belt tension between 3.5/4lb (is lb the correct term?) using a scale and raising the belt of 1 inch in the middle with the carriage all backwards using @RobertA_Rieke video as reference. I think I have pretty much setted an equal tension on both axis, I could have a tollerance of 0.5lb (holding the fish scale and a rule at the same time isn’t easy lol).

I also setted the X axis belt tension to 4lb, thinking that it only have 1 motor to work so a little bit of “force” on the pulley could be better.

Of course I have then re-calibrate all the stepper.

Anyway, I did the cut of the molding jig and basically all went perfect, since the customer asked me if could cut him some small template, and here come the problems: On the X axis the lenght of the templates was dead perfecet (420mm on the project and 420mm on the cut), BUT on the Y axis it miss 0.9/1mm! Also circles went little bit oval on a side (pretty much on 14 'o clock if I remember well).

When I have made the stepper calibration, I had a dead results on both X and Y (using a 600mm rule and a .48mm bit).

I cutted using a new router bit, 3mm depth per passes, 1100mm/h feeding. Mod on the machine is 30min X axis mod, eccentric nut mod, v-wheels mod, Z axis mod. 1000x1000 machine with dewalt 611, pot current setted. I think I have all setted up well since I recently re-built the machine because I had a not square waste-board that now I think is mm+/mm- okay.

Any thought? I’m starting to loose faith on have correct size/dimension cut, since I need to start cut hard wood soon I’m really worried about.


Quick things to check would be the stepper pulley screws (use blue loctite and make sure one screw is dead-center on a flat) and the V-wheels (it’s possible they’ll tighten on their own). If you have a stiffening modification, make sure your X-axis makerslides are perfectly parallel to each other.

Oh forgot to mention that I have replaced all the pulley nuts with 3mm screw. I have really thightened them, could be a problem?

Do you mean the Y axis? I usually use 2 perfect square block and push the axis to them then start the machine to be sure is parallel

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That is the first thing I’ll do tomorrow, well better say in a couple of hour. Is 4a.m. here in Italy!

Another add on. When trying to cut square and circles with a 0.48mm bit and 0.5mm depth. They were really perfect. Perfect circles! (and square)

2nd add on: When I calibrated the stepper, I have fixed the rules on the wasteboard just by pushing it against the screw of 2 clamp and tighten them a bit to make sure it doesn’t move. I’m sure the rule was in axis to the waste board because I have checked it.

When the carriage goes from 0 to 600mm it not goes parallel to the rule but always arrive some mm far from it. On both X and Y side.

Could be that the problem?

I usually put 2 square block at the end of the gantry then turn the machine on. Is that what you mean?

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Yes I’m missing that screw! All of the other screw I swapped are 100% thight, only that is missing. Don’t now how, when or why.

By thr flat shaft you mean the very end of the screw?

The flat part of the stepper motor shaft.
The stepper motors shafts may not have a flat spot.
Its cheap insurance to quickly file down the stepper motor shafts to create a small flat spot.
Even a minute flat spot will give you that much more area for the set screws to “grab” onto.

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Oh crap…first time I see that thing…

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I don’t remember if I have one cause I have assembled the machine in March, and never took of the pulley (in fact I don’t know if they will come off easily now, I rember a lot of pressure was needed to insert them), even when I reassembled the machine last month.

I guess, if the missing bolt will solve my problem that I can leave the machine as is for now and disassemble it again when the upgrade kit is ready to ship

Oh just to know: just one flat side is needed or I need to make two, one per bolt?

Blue Loctite even if have replaced grain with screw? I can really tight them!

Anyway, while I’m thinking if make it now or later when upgrade kit will be available, I remember that once I tried to pull off the Z axis pulley but it barely move from the motor shaft. There’s a method to pull them off?

Crystal clear. I assume is better to make everything from zero again when the kit is available. For now I only need the machine to cut MDF and don’t need decinal tollerance so I hope to solve the problem with the missing screw and make a more accurate calibration of the Y axis.

P.s. I checked the squareness of the machine and seem dead square. The X axis are square to the Y axis too.