Ball screw preload addresses axial clearance and stiffness in the screw–nut assembly. For an aluminum feeding or positioning system, ask what the component claim covers and how the complete axis was reviewed. “Preloaded” does not mean the assembled machine is perfectly rigid.
Start with the proposed axis function, not a general promise of accuracy. A material advance, an adjustable stop and another positioning task can require different movements and evidence. Identify the actual mechanism before comparing its preload description.
What ball screw preload is intended to do
THK’s ball-screw selection guidance describes preload as a way to eliminate axial clearance and reduce displacement under axial loading. It also cautions that excessive preload adversely affects service life and heat generation.
Read the claim with the component identity and conditions. Ask for the offered screw–nut assembly’s designation and documented preload or clearance requirement. A ball-screw category name does not identify that configuration.
Use the ball screw vs lead screw guide for the broader transmission comparison. This article focuses on the preload statement and the distinction between a component property and the assembled task.
Check 1: separate clearance from elastic displacement
A statement about clearance should name the assembly being described. Keep it separate from the displacement observed when a load is applied. Ask the supplier to define the relevant measurement and conditions for each field.
THK’s rigidity guidance relates axial load, feed-system rigidity and elastic displacement. It considers the shaft, nut, support bearings and their mounting brackets in the system review.
An invented stiffness calculation
For a simple arithmetic illustration, assume a complete axial system has a constant rigidity K of 20 N/μm under the condition being considered. Assume an applied axial load F of 200 N. Using displacement = F ÷ K gives:
200 N ÷ 20 N/μm = 10 μm
The load and rigidity are invented. They are not a recommended preload, a measured machine characteristic or a JiurunCut specification. The calculation assumes that the stated K represents the complete system for this load condition.
The result illustrates elastic movement under the assumed load. It does not calculate lost motion, choose a screw, set a controller or predict a finished cut length. Keep those different questions visible in the supplier’s explanation.
If a quotation gives only a nut’s rigidity, do not insert that value into this example as though it described the whole axis. Ask the machine designer to identify the applicable system value and the scope of its assessment.
Check 2: identify the complete quoted arrangement
Request a clear component list or approved arrangement drawing for the relevant axis. Identify the screw–nut package, support arrangement, guide and connection to the moving assembly. Keep the actual configuration beside the claim being compared.
Ask which items belong in the offer. A screw–nut assembly price and a complete positioning-system price include different scopes. Supports, integration, control and commissioning need explicit entries if the quotation combines them.
Record the expected movement sequence and the information available about the operating task. Give the supplier the aluminum section drawing and relevant stock-handling requirements. Have the responsible team determine the actual loads and selection basis.
Do not select a larger preload merely because it sounds more precise. Obtain the manufacturer’s approved application review for the offered configuration. This guide supplies no preload percentage, bearing adjustment, torque setting or maintenance modification.
A fictional quotation comparison
Imagine Offer A describing an invented feed axis as “preloaded ball screw.” Offer B identifies a screw–nut package and includes a defined axis check. There are no test results in either offer yet.
Ask A to identify the actual assembly and scope of its preload statement. Ask B to explain the defined check and included configuration. Both should respond to the same required movement and delivered machine scope.
Keep component documentation, proposed axis evidence and completed-part inspection as separate entries. This helps the buyer locate an unanswered question without assuming that one supplier’s wording proves a better result.
Check 3: connect the claim to the required task
Agree how the offered machine will be evaluated for the actual cutting job. Keep the representative material, drawing revision, length reference and operating sequence with the review plan. State which records the supplier must provide.
Where the approved sequence includes a direction change, include that condition in the agreed assessment. Ask the supplier to define its method and evidence. Procurement should not introduce a homemade axis adjustment or reversal routine.
Measure finished parts against their own requirements. A component’s clearance statement does not replace a cut-length record, and an axis observation does not establish every surface or geometry requirement of the component.
Our factory acceptance checklist helps assign the machine and part checks. Keep the evidence tied to the exact configuration demonstrated.
Questions to put beside the preload claim
- Which identified assembly does the statement describe?
- What component requirement and conditions are documented?
- What separate evidence addresses the complete axis?
- What evidence addresses the actual cut parts?
- Who reviews a component change after acceptance?
Keep any later replacement connected to its approved documentation. A similar-looking nut or a matching nominal screw size does not by itself establish equivalence to the demonstrated configuration.
Buyer questions
Does zero clearance mean zero movement under load?
Review the elastic-displacement question separately. The invented calculation above illustrates why a clearance statement does not supply a system rigidity value.
Can I infer preload from a control-panel photo?
Request the component identity and relevant documentation. A photograph of controls does not identify the installed screw–nut configuration.
Does this guide specify the correct preload for my saw?
No. The supplier’s responsible engineering review must establish the appropriate configuration for the real axis and task.
Send JiurunCut your profile drawing and cutting requirements. Request a configuration-specific explanation of ball screw preload where that mechanism is proposed, together with the agreed axis and part-review scope.